16 ms·

DIY Home EV Charger

112 points by nickt 3y ago

myself248 3y ago
Save you a click: It's an EVSE, not a charger. Looks very similar to OpenEVSE but he wrote his own code. Nice clean build. Not sure why the extra work instead of just downloading OpenEVSE.
- timthorn 3y ago
  I'd have called an EVSE a charger - I might be naive but what's the distinction you're trying to make?
  - Maxion 3y ago
    The actual AC charger is in the car - it is a pretty important distinction.
  - Moto7451 3y ago
    The name itself, Electric Vehicle Supply Equipment, indicates the focus of the hardware beyond simply being a fancy plug and a contactor. Higher end EVSE will do things like load balancing a shared supply of power (ie chaining multiple Tesla EVSEs to the same 50A line), setting supply power limits depending on how much power is in use (ie the Porsche Connect Plus modulating lower current when a clothing dryer starts), and managing Car to Grid functionality (Hyundai). EVSEs also manage DC charging in commercial settings, which bypasses part of the charging hardware in some cars. My Porsche Taycan is available with multiple chargers from the factory. I have the faster AC charger unit and there is a third unit that is only sold in Europe for Type 2 chargers. The actual charger handles converting AC to DC, which is car specific and why it’s not in the EVSE.
    - schiffern 3y ago
      > The name itself, Electric Vehicle Supply Equipment, indicates the focus of the hardware beyond simply being a fancy plug and a contactor. Thank you, I wasn't previously aware of this distinction. So for simple units that are just "a fancy plug and contactor" (no balancing, limiting, V2G, V1G, etc), what do we call them? I know not to say "EVSE" now, but what should I use? Thanks again.
  - elihu 3y ago
    The terminology is kind of confusing, but usually the thing called a "charger" is the part that converts AC to DC at whatever voltage the pack requires. For level 1 and 2 charging, the charger is in the car. J1772 ports are basically just fancy 110v or 220v AC plugs with some extra signalling. DC charging tends to happen at much higher power levels, and that equipment is expensive so the AC-DC converter is kept outside of the car. The car itself just has a couple contactors (i.e. high power relays) to connect the charge port directly to the battery, and a microcontroller to tell the charger how much current it can handle at what voltage.
    - KennyBlanken 3y ago
      Not by the general public. The general public typically refers to the EVSE itself as a "level 2 charger." The general public does not know or care about the distinction and in the grand scheme of things, it doesn't matter.
      - elihu 3y ago
        And yet the technical people need accurate names to call things so they can communicate without ambiguity. I think "charging station" is the least confusing term for the fixed infrastructure part. If regular people call those "chargers" in non-technical conversation, then I'm not going to lose sleep over it.
        gambiting 3y ago
        The thing that you use to provide your phone with electricity - do you call it an AC-DC converter, or do you call it a charger like nearly everyone on earth, even though the charger part is actually inside your phone?
        Dylan16807 3y ago
        It's funny that people don't want to call it a charger specifically because it doesn't do the AC-DC conversion, and your example of a thing people call a charger is an AC-DC converter. And depending on the sophistication of the phone, that converter outside the phone might be doing most of the work.
  - myself248 3y ago
    The EVSE is a glorified RCD/GFCI cord with a contactor that turns on power, so the cord is dead until that happens. It also generates a signal that tells the car how much power it's allowed to draw; the EVSE is configured at install time to know what size breaker feeds it upstream, so it tells the car not to trip that breaker, but the EVSE has no means of actually enforcing such a limit. There's some basic negotiation between the EVSE and the car, to decide when the plug is inserted and it's OK to turn on the contactor. The AC power passes straight through the EVSE, unaltered in voltage, current, or waveform. The EVSE may monitor the current to perform logging, and the EVSE is required to monitor the AC imbalance like any other RCD/GFCI does so it can open the contactor if there's a ground fault, but that's it. It's just a smart extension cord, basically. The charger is in the car, and is the component that actually converts the AC from the grid to DC for the batteries. The charger is what has all the silicon (or these days, probably gallium nitride?), and the inductors and capacitors and stuff to actually transform the power from one form to another. It changes the voltage to match whatever the battery needs at the moment. It controls its own DC output to match the battery's needs, and it limits its own AC input according to the signal from the EVSE so it doesn't trip the upstream breaker. The charger is also responsible for immediately turning itself off, reducing its input draw to zero, within a few milliseconds of someone pressing the latch of the EVSE connector handle. This indicates they're about to pull it out, and the contacts aren't designed to handle arcing, so the charger is required to drop its current _very_ quickly, allowing the contacts to be separated without creating an arc. That signal (called PP) is produced in the handle itself, there's just a tiny switch underneath the latch. The handle is technically part of the cord which is technically part of the EVSE, but the EVSE has no responsibilities related to the signal, that's all on the charger. If the SAE hadn't mandated that the EVSE perform RCD functions, it could be replaced by a literal extension cord. Many small DIY EVs do precisely that; the charge cord is the exact same one you'd use to run any appliance. It works just fine. But even small DIY EVs have a real charger too, which converts the AC from the cord to DC for the batteries. The charger plugs into the cord, but the charger is not the cord.
