16 ms·

My solar-powered blog is now on lithium iron phosphate

131 points by louwrentius 3y ago

coffeebeqn 3y ago
Not even mentioned is the incredible number of cycles lifepo4 can do before storage is degraded - thousands instead of hundreds
- cronix 3y ago
  Yes, usually around 3k charges before reaching 80% capacity, which is around 10 years.
  - megaman821 3y ago
    I have an LFP battery from EcoFlow, and now I am more worried about the inverter or BMS failing before the battery cells. End of useful life really isn't until 50% battery capacity, which could 30 years out.
- boulos 3y ago
  Yeah, that's why all the recent sprinter van conversions are using them for the "house" batteries.
- louwrentius 3y ago
  My cells are rated for 4000 cycles which is ~11 years. At 10% years they will have 80% of capacity. A-grade cells are often rated for 6000 cycles. It’s amazing. I've updated the article with those numbers.
anonymousiam 3y ago
I ran a similar off-grid system for 10 years (starting in 2003), but mine was of a somewhat larger scale. The server consumed about 400W and I had 1280W of solar panels. I started with lead-acid deep-cycle marine batteries, but later switched to sealed AGM because they did not vent hydrogen while charging. Admittedly, it was not 100% off-grid. I had a 50A 12V DC power supply on-grid that could power and/or charge the system if needed. I switched the marine batteries out after about four years of operation. I took down the solar panels in 2013 because the roof needed repair. If I were doing it today, I would probably give Lithium-Iron a try. They weigh less, have higher power density, and last longer.
- jandrese 3y ago
  It would be so much cheaper to do it today, especially if you're comfortable with DIY and don't mind buying some used panels. Easier too, there are so many turnkey and DIY friendly solutions on the market now.
- antisthenes 3y ago
  So what are you doing now in terms of renewables? Anything? Or were the renewables strictly to run the server?
  - anonymousiam 3y ago
    It's a long story. That solar plant was basically a UPS because the neighborhood where I bought a house had terrible power, and yes, they were just for the server. The root cause of the power problem was a 50-year old 4kV "last mile" which was finally upgraded to 16kV a few years before I took down the system. Power there is great right now, but maybe not for much longer because California keeps shutting down power plants. The NG plant less than a mile away will be gone next year. San Onofre is gone now too (https://www.sandiegouniontribune.com/business/story/2022-08-12/officials-say-8-year-plan-to-dismantle-the-nuclear-plant-at-san-onofre-is-on-track https://www.sandiegouniontribune.com/business/story/2022-08-...). I hope to sell the place in CA soon. I now have another house elsewhere with 4kW of solar on the roof. I would add more, but for two reasons: 1) There might be enough space up on the roof for another 2-3kW, but it's close. 2) The local laws governing grid-tie are such that I can't just add more panels. I can put up another separate system, but with a separate meter. I'm concerned that two separate systems on the same grid point trying to sync to the grid may have problems where they interfere with each other. I have read about such problems.
    - Logans_Run 3y ago
      Regarding point #2) Absolutely yes that can be (and is) a problem for exactly the reason you say in terms of synchronising 2 (or more) PV setups to the local grid and (I would imagine) have the facility for emitting volumous clouds of magic smoke. Fortunately the solution would appear to be use of a GPS central time clock that is fed to the 2x PV arrays individualy... if you run your own local time server you can 'skew' the clock signals to each array to get them in sync with each other and then in to a dummy load of spare lead-acids or a capacitor bank (if you want to get fancy and don't mind the 'large gray box' emitting smoke and launching itself off the wall from time to time). Then you sync your 'mini-grid' to their slightly larger mini-grid. Oh and when synching - never forget the old-school 4-light-bulb trick as a visual confirmation that things are synched correctly before tying in to the grid. Oh and fuses, large ones. With spares. If you can find a friendly H.V. engineer or Linesman they might be able to tell you what clock source 'their grid' uses (GPS, Network time etc etc) which makes synching to the local-ish grid a whole lot easier if you have the exact same setup. I think the main thing is to make sure you have the dummy-load ready to feed/smooth what can be at times be a large inrush/outrush till the load equalizes. Obviously, always seek out advice from someone that knows what they are talking about and has knolwedge of local laws, quirks of the grid etc.
