7 ms·

Tip to OP (I think they already have this idea, based on the post): when that lead-acid battery dies, replace it with a LiFePo4, which is substantially more ef

Tip to OP (I think they already have this idea, based on the post): when that lead-acid battery dies, replace it with a LiFePo4, which is substantially more efficient, lasts 3x as long, has a higher energy density, provides a usable voltage far further into its discharging %, etc. etc... A couple pages that describe the differences linked below... tl;dr if you are starting a solar battery project, LiFePo4 is the clear choice by far, unless you're going for the absolute cheapest possible build due to immediate budget constraints. https://www.canbat.com/a-detailed-comparison-of-lead-acid-batteries-and-lithium-iron-batteries/ https://www.canbat.com/a-detailed-comparison-of-lead-acid-ba... https://www.power-sonic.com/blog/lithium-vs-lead-acid-batteries/ https://www.power-sonic.com/blog/lithium-vs-lead-acid-batter...

walrus01 4y ago
I don't disagree with you but lifepo4 have a high upfront one time purchase cost for something equivalent in capacity to a 12V 100Ah AGM, like easily $450-500 per unit or more. They do pay for themselves over time with their much greater longevity. Might be more than the blog owner wants to spend for what is just a fun hobby project. There are some 3U rackmount size nominal 48vdc 50Ah lifepo4 (approx 4.8kWh capacity) with built in bms and LVD you can get from china now.
- amatecha 4y ago
  Yeah, there's def the upfront cost, which not everyone can justify. Though, at the same time, a lower-amp-hour battery can provide as much actually-usable energy as a higher-amp-hour-rated SLA battery (so you could purchase a LiFePo4 battery with a lower amp-hour rating than the equivalent SLA battery but still get the same run time). I wouldn't know how much lower you can go though offhand.
- sgt 4y ago
  With lead acids you just have to make sure you don't go below 40% charge. They don't tend to like that. The deep cycle ones are a bit better but I've experienced them deteriorating quickly too once you go too low. The other disadvantage is that they are quite heavy and might end up taking up lots of space. I'm personally still using lead acid, but with plans to go LiFePo4.
  - detrites 4y ago
    If you can't go below 40%, it might make sense to reduce the capacity by 40% accordingly when making comparison calculations against tech that can do that no problem. How does bang for buck look then with SLA versus LiFePO4?
    - sgt 4y ago
      I don't have the exact numbers but even then it's cheaper. The only issue is - can you trust yourself (or your planning) to ensure you don't go below 40%? Real life is hard to plan.
      - swores 4y ago
        What happens if you do let it go below 40% (either as a brief dip to high 30s, or letting it go to 0)? Is it closer to a case of "oops you hit 39%, this battery is now worthless" or "oops you went down to 0%, better not do that every day as statistically the battery will last 0.001% less long"? edit: I pasted my comment (prefaced with "context = lead-acid batteries") into ChatGPT and got this answer, maybe someone who knows could, instead of having to explain it all to me, just confirm GPT-4 got it right, or if not the correct it / add detail? > If a lead-acid battery is allowed to go below 40% state of charge (SOC), it can cause some issues, but the effects are not necessarily immediate or catastrophic. The depth of discharge (DoD) and frequency of these deep discharges can impact the battery's overall lifespan and performance. > 1. Brief dip to high 30s: If the battery's SOC occasionally dips into the high 30s, it may not cause significant harm. However, consistently discharging to that level can gradually decrease the battery's overall lifespan. > 2. Discharge to 0%: If a lead-acid battery is allowed to discharge to 0%, it can cause more serious damage. Repeatedly discharging the battery to this level will dramatically shorten its lifespan and could potentially cause it to fail prematurely. > The relationship between DoD and battery life is not linear. For example, discharging a battery to 50% DoD might give you around 1,000 to 1,200 cycles, while discharging it to 80% DoD might give you only 300 to 500 cycles. It is generally recommended to keep lead-acid batteries at a higher state of charge to maximize their lifespan and maintain optimal performance. > In summary, allowing a lead-acid battery to occasionally dip below 40% SOC may not cause immediate damage, but consistently doing so can reduce its lifespan. Discharging the battery to 0% can cause even more significant harm, especially if done repeatedly. It is best to keep lead-acid batteries at a higher state of charge to ensure their longevity and maintain optimal performance.
