10 ms·

Honestly I'd rather a battery that's super reliable and NOT using any lithium ion inside it in my home. As it doesn't need to move, it can sit there in an unus

Honestly I'd rather a battery that's super reliable and NOT using any lithium ion inside it in my home. As it doesn't need to move, it can sit there in an unused space and be really heavy. Lead Acid Batteries are a very good fit here (traditionally used as the 12V battery in cars). In Australia you can buy a 12V 42AH (amp-hour) battery for ~$150AUD or $100USD. 20 of these will give you 10kWh @ 240VDC. Couple this with a 6kW solar system and you'd be almost entirely free from grid electricity, especially in summer. You can individually test out the batteries and swap out bad ones. The batteries themselves typically last >5years in a car and I imagine much longer at home where they aren't exposed to high engine temps and large continuous current discharges (engine cranking on start up).

vardump 4y ago
Is there any data about battery safety, like NiMH vs LiFePO4 vs lead acid [add your favorite chemistry here]? I understand LiFePO4 batteries to be exceedingly safe. They don't overheat or catch fire even if punctured. Lead acid batteries, well, contain lead, which, as a father, is not something I want in our house. It can also produce hydrogen and oxygen, potentially causing an explosion.
- AbortedLaunch 4y ago
  Lead acid batteries can also produce hydrogen sulfide, which occasionally kills boat occupants using them.
beefield 4y ago
You might want to check LiFePO4 battery chemistry. Heavier than Li-Ion, but longevity is better, as well as safety. I have been told that you can hammer a nail through a cell and nothing spectacular happens. (One) trouble with lead acid is that deep discharges are really bad for the longevity of the battery. So you can use only a small fraction of the capacity if you want to run regular cycles form it.
- roflyear 4y ago
  LiFePO4 is great - especially as an addition to solar systems currently using lead acid. If you add a couple of LiFePO4 batteries before your lead acid (you should do some basic math where you have enough LiFePO4 to last about 1-2 days, depending on your location, without having to hit the lead) using a DC-DC charger (which does reduce efficiency - but that's ok) you increase the size of your pack, really help pull ALL the power out of your solar that you can, add a very safe battery (LiFePO4 is really safe compared to traditional lithium), and best of all, you really, really, really extend the lifespan of your lead. I mean like, you probably will never be able to kill your lead doing this, for multiple reasons: primarily, you're just not using it that much, but you're also really keeping it topped off when you do use it. The key is that lead acid isn't great at sucking up charge when it is 80-100% charged. So it is really hard to "catch up" charge with solar, even if you have a ton of it. Solar is not going to put out more than it draws. So if your batteries will only accept some X of AMPs to charge, that is all you're getting (well, you can use extra power for other stuff when this is happening, if you're set up that way, like powering appliances, so you can get some benefit still). However, with LiFePO4 - that bad boy will take all the power you can throw at it (well, not technically, but for the purposes of a solar array, sure) and top off really quick. Then, when the sun is down, it charges your lead. I think the benefits of this is more important for smaller arrays with fewer lead acid batteries, and where the LiFePO4 battery will be a single $500 100ah battery (rather than 10 of those), but I imagine even in large large setups this could really help. LiFePO4 is amazing but I think the cheapest you can go right now by buying used server rack equipment is like $250 for $100ah? So 2.5x or more the price of lead, and you're comparing a used battery vs a new battery (and with the lead, $100 will probably get you a reputable battery, not some no-name used LiFePO4 battery).
  - Siecje 4y ago
    If you are draining the LiFePO4 batteries faster than you can charge them and the lead batteries are charging the LiFePO4 batteries than wouldn't you have the same problem that will reduce the lifespan of the lead batteries?
    - 4y ago
layoric 4y ago
Lithium Titanate (LTO) is the only lithium based home battery I would feel comfortable with but same sentiment on safety. The chance of thermal runaway is low but results are catastrophic.
- shkkmo 4y ago
  I'm not familiar with LTO, what advantages does it have over LiFePO4?
  - rcxdude 4y ago
    It's basically LiFePO4 but even more so: really high charge (10C! and it doesn't even get warm to the touch) and discharge rates, even harder to damage to the point of failure, and really long lifetime (many, many full charge/discharge cycles). Slightly worse energy density. Main downside is it's pretty expensive and niche still. I wouldn't necessarily consider it optimal for solar power storage, where it really shines is high duty cycle high power operation like electric busses, because you can fast-charge it multiple times a day for years.