fgsfds028374 3y ago
Sailors are big into LFPs these days. I just upgraded my Beneteau to a 11kWh LFP bank and it's been game changing. I cook with a 1800W inductive cooktop, use the microwave, run the desalinator, for multiple consecutive days at anchor without running a generator or the motor. Unthinkable in the days of AGM deep cycles, they'd be dead in months.
- Scoundreller 3y ago
  get an instapot! Save lots of energy while cooking faster. (depends on what you're cooking of course).
  - fgsfds028374 3y ago
    Already got one (3qt), love it.
- kragen 3y ago
  how long will the lfps last that way
  - elihu 3y ago
    In theory they should be good for several thousand cycles, so -- a long time. As long as you don't overcharge them, drain them too low, or try to charge them in below freezing temperatures. Also, they say that usually LFPs will last a bit longer if they're installed such that they're under a bit of sideways compression. I don't know why that is.
    - jacquesm 3y ago
      That only goes for prismatic cells (boxes rather than cylinders). The reason is that they tend to swell up while charging if you don't compress them so manufacturers will specify a clamping force required for the cells to keep their shape. If they change shape in such a way that you can observe it then your cells are toast so better stick to that mfg indicated compression. There are a number of articles out there that show how to do this the right way and also some that get it hilariously wrong. The direction to compress the cells in is in such a way that the electrodes remain under compression perpendicular to their surface. So compressing from the top and compressing from the front will do absolutely nothing.
langsoul-com 3y ago
Isn't it easier to just have solar panels on the roof and an actual battery pack for the house? Though, I suppose this is more of a challenge thing
- unwind 3y ago
  I think the OP lives in an apartment, where that kind of invasive mod is not possible.
- csteubs 3y ago
  Not OP but I rent and have to use my deck for solar. I only have 2 x 100W panels that sit on the ground, and that feeds a 135Ah AGM battery in a box. The box has a 500W inverter on top connected to the battery and powers a mini fridge, deck lighting, and a few other things out there. I would love to put them on the roof and my landlord would probably be cool with it, but I take it camping all the time so it's nice being able to pack them up quick. Panels and batteries are relatively cheap (and getting cheaper) to the point that it can makes sense to have purpose-built setups.
  - nvy 3y ago
    Which panels are you using?
  - jondwillis 3y ago
    I recently went from deck solar to landlord-permitted roof solar.
- Gigachad 3y ago
  From an actual practicality sense, the whole setup doesn't make that much sense. You could drop the files on a static site host and it would use 0 watts while not in use and a negligible amount while in use. Another interesting case would be to use an API to get your areas power generation stats and when the wholesale pricing is low due to solar/wind generation peaks, charge your battery off the grid.
- louwrentius 3y ago
ttul 3y ago
I bought a low speed vehicle last summer that the previous owner had outfitted with a home made 24-cell LiFePO4 pack, complete with a cheap Chinese BMS and balancer unit. Within a week of purchase, his haphazardly installed balancer wires had melted in various places where they pressed against the high current conductors. Long story short, balancing didn’t work properly on account of the sensor wires being shorted together and, resultingly, many cells went to zero and I suppose I’m glad it didn’t also catch fire. These things are fun, but they pack a whole lot of energy!
- jacquesm 3y ago
  This is a pretty common error and the reason why in my long distance e-bike pack I spent a lot of time getting the balance wire routing done without any wires crossing. Even Bosch got this wrong on their pannier mounted battery packs, I've opened up a whole pile of failed Bosch packs to see how they fail as a guide to my own pack design and the most common failure was water ingestion due to bad seals followed by burned out balancing wires that some how got worn out or pinched. This stuff is very critical and I would (1) never buy a pack that some other hobbyist made and (2) never sell the pack that I made to someone else.