- MostlyStable 3y ago
  I would have liked to see a cost breakdown. If it's significantly cheaper than OpenEVSE (somewhwere between $500-$600 depending on which kit you get), then maybe some people would be willing to take the risk (it seems like there are some safety concerns with his design that I don't feel qualified to adjudicate). But without some kind of a cost difference, I'd probably stick with something like OpenEVS, which seems to have some level of official certification [0]. I personally regret my decision to not go with them when I got my EVSE this year. I went with an EnelX Juicenet because A) it was on the list of devices my power company would mostly pay for and B) at the time it had API availability to integrate with HomeAssistant. They have since killed that second part, which I would have loved to still have. In the long term, the ~$500 I saved by having my power company reimburse was probably not worth the lack of control I now have. [0] https://openev.freshdesk.com/support/solutions/articles/6000113537-openevse-safety-features https://openev.freshdesk.com/support/solutions/articles/6000... -edit- He does have a total cost, I just missed it: he claims that it was ~£200. I leave it up to the reader if that's enough savings to give up the certification.
  - myself248 3y ago
    OpenEVSE can be a codebase or a kit. If you want to source all your own parts, or maybe reuse significant parts of a non-open EVSE and just drop the processor into it or whatever, then it can be very cheap indeed. If you buy their branded kit, then full price applies. When OpenEVSE was new, I built one on perfboard, actually a very compact modular stack of perfboards, one layer per subsystem. Handed it off to my software-savvy friend, and he couldn't get it to pass self-test, despite both of us agreeing that every piece of the circuit appeared correct as per the published schematic. Eventually he gave up and ordered one of OpenEVSE's commercially-produced boards, and it failed self-test at the exact same place. Apparently there was some unclear documentation and it was supposed to fail there until something else was hooked up, I don't remember the details, but there was nothing wrong with my stack of perf in the first place. Argh. All of which is to say, it's not hard at all to build one of these things. if you want to lobotomize your closed-crap EVSE and lash an open board to it, do so! I'm pretty sure the JuiceBox is OpenEVSE-based in the first place so it might be as simple as reflashing some firmware.
- KennyBlanken 3y ago
  Everyone calls them chargers. If you said "do you like the EVSE you have?" or "do you know where the nearest EVSE is?" most people would stare at you with a blank expression.
  - Dylan16807 3y ago
    > If you said "do you like the EVSE you have?" or "do you know where the nearest EVSE is?" most people would stare at you with a blank expression. Because you'd need to use a word like "plug" or something, not because of whether it's "charger" specifically.
photonbeam 3y ago
mirror https://web.archive.org/web/20231203183047/https://jamesfotherby.com/index-page/electric-vehicle-charger/ https://web.archive.org/web/20231203183047/https://jamesfoth...
greenthrow 3y ago
This is such a bad DIY project because the costs of screwing up can be burning your house down. This is non-trivial amounts of power. If you spend the money fot an EV, buy something safe and have it professionally installed. Keep the DIY projects to something less dangerous.
- thebigman433 3y ago
  I love higher power DIY stuff in general, but yea this project really doesnt thrill me. It does sound like the author did adequate research, which is good, but the soldering joints dont inspire a ton of confidence in overall quality. Stuff like this is absolutely what I would consider "worth" paying a professional to do. Especially since buying a retail unit/paying a professional to install it will come with warranties.
- wannacboatmovie 3y ago
  Software engineers have a tendency to overestimate their own abilities, the arrogance is often on full display here for all to see. Maybe we need a few to burn their own houses down to act as a deterrent and encourage others to stay in their lane.
  - newZWhoDis 3y ago
    Some of us here are actually Engineers (Electrical). I’ve installed 3x 240V 60A EV chargers, was a cakewalk. I didn’t build my own in this case since I was going for an aesthetic match. Meanwhile you can enjoy paying some alcoholic $1000 for 30 minutes of work to: * pop out a hole on the back * Tap and install 2x screws into studs * pull 3 wires 6” through, wrap around the strain relief, strip/insert/torque * flip a breaker It’s not rocket science, as long as you’re not a complete idiot and turn the breaker off before hand it’s completely safe. 240V isn’t even “high” voltage.
    - shmoe 3y ago
      You're 100% right, but it not being "high voltage" is totally negated by the fact that the two legs together will kill me if it seeks ground via the right (wrong?) path for sure.
eigenvalue 3y ago
More like a DIY arson investigation. You might not only burn down your house, but also get in trouble with the law and not receive compensation from your property insurance company. This is a horrendous idea. Just do basically anything else DIY besides high current/voltage electronics.
- wayfinder 3y ago
  Some of us on here don’t know just software engineering and nothing else Congrats to OP on a clean project source: electrical engineer who writes high performance software you’ve definitely have used
- dreamcompiler 3y ago
  Page is hugged to death right now but I strongly disagree with parent. I'm an EE and I'm quite familiar with the National Electric Code. I build high current/voltage devices and I've wired two houses (both of which passed inspection). If you're trained, experienced, and generally know what you're doing there's nothing wrong with working on high power electronics.
  - Comfy-Tinwork 3y ago