    - layoric 4y ago
      Spot on. The cost is definitely the main issue IMO. I think they make for great option for home backup/offgrid use mainly due to their crazy high cycles like you pointed out. An Australian company (Zenaji) sells a solution with a warranty on 22,000 cycles. Again, super expensive (~$3k AUD per 1.95kWh) but IMO a superior tech other than density (not a huge difference but definitely not as good as LiFePO4/NMC), which doesn't matter as much in home/commercial stationary backup scenarios.
    - deleted 4y ago
      [deleted]
gonzo41 4y ago
I would still want to house that power pack in a brick box on the street. If only to simplify any emergency response and save my house.
- dijonman2 4y ago
  You can buy rack mount lipo batteries and buy a climate controlled nema 4x rack and put it all away from your house. I have this, just haven’t installed it yet. $5500 for a half rack.
londons_explore 4y ago
> The batteries themselves typically last >5years in a car In a home you will be using up a good chunk of the capacity every night. Lead acid batteries don't last many cycles[1], and I suspect you would be replacing them every 18 months if you powered your house off them. Boats often have a solar+lead acid setup, and the owners of such systems typically have to make lifestyle changes to adapt around the limitations of the power system. Things like running only one appliance at a time, only starting the washing machine if the batteries are over 50%, never use any electric heaters, etc. [1]: https://batteryuniversity.com/article/bu-804-how-to-prolong-lead-acid-batteries https://batteryuniversity.com/article/bu-804-how-to-prolong-...
- smileysteve 4y ago
  This, op seem to think cycles, depth of discharge aren't important
deleted 4y ago
[deleted]
cycomanic 4y ago
Yes I've seen very little about lead acid batteries for solar storage. Considering that home installments are almost never weight constrains and often size is not a big issue either, they seem like a perfect solution. I wonder if there is some important bit of information missing that makes them unsuitable?
- wongarsu 4y ago
  The cheap lead-acid batteries you find in your car don't handle deep discharge very well, let it go empty a couple times and you have to replace it (at least they can be recycled easily). There are variants that can handle that better, but they cost easily twice as much. If you charge them too much they start venting hydrogen, which could build up to dangerous levels in buildings. I think that was discussed as a cause in the OVH datacenter fire. So they do have some problems, but still almost all battery backup is done with lead acid (with lithium-iron catching up as a good replacement). I think most of these li-ion backup batteries are more about using surplus production when you scale your battery production faster than vehicle sales.
- realreality 4y ago
  Lead acid batteries are commonly used for solar storage. They require more physical maintenance than lithium ion, and they have more specific charging requirements.
- yencabulator 4y ago
  There is really nothing "perfect" about lead acid. They let out fire-hazard gases when they charge. You need to maintain their internal water levels. They tend to spew acid on their surfaces. Their voltage droops as you use them. They can't tolerate deep discharge at all, and in general wear out quite quickly when heavily used. LiFePO4 is a huge improvement over lead acid.
elif 4y ago
What is your reason for skepticism of lithium batteries? The Australian megapack that caught fire during debugging? Hoverboards on airplanes? I ask because I have a powerwall under the floor where i'm sitting right now and zero hesitation about it. Indeed, with my ~6.5kw nominal solar, I am essentially net neutral. The car in my driveway has a lithium battery 5x the size and hits 50 degrees during this heat wave. It also charges at about 3x the rate. So the relatively cool crawlspace seems like a totally normal place to discharge at 5kw? If you go with another chemistry, I think you'll find that cycling from 100% to 0-20% daily will not last for many years..
mtreis86 4y ago
That is basically what a forklift battery is. You can pick those up for the scrap cost of the lead as many places either recycle them on a timeline and not when the battery is dead, or recycle them when a cell or two needs replacing. I've seen forklifts with 20-year-old batteries - being in a heated climate, never being deep cycled, and the purity of the lead are all factors in longevity.
iampivot 4y ago
You want about 20kWh at a minimum to be self sufficient. We have a 10kWh Tesla battery, and it only lasts until the evening (saving 20%) for grid outage backup.
- vardump 4y ago
  For your case. Because this really depends on climate and the house. In our case, 100 kWh would be required to cover one day normal power requirements in the worst case. Median would be about 50 kWh. I could probably stretch 100 kWh for max 3 days (worst case) by adjusting temperature, using water minimally and unplugging everything that's not absolutely required. There are also households who could stretch 8.7 kWh for several days. And houses that require significantly more power to maintain liveable conditions.
