Or “How to not pay full price for your portable tool battery packs ever again.”
When I first started purchasing Electric Kobalt lawn tools (lawn mower, edger, blower, etc.) some of those came with 2.0ah batteries, while others came with 5.0ah batteries. The lower capacity batteries have begun to give up the ghost with very low run times so I checked prices for replacements, out of stupid curiosity. They don’t even sell the 2.0ah anymore, but the 2.5ah 40V is $79.98!!!!!!!
If I had to replace the 5.0ah battery that I use for the lawnmower, that’s $149!!!!!!!
So I decided to take the weakest 2ah one apart.
Now I know why it’s so much lighter than the 5Ah one. It’s only got half of its battery cell slots filled. Arghhhh!!!!!
40Volts and 2Ah of capacity with just 10 cells means only 2000mAh 4volt cells in series.
Fairly good construction but they’re using way too much energy when they spot weld the metal strips to the cells. When pulling them off it ripped holes in the cell’s case.
After removing them all I inspected them for damage and checked their voltages. Nothing extreme, but they weren’t perfectly balanced. Which they should have been as they were all in series. Meaning? Some of the cells are definitely struggling.
I know it sounds crazy, and “don’t try this at home kids!”, but I wanted to see how much capacity they still had remaining.
Keeping a close eye on them for leaks, deformation, or getting hot I took the time to perform a capacity check with my Opus BT-C3100, using 500mA for charge/discharge, the most gentle setting. I guess those holes aren’t all the way into the “jelly roll” because they all cycled up and down without a problem. Not that I’m EVER going to use these cells again but they all came in around 1300mAh capacity.
FUTURE POST: How to turn a 2Ah into a 5Ah battery for around $50
And how do we do that you ask? Well, my company purchases refurbished or “new/old” stock cells that still have 95%-99% of their capacity remaining at a fraction of the price of new. And then our US Military Veteran interns and apprentices, looking for a new career in IT or High Tech, take the time to process and find these gems. We’re currently doing a feasibility study to see if this is something we could scale up and do at volume to help get Veterans back to work. If you’re interested in learning more or helping, please get in touch.
Now that we got it apart and we see the setup inside, we know how they make the 5Ah battery. It’s nothing more than twenty 2500mAh cells in a 2P10S configuration. And although there wouldn’t need to be anything different in the battery’s BMS, we’d still have to check that to be sure.
FYI, at the time of this writing we’re able to get 2200mAh cells for around $0.50 each, not including shipping, shucking, cleaning, capacity testing, waiting for 30 days to check for self-draining, and then discharging them to storage levels.
Stay Tuned for a future post where we tell the whole story of a possible future line of business that helps the economy, helps the planet, and helps our Veterans. See you soon.
Thales of Miletus 