- Inviz 4y ago
  48v 100ah LifePO4 is under 1000$ in China
  - jacquesm 4y ago
    It is but you have to make very sure that you actually get what you ordered and not some substitute with lower grade cells than what's advertised.
    - swores 4y ago
      Are there easy(/cheap) ways to verify this if one does buy, as an individual, a cheap battery like that? Or do you need to either rely on brand reputation or have access to expensive equipment for testing?
      - jacquesm 4y ago
        I think vendor reputation is almost as important (or maybe even more important) as brand reputation. In many cases a brand is just a sticker, and your vendor may well have a longer relationship with their customer. For instance, telling a brand name cell from a fake cell can be extremely hard, but your vendor knows exactly where they bought them. I buy cells from nkon.nl, who are a high rep local vendor and I've yet to be disappointed but buying a pack that is sealed from a low rep vendor may well incur a lot of risk. You'd almost have to split open the shrink wrap to make sure you got what you paid for. One quick and dirty way to check is to weigh the pack and to compare the weight to the manufacturers spec for the cells. It's obviously not perfect but many fake cells have weights that are wildly different from the cells they pretend to copy (usually due to much lower actual capacity).
      - AdrianB1 4y ago
        You can do a capacity test quite easily, that will only tell if the capacity is the rated one. You will have to check for physical signs of bad cells, they enlarge (bloat), but that means you need to open the case (sometimes it will void any warranty) and check each cell.
      - 4y ago
beachy 4y ago
Are these more or less a plug in replacement for lead acid, likely to work with our existing charge controller?
- adamcharnock 4y ago
  Not all are, but the Simpliphi batteries are designed to be plug-in replacements more or less
- jacquesm 4y ago
  Most charge controllers made for serious applications allow for the selection of battery chemistry.
- hdkwkevf 4y ago
  It seems not: https://www.power-sonic.com/blog/how-to-charge-lithium-iron-phosphate-lifepo4-batteries/ https://www.power-sonic.com/blog/how-to-charge-lithium-iron-... They may work for the the initial phases of charging but not for “float” I.e keeping the battery as close to 100% charge over a longer period.
madaxe_again 4y ago
By far… not so. Just, marginally, as of the last year, perhaps - but the total cost over the lifetime per Wh of storage is still on a par with lead, because lead acid batteries are cheap as chips, require little or no maintenance if you’re sealed, and if you get something like OPzS cells and treat them well, you will get 20 years of life from them. LiFePo4, you’re looking at a decade, maximum, before they’re trash. I set us up here, totally off grid, three years ago, using a bank of OPzS cells, giving us 42kWh of usable storage. I rarely take them below 70%. Their performance has barely budged since installation, and with the condenser caps, they have required zero maintenance - I check the specific gravity of the acid once a year, and go “yup”, and that’s it. LiFePo4 I am considering for a booster bank at our cabin, which is 500m from our power shed, as the cable limits us to ~2.5kW here before we see significant voltage drop - it’s either that or step-up/step-down at either end, but transformers are surprisingly expensive. Main reason I’m leaning towards them for this application is mass, as our only access is either by foot or an aerial cableway - our lead bank weighs about 2000kg, equivalent LiFePo4 is about 450kg. So - LiFePo4 is a decent choice, but depending on your application, a pile of big lead acid cells can be better. See, for instance, storage at various solar projects - it’s virtually all OPzS cells, as the amortised cost is still favourable.
- louwrentius 4y ago
  > LiFePo4, you’re looking at a decade, maximum, before they’re trash. I think they will be at 80% after a decade, thus not trash. > if you’re sealed, and if you get something like OPzS cells and treat them well, you will get 20 years of life from them. If you have the space, 6V or even 2V OPzS cells can be huge.
  - madaxe_again 4y ago
    Mine are 2v 660Ah cells - 24 of them take up about 3m^2 of floor, and they’re about 80kg each. Power density, they do not have.
    - louwrentius 4y ago
      Thank for sharing, almost 2 ton in weight. But I believe that can work.
op00to 4y ago
