Why not use Lead Acid batteries?

[Possum Bobby]

I am planning to develop a solar power source, and I have a battery question. I love Lithium ion batteries for their light weight, energy density, etc. But I do not need light weight for my permanent-mounted solar system, nor do I care about size. Why not resort to Lead Acid Batteries (Called FLA batteries here)? Heavy, yes, but they are gonna stay put. Require more space, yes, but I am rural, got lots of space. Do require maintenance, gotta water 'em. Still lots cheaper. They last if kept up. And in my small town, I'd like to trade with JJ, who has an electric golf cart operation. Why not go FLA?

My solar aims:
I live on 100 acres in Alabama along the Florida line. We get hurricanes and can be out of electricity for days. There might be other long-term disruptions where no other power source was available, except the sun, for periods of time. But I am not looking to power my entire home. Rather, I want recharging for cell phones, computers, and hand tools (drills, saws), and an occasional power source for say, a log splitter, a table saw, etc. Not all at once of course. Perhaps we could slowly recharge our Tesla, which can get 4-5 miles range for every hour on a regular 110v socket and is often sitting in the garage when the sun is shining bright outside.

So why not locally obtained, old-fashioned Lead-Acid Deep Cycle batteries?

 

[BatteryBuff]

LiFePO4 is at a price point now where it is close to the price of FLA but: lasts several times longer, allows higher charge and discharge rates, is more efficient, allows use of 80% or more of capacity, 6,000+ cycles, etc. I don't see a good reason to use FLA for solar unless you get them for free.

 

[AntronX]

They cant be deep cycled, have lower charge/discharge efficiency, not much cheaper than LFP cells, are very heavy.

 

[ohmboy]

Found this reply from Will on a discussion from 2021. I think it's still relevant. FLA vs LiFePo4

 

[yodamota]

lithium was cheaper than FLA for us. Ontop of having to barge the batteries over and move each 120 pound battery. all just so i can put distilled water into them every 2 months. Whilst having to deal with corrosion issues.

This of course was comparing lifepo4 to roll's surrette batteries and trojan FLA.

 

[ohmboy]

Found this reply from Will on a discussion from 2021. I think it's still relevant. FLA vs LiFePo4

Here's the link to the thread. FLA vs LiFePo4 discussion

 

[EastTexCowboy]

There's literally zero reason to use FLA batteries for solar unless, as @BatteryBuff stated, you're getting them free. If you're willing to put in a little work and build DIY batteries you can really get the cost down. I just built 57kwh of batteries, four x 280ah units, including the Apex cases, for $7,200. To build the equivalent with FLA you would need 48 100ah 12v batteries. But that doesn't really get you there because FLA can only be discharged to 50% while the LifePO4 batteries can be discharged pretty much to zero in a jam, but even using 20% as the lowest SOC you're going to now need a little over 90kwh of FLA to get the same capacity, or about 76 of those FLA batteries. And finally, look at the life cycles. The LifePO4 cells I used are rated for 6000 cycles. Most FLA batteries are at best 2000 cycles but let's be generous and say 3000 cycles. If you run these numbers you'll find that with off the shelf LifePO4 batteries you're probably going to save quite a bit and if you do DIY batteries you may actually cut the cost in half. You have a much smaller footprint, cleaner install, and no maintenance.

Hopefully this gives you something to think about before going with FLA. Good luck!

 

[Bluedog225]

Watering a battery for a decade is a royal pain. Like some people, they drink more as they age.

 

[Hedges]

Four years ago I paid $5000 for 20kWh AGM (14kWh usable). Wanted zero maintenance so willing to pay more than FLA. Backup, don't expect to use 700 cycles to 70% DoD in 10 year float life.

I'm now setting up my first LiFePO4 batteries, expect to spend about $1000 per 12kWh (almost all usable).

1/4 the up-front cost, 5x to 10x the cycle life, expecting at least 1.5x maybe more float life.

Purpose of these batteries will be peak shaving, now that net metering is dead. Nightly cycling.

Your location shouldn't freeze, one situation where lead-acid may win out.
Heat is bad for either chemistry, so try to keep yours at earth temperature.

 

[Rednecktek]

Unless your batteries are going to be below freezing regularly, go LFP. The biggest differences in my usages is that the cost Per Usable Watt on LFP is cheaper than FLA and the lifespan. Sure, you can go to WallyWorld and pick up a DC29 120ah FLA battery for $130 any day of the week, but at 60-ish amp hours of drain you start damaging the batteries, so that $130 only got you 60ah for the next 5-7 years on average.

