I doubt that it'll work. Practically, you can get about half the current out of a cell that they say you can. The more current you take from a cell, the more sag you get. The older the cell you use, the more sag you get. You'll be losing on both counts using used cells in a 1P configuration.
Review my latest battery build? Molicel p42a 10s4p 21700
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It’s only really worth it if you are building batteries regularly. For a one off build, once you have bought all of the equipment its close to and possibly more than the cost of buying a new battery with proper cells.
I considered building one myself but the cost, hassle and especially risk of a one off high current diy battery wasn’t worth it.
A few bad welds can lead to all sorts of trouble.
I considered building one myself but the cost, hassle and especially risk of a one off high current diy battery wasn’t worth it.
A few bad welds can lead to all sorts of trouble.
You are right of course. I am only really trying these things for interest/'a learning exercise', and as a retired industrial chemist I am fairly used to dealing with hazardous materials. So bearing in mind Saneagle's comments I will try a build of a 3P,10s (done in the 'lean-to' outside), for which I still have just about enough 'good' cells. However I will initially experiment without a BMS which often seems to be root of too many problems of its own (but I will include a cell voltage monitor) . It goes against the grain to bin anything which might (safely) have a second life, and which originally 'died' before its time.
You can build a 36v 10S battery in two halves a 5S with two 5S balance connectors on them, then you can use a lipo balance charger and two 5S cell alarms, or you can do the same with two 6S packs. That's quite a lot of messing about, and by the time you get all the stuff, it can be more expensive. I used to do all that, but now I find it easier to fit a BMS to have plug and play charging and use.
If you just want to test a load of old cells that are going to be all over the place, the lipo method might be better than a BMS because you can see what's going on with the cells when you charge and discharge, so you get clues as to which cells to chuck.
Just as an update, I’ve put many miles on the battery, and all I can say is WOW. These cells are nuts- the added capacity is incredible.
If anyone is having trouble choosing between 18650 vs 21700, it’s a no brainer IMO. I’ll only be building 21700 from now on.
These cells are great.
If anyone is having trouble choosing between 18650 vs 21700, it’s a no brainer IMO. I’ll only be building 21700 from now on.
These cells are great.