Unless you will be in cold temperatures, then LiFePo batteries will die if you charge them.
- hellweaver666 4y ago
  How cold is "cold" ? Here in the Netherlands we rarely get more than a couple of days per year with temperatures much below zero.
  - magicalhippo 4y ago
    Below freezing seems to be the standard rule[1]. One typical solution is to use the charging current to heat up the battery instead until it's above freezing, then start the charging. You could of course also use some of the charge from the battery itself to heat it up. [1]: https://relionbattery.com/blog/lithium-battery-cold-weather https://relionbattery.com/blog/lithium-battery-cold-weather
  - op00to 4y ago
    Anything below 0C is problematic for LiFePo4. I have a small solar powered device (Pi Zero controlling an antenna switch) in my backyard that I use a little mechanical temperature switch to turn on and off a teeny tiny mat heater attached to the battery. It's all in an enclosure that's water tight, so I doubt it got below 0 during the day in there in the first place. We didn't get temperatures below 0C this winter in the NE USA (which is not ordinary), and even with some dips below 0 the battery seems fine.
louwrentius 4y ago
I've addressed LiFePo4 in my blog and why I'm not yet running this. I'm trying to respond to some comments, but since this is not my thread, I'm rate-limited. > Let's talk about the battery. I've chosen to use a large used lead-acid battery even though Lithium (LiFePO4) batteries beat lead-acid in every metric. I bought the battery second-hand for €100 so that's not a significant investment for a battery. Although it's a bit worn-down and the capacity is reduced, it is still good enough for me to run my computer setup for 10 hours after a full charge. The lead-acid battery also serves another purpose: is a relatively cheap option for me to validate my setup. If it works as intended, I might opt to upgrade to lithium (LiFePO4) at some point."
- throwaway894345 4y ago
  I think the rate limiting is not based on which thread you're active in, but whether the mods have placed a rate limit on you. It's hard to say since it's not very transparent, but it seems the mods here are pretty liberal about dispensing permanent rate limit penalties.
  - louwrentius 4y ago
    Thanks, the limit seems removed now. With my own submissions I’m never rate limited.
roeles 4y ago
How safe are LiFePo4 batteries these days? Can one use these in -20 to +60 degrees Celcius environments without a fire hazard? I'm asking because I'm creating a similar setup to OP to control the climate in my glider's trailer.
- GuB-42 4y ago
  LiFePo4 are the safest of the commercially available lithium batteries. They can still catch fire if you insist, but it is nothing like the kind of batteries typically found in cell phones that can readily turn into fireworks. Some models are rated from -20C to 60C. Lead acid also have their own set of problems. Some types can produce hydrogen gas while charging, which can be an explosion hazard in an poorly ventilated room. Also, all types of battery are energy storage, and in case of a short circuit, they will release a lot of it as heat, and even if the battery itself can handle it, it can ignite flammable material in the vicinity.
  - eldaisfish 4y ago
    Any lithium battery claiming to be rated for operation down to -20 C is likely lying. Lithium chemistries are sensitive to temperature and operate well in a narrow temperature range. Operation below freezing ambient temperatures requires a heater and heaters need energy - hence why they are uncommon and only add cost. Au contraire, lead-acid batteries work pretty well at temperature extremes, needing only changes in charging (e:) voltage and being limited by discharge current.
    - hanche 4y ago
      GP said rated, not necessarily for operation. It could just mean that the battery will survive such low temperatures unharmed. I have a summer cabin with a solar panel and a couple 12 V lead acid batteries. It would be great to be able to install some lithium type batteries instead, so long as I know they will survive winter.
    - LinuxBender 4y ago
      Any lithium battery claiming to be rated for operation down to -20 C is likely lying. Not necessarily lying but rather there are heating pads that use some of the energy to bring the battery up to safe operating temperature based on BMS readings. There are some LiFePo4 battery breakdowns on Will's YouTube channel that show the various heating pads used by each vendor. [1] So probably better to say they leave out some details that will affect capacity at lower temperatures. He has a HN account so maybe he will also comment. [1] - https://www.youtube.com/c/WillProwse/videos https://www.youtube.com/c/WillProwse/videos