    Suppose you aren't trained, experienced or generally know about working with high voltage systems, like the author?
    - beej71 3y ago
      Then you learn you some, like the author.
      - Comfy-Tinwork 3y ago
        Same way I learned to drive actually, behind the wheel of an 18 wheeler going down the freeway in the snow.
  - ClassyJacket 3y ago
Animats 3y ago
1. Two words: strain relief. 2. If it's outdoors, at least spray the electronics with Fine-L-Kote or similar to keep water vapor out. 3. Those relays look undersized for the load. Look at Grainger for similar ratings. Do not buy power relays on eBay or Alibaba. Current ratings there tend to be wildly exaggerated. 4. Er, overcurrent protection? An approved circuit breaker?
- sokoloff 3y ago
  He says he installed a 50A OCPD, which is the same overcurrent protection an electrician would install and used relays from TE Connectivity (a respected brand) rated at 125% of the current the EVSE advertises as available. Both of those decisions seem perfectly sane/safe to me.
  - StillBored 3y ago
    Are you an EE with a specialty in power electronics? Cause that seems insane to me, inductive loads will cause a voltage spike (flyback) when disconnected, which will exceed that easily. That is why there is generally a reverse diode across the contacts, which I didn't see in the diagram. Granted the article notes it appears to be largely a resistive load, but I would want data sheets on the car/charging requirements, not measurements, to ensure this is true 100% of the time. Maybe the car has an AC compressor or a pump to cool the battery during charging, which draws directly from the charger when plugged in. You might not see that doing a few random measurements because it turns on only after some time or if someone is sitting in the car.
    - ferongr 3y ago
      >Maybe the car has an AC compressor or a pump to cool the battery during charging, which draws directly from the charger when plugged in No it doesn't. A/C compressors in EVs are 3 phase AC powered by an inverter supplied by the traction battery. The contactors in an EVSE open and close at practically zero current, the OBC ramps the current up or down accordingly. And as another sibling comment noted, the OBCs are PFC corrected and act as a largely resistive load.
foobarian 3y ago
I'm disappointed at the anti-DIY sentiments here, it's this safety obsessed mentality that got us to where kids can't walk outside by themselves any longer. The box in that guy's build is outside and could probably burn to a crisp without hurting anything else. I suspect it would not hurt anything even inside a garage, other than making a lot of smoke and setting off smoke detectors.
- wannacboatmovie 3y ago
  Fairly certain most DIY electrical work is strictly verboten in the UK, where the author is located. I would think at a minimum you need approval from the council. Not too dissimilar to the permitting process in the US, but the UK is noticeably more safety-obsessed.
  - rcxdude 3y ago
    Well, there's a pretty large fraction which is still fine to do full DIY. (but not EV chargers) The next level basically either requires some certification or to get the council to inspect it, but plenty of people just ignore that.
    - folmar 3y ago
      It seems things are pretty lax in the UK. Here in Poland you need a qualification certificate to replace a broken socket and a supervisors' certificate to move it half a meter.
  - OJFord 3y ago
    > Fairly certain most DIY electrical work is strictly verboten in the UK No. You can't touch the consumer unit, and there's a restricted zone around bath/shower for example (by distance), but most things a homeowner might want to do are perfectly legal to DIY. > the US, but the UK is noticeably more safety-obsessed. Crikey, are you joking? Internet forums are awash with US concern over 'code', and to extend beyond electricity: food safety, FDA guidelines, all sorts of common senseless rubbish.
jtagen 3y ago
Given what's in this, why are EVSEs so expensive? Given the quantities we see, the $150 range should be more than enough for a decent profit.
- sowbug 3y ago
  Supply and demand. See also $40 HDMI cables at Best Buy.
  - jtagen 3y ago
    I'm not sure I buy this. If someone can hack this together for <$100 at home, there should be plenty of supply to meet the demand. $40 HDMI cables are an option (albeit a terrible one). For EVSEs, there really isn't a reasonably-priced alternative on the market right now.
    - dylan604 3y ago
      Most people aren't going to DIY something like this. Also, most people think that the price of a product should only be based on the price of its components, and possibly willing to accept a mark up on labor. However, the companies making a thing, whatever that thing might be, also has to make money to be able to pay the people that work for the company, the utility bills, and the rent. There's also the fact that the companies making a thing don't get the retail price you pay. They sell it at the wholesale rate to the vendors, so there's even less margin than the retail price suggest for the makers. Just some things to keep in mind
      - sokoloff 3y ago
        In engineering university, I learned the “retail needs to be 5x the BoM* cost” rule of thumb. For a very high value or very high units product, maybe you could shave that to 4x or slightly less, but there are a lot of hands between the designed part and the retail consumer and none of them want to work for free. * BoM - Bill of Materials (“what stuff goes into this thing?”)
savrajsingh 3y ago
Fun kit versions at openevse https://openevse.com/index.html https://openevse.com/index.html
oceanplexian 3y ago
Level 2 chargers aren’t actually chargers, they just pass mains voltage and some signaling. The charger is inside the vehicle.
- NotSammyHagar 3y ago
  The evse (misnamed charger here) needs to reduce the amperage based on what the car side wants. So it does more than just pass mains voltage.
  - Johnny555 3y ago
    Got a reference for that? As far as I know (as the linked article says), the EVSE doesn't do anything to control the current other than telling the car how much it can draw.