  - cagenut 4y ago
    whats the opposite of a humble brag
  - vardump 4y ago
    My point is one size doesn't fit all. Some places on this planet can get very cold or very hot. If you're running a [ground source] heat pump as your primary heat/cooling source, even with high COP, on extreme days the system can draw massive amounts of power. You know, those days when losing power could truly hurt. Like destroy water pipes (including underfloor heating pipes) type hurt. Or make the house unlivable hot. No bragging (I have no idea how someone could read it like that!) or anything. Just facts. There's more variability than you might think.
- bradstewart 4y ago
  That's probably at "full load" for your house though, no? If you're looking at an extended outage, you can alter your use patterns. I have a 5kW gasoline generator that most certainly cannot run the whole house, but in emergency situations, I turn off most things at the breaker box. We can run one AC unit to cool part of the house, then shut down that, and power up the kitchen for dinner, etc, etc.
shkkmo 4y ago
The apples to apples comparison of capacity kWh is misleading. The cheaper lead acid should not be discharged below 50% regularly, cutting the useful kWh in half for regular use. When I did the math for my RV on Lifepo4 vs lead acid, the cost per usable kWh was higher unless you looked at the expected lifetime replacement costs, then it was even. I haven't followed battery prices too closely but my impression is that Lifepo4 has dropped in price ~30-50% since then so is probably now cheaper for usable kWh×cycle than lead acid but still might have a higher upfront cost. The supported tempurature ranges, space contraints (venting, size, weight) and other factors all seem to favor Lifepo4. That said, if your house battery is a backup for power outages and not intended to power your house every night, then lead acid may still be the way to go because you don't care about kWh not kWh×cycle. Edit: replaced * with × to fix formatting
happyopossum 4y ago
> 20 of these will give you 10kWh Not really - lead acid batteries are limited to only using about 50% of their capacity, go any deeper more than a handful of times and you'll pretty much destroy it.
- Syonyk 4y ago
  No, they're not. It depends on what battery you pick, and if you go with a deep cycle battery designed for that sort of storage use, you typically get charts of cycle life down to 80% DoD or so, and still have "hundreds of cycles" there on anything competent. With thousands of cycles for shallower cycling that you'd see on a daily basis. Please go find a good, modern lead acid datasheet and familiarize yourself with it, because I'm tired of people who've clearly not been around anything from the last decade or two parroting this line endlessly when it comes to lithium and lead. Here's the datasheet for a GC2 form factor Trojan T105-RE from about a decade ago (I've got a 6 year old pack in my office): https://www.trojanbattery.com/pdf/datasheets/T105RE_TrojanRE_Data_Sheets.pdf https://www.trojanbattery.com/pdf/datasheets/T105RE_TrojanRE... Notice that it's rated for about 700 cycles, to 100% DoD. And about 4000 cycles at 20% DoD. Lead has many advantages for stationary storage, and they're not the same batteries you found 40 years ago.
- sfteus 4y ago
  Most of the time I've read about DIY systems, deep cycle marine batteries are preferred for this reason.
robonerd 4y ago
Backyard sheds seem like the best place for battery packs this large. However, I think a lot of people with electric cars and attached garages don't think twice about it.
- elric 4y ago
  I guess that rules out 99% of city dwellers then.
  - robonerd 4y ago
    Are you sure your lease doesn't rule it out anyway?
  - dahfizz 4y ago
    Where would a city dweller put a huge battery pack anyway? Maybe ask your landlord to put one in the basement for the whole building? Obviously he won't; it doesn't provide any benefit to him.
raxxorraxor 4y ago
Having 20 lead batteries in your basement also adds a lot of prepper flair and scares away those annoying fire protection guys too. It is just 10kWh regardless of voltage aside from small conversion losses here and there. Provided you have a computer that uses 500W, a monitor that uses 100W plus your internet router of 20W, you can run it for a bit over 16 hours. Just answering the important questions. Although these type of battery also wants to be handled correctly. Don't discharge completely and yet also do not charge them fully. You also have to know about the hundreds of other partially true myths about lead batteries. Their most prominent positive property is indeed the price and not too much else.
jhgb 4y ago
> Honestly I'd rather a battery that's super reliable and NOT using any lithium ion inside it in my home. As it doesn't need to move, it can sit there in an unused space and be really heavy. It sounds to me like you're asking for a nickel-iron battery.

