4 ms·

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 p

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.
      - sgt 4y ago
        ChatGPT is not wrong... but in my personal experience, once you go below 40% it's all downhill from there. At least if you've done it 2-3 times. Batteries are not always exactly the same, and temperature conditions vary as well. I've been nursing batteries for years, and this is just my anecdotal comments on that. One thing that we can all agree on though is that you must never ever use car batteries. Lead acid need to be the deep cycle kind.
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

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.
    - sgt 4y ago
      ChatGPT is not wrong... but in my personal experience, once you go below 40% it's all downhill from there. At least if you've done it 2-3 times. Batteries are not always exactly the same, and temperature conditions vary as well. I've been nursing batteries for years, and this is just my anecdotal comments on that. One thing that we can all agree on though is that you must never ever use car batteries. Lead acid need to be the deep cycle kind.

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