- louwrentius 3y ago
  Building batteries like these based on LiFePO4 is very easy to do, but you have to think about safety, especially if you put a battery in a moving vehicle. If something goes wrong with these kind of batteries, it's never the batteries themselves (specifically LiFePO4) but it's always a bad connection or an undersized wire causing high resistance and thus heat --> fire. In my case, my wires are quite oversized and I bought a proper lug nut crimping tool (and not use a vice or soldering (Don't do it)) to make the connections. I've also really made all connections tight, double-checking them.
  - ttul 3y ago
    Yeah for sure. I am redoing all the wiring and replacing about half the cells because they went to zero… Will be over-specifying everything and making the routing super tidy. If you have the patience for that, DIY batteries are fun!
formvoltron 3y ago
my popcorn is made by stored solar power from my 2.2 kwh lifepo4 pack. so what?
Andys 3y ago
My household of 3 is off-grid, running off a 15kW PV array and 24kWh of LiFePO4 batteries, with 100% electric appliances and hot water. (Location is mid-latitude Australian, plenty of sunlight most of the time)
- duckmysick 3y ago
  What do you use for hot water? Solar thermal collectors?
  - originalvichy 3y ago
    I’d be curious to know if an inland Aussie would like hot water at all besides for cooking. Some nightmarish temps there.
    - Andys 3y ago
      It gets cold at night :)
  - Andys 3y ago
    A 250L tank with a 3.6kW electric heater element, programmed to turn on when batteries hit 98% full (and off again when batteries fall below 95%). We really only use it for short showers, and it stays warm enough for that, for about 3 days without power.
- louwrentius 3y ago
  That is really cool and would be my dream. In the Netherlands it's near impossible unfortunately to achieve 100% off-grid due to the winter months, when you basically have no solar. Maybe there are Dutchies who have somehow achieved it (with overprovisioned solar). Do you still have a grid connection for backup or are you 100% disconnected from the grid?
  - Andys 3y ago
    100% disconnected; it was cheaper this way (grid was too far away). What is the typical kWh/day consumption of a household there in winter months?
yobuko 3y ago
I've been enjoying each of your posts you share here regarding this set up. I have two questions if you please? 1. Have you considered adding a small wind turbine (DIY of course) to supplement? 2. Although the costs are certainly coming down and within the realm of possibility for many, they are still too prohibitive for those that would benefit the most. Do you see any way that you could recreate your project on a shoe-string budget?
- louwrentius 3y ago
  Thank you! Yes, I've looked into running a small wind turbine but from what I can tell it's not worth the money or effort. There is a reason why they build wind turbines so large and high. At small sizes, with our wind speeds, they barely produce any energy. I can't also just put one on my balcony as I'm not allowed to (building regulations). If I ever want to build my dream renewable energy build, I really have to relocate :) Regarding a shoe-string budget: it all depends on your goals. A key thing is doing everything second-hand, maybe except for the LiFePO4 batteries, unless you can find those. In the Netherlands, There's a lot of solar gear moving through our local Ebay (Marktplaats, owned by Ebay) so that's something to look out for.
supermatt 3y ago
3 kWh for 500$! How times have changed! Anyone know of a three-phase UPS I could power with such a battery?
- jondwillis 3y ago
  personally my UPS is connected to a 2kWh battery (with an inverter) via AC. Even when something happens to the battery to cut power too the UPs, the UPS has enough battery to last until it is resolved.
nahnahg 3y ago
[dead]
brunojppb 3y ago
> There was a handful of new data that had been created in the intervening ~30 minutes. We pulled that diff data manually, and uploaded it to the new database. But doesn’t that mean you had some partial downtimes? How did you manage to keep everything running during these 30 minutes where data was copied from the old DB to the new one? Let’s say there is a cron job that must be executed and its result would be stored back to the DB. Did you “pause” everything and reschedule it in the new instance once the diff copy was over?