vardump 4y ago

Is there any data about battery safety, like NiMH vs LiFePO4 vs lead acid [add your favorite chemistry here]? I understand LiFePO4 batteries to be exceedingly safe. They don't overheat or catch fire even if punctured. Lead acid batteries, well, contain lead, which, as a father, is not something I want in our house. It can also produce hydrogen and oxygen, potentially causing an explosion.

AbortedLaunch 4y ago
Lead acid batteries can also produce hydrogen sulfide, which occasionally kills boat occupants using them.

beefield 4y ago

You might want to check LiFePO4 battery chemistry. Heavier than Li-Ion, but longevity is better, as well as safety. I have been told that you can hammer a nail through a cell and nothing spectacular happens. (One) trouble with lead acid is that deep discharges are really bad for the longevity of the battery. So you can use only a small fraction of the capacity if you want to run regular cycles form it.

roflyear 4y ago
LiFePO4 is great - especially as an addition to solar systems currently using lead acid. If you add a couple of LiFePO4 batteries before your lead acid (you should do some basic math where you have enough LiFePO4 to last about 1-2 days, depending on your location, without having to hit the lead) using a DC-DC charger (which does reduce efficiency - but that's ok) you increase the size of your pack, really help pull ALL the power out of your solar that you can, add a very safe battery (LiFePO4 is really safe compared to traditional lithium), and best of all, you really, really, really extend the lifespan of your lead. I mean like, you probably will never be able to kill your lead doing this, for multiple reasons: primarily, you're just not using it that much, but you're also really keeping it topped off when you do use it. The key is that lead acid isn't great at sucking up charge when it is 80-100% charged. So it is really hard to "catch up" charge with solar, even if you have a ton of it. Solar is not going to put out more than it draws. So if your batteries will only accept some X of AMPs to charge, that is all you're getting (well, you can use extra power for other stuff when this is happening, if you're set up that way, like powering appliances, so you can get some benefit still). However, with LiFePO4 - that bad boy will take all the power you can throw at it (well, not technically, but for the purposes of a solar array, sure) and top off really quick. Then, when the sun is down, it charges your lead. I think the benefits of this is more important for smaller arrays with fewer lead acid batteries, and where the LiFePO4 battery will be a single $500 100ah battery (rather than 10 of those), but I imagine even in large large setups this could really help. LiFePO4 is amazing but I think the cheapest you can go right now by buying used server rack equipment is like $250 for $100ah? So 2.5x or more the price of lead, and you're comparing a used battery vs a new battery (and with the lead, $100 will probably get you a reputable battery, not some no-name used LiFePO4 battery).
- Siecje 4y ago
  If you are draining the LiFePO4 batteries faster than you can charge them and the lead batteries are charging the LiFePO4 batteries than wouldn't you have the same problem that will reduce the lifespan of the lead batteries?
  - 4y ago

layoric 4y ago

Lithium Titanate (LTO) is the only lithium based home battery I would feel comfortable with but same sentiment on safety. The chance of thermal runaway is low but results are catastrophic.

shkkmo 4y ago
I'm not familiar with LTO, what advantages does it have over LiFePO4?
- rcxdude 4y ago
  It's basically LiFePO4 but even more so: really high charge (10C! and it doesn't even get warm to the touch) and discharge rates, even harder to damage to the point of failure, and really long lifetime (many, many full charge/discharge cycles). Slightly worse energy density. Main downside is it's pretty expensive and niche still. I wouldn't necessarily consider it optimal for solar power storage, where it really shines is high duty cycle high power operation like electric busses, because you can fast-charge it multiple times a day for years.
  - layoric 4y ago
    Spot on. The cost is definitely the main issue IMO. I think they make for great option for home backup/offgrid use mainly due to their crazy high cycles like you pointed out. An Australian company (Zenaji) sells a solution with a warranty on 22,000 cycles. Again, super expensive (~$3k AUD per 1.95kWh) but IMO a superior tech other than density (not a huge difference but definitely not as good as LiFePO4/NMC), which doesn't matter as much in home/commercial stationary backup scenarios.
  - deleted 4y ago
    [deleted]

gonzo41 4y ago

I would still want to house that power pack in a brick box on the street. If only to simplify any emergency response and save my house.

