Phil wrote: > Surprisingly most power tool batteries DO NOT BALANCE! What about adding a simple balancer? For example, some sort of zener-diode-like device across each cell to clamp its max voltage.
Years ago, I designed the zener-lamp regulator to balance lead-acid batteries. <http://www.sunrise-ev.com/LeesEVs.htm#zenerlamp> For a string of 12v batteries, it was just two 5w zener diodes and a 2.5v 500mA flashlight bulb in series. The current was essentially zero at 13v, and rose to 500mA at 15v. I made a version for lithium cells, too. Zeners below 5v are poor regulators, so I used a string of 1N4001 diodes in series to get the desired clamping voltage. There is room between the cells to add something like this. Lee -- Excellence does not require perfection. -- Henry James But it *does* require attention to detail! -- Lee Hart -- Lee A. Hart https://www.sunrise-ev.com I wasshocked to find this out. I bought into the DeWalt series, and I've always treated my tool batteries very carefully, but when I tested, I found many old packs wildly out of balance. The charger still senses the strings, so nothing bad will happen other than shorter pack life. I've since built my own DeWalt charger with balancing, and adjustable cutoff, so I can charge to much lower voltages if desired (which I usually use). The other issue is, unless you get lucky like Bill, these packs are super expensive for what they are! -Phil On Tue, Oct 7, 2025 at 6:52 AM Lee Hart via EV wrote: > Bill Dube wrote: > > Awhile back I adapted a ~40 volt Ryobi lawnmower battery to fit my > eBike. Seems to work perfectly. > > A friend of mine did something similar. He converted a go-kart to EV with > six 18v Ryobi battery packs, an Advanced DC motor, and golf cart > controller. He opened the packs and bypassed the internal circuit breaker > to get more current. My gawd the thing was fast! > -- > Excellence does not require perfection. -- Henry James > But it *does* require attention to detail! -- Lee Hart > -- > Lee A. Hart https://www.sunrise-ev.com > > _______________________________________________ > Address messages to [email protected] > No other addresses in TO and CC fields > HELP: http://www.evdl.org/help/ > > -------------- next part -------------- An HTML attachment was scrubbed... URL: _______________________________________________ Address messages to [email protected] No other addresses in TO and CC fields HELP: http://www.evdl.org/help/ _______________________________________________ Address messages to [email protected] No other addresses in TO and CC fields HELP: http://www.evdl.org/help/
