@raccoon city, that is an excellent idea. It would have to be rather conservative however, as to only allow currents based on previous charging measurements or set in by the user.
Enable it to keep four cells in trickle charge indefinitely and put a floody LED with a smart (TK) user interface on it — so it becomes a grab-and-go item for those of us in earthquake territory.
@contactcr, no problem. Just upped the discharging current to 700mA. 1A could be possible, but you’d have to limit discharging current to 1A/2 bays to help with heat dissapation.
Also, putting a small aluminium heatsink on these resistors would help a lot.
@hank, that is easy peasy. Just set the charging voltage to 3,9V, and be off with it. Charge it normally up to 4,2V once you need it.
I love the idea of a perfect charger. I have to use a Folomov A1 to charge my Wuben 21700 that is 75.1mm. Could this project somehow ensure that the longest 21700s fit?
That is possible, but is slightly harder and more error prone.
Chemistry is just based on the internal resistance analysis, but it has to be conservative. Currently, the C4-12 that I have likes to go at 3A on my 30Q during automatic charging, while I would prefer 1,5A at max.
Length would be slightly harder, but would require additional hardware.
I would refer the option to custom selecting cell chemistry, type, size, and amps-charge rate when required, ( but have a auto 18650 LiIon & AA NiMH as standard automatic with a default charge rate, ( but also customizable. Also woudl be good to have one of the charge Bays adaptable with an output port, (the charger would be great with at least four bays) that output port would have leads for charging wired cells like square LiIon and other packs, large cells like 32650s, (i have 7 of them) and even have the lead-adapter with tiny magnetic positive & negative connectors so they can snap to everything in cell size from a 10180. I know cost may be an issue for that, but a true “universal” charger needs to be able to charge every type of cell at every amp range selected, and connect to them easily. One great single cell charger i really like that can charge nearly every size cell is the Olight mini USB magnetic charger, (I have 5 of them) ( that senses the polarity and charges them, But the only issue its set at one charge rate only.