dijonman2 4y ago
You can buy rack mount lipo batteries and buy a climate controlled nema 4x rack and put it all away from your house. I have this, just haven’t installed it yet. $5500 for a half rack.

londons_explore 4y ago

> The batteries themselves typically last >5years in a car In a home you will be using up a good chunk of the capacity every night. Lead acid batteries don't last many cycles[1], and I suspect you would be replacing them every 18 months if you powered your house off them. Boats often have a solar+lead acid setup, and the owners of such systems typically have to make lifestyle changes to adapt around the limitations of the power system. Things like running only one appliance at a time, only starting the washing machine if the batteries are over 50%, never use any electric heaters, etc. [1]: https://batteryuniversity.com/article/bu-804-how-to-prolong-lead-acid-batteries https://batteryuniversity.com/article/bu-804-how-to-prolong-...

smileysteve 4y ago
This, op seem to think cycles, depth of discharge aren't important

deleted 4y ago

[deleted]

cycomanic 4y ago

Yes I've seen very little about lead acid batteries for solar storage. Considering that home installments are almost never weight constrains and often size is not a big issue either, they seem like a perfect solution. I wonder if there is some important bit of information missing that makes them unsuitable?

wongarsu 4y ago
The cheap lead-acid batteries you find in your car don't handle deep discharge very well, let it go empty a couple times and you have to replace it (at least they can be recycled easily). There are variants that can handle that better, but they cost easily twice as much. If you charge them too much they start venting hydrogen, which could build up to dangerous levels in buildings. I think that was discussed as a cause in the OVH datacenter fire. So they do have some problems, but still almost all battery backup is done with lead acid (with lithium-iron catching up as a good replacement). I think most of these li-ion backup batteries are more about using surplus production when you scale your battery production faster than vehicle sales.
realreality 4y ago
Lead acid batteries are commonly used for solar storage. They require more physical maintenance than lithium ion, and they have more specific charging requirements.
yencabulator 4y ago
There is really nothing "perfect" about lead acid. They let out fire-hazard gases when they charge. You need to maintain their internal water levels. They tend to spew acid on their surfaces. Their voltage droops as you use them. They can't tolerate deep discharge at all, and in general wear out quite quickly when heavily used. LiFePO4 is a huge improvement over lead acid.

elif 4y ago

What is your reason for skepticism of lithium batteries? The Australian megapack that caught fire during debugging? Hoverboards on airplanes? I ask because I have a powerwall under the floor where i'm sitting right now and zero hesitation about it. Indeed, with my ~6.5kw nominal solar, I am essentially net neutral. The car in my driveway has a lithium battery 5x the size and hits 50 degrees during this heat wave. It also charges at about 3x the rate. So the relatively cool crawlspace seems like a totally normal place to discharge at 5kw? If you go with another chemistry, I think you'll find that cycling from 100% to 0-20% daily will not last for many years..

mtreis86 4y ago

That is basically what a forklift battery is. You can pick those up for the scrap cost of the lead as many places either recycle them on a timeline and not when the battery is dead, or recycle them when a cell or two needs replacing. I've seen forklifts with 20-year-old batteries - being in a heated climate, never being deep cycled, and the purity of the lead are all factors in longevity.

iampivot 4y ago

You want about 20kWh at a minimum to be self sufficient. We have a 10kWh Tesla battery, and it only lasts until the evening (saving 20%) for grid outage backup.

