I’ve used the Ryobi One+ system since the days of the blue tools / yellow NiCad batteries.
I’m well familiar with the problem you describe. I’ve inspected dozens of the various Lithium protection boards and despite seemingly complex circuitry, I’ve never once seen any evidence of any balancing capability whatsoever. No bleed resistors, transistors etc. And I’ve done tests leaving working, but unbalanced packs on the charger for days - in the green light / fully charged state - and the cell voltage differentials never move.
My method for “ balancing” is simply using 5 separate isolated 1 cell chargers, all at once, connected to the individual cells with small flat-jawed copper alligator clips. I have a plug strip with 5 of the 6 plugs occupied with 1amp apple 5w USB iPhone chargers. Each is connected to a TPA4056 1 cell eBay charger board.
If I were to build another I would probably use the newer TP5000 charger boards, and neodymium magnets instead of the alligator clips..
If you go for a similar setup, please beware of a couple critical points:
- you MUST use five **seperate** USB AC adapters. otherwise your outputs won’t be isolated from each other.
- you must be very careful to not connect any of the chargers reverse polarity. if you do then that module is instant toast, even if unpowered by USB 5v in. i recommend buy some extra modules for when/if you make this connection mistake.
- you bypass all bms protection with this method. if you want extra peace of mind you can get the charger boards with built in 1S single cell BMS protection against overcharge, overcurrent etc. I personally don’t use these because i had reliability problems with the particular ones/batch I tried. but I’ve never had an issue using the basic unprotected 4056 modules and have been using this method for around five years. And the (Samsung, LG, Sony) cells in these ryobi One+ batteries are pretty safe themselves..
This method is also quite speedy. I haven’t spent much time trying to come up with a more traditional balancer-type solution. I did try one of those new Chinese black-colored active buck/boost multi cell balancers earlier this year, and it functioned poorly.
Edit: I forgot to mention that you could buy five Olight 1 cell chargers instead of the 4056 modules. They have polarity-agnostic magnetic connections with automatic polarity detection. You still need five separate usb adapters. It’s a more expensive solution but less work and is basically foolproof. Good luck !
