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Comment by jeffbee | Hacker News Reader

The big, large, heavy, cheap battery you are looking for is the lead-acid battery. The market for them is still larger than the global lithium-ion market, and they're quite suitable for stationary applications. Many off-the-grid houses use banks of lead-acid batteries.

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LiFePo are starting to make a splash (pun intended) in the marine sector now that costs have started to fall, but lead acid still rules the roost. I have 4 AGMs and one Lithium in my vessel.

I have heard that large contracts on LFP batteries have touched under 100$/kwh in China, but on the retail side i have never seen anything cheaper than 300$/kwh ever sold. I guess even touching something like 200$/kwh retail is a big deal and might happen sooner than later with the flood of battery makers coming in.

On aliexpress you find LFP at about 130-140 USD/kWh

https://www.aliexpress.com/item/1005002625171294.html

(random link, never tested this vendor).

Prices have gone up a bit in the last few monthes.

Good source of information on Chinese LFP vendors here: https://diysolarforum.com

Yeah, China domestically got really good at LFP chemistry. The US doesn’t make LFP domestically, and from what I understand it’s overall less common outside of China. I’m a big LFP fan. Under-rated and already capable of many things people claim for new chemistries (long cycle life, much safer, low cost, using very abundant minerals, etc).

Yeah, LFP is where it’s at as far as longevity and price and price per cycle and safety.

Lead acid are still more forgiving (although with the caveat that they don’t last long even if we’ll cared for), but LFP is pretty wonderful.

I'm on year 3 with some AGMs. I bought used group 24 AGM batteries from a local used/recycler battery joint that were used in large hospital battery backup applications - they're typically never cycled but once for testing and always kept topped off. Very common to find these kinds of batteries in bulk a few times a year where I'm at. The flooded batteries (mostly Interstate) that I used in years prior would last at most two years even when properly maintained. The FL heat just nukes those things.

Lead acid are not particularly great as far as DOD (depth of discharge) or longevity.

Comparing for example a 100ah lifepo4 to 100ah lead acid, the useable capacity of the lithium will be close to 4x more. Using the full capacity of the lead acid will make them wear out quickly.

What about the deep cycle batteries that are designed specifically for full discharge? Or am I believing marketing? I have a couple Optima Blutops that I've built a remote cart off of, but I don't use them nearly as much as the market they are targeted which is fishing boats. Run your pumps, gadgets, and trolling motor all day on the water, then charge them back up over night.

You'll still be lucky to get 300-500 cycles out of them if you go down to 20% charge or so. A 'Normal' car battery can fail in 30-150 cycles if you do that, hence the 'deep cycle' part of it.

Fine for a trolling motor, but if you're deep cycling them in a power system, that could kill them in a couple years. Usually you'll want to size them so you never go below 50% discharge on a normal basis.

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