131 points by louwrentius 3y ago

Not even mentioned is the incredible number of cycles lifepo4 can do before storage is degraded - thousands instead of hundreds

cronix 3y ago
Yes, usually around 3k charges before reaching 80% capacity, which is around 10 years.
- megaman821 3y ago
  I have an LFP battery from EcoFlow, and now I am more worried about the inverter or BMS failing before the battery cells. End of useful life really isn't until 50% battery capacity, which could 30 years out.
boulos 3y ago
Yeah, that's why all the recent sprinter van conversions are using them for the "house" batteries.
louwrentius 3y ago
My cells are rated for 4000 cycles which is ~11 years. At 10% years they will have 80% of capacity. A-grade cells are often rated for 6000 cycles. It’s amazing. I've updated the article with those numbers.

anonymousiam 3y ago

I ran a similar off-grid system for 10 years (starting in 2003), but mine was of a somewhat larger scale. The server consumed about 400W and I had 1280W of solar panels. I started with lead-acid deep-cycle marine batteries, but later switched to sealed AGM because they did not vent hydrogen while charging. Admittedly, it was not 100% off-grid. I had a 50A 12V DC power supply on-grid that could power and/or charge the system if needed. I switched the marine batteries out after about four years of operation. I took down the solar panels in 2013 because the roof needed repair. If I were doing it today, I would probably give Lithium-Iron a try. They weigh less, have higher power density, and last longer.

jandrese 3y ago
It would be so much cheaper to do it today, especially if you're comfortable with DIY and don't mind buying some used panels. Easier too, there are so many turnkey and DIY friendly solutions on the market now.
antisthenes 3y ago
So what are you doing now in terms of renewables? Anything? Or were the renewables strictly to run the server?
- anonymousiam 3y ago
  It's a long story. That solar plant was basically a UPS because the neighborhood where I bought a house had terrible power, and yes, they were just for the server. The root cause of the power problem was a 50-year old 4kV "last mile" which was finally upgraded to 16kV a few years before I took down the system. Power there is great right now, but maybe not for much longer because California keeps shutting down power plants. The NG plant less than a mile away will be gone next year. San Onofre is gone now too (https://www.sandiegouniontribune.com/business/story/2022-08-12/officials-say-8-year-plan-to-dismantle-the-nuclear-plant-at-san-onofre-is-on-track https://www.sandiegouniontribune.com/business/story/2022-08-...). I hope to sell the place in CA soon. I now have another house elsewhere with 4kW of solar on the roof. I would add more, but for two reasons: 1) There might be enough space up on the roof for another 2-3kW, but it's close. 2) The local laws governing grid-tie are such that I can't just add more panels. I can put up another separate system, but with a separate meter. I'm concerned that two separate systems on the same grid point trying to sync to the grid may have problems where they interfere with each other. I have read about such problems.
  - Logans_Run 3y ago
    Regarding point #2) Absolutely yes that can be (and is) a problem for exactly the reason you say in terms of synchronising 2 (or more) PV setups to the local grid and (I would imagine) have the facility for emitting volumous clouds of magic smoke. Fortunately the solution would appear to be use of a GPS central time clock that is fed to the 2x PV arrays individualy... if you run your own local time server you can 'skew' the clock signals to each array to get them in sync with each other and then in to a dummy load of spare lead-acids or a capacitor bank (if you want to get fancy and don't mind the 'large gray box' emitting smoke and launching itself off the wall from time to time). Then you sync your 'mini-grid' to their slightly larger mini-grid. Oh and when synching - never forget the old-school 4-light-bulb trick as a visual confirmation that things are synched correctly before tying in to the grid. Oh and fuses, large ones. With spares. If you can find a friendly H.V. engineer or Linesman they might be able to tell you what clock source 'their grid' uses (GPS, Network time etc etc) which makes synching to the local-ish grid a whole lot easier if you have the exact same setup. I think the main thing is to make sure you have the dummy-load ready to feed/smooth what can be at times be a large inrush/outrush till the load equalizes. Obviously, always seek out advice from someone that knows what they are talking about and has knolwedge of local laws, quirks of the grid etc.