Gordonjcp 4y ago
> unless you're going for the absolute cheapest possible build due to immediate budget constraints. Or, you know, you get limitless amounts of 24Ah 12V SLABs free for the hauling away because they test at a bawhair under factory spec after five years of having an easy life.
mnw21cam 4y ago
I'm going to disagree with you, because decent deep-cycle lead-acid batteries can last very well, and they are very much cheaper than LiFePO4. https://youtube.com/watch?v=LPPUqLZOqCQ https://youtube.com/watch?v=LPPUqLZOqCQ is the video that persuaded me, even if he does ramble on a bit. LiFePO4 age by elapsed time more than cycle count, so after 10 years they will be reaching the end of their useful life regardless of how much you have used them. Lead-acid age by cycle count more than elapsed time, so you could have a battery last well longer than 10 years if you treat it well. I'd note that lead-acid batteries are divided into deep-cycle batteries that have are designed for longevity and basic batteries that are optimised for peak supply current (for vehicle starter motors). Use a deep-cycle battery, otherwise yes it will die very quickly. I'd argue that if you're in a part of the world that has unreliable sunlight, such that you want to store say 4 days of energy but rarely actually use it all, then lead-acid is a perfect fit, because you just buy lots of storage at a cheaper price than LiFePO4, and that regime automatically treats the batteries well. If you're in a part of the world where sunlight is reliably every day and you only want to buy enough battery to last a single night, then I can see that LiFePO4 may be a better option. But I'd still be inclined to buy several days of lead-acid instead. If you want to charge your batteries from cheap early morning grid power and effectively cycle twice a day, then LiFePO4 is definitely the better option. The other thing that is nice about lead-acid batteries is the recycling rate - they are very easily recyclable and very highly recycled. I don't think we're there with LiFePO4 yet.
- toomuchtodo 4y ago
  Flooded lead acid needs to be topped up with distilled water, and shouldn't be kept near living quarters due to possible outgassing. If you run them dry, you will permanently damage the batteries. To recycle them, you have to drag them somewhere automotive. The premium you pay for LiFePO4 over lead acid is almost no maintenance and you can drop them off almost anywhere electronics are recycled to enter the recycling supply chain. Batteries are going to improve rapidly over the next decade, and the battery you replace your current LiFePO4 with at end of life is likely to be much better when that time comes.
- outworlder 4y ago
  The video is ok for the spreadsheet-like comparison, but it claims that all batteries have "memory". Also claims that depth of discharge doesn't matter to lead acid (what happened to sulfation?). One good point that was made is that lead acid starts to behave terribly after losing 20% of its capacity, to the point that they fail outright and can no longer hold a charge. Lithium can usually keep working way longer than that, just with a reduced runtime. Those cycle life numbers look great, but lead acid batteries in practical applications tend not to last the lifespan advertised on brochures. We can gauge that by how confident the manufacturers are: * The Trojan SIND 06 610 has a 2 year warranty. * The NSB100FT - 3 years. * The Battleborn BB10012: 10 years The Trojan battery weights a whopping 220lbs and holds 600amp hours. It's not even in the same category as the other two. You need a minimum of two as they output 6v. The price for the amount of storage they provide is pretty good though. > Lead-acid age by cycle count more than elapsed time, so you could have a battery last well longer than 10 years if you treat it well. Have you ever seen a lead acid battery last this long? Was it able to hold a meaningful amount of charge? Lead acid batteries may be cheaper but they are unlikely to survive for as long as claimed. That said - if you want a battery backup that you basically never use, there is a chance that you'll get a good return on investment on deep cycle lead acid (specifically those industrial ones) – if they don't fail for whatever reason and are properly maintained. For the same amount of money you can buy a ridiculous amount of storage for a real emergency. Good point about the recycle rate. Lithium is theoretically just as recyclable as lead acid, but the logistics are not there yet (but how will that look like in 10 years?).

