I didn't add a BMS, I simply use an off-the-shelf balancing charger made for RC LiPos. It's great because you can set the termination voltage, which I usually set to 4.0v/cell for normal use instead of the typical 4.2v/cell. This MASSIVELY extends the life.
Here's a picture of the setup: http://ingineerix.com/pic/?dewalt-balancer I just bought a cheap knock-off charger on Amazon (https://amzn.to/4nGGVSb) that had all the terminals and removed the PCB and soldered in external balance and charge leads. On Wed, Oct 8, 2025 at 6:14 AM Rod Hower via EV <[email protected]> wrote: > I also use Dewalt 20V tools. I have 2, 20V 5Ahr batteries and several I've > bought from Amazon that are supposed to be compatible. I would really like > to see the design used for your BMS. I have several drills with 20V 2.5 > Ahr packs as well. My grandkids have 5 different Power Wheels ride on toys > that I acquired with dead 12V batteries for either $25 or free from > the trash. I changed the programming on one of my BLDC external controls > so it operates like an H-bridge brush control. The switches on these toys > simply reverse the polarity on the PM brush motors for reverse. With my > control I can ramp up the acceleration and use a controlled reverse so it > doesn't slam the gearbox. I use the 20V lithium packs on all of these and > can adjust the top speed, typically a PWM at 20kHz that supplies 12V to the > motors (I can crank it up to 20V, but they go too fast for the grandkids). > It's really amazing how long they can ride on a small 5 Ahr pack! > > On Tue, Oct 7, 2025 at 11:09 AM (-Phil-) via EV <[email protected]> wrote: > > > 2 things: Surprisingly most power tool batteries DO NOT BALANCE! I was > > shocked 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 <[email protected]> > 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: < > > > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20251007/272c5e3e/attachment.htm > > > > > _______________________________________________ > > 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: < > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20251008/5d132885/attachment.htm > > > _______________________________________________ > 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: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20251008/0ecf2752/attachment.htm> _______________________________________________ Address messages to [email protected] No other addresses in TO and CC fields HELP: http://www.evdl.org/help/
