balancing storage

As you may know I like to get things as right as I can and if you've read my blog (and perhaps more specifically this post about my battery storage) you'll know that I keep going on solving until I get a result I'm satisfied with. Well after a little testing I'm comfortable to report that I've found a balancing solution (thanks to that guy on Reddit) for a small amount of money.

If you follow the wires you will see +ve from the A side goes to the 24V +ve, the black to the 24V -ve and the white to the place where the two 12V batteries are joined in series to make a single 24V battery.

The box is as simple as it gets, it "powers" itself from the battery its attached to and The A and B labels on the box have an LED which lights up when they are transferring the power. The manual says this about how much power it sucks from the system.

so not much goes outside the system from this and it even prevents discharging a pair of batteries not being charged regularly from being drained to death.

Its wired up like this

and as you can see will even scale up to work with more batteries easily by just adding more.

So as you may observe in the top picture there is a small voltage difference between the batteries, but this is just a calibration problem of those cheap voltage displays. I just couldn't get it to be less than 0.5V by turn and so the small differences present the way they are.

I don't mind really because at a glance I can see big problems (like more than half a volt) then I don't need to look further. Now and then I see what the voltages are with my Fluke volt meter, and they've been good.

So basically this unit helps to keep the drift of one bunch of cells (the 6 cells within one of the 12V batteries) getting too far from the other bunch of cells (within the other battery). The ideal would be cell by cell comparisons but as each 12V battery is sealed that's not going to happen without surgery. However my experience is that this system works pretty well.

As I discussed my existing system was indeed drifting, which is not surprising when you stop thinking of maths and start thinking about 1) chemistry and 2) the reality of productions. Tiny differences exist in things (except perhaps those made for NASA) and these set up the beginnings of drift. Things like

1. under load do all cells in a battery discharge the same? Does indeed each of the two batteries??
2. what about under charging?

So this system basically works electrically "inside the battery" to keep the two bundles of cells together.

The best thing is that this little box only cost $15

Fantastic

Win Win