My own battery + solar powered blog [0] is 100% inspired by lowtechmagazine.
I am based in The Netherlands and due to my sub optimal location, I have to cheat in the winter by recharging from mains about weekly. I still do get some sun, but nowhere nearly enough to get through the day, let alone the night.
And lead acid is also terrible for solar applications because no matter the capacity, recharging is very slow. Even solar could recharge the battery, the slow adsorption rate prevents it from doing so.
Lifepo or similar Chemistry is probably the better choice for a project like this.
> And lead acid is also terrible for solar applications because no matter the capacity, recharging is very slow. Even solar could recharge the battery, the slow adsorption rate prevents it from doing so.
This doesn't make sense to me. Surely you can reach a sufficient rate by adding more lead-acid cells in parallel? You're kind of forced to do this anyways since they don't like being discharged below 50% of their actual capacity. So you end up building in a shitload of excess capacity in parallel, in the process attaining high aggregate discharge/charge rates.
It's just annoying because you waste a lot of physical space on underutilized batteries. But for a stationary system, it's not such a big deal, assuming you're not trying to fit it into a studio apartment. You end up with a dedicated battery shed or cellar, at least they're cheap.
I actually run quite a few of them in parallel, but that doesn't solve the problem:
As the other person stated: charging lead acid is time constrained. And that means that you can't fully charge the battery within the time period when you have sun.
Lead acid deteriorates quickly if left (partially) discharged. This is why lead acid works so well with cars (almost always fully charged at all times).
Depleted lead acid (50% charge) needs to be recharged within 24 or serious damage will occur, accumulating over time. A week of bad weather may thus be hard on battery longevity.
Can't you just alternate between sets of cells with sufficient excess capacity then? They don't all need to be in lockstep at the same phase of their charge:discharge cycles if it takes so long.
Perhaps that becomes cost prohibitive even with the low cost of lead-acid, I've never attempted this. It just appears obvious from a high level that excess capacity can overcome all these limitations.
Lead acid have the advantage of being easy to buy and needing no balancer. Also they don't get damaged by overcharging. They handle full deplation way better too. Also lower initial cost.
Lithium batteries don't need a balancer either. I've been running a 3.6kWh pack of 12 cells for almost 5 years with no BMS or balancer.
I bottom balanced all the cells before building the pack and setup my chargers to only go to about 98%. This leaves more than enough leeway to avoid problems if one or more cells drift.
I've rebalanced a couple of cells once because they were off by a few hundreds of a volt. They're probably about due for another minor rebalance.
That said, this is in controlled conditions with regular use and monitoring. The cells are LiFePO4. I wouldn't run other chemistries without a BMS. Next pack I build will be much larger and have BMSes for safety and so I don't have to think about it.
Hmm ok. My experience with Lithium batteries is with EVs. Do you have a low discharge rate on your pack? Because the EV battery pack needed balancing like every charge. Otherwise it has to be a quality difference.
Most EVs don't use LiFePO4 although some are moving to it. There are also hundreds or thousands of small cells in most EV packs. With that volume you'll get more variation between the best and worst cells. You also need it to be foolproof and require no maintenance.
My average discharge rate is much lower than 1C which does help. The max is around 0.9C but that is pretty uncommon.
[0]: https://louwrentius.com/this-blog-is-now-running-on-solar-po...
And lead acid is also terrible for solar applications because no matter the capacity, recharging is very slow. Even solar could recharge the battery, the slow adsorption rate prevents it from doing so.
Lifepo or similar Chemistry is probably the better choice for a project like this.