  - cpitman 3y ago
    That's not accurate. The EVSE communicates a max current to the vehicle, but does nothing to actively control the current. It should monitor the current and kill the circuit if the vehicle attempts to draw too much, but that only happens after the vehicle has misbehaved.
    - aaronmdjones 3y ago
      Correct. The control pilot signal from EVSE to EV is a PWM signal that indicates to the EV how much current is available. It could drop at any time due to, for example, many chargers being connected to 1 circuit and the chargers coordinating with each-other to load-balance their connected vehicles (everyone gets their fair share), or it could be tied to solar PV generation so that charging doesn't import from the grid; the available current will change with how much excess PV is available, etc. A well-engineered EVSE will notice when the EV is drawing more than the EVSE wants it to. It should then open the mains contactor at this point; cutting the EV's electricity supply. It will also hold the control pilot low to signal a fault to the EV.
  - throitallaway 3y ago
NotYourLawyer 3y ago
> The relay resistors are dissipating 900mW (They’re 1W rated) which gets them to about 60 celsius above ambient Yikes. Get some 5 watt resistors.
mrb 3y ago
"It costs about £900 in the UK to have an EV charger installed by an electrician" £900 is $1140. In southern California, it cost me $750 for top notch work and hardware, including: $400 to have an electrician install a 240V 50A outdoor outlet (NEMA 14-50), plus $350 for a good quality level 2 40A EVSE (this one: https://www.amazon.com/dp/B082LMVSLY https://www.amazon.com/dp/B082LMVSLY) that I installed myself as it simply plugs in the outlet and it's just a 5-minute job to secure it to the wall with two screws. It's possible to bring the cost down to around $600 when picking a cheaper EVSE (like https://www.amazon.com/dp/B08LMX4TJR?th=1 https://www.amazon.com/dp/B08LMX4TJR?th=1), so about half the UK cost as reported in the blog post. I would love to see a breakdown of that £900... that seems really high.
- Symbiote 3y ago
  From some searching, I think paying an electrician to install a 32A CEE socket (often called "Commando" in Britain after a particular manufacturer) and then installing the EVSE yourself would be similar. Although there do seem to be some safety requirements for the socket if it's to be used for charging EVs, which increase the cost. Also, the £900 includes 20% tax.
  - dbrgn 3y ago
    I talked to the electrician about using a CEE16 connector to charge the car. He said that this should only be done if you don't load it near its max (16A) for long periods of time. He's seen multiple CEE16 connectors that deformed condsiderably after a year of use with regular charging sessions at 16A. If you load it to 10-12A, it should be fine.
    - Symbiote 3y ago
      I have servers and UPSs and so on connected with these sockets, drawing a high current 24/7. Just like every datacentre in Europe, UK included. They are only very rarely unplugged though. Is it a case of using a high quality socket which costs 2-3 times as much?
gboza1 3y ago
[flagged]
progbits 3y ago
Disagree with the fire risk comments, even if it burns it's outside in a suitable enclosure. The real problem here is DIY RCD with microcontroller in the loop. The soldering on the high voltage wires is absolutely horrendous and if those come loose and the enclosure or chassis becomes live you are trusting your life on the atmel interrupt delay and software. Good luck! Edit: it's not even an interrupt, its just part of the Arduino loop(): https://github.com/fotherja/EV_Charger/blob/main/EV_Charger.ino#L154 https://github.com/fotherja/EV_Charger/blob/main/EV_Charger....
- Faaak 3y ago
  I agree on the RCD part. An "off the shelf" one would be cheaper and more safe IMHO. Appart from that, good job ! :-)
adev_ 3y ago
Thanks for the experience sharing and the blog, it is very interesting to read and your humility about the feedback is definitively appreciated. I currently also did my own DIY EVSE charger mainly for fun [1]. If you are interested about the main differences between your approach and mine: (1) I use an industrial contactor DIN form factor for the power switch instead of passing the power through the relay directly. Mainly for safety reasons (I do not trust much small relays) and also because I wanted to support three-phase power for an European T2 installation. (2) Instead of printing my own PCB with an Arduino for the PWN, I just bought one command module from China/UK provider. Mainly for pure lazyness reason :) The module itself is shield behind the RCD class B. (3) I have added a shelly 3EM front of the system. To use it as a watt-meter with MQTT report and also as a remote control system. My little advice for people interested to do their own: DIY is always an excellent way to learn and if you want to do your own, do it... BUT please make your installation reviewed by someone with an electrical engineering or technician background if possible. These systems can easily pump 7 to 22KW during extended period of time: Any cable which is not screwed properly or under-sized can bring you a fire. [1]: https://github.com/adevress/open-ev-station/blob/master/README-fr.md https://github.com/adevress/open-ev-station/blob/master/READ...
urtie 3y ago
I've run something similar for 5 years, using https://www.smartevse.nl/ https://www.smartevse.nl/ as the brains. The main advantages over commercial EVSE's in my case were that I could loadbalance charging the car with the electricity demands of the house, and that I could have the EVSE itself inside, so that there's no 240V current on any circuit from the breaker box indoors towards the car when there's no car present. I do intend to add a second sometime, so that I can put the EVSE in my home automation UI as well; the version 2 of smartevse that I use does not have a network connection, but it can be connected to be controlled by a version 3 that does.