walrus01 4y ago

I don't disagree with you but lifepo4 have a high upfront one time purchase cost for something equivalent in capacity to a 12V 100Ah AGM, like easily $450-500 per unit or more. They do pay for themselves over time with their much greater longevity. Might be more than the blog owner wants to spend for what is just a fun hobby project. There are some 3U rackmount size nominal 48vdc 50Ah lifepo4 (approx 4.8kWh capacity) with built in bms and LVD you can get from china now.

amatecha 4y ago
Yeah, there's def the upfront cost, which not everyone can justify. Though, at the same time, a lower-amp-hour battery can provide as much actually-usable energy as a higher-amp-hour-rated SLA battery (so you could purchase a LiFePo4 battery with a lower amp-hour rating than the equivalent SLA battery but still get the same run time). I wouldn't know how much lower you can go though offhand.
sgt 4y ago
With lead acids you just have to make sure you don't go below 40% charge. They don't tend to like that. The deep cycle ones are a bit better but I've experienced them deteriorating quickly too once you go too low. The other disadvantage is that they are quite heavy and might end up taking up lots of space. I'm personally still using lead acid, but with plans to go LiFePo4.
- detrites 4y ago
  If you can't go below 40%, it might make sense to reduce the capacity by 40% accordingly when making comparison calculations against tech that can do that no problem. How does bang for buck look then with SLA versus LiFePO4?
  - sgt 4y ago
    I don't have the exact numbers but even then it's cheaper. The only issue is - can you trust yourself (or your planning) to ensure you don't go below 40%? Real life is hard to plan.
    - swores 4y ago
      What happens if you do let it go below 40% (either as a brief dip to high 30s, or letting it go to 0)? Is it closer to a case of "oops you hit 39%, this battery is now worthless" or "oops you went down to 0%, better not do that every day as statistically the battery will last 0.001% less long"? edit: I pasted my comment (prefaced with "context = lead-acid batteries") into ChatGPT and got this answer, maybe someone who knows could, instead of having to explain it all to me, just confirm GPT-4 got it right, or if not the correct it / add detail? > If a lead-acid battery is allowed to go below 40% state of charge (SOC), it can cause some issues, but the effects are not necessarily immediate or catastrophic. The depth of discharge (DoD) and frequency of these deep discharges can impact the battery's overall lifespan and performance. > 1. Brief dip to high 30s: If the battery's SOC occasionally dips into the high 30s, it may not cause significant harm. However, consistently discharging to that level can gradually decrease the battery's overall lifespan. > 2. Discharge to 0%: If a lead-acid battery is allowed to discharge to 0%, it can cause more serious damage. Repeatedly discharging the battery to this level will dramatically shorten its lifespan and could potentially cause it to fail prematurely. > The relationship between DoD and battery life is not linear. For example, discharging a battery to 50% DoD might give you around 1,000 to 1,200 cycles, while discharging it to 80% DoD might give you only 300 to 500 cycles. It is generally recommended to keep lead-acid batteries at a higher state of charge to maximize their lifespan and maintain optimal performance. > In summary, allowing a lead-acid battery to occasionally dip below 40% SOC may not cause immediate damage, but consistently doing so can reduce its lifespan. Discharging the battery to 0% can cause even more significant harm, especially if done repeatedly. It is best to keep lead-acid batteries at a higher state of charge to ensure their longevity and maintain optimal performance.
Inviz 4y ago
48v 100ah LifePO4 is under 1000$ in China
- jacquesm 4y ago
  It is but you have to make very sure that you actually get what you ordered and not some substitute with lower grade cells than what's advertised.
  - swores 4y ago
    Are there easy(/cheap) ways to verify this if one does buy, as an individual, a cheap battery like that? Or do you need to either rely on brand reputation or have access to expensive equipment for testing?
    - jacquesm 4y ago
      I think vendor reputation is almost as important (or maybe even more important) as brand reputation. In many cases a brand is just a sticker, and your vendor may well have a longer relationship with their customer. For instance, telling a brand name cell from a fake cell can be extremely hard, but your vendor knows exactly where they bought them. I buy cells from nkon.nl, who are a high rep local vendor and I've yet to be disappointed but buying a pack that is sealed from a low rep vendor may well incur a lot of risk. You'd almost have to split open the shrink wrap to make sure you got what you paid for. One quick and dirty way to check is to weigh the pack and to compare the weight to the manufacturers spec for the cells. It's obviously not perfect but many fake cells have weights that are wildly different from the cells they pretend to copy (usually due to much lower actual capacity).
    - AdrianB1 4y ago
      You can do a capacity test quite easily, that will only tell if the capacity is the rated one. You will have to check for physical signs of bad cells, they enlarge (bloat), but that means you need to open the case (sometimes it will void any warranty) and check each cell.
    - 4y ago