fgsfds028374 3y ago

Sailors are big into LFPs these days. I just upgraded my Beneteau to a 11kWh LFP bank and it's been game changing. I cook with a 1800W inductive cooktop, use the microwave, run the desalinator, for multiple consecutive days at anchor without running a generator or the motor. Unthinkable in the days of AGM deep cycles, they'd be dead in months.

Scoundreller 3y ago
get an instapot! Save lots of energy while cooking faster. (depends on what you're cooking of course).
- fgsfds028374 3y ago
  Already got one (3qt), love it.
kragen 3y ago
how long will the lfps last that way
- elihu 3y ago
  In theory they should be good for several thousand cycles, so -- a long time. As long as you don't overcharge them, drain them too low, or try to charge them in below freezing temperatures. Also, they say that usually LFPs will last a bit longer if they're installed such that they're under a bit of sideways compression. I don't know why that is.
  - jacquesm 3y ago
    That only goes for prismatic cells (boxes rather than cylinders). The reason is that they tend to swell up while charging if you don't compress them so manufacturers will specify a clamping force required for the cells to keep their shape. If they change shape in such a way that you can observe it then your cells are toast so better stick to that mfg indicated compression. There are a number of articles out there that show how to do this the right way and also some that get it hilariously wrong. The direction to compress the cells in is in such a way that the electrodes remain under compression perpendicular to their surface. So compressing from the top and compressing from the front will do absolutely nothing.

langsoul-com 3y ago

Isn't it easier to just have solar panels on the roof and an actual battery pack for the house? Though, I suppose this is more of a challenge thing

unwind 3y ago
I think the OP lives in an apartment, where that kind of invasive mod is not possible.
csteubs 3y ago
Not OP but I rent and have to use my deck for solar. I only have 2 x 100W panels that sit on the ground, and that feeds a 135Ah AGM battery in a box. The box has a 500W inverter on top connected to the battery and powers a mini fridge, deck lighting, and a few other things out there. I would love to put them on the roof and my landlord would probably be cool with it, but I take it camping all the time so it's nice being able to pack them up quick. Panels and batteries are relatively cheap (and getting cheaper) to the point that it can makes sense to have purpose-built setups.
- nvy 3y ago
  Which panels are you using?
- jondwillis 3y ago
  I recently went from deck solar to landlord-permitted roof solar.
Gigachad 3y ago
From an actual practicality sense, the whole setup doesn't make that much sense. You could drop the files on a static site host and it would use 0 watts while not in use and a negligible amount while in use. Another interesting case would be to use an API to get your areas power generation stats and when the wholesale pricing is low due to solar/wind generation peaks, charge your battery off the grid.
louwrentius 3y ago

ttul 3y ago

I bought a low speed vehicle last summer that the previous owner had outfitted with a home made 24-cell LiFePO4 pack, complete with a cheap Chinese BMS and balancer unit. Within a week of purchase, his haphazardly installed balancer wires had melted in various places where they pressed against the high current conductors. Long story short, balancing didn’t work properly on account of the sensor wires being shorted together and, resultingly, many cells went to zero and I suppose I’m glad it didn’t also catch fire. These things are fun, but they pack a whole lot of energy!