112 points by nickt 3y ago

Save you a click: It's an EVSE, not a charger. Looks very similar to OpenEVSE but he wrote his own code. Nice clean build. Not sure why the extra work instead of just downloading OpenEVSE.

timthorn 3y ago
I'd have called an EVSE a charger - I might be naive but what's the distinction you're trying to make?
- Maxion 3y ago
  The actual AC charger is in the car - it is a pretty important distinction.
- Moto7451 3y ago
  The name itself, Electric Vehicle Supply Equipment, indicates the focus of the hardware beyond simply being a fancy plug and a contactor. Higher end EVSE will do things like load balancing a shared supply of power (ie chaining multiple Tesla EVSEs to the same 50A line), setting supply power limits depending on how much power is in use (ie the Porsche Connect Plus modulating lower current when a clothing dryer starts), and managing Car to Grid functionality (Hyundai). EVSEs also manage DC charging in commercial settings, which bypasses part of the charging hardware in some cars. My Porsche Taycan is available with multiple chargers from the factory. I have the faster AC charger unit and there is a third unit that is only sold in Europe for Type 2 chargers. The actual charger handles converting AC to DC, which is car specific and why it’s not in the EVSE.
  - schiffern 3y ago
    > The name itself, Electric Vehicle Supply Equipment, indicates the focus of the hardware beyond simply being a fancy plug and a contactor. Thank you, I wasn't previously aware of this distinction. So for simple units that are just "a fancy plug and contactor" (no balancing, limiting, V2G, V1G, etc), what do we call them? I know not to say "EVSE" now, but what should I use? Thanks again.
- elihu 3y ago
  The terminology is kind of confusing, but usually the thing called a "charger" is the part that converts AC to DC at whatever voltage the pack requires. For level 1 and 2 charging, the charger is in the car. J1772 ports are basically just fancy 110v or 220v AC plugs with some extra signalling. DC charging tends to happen at much higher power levels, and that equipment is expensive so the AC-DC converter is kept outside of the car. The car itself just has a couple contactors (i.e. high power relays) to connect the charge port directly to the battery, and a microcontroller to tell the charger how much current it can handle at what voltage.
  - KennyBlanken 3y ago
    Not by the general public. The general public typically refers to the EVSE itself as a "level 2 charger." The general public does not know or care about the distinction and in the grand scheme of things, it doesn't matter.
    - elihu 3y ago
      And yet the technical people need accurate names to call things so they can communicate without ambiguity. I think "charging station" is the least confusing term for the fixed infrastructure part. If regular people call those "chargers" in non-technical conversation, then I'm not going to lose sleep over it.
      - gambiting 3y ago
        The thing that you use to provide your phone with electricity - do you call it an AC-DC converter, or do you call it a charger like nearly everyone on earth, even though the charger part is actually inside your phone?
        Dylan16807 3y ago
        It's funny that people don't want to call it a charger specifically because it doesn't do the AC-DC conversion, and your example of a thing people call a charger is an AC-DC converter. And depending on the sophistication of the phone, that converter outside the phone might be doing most of the work.
- myself248 3y ago
  The EVSE is a glorified RCD/GFCI cord with a contactor that turns on power, so the cord is dead until that happens. It also generates a signal that tells the car how much power it's allowed to draw; the EVSE is configured at install time to know what size breaker feeds it upstream, so it tells the car not to trip that breaker, but the EVSE has no means of actually enforcing such a limit. There's some basic negotiation between the EVSE and the car, to decide when the plug is inserted and it's OK to turn on the contactor. The AC power passes straight through the EVSE, unaltered in voltage, current, or waveform. The EVSE may monitor the current to perform logging, and the EVSE is required to monitor the AC imbalance like any other RCD/GFCI does so it can open the contactor if there's a ground fault, but that's it. It's just a smart extension cord, basically. The charger is in the car, and is the component that actually converts the AC from the grid to DC for the batteries. The charger is what has all the silicon (or these days, probably gallium nitride?), and the inductors and capacitors and stuff to actually transform the power from one form to another. It changes the voltage to match whatever the battery needs at the moment. It controls its own DC output to match the battery's needs, and it limits its own AC input according to the signal from the EVSE so it doesn't trip the upstream breaker. The charger is also responsible for immediately turning itself off, reducing its input draw to zero, within a few milliseconds of someone pressing the latch of the EVSE connector handle. This indicates they're about to pull it out, and the contacts aren't designed to handle arcing, so the charger is required to drop its current _very_ quickly, allowing the contacts to be separated without creating an arc. That signal (called PP) is produced in the handle itself, there's just a tiny switch underneath the latch. The handle is technically part of the cord which is technically part of the EVSE, but the EVSE has no responsibilities related to the signal, that's all on the charger. If the SAE hadn't mandated that the EVSE perform RCD functions, it could be replaced by a literal extension cord. Many small DIY EVs do precisely that; the charge cord is the exact same one you'd use to run any appliance. It works just fine. But even small DIY EVs have a real charger too, which converts the AC from the cord to DC for the batteries. The charger plugs into the cord, but the charger is not the cord.
MostlyStable 3y ago
I would have liked to see a cost breakdown. If it's significantly cheaper than OpenEVSE (somewhwere between $500-$600 depending on which kit you get), then maybe some people would be willing to take the risk (it seems like there are some safety concerns with his design that I don't feel qualified to adjudicate). But without some kind of a cost difference, I'd probably stick with something like OpenEVS, which seems to have some level of official certification [0]. I personally regret my decision to not go with them when I got my EVSE this year. I went with an EnelX Juicenet because A) it was on the list of devices my power company would mostly pay for and B) at the time it had API availability to integrate with HomeAssistant. They have since killed that second part, which I would have loved to still have. In the long term, the ~$500 I saved by having my power company reimburse was probably not worth the lack of control I now have. [0] https://openev.freshdesk.com/support/solutions/articles/6000113537-openevse-safety-features https://openev.freshdesk.com/support/solutions/articles/6000... -edit- He does have a total cost, I just missed it: he claims that it was ~£200. I leave it up to the reader if that's enough savings to give up the certification.
- myself248 3y ago
  OpenEVSE can be a codebase or a kit. If you want to source all your own parts, or maybe reuse significant parts of a non-open EVSE and just drop the processor into it or whatever, then it can be very cheap indeed. If you buy their branded kit, then full price applies. When OpenEVSE was new, I built one on perfboard, actually a very compact modular stack of perfboards, one layer per subsystem. Handed it off to my software-savvy friend, and he couldn't get it to pass self-test, despite both of us agreeing that every piece of the circuit appeared correct as per the published schematic. Eventually he gave up and ordered one of OpenEVSE's commercially-produced boards, and it failed self-test at the exact same place. Apparently there was some unclear documentation and it was supposed to fail there until something else was hooked up, I don't remember the details, but there was nothing wrong with my stack of perf in the first place. Argh. All of which is to say, it's not hard at all to build one of these things. if you want to lobotomize your closed-crap EVSE and lash an open board to it, do so! I'm pretty sure the JuiceBox is OpenEVSE-based in the first place so it might be as simple as reflashing some firmware.
KennyBlanken 3y ago
Everyone calls them chargers. If you said "do you like the EVSE you have?" or "do you know where the nearest EVSE is?" most people would stare at you with a blank expression.
- Dylan16807 3y ago
  > If you said "do you like the EVSE you have?" or "do you know where the nearest EVSE is?" most people would stare at you with a blank expression. Because you'd need to use a word like "plug" or something, not because of whether it's "charger" specifically.