beachy 4y ago

Are these more or less a plug in replacement for lead acid, likely to work with our existing charge controller?

adamcharnock 4y ago
Not all are, but the Simpliphi batteries are designed to be plug-in replacements more or less
jacquesm 4y ago
Most charge controllers made for serious applications allow for the selection of battery chemistry.
hdkwkevf 4y ago
It seems not: https://www.power-sonic.com/blog/how-to-charge-lithium-iron-phosphate-lifepo4-batteries/ https://www.power-sonic.com/blog/how-to-charge-lithium-iron-... They may work for the the initial phases of charging but not for “float” I.e keeping the battery as close to 100% charge over a longer period.

madaxe_again 4y ago

By far… not so. Just, marginally, as of the last year, perhaps - but the total cost over the lifetime per Wh of storage is still on a par with lead, because lead acid batteries are cheap as chips, require little or no maintenance if you’re sealed, and if you get something like OPzS cells and treat them well, you will get 20 years of life from them. LiFePo4, you’re looking at a decade, maximum, before they’re trash. I set us up here, totally off grid, three years ago, using a bank of OPzS cells, giving us 42kWh of usable storage. I rarely take them below 70%. Their performance has barely budged since installation, and with the condenser caps, they have required zero maintenance - I check the specific gravity of the acid once a year, and go “yup”, and that’s it. LiFePo4 I am considering for a booster bank at our cabin, which is 500m from our power shed, as the cable limits us to ~2.5kW here before we see significant voltage drop - it’s either that or step-up/step-down at either end, but transformers are surprisingly expensive. Main reason I’m leaning towards them for this application is mass, as our only access is either by foot or an aerial cableway - our lead bank weighs about 2000kg, equivalent LiFePo4 is about 450kg. So - LiFePo4 is a decent choice, but depending on your application, a pile of big lead acid cells can be better. See, for instance, storage at various solar projects - it’s virtually all OPzS cells, as the amortised cost is still favourable.

louwrentius 4y ago
> LiFePo4, you’re looking at a decade, maximum, before they’re trash. I think they will be at 80% after a decade, thus not trash. > if you’re sealed, and if you get something like OPzS cells and treat them well, you will get 20 years of life from them. If you have the space, 6V or even 2V OPzS cells can be huge.
- madaxe_again 4y ago
  Mine are 2v 660Ah cells - 24 of them take up about 3m^2 of floor, and they’re about 80kg each. Power density, they do not have.
  - louwrentius 4y ago
    Thank for sharing, almost 2 ton in weight. But I believe that can work.

op00to 4y ago

Unless you will be in cold temperatures, then LiFePo batteries will die if you charge them.

