Sometime early last year I bought a pack of 4 lithium ion cells for no better reason than that they were crazy cheap, and seemed (to my befogged consciousness) like they might be useful for portable radio. Then, to get some use out of them, I needed to get a battery management system board (or to be precise, 3 of them, due to the quirks of Amazon marketing (pay $9.47 for 3, or $11.76 for 1? )).
After a year or so of neglect, I found the BMS boards the other day, laying around on the bench, and started searching for the cells … eventually turning them up on a shelf over the bench.
This project was so overdue, and seemed so simple, that I invoked the Just Git ‘Er Done clause and started right in: snip off connector, strip & solder black wire to 0V pad. Snip another connector, twist red and black wires, solder to 3.7V pad. Repeat, at 7.4V pad. Red wire to 11.1 volt pad. Simple, right?
Uhuh. Not so fast!
Unsolder one connection and untwist tangled wires. Still not possible to stack cells neatly; unsolder another wire and add an extension. Do it again to another wire. Okay, that’s better.
Cut off a foot of 16 AWG silicone zip cord and affix powerpoles to one end; solder the other end to the board. Some Kapton tape. Find a long, skinny zip-tie and complete the assembly.
Nice! It works! 11.4 volts at no load. I charged it at 1 amp constant current for 5 hours, now it’s 12.26 volts no load. I’m going to put it through 3 charge / discharge cycles in the next week or so; if convenient I might try measuring the amp-hour capacity, too.
I will update this post with test results; thanks for visiting driftlessqrp!
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