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Comment by Faaak | Hacker News Reader

I'd love to be able to buy "cheap" batteries that are big, large, heavy, but cheap (per kWh). Sadly there are many startups but none are selling as of now. The only one I found ("Salt battery") was more expensive than Lithium but with less cycles...

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Edison batteries (Nickle-iron), although expensive initialy, are apparently the cheapest batteries once you factor in their lifetime of multiple decades without degradation.

I'd also look into LTO (lithium titanate oxide) if you're interested in long term cost per KWh, not because they are cheap by any means but because they (allegedly) last so long that you'd only be able to replace them maybe twice over your lifetime, it's a pretty new chemistry so unfortunately it's rather early days to verify whether any of the consumer offerings available today will actually perform for as long as the companies manufacturing them suggest (I've seen figures quoted everywhere between 5000 and 30000 cycles at 70% DoD), or whether you could even take advantage of those kinds of cycle counts before the cells just died from calendar ageing.

Back to NiFe though, you can certainly get decades of use comfortably out of NiFe cells, but it's worth taking into account that they require a lot of maintenance, routinely topping up each cell with deionized water (there are automated systems you can buy or build yourself to manage this though), and every few years the KOH electrolyte inside them will need replacing every few years, plus you will want to keep your cells adequately ventilated as they vent hydrogen periodically.

I would definitely NOT recommend lead-acid, sure the upfront cost is lower than anything else by quite a ways, but they won't last long at all, and as a result I'd be surprised if you weren't paying a lot more in the long run.

Do you think they are expensive because new and not manufactured at scale, or because titanium/titanate is expensive ? I know that Toshiba manufactures these and apparently it was in talk with Apple to contract manufacture it for them.

It’s worth mentioning that cheap (and safe and and abundant mineral resource) LiFePO4 batteries can last 5000 cycles or more if you charge and discharge them carefully.

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.

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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