hellweaver666 4y ago
How cold is "cold" ? Here in the Netherlands we rarely get more than a couple of days per year with temperatures much below zero.
- magicalhippo 4y ago
  Below freezing seems to be the standard rule[1]. One typical solution is to use the charging current to heat up the battery instead until it's above freezing, then start the charging. You could of course also use some of the charge from the battery itself to heat it up. [1]: https://relionbattery.com/blog/lithium-battery-cold-weather https://relionbattery.com/blog/lithium-battery-cold-weather
- op00to 4y ago
  Anything below 0C is problematic for LiFePo4. I have a small solar powered device (Pi Zero controlling an antenna switch) in my backyard that I use a little mechanical temperature switch to turn on and off a teeny tiny mat heater attached to the battery. It's all in an enclosure that's water tight, so I doubt it got below 0 during the day in there in the first place. We didn't get temperatures below 0C this winter in the NE USA (which is not ordinary), and even with some dips below 0 the battery seems fine.

louwrentius 4y ago

I've addressed LiFePo4 in my blog and why I'm not yet running this. I'm trying to respond to some comments, but since this is not my thread, I'm rate-limited. > Let's talk about the battery. I've chosen to use a large used lead-acid battery even though Lithium (LiFePO4) batteries beat lead-acid in every metric. I bought the battery second-hand for €100 so that's not a significant investment for a battery. Although it's a bit worn-down and the capacity is reduced, it is still good enough for me to run my computer setup for 10 hours after a full charge. The lead-acid battery also serves another purpose: is a relatively cheap option for me to validate my setup. If it works as intended, I might opt to upgrade to lithium (LiFePO4) at some point."

throwaway894345 4y ago
I think the rate limiting is not based on which thread you're active in, but whether the mods have placed a rate limit on you. It's hard to say since it's not very transparent, but it seems the mods here are pretty liberal about dispensing permanent rate limit penalties.
- louwrentius 4y ago
  Thanks, the limit seems removed now. With my own submissions I’m never rate limited.

roeles 4y ago

How safe are LiFePo4 batteries these days? Can one use these in -20 to +60 degrees Celcius environments without a fire hazard? I'm asking because I'm creating a similar setup to OP to control the climate in my glider's trailer.

GuB-42 4y ago
LiFePo4 are the safest of the commercially available lithium batteries. They can still catch fire if you insist, but it is nothing like the kind of batteries typically found in cell phones that can readily turn into fireworks. Some models are rated from -20C to 60C. Lead acid also have their own set of problems. Some types can produce hydrogen gas while charging, which can be an explosion hazard in an poorly ventilated room. Also, all types of battery are energy storage, and in case of a short circuit, they will release a lot of it as heat, and even if the battery itself can handle it, it can ignite flammable material in the vicinity.
- eldaisfish 4y ago
  Any lithium battery claiming to be rated for operation down to -20 C is likely lying. Lithium chemistries are sensitive to temperature and operate well in a narrow temperature range. Operation below freezing ambient temperatures requires a heater and heaters need energy - hence why they are uncommon and only add cost. Au contraire, lead-acid batteries work pretty well at temperature extremes, needing only changes in charging (e:) voltage and being limited by discharge current.
  - hanche 4y ago
    GP said rated, not necessarily for operation. It could just mean that the battery will survive such low temperatures unharmed. I have a summer cabin with a solar panel and a couple 12 V lead acid batteries. It would be great to be able to install some lithium type batteries instead, so long as I know they will survive winter.
  - LinuxBender 4y ago
    Any lithium battery claiming to be rated for operation down to -20 C is likely lying. Not necessarily lying but rather there are heating pads that use some of the energy to bring the battery up to safe operating temperature based on BMS readings. There are some LiFePo4 battery breakdowns on Will's YouTube channel that show the various heating pads used by each vendor. [1] So probably better to say they leave out some details that will affect capacity at lower temperatures. He has a HN account so maybe he will also comment. [1] - https://www.youtube.com/c/WillProwse/videos https://www.youtube.com/c/WillProwse/videos