photonbeam 3y ago

mirror https://web.archive.org/web/20231203183047/https://jamesfotherby.com/index-page/electric-vehicle-charger/ https://web.archive.org/web/20231203183047/https://jamesfoth...

greenthrow 3y ago

This is such a bad DIY project because the costs of screwing up can be burning your house down. This is non-trivial amounts of power. If you spend the money fot an EV, buy something safe and have it professionally installed. Keep the DIY projects to something less dangerous.

thebigman433 3y ago
I love higher power DIY stuff in general, but yea this project really doesnt thrill me. It does sound like the author did adequate research, which is good, but the soldering joints dont inspire a ton of confidence in overall quality. Stuff like this is absolutely what I would consider "worth" paying a professional to do. Especially since buying a retail unit/paying a professional to install it will come with warranties.
wannacboatmovie 3y ago
Software engineers have a tendency to overestimate their own abilities, the arrogance is often on full display here for all to see. Maybe we need a few to burn their own houses down to act as a deterrent and encourage others to stay in their lane.
- newZWhoDis 3y ago
  Some of us here are actually Engineers (Electrical). I’ve installed 3x 240V 60A EV chargers, was a cakewalk. I didn’t build my own in this case since I was going for an aesthetic match. Meanwhile you can enjoy paying some alcoholic $1000 for 30 minutes of work to: * pop out a hole on the back * Tap and install 2x screws into studs * pull 3 wires 6” through, wrap around the strain relief, strip/insert/torque * flip a breaker It’s not rocket science, as long as you’re not a complete idiot and turn the breaker off before hand it’s completely safe. 240V isn’t even “high” voltage.
  - shmoe 3y ago
    You're 100% right, but it not being "high voltage" is totally negated by the fact that the two legs together will kill me if it seeks ground via the right (wrong?) path for sure.

eigenvalue 3y ago

More like a DIY arson investigation. You might not only burn down your house, but also get in trouble with the law and not receive compensation from your property insurance company. This is a horrendous idea. Just do basically anything else DIY besides high current/voltage electronics.

wayfinder 3y ago
Some of us on here don’t know just software engineering and nothing else Congrats to OP on a clean project source: electrical engineer who writes high performance software you’ve definitely have used
dreamcompiler 3y ago
Page is hugged to death right now but I strongly disagree with parent. I'm an EE and I'm quite familiar with the National Electric Code. I build high current/voltage devices and I've wired two houses (both of which passed inspection). If you're trained, experienced, and generally know what you're doing there's nothing wrong with working on high power electronics.
- Comfy-Tinwork 3y ago
  Suppose you aren't trained, experienced or generally know about working with high voltage systems, like the author?
  - beej71 3y ago
    Then you learn you some, like the author.
    - Comfy-Tinwork 3y ago
      Same way I learned to drive actually, behind the wheel of an 18 wheeler going down the freeway in the snow.
- ClassyJacket 3y ago