vardump 4y ago
For your case. Because this really depends on climate and the house. In our case, 100 kWh would be required to cover one day normal power requirements in the worst case. Median would be about 50 kWh. I could probably stretch 100 kWh for max 3 days (worst case) by adjusting temperature, using water minimally and unplugging everything that's not absolutely required. There are also households who could stretch 8.7 kWh for several days. And houses that require significantly more power to maintain liveable conditions.
- cagenut 4y ago
  whats the opposite of a humble brag
- vardump 4y ago
  My point is one size doesn't fit all. Some places on this planet can get very cold or very hot. If you're running a [ground source] heat pump as your primary heat/cooling source, even with high COP, on extreme days the system can draw massive amounts of power. You know, those days when losing power could truly hurt. Like destroy water pipes (including underfloor heating pipes) type hurt. Or make the house unlivable hot. No bragging (I have no idea how someone could read it like that!) or anything. Just facts. There's more variability than you might think.
bradstewart 4y ago
That's probably at "full load" for your house though, no? If you're looking at an extended outage, you can alter your use patterns. I have a 5kW gasoline generator that most certainly cannot run the whole house, but in emergency situations, I turn off most things at the breaker box. We can run one AC unit to cool part of the house, then shut down that, and power up the kitchen for dinner, etc, etc.

shkkmo 4y ago

The apples to apples comparison of capacity kWh is misleading. The cheaper lead acid should not be discharged below 50% regularly, cutting the useful kWh in half for regular use. When I did the math for my RV on Lifepo4 vs lead acid, the cost per usable kWh was higher unless you looked at the expected lifetime replacement costs, then it was even. I haven't followed battery prices too closely but my impression is that Lifepo4 has dropped in price ~30-50% since then so is probably now cheaper for usable kWh×cycle than lead acid but still might have a higher upfront cost. The supported tempurature ranges, space contraints (venting, size, weight) and other factors all seem to favor Lifepo4. That said, if your house battery is a backup for power outages and not intended to power your house every night, then lead acid may still be the way to go because you don't care about kWh not kWh×cycle. Edit: replaced * with × to fix formatting

happyopossum 4y ago

> 20 of these will give you 10kWh Not really - lead acid batteries are limited to only using about 50% of their capacity, go any deeper more than a handful of times and you'll pretty much destroy it.

Syonyk 4y ago
No, they're not. It depends on what battery you pick, and if you go with a deep cycle battery designed for that sort of storage use, you typically get charts of cycle life down to 80% DoD or so, and still have "hundreds of cycles" there on anything competent. With thousands of cycles for shallower cycling that you'd see on a daily basis. Please go find a good, modern lead acid datasheet and familiarize yourself with it, because I'm tired of people who've clearly not been around anything from the last decade or two parroting this line endlessly when it comes to lithium and lead. Here's the datasheet for a GC2 form factor Trojan T105-RE from about a decade ago (I've got a 6 year old pack in my office): https://www.trojanbattery.com/pdf/datasheets/T105RE_TrojanRE_Data_Sheets.pdf https://www.trojanbattery.com/pdf/datasheets/T105RE_TrojanRE... Notice that it's rated for about 700 cycles, to 100% DoD. And about 4000 cycles at 20% DoD. Lead has many advantages for stationary storage, and they're not the same batteries you found 40 years ago.
sfteus 4y ago
Most of the time I've read about DIY systems, deep cycle marine batteries are preferred for this reason.

robonerd 4y ago

Backyard sheds seem like the best place for battery packs this large. However, I think a lot of people with electric cars and attached garages don't think twice about it.

elric 4y ago
I guess that rules out 99% of city dwellers then.
- robonerd 4y ago
  Are you sure your lease doesn't rule it out anyway?
- dahfizz 4y ago
  Where would a city dweller put a huge battery pack anyway? Maybe ask your landlord to put one in the basement for the whole building? Obviously he won't; it doesn't provide any benefit to him.

raxxorraxor 4y ago

Having 20 lead batteries in your basement also adds a lot of prepper flair and scares away those annoying fire protection guys too. It is just 10kWh regardless of voltage aside from small conversion losses here and there. Provided you have a computer that uses 500W, a monitor that uses 100W plus your internet router of 20W, you can run it for a bit over 16 hours. Just answering the important questions. Although these type of battery also wants to be handled correctly. Don't discharge completely and yet also do not charge them fully. You also have to know about the hundreds of other partially true myths about lead batteries. Their most prominent positive property is indeed the price and not too much else.

jhgb 4y ago

> Honestly I'd rather a battery that's super reliable and NOT using any lithium ion inside it in my home. As it doesn't need to move, it can sit there in an unused space and be really heavy. It sounds to me like you're asking for a nickel-iron battery.