Quote:
Originally Posted by Piwoslaw
The wife recently came across some blog with people who use huge banks of old 18650 batteries (hundreds or thousands) from old equipment and appliances for energy storage, like a DIY Tesla Powerwall, but for a fraction of the price.
The ones I've seen claim that the more batteries you use, the lower the current running through them, which extends their useable life. This supposedly makes any safety risks negligible.
I admit that adding 10-20 kWh of storage to our PV system for the price of 3-5 kWh is tempting, but...
Just skimming through search results showed that some experimented with AGM batteries (instead of 18650's), but with worse results.
I haven't found anyone trying this with cellphone batteries, of which there are more and more in the waste stream.
Anyone here tried this, or came across anything interesting?
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I did it with a score of LiFePo4 batteries (see photo). I'm pretty good at this but the problem was balancing. I tried several systems and even commercial ones but could never get the batteries at high enough voltage for decent run times.
As you approach 3.6v on LFP batts the internal resistance rises and when that happens you start getting unbalanced cells.
I'm using the batteries in my electric tractor this summer and went with EG4 batteries from Signature Solar. They run 7k cycles with deep discharges and are much better in my system.
I went with three of these:
https://signaturesolar.com/eg4-lifep...ery-48v-100ah/
I can monitor each cell, the charge level, battery life and health and battery cell differentials. (see photo)