Animats 3y ago

1. Two words: strain relief. 2. If it's outdoors, at least spray the electronics with Fine-L-Kote or similar to keep water vapor out. 3. Those relays look undersized for the load. Look at Grainger for similar ratings. Do not buy power relays on eBay or Alibaba. Current ratings there tend to be wildly exaggerated. 4. Er, overcurrent protection? An approved circuit breaker?

sokoloff 3y ago
He says he installed a 50A OCPD, which is the same overcurrent protection an electrician would install and used relays from TE Connectivity (a respected brand) rated at 125% of the current the EVSE advertises as available. Both of those decisions seem perfectly sane/safe to me.
- StillBored 3y ago
  Are you an EE with a specialty in power electronics? Cause that seems insane to me, inductive loads will cause a voltage spike (flyback) when disconnected, which will exceed that easily. That is why there is generally a reverse diode across the contacts, which I didn't see in the diagram. Granted the article notes it appears to be largely a resistive load, but I would want data sheets on the car/charging requirements, not measurements, to ensure this is true 100% of the time. Maybe the car has an AC compressor or a pump to cool the battery during charging, which draws directly from the charger when plugged in. You might not see that doing a few random measurements because it turns on only after some time or if someone is sitting in the car.
  - ferongr 3y ago
    >Maybe the car has an AC compressor or a pump to cool the battery during charging, which draws directly from the charger when plugged in No it doesn't. A/C compressors in EVs are 3 phase AC powered by an inverter supplied by the traction battery. The contactors in an EVSE open and close at practically zero current, the OBC ramps the current up or down accordingly. And as another sibling comment noted, the OBCs are PFC corrected and act as a largely resistive load.

foobarian 3y ago

I'm disappointed at the anti-DIY sentiments here, it's this safety obsessed mentality that got us to where kids can't walk outside by themselves any longer. The box in that guy's build is outside and could probably burn to a crisp without hurting anything else. I suspect it would not hurt anything even inside a garage, other than making a lot of smoke and setting off smoke detectors.

wannacboatmovie 3y ago
Fairly certain most DIY electrical work is strictly verboten in the UK, where the author is located. I would think at a minimum you need approval from the council. Not too dissimilar to the permitting process in the US, but the UK is noticeably more safety-obsessed.
- rcxdude 3y ago
  Well, there's a pretty large fraction which is still fine to do full DIY. (but not EV chargers) The next level basically either requires some certification or to get the council to inspect it, but plenty of people just ignore that.
  - folmar 3y ago
    It seems things are pretty lax in the UK. Here in Poland you need a qualification certificate to replace a broken socket and a supervisors' certificate to move it half a meter.
- OJFord 3y ago
  > Fairly certain most DIY electrical work is strictly verboten in the UK No. You can't touch the consumer unit, and there's a restricted zone around bath/shower for example (by distance), but most things a homeowner might want to do are perfectly legal to DIY. > the US, but the UK is noticeably more safety-obsessed. Crikey, are you joking? Internet forums are awash with US concern over 'code', and to extend beyond electricity: food safety, FDA guidelines, all sorts of common senseless rubbish.

jtagen 3y ago

Given what's in this, why are EVSEs so expensive? Given the quantities we see, the $150 range should be more than enough for a decent profit.

sowbug 3y ago
Supply and demand. See also $40 HDMI cables at Best Buy.
- jtagen 3y ago
  I'm not sure I buy this. If someone can hack this together for <$100 at home, there should be plenty of supply to meet the demand. $40 HDMI cables are an option (albeit a terrible one). For EVSEs, there really isn't a reasonably-priced alternative on the market right now.
  - dylan604 3y ago
    Most people aren't going to DIY something like this. Also, most people think that the price of a product should only be based on the price of its components, and possibly willing to accept a mark up on labor. However, the companies making a thing, whatever that thing might be, also has to make money to be able to pay the people that work for the company, the utility bills, and the rent. There's also the fact that the companies making a thing don't get the retail price you pay. They sell it at the wholesale rate to the vendors, so there's even less margin than the retail price suggest for the makers. Just some things to keep in mind
    - sokoloff 3y ago
      In engineering university, I learned the “retail needs to be 5x the BoM* cost” rule of thumb. For a very high value or very high units product, maybe you could shave that to 4x or slightly less, but there are a lot of hands between the designed part and the retail consumer and none of them want to work for free. * BoM - Bill of Materials (“what stuff goes into this thing?”)

savrajsingh 3y ago

Fun kit versions at openevse https://openevse.com/index.html https://openevse.com/index.html

oceanplexian 3y ago

Level 2 chargers aren’t actually chargers, they just pass mains voltage and some signaling. The charger is inside the vehicle.

