Poor man's smart charger - reload

[AZguy]

I've mentioned many times about how I've put some diodes in series on cheap charger outputs to limit the termination voltage and it's always worked pretty well

I've got enough batteries now that I wanted to be able to get them to a better "storage" voltage since they often sit around for a while before I use them so I built a much longer string. I got a bunch of cheap 6A Si diodes at a local place for ~$0.15 each and put ten in series plus one schottky diode. Each Si diode gives me a little over 0.5V drop at termination and the schottky about half that for fine tuning. With them all in series it drops about 6V at termination although it creeps down very slowly but that's more than enough to only get a 52V battery to the ~70% "storage" voltage. I use an alligator jumper to bypass however many to get anything between 70-100%...

YMMV

[Sebz]

AZguy Wow I missed that post.. very smart!!! Thank you for your contribution :)

[bpratl]

Thanks, very good, simple and efficient idea.

[AZguy]

I use it all the time with the 2-3A chargers. It works really well considering how simple it is.

When I put a fresh battery on a bike I'll take the old one off (I log the details - start and finish voltages, distance, moving time, Ah, Wh, etc.) and charge it to about 3.7V per cell. When it looks like I'm going to need a battery soon I'll take the appropriate one in rotation to about 3.9-4.0V/cell depending on how soon I think I'll need it then top it to whatever level appropriate for the riding and take into account the last time it was charged fully to ensure balancing enough.

They get hot at 2-3A. They are 6A diodes and made to be able to get hot - too hot to leave a finger on but not hot enough to burn but the diode junctions are rated to get silly hot and even if they failed the worst case is they'd either open or short and neither would hurt the battery - so I don't worry about it but I don't think I'd do this with the 5A charger just because they're likely get hot enough to burn skin. I generally only use the 5A charger for the monster battery and that charger has three charge levels anyway (storage, ~90% and 100%) and only gets used on smaller batteries when in a big hurry which isn't often... but every now and then I'll get that phone call to go ride and want to top off quickly...

[hoggdoc]

Another brilliant thread I didn't see it until I bought a Luna charger that has settings for 80, 90 and 100% charge.