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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

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?
  - shkkmo 4y ago
    You would probably need switch (battery isolator, Dc-DC charger, etc ) of some sort to isolate the two systems to fully eliminate this, but part of the answer is the Lifepo4 keeps its voltage higher through most of it's capacity than lead does. Thus the voltage of a Lifepo4 at ~20% is the same as a lead acid at ~100%.
    - roflyear 4y ago
      This is true, but in my case I use a DC-DC charger that does not allow the lead to charge the lithium (I don't want this or want to think about it, even if it was beneficial, in my case the complexity is not worth it) - the only way the voltage can travel is from the lithium to the lead.
      - Siecje 4y ago
        Okay and you discharge the lead first and the lead only fully drains when all of the batteries fully drain.
        roflyear 4y ago
        Yes this is correct - but by not really discharging the lead, you will keep it alive for essentially forever.
        foobarian 4y ago
        How does this switching black magic work. Is there a power interruption while it changes the source power bank?
briffle 4y ago
With RV Lead Acid Batteries, you typically can only discharge half of the battery safely. So a 100Ah battery really gets you 50Ah. With the LifePo4 batteries (also much less fire hazard than regular li-ion), you can regularly discharge >90% of the capacity.
dylan604 4y ago
>(One) trouble with lead acid is that deep discharges are really bad for the longevity of the battery. Let me introduce you to the Optima Blue Top[0] marine battery which is designed specifically for draining to 0 and recovering to full charge. Doing this to a typical SLA battery found in cars is definitely not recommended. These are commonly used in fishing boats to run trolling motors and pumps in the boat's live wells. Being the hacker nerd type, I built a DIT cart around these with an inverter to power my gear in remote locations without needing puttputts. [0]https://www.optimabatteries.com/optima-product-categories/batteries//OPT/part/bluetop%2525C2%2525AE-34m/34M?cat1=PZ_ALL&cat2=Batteries&cat3=Batteries&cp=0&catalog=CLARIOS&partType=PART https://www.optimabatteries.com/optima-product-categories/ba...
- bradstewart 4y ago
  Are the Blues much different from the Yellow Tops? I've been running Yellows in my Jeep due to the heavy electrical load from the winch--I've nearly drained the battery a few times having to winch myself out with the motor off--without issue. From a quick glance, they seem to be the same construction?
  - dylan604 4y ago
    It's been a long while since I looked at the differences. I know the red top are typical car use for starting with high surge loads. these are not recommended for deep drain usage. There are 2 blue tops, and just realized the one I linked previosly is not the same version (dark gray) as the one I have being the light gray. Essentially, the differences are in use cases. Lots of short but heavy loads vs long sustained loads. Looks like the blue tops are still Optima's best "drain to 0 frequently" type of battery where the yellows look like an occassional drain to 0 is survivable but not the recommended use case. I had forgotten the differences after making the decision years ago. Just looked them up again for a quick refresher

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?
- shkkmo 4y ago
  You would probably need switch (battery isolator, Dc-DC charger, etc ) of some sort to isolate the two systems to fully eliminate this, but part of the answer is the Lifepo4 keeps its voltage higher through most of it's capacity than lead does. Thus the voltage of a Lifepo4 at ~20% is the same as a lead acid at ~100%.
  - roflyear 4y ago
    This is true, but in my case I use a DC-DC charger that does not allow the lead to charge the lithium (I don't want this or want to think about it, even if it was beneficial, in my case the complexity is not worth it) - the only way the voltage can travel is from the lithium to the lead.
    - Siecje 4y ago
      Okay and you discharge the lead first and the lead only fully drains when all of the batteries fully drain.
      - roflyear 4y ago
        Yes this is correct - but by not really discharging the lead, you will keep it alive for essentially forever.
        foobarian 4y ago
        How does this switching black magic work. Is there a power interruption while it changes the source power bank?

briffle 4y ago

With RV Lead Acid Batteries, you typically can only discharge half of the battery safely. So a 100Ah battery really gets you 50Ah. With the LifePo4 batteries (also much less fire hazard than regular li-ion), you can regularly discharge >90% of the capacity.

dylan604 4y ago

>(One) trouble with lead acid is that deep discharges are really bad for the longevity of the battery. Let me introduce you to the Optima Blue Top[0] marine battery which is designed specifically for draining to 0 and recovering to full charge. Doing this to a typical SLA battery found in cars is definitely not recommended. These are commonly used in fishing boats to run trolling motors and pumps in the boat's live wells. Being the hacker nerd type, I built a DIT cart around these with an inverter to power my gear in remote locations without needing puttputts. [0]https://www.optimabatteries.com/optima-product-categories/batteries//OPT/part/bluetop%2525C2%2525AE-34m/34M?cat1=PZ_ALL&cat2=Batteries&cat3=Batteries&cp=0&catalog=CLARIOS&partType=PART https://www.optimabatteries.com/optima-product-categories/ba...

bradstewart 4y ago
Are the Blues much different from the Yellow Tops? I've been running Yellows in my Jeep due to the heavy electrical load from the winch--I've nearly drained the battery a few times having to winch myself out with the motor off--without issue. From a quick glance, they seem to be the same construction?
- dylan604 4y ago
  It's been a long while since I looked at the differences. I know the red top are typical car use for starting with high surge loads. these are not recommended for deep drain usage. There are 2 blue tops, and just realized the one I linked previosly is not the same version (dark gray) as the one I have being the light gray. Essentially, the differences are in use cases. Lots of short but heavy loads vs long sustained loads. Looks like the blue tops are still Optima's best "drain to 0 frequently" type of battery where the yellows look like an occassional drain to 0 is survivable but not the recommended use case. I had forgotten the differences after making the decision years ago. Just looked them up again for a quick refresher