NotSammyHagar 3y ago
The evse (misnamed charger here) needs to reduce the amperage based on what the car side wants. So it does more than just pass mains voltage.
- Johnny555 3y ago
  Got a reference for that? As far as I know (as the linked article says), the EVSE doesn't do anything to control the current other than telling the car how much it can draw.
- cpitman 3y ago
  That's not accurate. The EVSE communicates a max current to the vehicle, but does nothing to actively control the current. It should monitor the current and kill the circuit if the vehicle attempts to draw too much, but that only happens after the vehicle has misbehaved.
  - aaronmdjones 3y ago
    Correct. The control pilot signal from EVSE to EV is a PWM signal that indicates to the EV how much current is available. It could drop at any time due to, for example, many chargers being connected to 1 circuit and the chargers coordinating with each-other to load-balance their connected vehicles (everyone gets their fair share), or it could be tied to solar PV generation so that charging doesn't import from the grid; the available current will change with how much excess PV is available, etc. A well-engineered EVSE will notice when the EV is drawing more than the EVSE wants it to. It should then open the mains contactor at this point; cutting the EV's electricity supply. It will also hold the control pilot low to signal a fault to the EV.
- throitallaway 3y ago

NotYourLawyer 3y ago

> The relay resistors are dissipating 900mW (They’re 1W rated) which gets them to about 60 celsius above ambient Yikes. Get some 5 watt resistors.

mrb 3y ago

"It costs about £900 in the UK to have an EV charger installed by an electrician" £900 is $1140. In southern California, it cost me $750 for top notch work and hardware, including: $400 to have an electrician install a 240V 50A outdoor outlet (NEMA 14-50), plus $350 for a good quality level 2 40A EVSE (this one: https://www.amazon.com/dp/B082LMVSLY https://www.amazon.com/dp/B082LMVSLY) that I installed myself as it simply plugs in the outlet and it's just a 5-minute job to secure it to the wall with two screws. It's possible to bring the cost down to around $600 when picking a cheaper EVSE (like https://www.amazon.com/dp/B08LMX4TJR?th=1 https://www.amazon.com/dp/B08LMX4TJR?th=1), so about half the UK cost as reported in the blog post. I would love to see a breakdown of that £900... that seems really high.

Symbiote 3y ago
From some searching, I think paying an electrician to install a 32A CEE socket (often called "Commando" in Britain after a particular manufacturer) and then installing the EVSE yourself would be similar. Although there do seem to be some safety requirements for the socket if it's to be used for charging EVs, which increase the cost. Also, the £900 includes 20% tax.
- dbrgn 3y ago
  I talked to the electrician about using a CEE16 connector to charge the car. He said that this should only be done if you don't load it near its max (16A) for long periods of time. He's seen multiple CEE16 connectors that deformed condsiderably after a year of use with regular charging sessions at 16A. If you load it to 10-12A, it should be fine.
  - Symbiote 3y ago
    I have servers and UPSs and so on connected with these sockets, drawing a high current 24/7. Just like every datacentre in Europe, UK included. They are only very rarely unplugged though. Is it a case of using a high quality socket which costs 2-3 times as much?

gboza1 3y ago

[flagged]

progbits 3y ago

Disagree with the fire risk comments, even if it burns it's outside in a suitable enclosure. The real problem here is DIY RCD with microcontroller in the loop. The soldering on the high voltage wires is absolutely horrendous and if those come loose and the enclosure or chassis becomes live you are trusting your life on the atmel interrupt delay and software. Good luck! Edit: it's not even an interrupt, its just part of the Arduino loop(): https://github.com/fotherja/EV_Charger/blob/main/EV_Charger.ino#L154 https://github.com/fotherja/EV_Charger/blob/main/EV_Charger....

Faaak 3y ago
I agree on the RCD part. An "off the shelf" one would be cheaper and more safe IMHO. Appart from that, good job ! :-)

adev_ 3y ago

Thanks for the experience sharing and the blog, it is very interesting to read and your humility about the feedback is definitively appreciated. I currently also did my own DIY EVSE charger mainly for fun [1]. If you are interested about the main differences between your approach and mine: (1) I use an industrial contactor DIN form factor for the power switch instead of passing the power through the relay directly. Mainly for safety reasons (I do not trust much small relays) and also because I wanted to support three-phase power for an European T2 installation. (2) Instead of printing my own PCB with an Arduino for the PWN, I just bought one command module from China/UK provider. Mainly for pure lazyness reason :) The module itself is shield behind the RCD class B. (3) I have added a shelly 3EM front of the system. To use it as a watt-meter with MQTT report and also as a remote control system. My little advice for people interested to do their own: DIY is always an excellent way to learn and if you want to do your own, do it... BUT please make your installation reviewed by someone with an electrical engineering or technician background if possible. These systems can easily pump 7 to 22KW during extended period of time: Any cable which is not screwed properly or under-sized can bring you a fire. [1]: https://github.com/adevress/open-ev-station/blob/master/README-fr.md https://github.com/adevress/open-ev-station/blob/master/READ...

urtie 3y ago

I've run something similar for 5 years, using https://www.smartevse.nl/ https://www.smartevse.nl/ as the brains. The main advantages over commercial EVSE's in my case were that I could loadbalance charging the car with the electricity demands of the house, and that I could have the EVSE itself inside, so that there's no 240V current on any circuit from the breaker box indoors towards the car when there's no car present. I do intend to add a second sometime, so that I can put the EVSE in my home automation UI as well; the version 2 of smartevse that I use does not have a network connection, but it can be connected to be controlled by a version 3 that does.