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Comment by stevejb | Hacker News Reader

I just bought a 12v 200ah battery for $2300 AUD. It could be done for less, but this was a premium model. Hopefully when I purchase a second one in a year or two, it will be a bit cheaper.

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What’s the application? Sounds like the capacity of a standard $200 (yes AUD) car battery. I guess you want to hold onto that energy for a long time?

Lead acid batteries can emit fumes, so they are not useful in the same settings as li-ion batteries.

Aren't most lead-acid batteries sealed? The one in my mobility scooter certainly is.

I imagine many are. But in small spaces with poor ventilation (e.g. vehicle interiors) that might not be enough. The sealed batteries still have a vent for the gas to leak (in a controlled manner).

https://electronics.stackexchange.com/questions/175649/are-s...

But besides that, li-ion batteries have more energy per weight, are more efficient at storing energy, and can be discharged to a farther level without negatively impacting the battery.

Sorry for the annoying popups, this is the best source I could find: https://news.energysage.com/lithium-ion-vs-lead-acid-batteri...

Only smaller ones are, and they can still vent hydrogen in some cases. All sealed lead-acid batteries have shorter lifespans as you can’t add water to them to replace water lost to hydrogen gas production.

I just picked up 4 40AH for $70US each so wow.

Mine are like, scooter batteries, LiFePO4. Do yours have like internet connectivity to monitor the charge? Or is it a factor of battery fees in AUS?

Or just 200AH in a single pack? I'm wiring mine in parallel in order to increase AH at 12v. I imagine you're also doing some type of off-grid power via solar/wind?

I've noticed that 12V lithium iron phosphate car-battery replacements tend to be very expensive. I figure part of it is that they need a built-in BMS to keep the cells balanced, but still it seems like there should be cheaper options.

It's not your average BMS that can support 500A cranking currents and horrifically noisy, unstable currents and voltages during charging. I wonder if crashworthiness is a factor as well.

I guess BMSs can vary in terms of what they do, but if it just has to monitor the voltages of the cells and bleed small amounts of current through a resistor if it needs to drop the voltage of one or more cells to keep them balanced, then it doesn't have to be all that complicated, nor handle very much current at a time.

Crashworthiness might be a factor, though... lead acid batteries act sort of like a cushion in an impact, whereas lithium-ion batteries that break can cause worse problems than spilling sulfuric acid all over the engine bay.

That's if your only objective is balancing. Many BMS's go far beyond that, preventing the cells from being overloaded via excessive draw, short circuited, over charged etc.

Ive seen them on ebay for $850. Seem premium too. From a company that has been around for 12 years.

I wanted to get one for my boat, but they are the wrong size. They seem to make them longer, instead of wider, so can't drop in replace the 2x100ah I have now.

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