Meanwhile the budget funny name LFP batteries (I've been happy with my Vatrers) with low temp cutoff are regularly on sale for about $150 and I can draw 90ah+ every day for the next 10 years and never have to bat an eye, add water, climb under a bench and stuff a tube in the holes, make sure the ventilation is adequate, etc.

Now, having said that, I do have a couple of 12v banks made from FLA WallyWorld DC29's that are still working fine, but I have 4 batteries in parallel to run the low voltage lighting and diesel heaters at my camp where I keep them charging and floating all year long regardless of how much snow is on the ground. Because I need that cold weather reliability I keep my 12v bus on FLA. My LFP bank has heaters but as little light as is out there and as cold as it gets, the heaters would kill my batteries while I'm overseas for 6-10 months.

They do have their place for sure, cold weather and learner systems primarily (if you might destroy something, destroy a CHEAP something) but as low as LFP costs per usable amp hour there's really only the 2 use cases.

 

[DIYrich]

Benefit of lead acid battery: lower temps, surge power.

Biggest downsides: self discharge. 3% per month minimum. Hot weather, 3% per week. Round trip efficiency is about 80% compared to 90+% for lifep04.

I belive optimal top charge rate for lead acid battery is lower. I think it is 0.3c for lead acid, and 0.5 for lifep04.

 

[wpns]

And in my small town, I'd like to trade with JJ, who has an electric golf cart operation.

Please tell me you aren’t getting a special deal on used golf cart batteries!

 

[Daddy Tanuki]

Watering a battery for a decade is a royal pain. Like some people, they drink more as they age.

My ears are burning again dammit.

 

[shadowmaker]

I have both (single forklift 36kWh LFA, 95kWh LFP) and would never recommend FLA to anybody (well cold conditions maybe). I got my FLA for free and next year it is going to be 20 years old. I'm extremely stingy and even get my distilled water for free and still I'm thinking of ditching my FLA for good. I have watering system on it so it only takes few minutes weekly to fill it, but round trip efficiency is only 79% while with my LFP it is 97,3%. Biggest problem for me is that it don't like being empty, even little. Here winter lasts 5-6 months, so keeping it full daily is a problem. I'm just curious to see how long it will work + getting ~15kWh storage for free. It was 18 years old when I got it, so maybe new FLA would be much better, but even so I wouldn't waste my money on it.

 

[wpns]

I have both (single forklift 36kWh LFA, 95kWh LFP) and would never recommend FLA to anybody (well cold conditions maybe). I got my FLA for free and next year it is going to be 20 years old. I'm extremely stingy and even get my distilled water for free and still I'm thinking of ditching my FLA for good. I have watering system on it so it only takes few minutes weekly to fill it, but round trip efficiency is only 79% while with my LFP it is 97,3%. Biggest problem for me is that it don't like being empty, even little. Here winter lasts 5-6 months, so keeping it full daily is a problem. I'm just curious to see how long it will work + getting ~15kWh storage for free. It was 18 years old when I got it, so maybe new FLA would be much better, but even so I wouldn't waste my money on it.

When I first looked at solar power and battery systems a couple of decades ago, the power required to float charge a large FLA battery bank cost more than buying power from the utility would have. Upsizing the system to cover float, equalization, and round-trip efficiency would have eaten my lunch.

 

[Q-Dog]

For lead acid to last they need to be charged fully and held at full charge as often as possible, which can be difficult to accomplish during winter or the rainy season. LiFePO4 doesn't really care if they are charged fully or not, they seem to like to cycle.

 

[Daddy Tanuki]

i started with AGM's on my camper back in 2012 and went with AGM's for my cabin initially but I quickly found out there is a huge differenace between filling up a 600 a/h lead acid bank and filling up a 600 LiFePo4 bank.

the ones on my camper lasted around 10 years, but that's because they had a week of daily charging at the bare minimum between camping trips. sometimes they would have a month of daily charging. with AGM's on the cabin they were dead after 3 years. thats when I made the jump to Lithium and then later found this forum while researching cold weather charging. i already had plans for a battery heater, but after joining the forum I found even more ideas and I can tell you lithium is way easier in the long run for a structure, even with heating requirements. in a camper its a toss up due to the small size of the system, but on anything larger than a camper or travel trailer lithium is the way to go.

 

[seneysolar]

I am very happy with my Trojan lead acid bank. I just serviced water for the second time this year, it took 2 quarts over 4 L-16s. I do it spring and fall. Literally 5 minuites, no big deal. These have been at my cabin for over 7 years, exposed to sub zero weather and the occasional deep cycle when we have alot of guests. Zero issues. No balance problems, no BMS problems, no communication problems, no low temp cut-off, no individual cell monitoring and they didn't come from china. When its time to replace them ill haul them in for scrap $, and get another set.

