Solar ammo can update (12/28/2022):
It’s been a while since I have posted. I have been working on and off (mostly off, such is life) on my larger build HERE:
https://permies.com/t/174618/Building-battery-generator
I am at a point on my larger build where I need to install a coulomb meter or charge meter. This is different from a regular volt meter on a lead-acid battery because the discharge profile of lithium batteries is so flat that measuring voltage alone does not really give a very good indication of total charge in a LiFePo4 battery. The charge meter also gives all sorts of good information like amperage and such.
Unfortunately I have had 3 such meters that have failed to some degree. These were cheap Amazon specials so I guess I get what I pay for, but I have a 4th(!) coming and I want to test it out by giving it power before I hook it up and install it. I plan to use my ammo can battery box as the power supply as it is very convenient for these purposes and I thought I would update it as it has been sitting around unused for 10 months.
The battery may have been a bit over discharged. I once discharged it to about 11.9 volts and apparently 12.1 is the lowest I should go. Yesterday I wired up an old laptop power supply (19v, 6 amps) and let it charge the battery box for a couple of hours. The charge went right up to 13 volts but quickly came back down to 12.6 volts, barely .2 volts above where it had been at after sitting for 10 months unused.
Right now I have sunny skies so I am letting it charge outside in the sun on a solar panel. I am curious to see if the solar panel charges any better than the laptop brick. I don’t know why it would, but I will report my findings.
Eric