jacquesm 3y ago
This is a pretty common error and the reason why in my long distance e-bike pack I spent a lot of time getting the balance wire routing done without any wires crossing. Even Bosch got this wrong on their pannier mounted battery packs, I've opened up a whole pile of failed Bosch packs to see how they fail as a guide to my own pack design and the most common failure was water ingestion due to bad seals followed by burned out balancing wires that some how got worn out or pinched. This stuff is very critical and I would (1) never buy a pack that some other hobbyist made and (2) never sell the pack that I made to someone else.
louwrentius 3y ago
Building batteries like these based on LiFePO4 is very easy to do, but you have to think about safety, especially if you put a battery in a moving vehicle. If something goes wrong with these kind of batteries, it's never the batteries themselves (specifically LiFePO4) but it's always a bad connection or an undersized wire causing high resistance and thus heat --> fire. In my case, my wires are quite oversized and I bought a proper lug nut crimping tool (and not use a vice or soldering (Don't do it)) to make the connections. I've also really made all connections tight, double-checking them.
- ttul 3y ago
  Yeah for sure. I am redoing all the wiring and replacing about half the cells because they went to zero… Will be over-specifying everything and making the routing super tidy. If you have the patience for that, DIY batteries are fun!

formvoltron 3y ago

my popcorn is made by stored solar power from my 2.2 kwh lifepo4 pack. so what?

Andys 3y ago

My household of 3 is off-grid, running off a 15kW PV array and 24kWh of LiFePO4 batteries, with 100% electric appliances and hot water. (Location is mid-latitude Australian, plenty of sunlight most of the time)

duckmysick 3y ago
What do you use for hot water? Solar thermal collectors?
- originalvichy 3y ago
  I’d be curious to know if an inland Aussie would like hot water at all besides for cooking. Some nightmarish temps there.
  - Andys 3y ago
    It gets cold at night :)
- Andys 3y ago
  A 250L tank with a 3.6kW electric heater element, programmed to turn on when batteries hit 98% full (and off again when batteries fall below 95%). We really only use it for short showers, and it stays warm enough for that, for about 3 days without power.
louwrentius 3y ago
That is really cool and would be my dream. In the Netherlands it's near impossible unfortunately to achieve 100% off-grid due to the winter months, when you basically have no solar. Maybe there are Dutchies who have somehow achieved it (with overprovisioned solar). Do you still have a grid connection for backup or are you 100% disconnected from the grid?
- Andys 3y ago
  100% disconnected; it was cheaper this way (grid was too far away). What is the typical kWh/day consumption of a household there in winter months?

yobuko 3y ago

I've been enjoying each of your posts you share here regarding this set up. I have two questions if you please? 1. Have you considered adding a small wind turbine (DIY of course) to supplement? 2. Although the costs are certainly coming down and within the realm of possibility for many, they are still too prohibitive for those that would benefit the most. Do you see any way that you could recreate your project on a shoe-string budget?

louwrentius 3y ago
Thank you! Yes, I've looked into running a small wind turbine but from what I can tell it's not worth the money or effort. There is a reason why they build wind turbines so large and high. At small sizes, with our wind speeds, they barely produce any energy. I can't also just put one on my balcony as I'm not allowed to (building regulations). If I ever want to build my dream renewable energy build, I really have to relocate :) Regarding a shoe-string budget: it all depends on your goals. A key thing is doing everything second-hand, maybe except for the LiFePO4 batteries, unless you can find those. In the Netherlands, There's a lot of solar gear moving through our local Ebay (Marktplaats, owned by Ebay) so that's something to look out for.

supermatt 3y ago

3 kWh for 500$! How times have changed! Anyone know of a three-phase UPS I could power with such a battery?

jondwillis 3y ago
personally my UPS is connected to a 2kWh battery (with an inverter) via AC. Even when something happens to the battery to cut power too the UPs, the UPS has enough battery to last until it is resolved.

nahnahg 3y ago

[dead]

brunojppb 3y ago

> There was a handful of new data that had been created in the intervening ~30 minutes. We pulled that diff data manually, and uploaded it to the new database. But doesn’t that mean you had some partial downtimes? How did you manage to keep everything running during these 30 minutes where data was copied from the old DB to the new one? Let’s say there is a cron job that must be executed and its result would be stored back to the DB. Did you “pause” everything and reschedule it in the new instance once the diff copy was over?