Golf cart 6v are a good option for standby systems. Dont get used batteries.

Not a fan of AGM. I dont think it should be in the same category as lead acid. Its basically a lead acid that you cant service.

If i was in a warm climate like Alabama, sure id be tempted to use LFP but it sure isnt a requirement like everyone makes it out to be. Whatever you decide, the most important step is educate yourself on the specific charge profiles no matter what chemistry.

 

[HighDesertDrifter]

So there you have it. I ran Golf Cart batteries for nearly 10 years and have recently changed to LifePo4 batteries.
Once you change, you will never go back. You can decide for yourself if all these guys are just in love with a "newer technology."
Or if they really have a legit reason for being overwhelmingly in favor of recommending Life Po4 batteries.
It's your call, but don't let a few bucks and trading with a friend be what determines your decision.

 

[shadowmaker]

When I first looked at solar power and battery systems a couple of decades ago, the power required to float charge a large FLA battery bank cost more than buying power from the utility would have. Upsizing the system to cover float, equalization, and round-trip efficiency would have eaten my lunch.

True, but back then solar/inverter used to be $$$. Now it's the storage capacity that costs and the rest is fairly cheap (at least here).

Even still I'd prefer to pay 4-5x FLA to get same capacity Lifepos (which is ~100e/kWh premade with home delivery ATM).

 

[Mattb4]

...

My solar aims:
I live on 100 acres in Alabama along the Florida line. We get hurricanes and can be out of electricity for days. There might be other long-term disruptions where no other power source was available, except the sun, for periods of time. But I am not looking to power my entire home. Rather, I want recharging for cell phones, computers, and hand tools (drills, saws), and an occasional power source for say, a log splitter, a table saw, etc. Not all at once of course. Perhaps we could slowly recharge our Tesla, which can get 4-5 miles range for every hour on a regular 110v socket and is often sitting in the garage when the sun is shining bright outside.

...

Keep in mind that batteries are storage and not a supply. Lithium just happens to be better than lead acid at doing this for most applications. Your Tesla does not run on lead acid batteries for several good reasons.

Lead acid is pretty much a relic of the past. Still handy in intermittent use (hunting/fishing cabins)and locations that cold temperatures may be an issue.

 

[45North]

I wouldn't be swayed too much by the fact golf carts still use lead acid.
At some point they'll see the light and switch to LFP too - probably as they need to replace old stock.

 

[JoeHam]

Why not ride a horse instead of drive a car ?

Please yourself but a car makes more sense for the vast majority of people and their daily applications.

 

[sunsurfer]

Something to consider about LFP vs Lead. If you have a large enough LFP bank, you can capture what ever your panel throw at it. Can't do that with lead, to much charging resistance and if you don't use the sun some other way, it's missed power for the day.

Lead acid has to be topped off everyday but LFP actually does better not topped off everyday and will last longer. Of course you might need an active balancer if you do it often or run some cells in parallel helps. Point is, you stay in a low resistance window and the controllers never have to throttle down. You capture all the sun. And you can be in the very high 97%+ percentile range.

You will harvest much higher kwh's with LFP

 

[Glock24]

I started my solar energy adventure 5 years ago. At that time lithium was absurdly expensive, at least where I live. I made a little research and got the best batteries I could find locally, which were some Trojan 6V 415Ah lead-carbon "solar" batteries. As my system was 48V it was 8 batteries.
The batteries were marketed as 415Ah but usable capacity was actually around 128Ah with my discharge rate and charge/discharge losses. I spent like $5k for those.
It was a chore maintaining them, I spent like $10 a month in distilled water (it is expensive here) and double that during the hot months. Plus the time to check SG and water level, euqlize them when needed, cleaning them, etc. It adds up.
This year's dry season was really hot and I had to travel for 4 weeks because of my wife's health issues, I was not there to babysit the batteries. When I came back they required almost a gallon of water each. About a month later batteries started failing (at least two of them). I was two months from breaking even on my initial investment, but maybe I was past that point because of energy costs increase and having energy during outages. Who knows.
While I was looking for replacements (which I were not in stock and were at least $650 each) I was offered some used LG 48V 125Ah modules for $500 each. I got one to try and it replaced my 8 Lead batteries with almost the same usable capacity. I was thrilled! I bought another module the next month and in the end I got 5 modules. I got around 25KWh worth of batteries for $2500.
Of course this was a one-off situation, but I would never ever go back to lead batteries.