Gordonjcp 4y ago

> unless you're going for the absolute cheapest possible build due to immediate budget constraints. Or, you know, you get limitless amounts of 24Ah 12V SLABs free for the hauling away because they test at a bawhair under factory spec after five years of having an easy life.

mnw21cam 4y ago

I'm going to disagree with you, because decent deep-cycle lead-acid batteries can last very well, and they are very much cheaper than LiFePO4. https://youtube.com/watch?v=LPPUqLZOqCQ https://youtube.com/watch?v=LPPUqLZOqCQ is the video that persuaded me, even if he does ramble on a bit. LiFePO4 age by elapsed time more than cycle count, so after 10 years they will be reaching the end of their useful life regardless of how much you have used them. Lead-acid age by cycle count more than elapsed time, so you could have a battery last well longer than 10 years if you treat it well. I'd note that lead-acid batteries are divided into deep-cycle batteries that have are designed for longevity and basic batteries that are optimised for peak supply current (for vehicle starter motors). Use a deep-cycle battery, otherwise yes it will die very quickly. I'd argue that if you're in a part of the world that has unreliable sunlight, such that you want to store say 4 days of energy but rarely actually use it all, then lead-acid is a perfect fit, because you just buy lots of storage at a cheaper price than LiFePO4, and that regime automatically treats the batteries well. If you're in a part of the world where sunlight is reliably every day and you only want to buy enough battery to last a single night, then I can see that LiFePO4 may be a better option. But I'd still be inclined to buy several days of lead-acid instead. If you want to charge your batteries from cheap early morning grid power and effectively cycle twice a day, then LiFePO4 is definitely the better option. The other thing that is nice about lead-acid batteries is the recycling rate - they are very easily recyclable and very highly recycled. I don't think we're there with LiFePO4 yet.

toomuchtodo 4y ago
Flooded lead acid needs to be topped up with distilled water, and shouldn't be kept near living quarters due to possible outgassing. If you run them dry, you will permanently damage the batteries. To recycle them, you have to drag them somewhere automotive. The premium you pay for LiFePO4 over lead acid is almost no maintenance and you can drop them off almost anywhere electronics are recycled to enter the recycling supply chain. Batteries are going to improve rapidly over the next decade, and the battery you replace your current LiFePO4 with at end of life is likely to be much better when that time comes.
outworlder 4y ago
The video is ok for the spreadsheet-like comparison, but it claims that all batteries have "memory". Also claims that depth of discharge doesn't matter to lead acid (what happened to sulfation?). One good point that was made is that lead acid starts to behave terribly after losing 20% of its capacity, to the point that they fail outright and can no longer hold a charge. Lithium can usually keep working way longer than that, just with a reduced runtime. Those cycle life numbers look great, but lead acid batteries in practical applications tend not to last the lifespan advertised on brochures. We can gauge that by how confident the manufacturers are: * The Trojan SIND 06 610 has a 2 year warranty. * The NSB100FT - 3 years. * The Battleborn BB10012: 10 years The Trojan battery weights a whopping 220lbs and holds 600amp hours. It's not even in the same category as the other two. You need a minimum of two as they output 6v. The price for the amount of storage they provide is pretty good though. > Lead-acid age by cycle count more than elapsed time, so you could have a battery last well longer than 10 years if you treat it well. Have you ever seen a lead acid battery last this long? Was it able to hold a meaningful amount of charge? Lead acid batteries may be cheaper but they are unlikely to survive for as long as claimed. That said - if you want a battery backup that you basically never use, there is a chance that you'll get a good return on investment on deep cycle lead acid (specifically those industrial ones) – if they don't fail for whatever reason and are properly maintained. For the same amount of money you can buy a ridiculous amount of storage for a real emergency. Good point about the recycle rate. Lithium is theoretically just as recyclable as lead acid, but the logistics are not there yet (but how will that look like in 10 years?).