Electrified Downhill bike

[BrianG]

On the topic of charging: A simple way to do it would be to use a transformer that, when rectified and filtered, has ~5v higher voltage than the max voltage of the pack you are using, set up a constant current charge circuit (pretty simple), and then use a comparator IC that shuts off the charger at 3.6v/cell. It won't have the CV charge phase, but from what people say, very little charge is done at that point anyway.

So, if you are running 14s packs, that's 50.4v. Add 5v (to account for current source dropout) for 55v. The Y23695 3 in the link above would be ideal; wire the primaries in parallel and the secondaries in parallel, use bridge rectification, around 0.5F capacitance (can use an inexpensive car audio cap). The 40v AC output would be around 56v once rectified and filtered, and would provide over 10A charge rate. Add the CC source and cutoff circuits and be done with it. Balancing, if desired, can be done using multiple balancers, just overlap a cell on each so they are in sync.

Of course, this doesn't have cell count protection, but since it will be used just for a single application, it's fine.

[zeropointbug]

That sounds like a good idea actually... although half the stuff you said went over my head (source current dropout? )

I checked out the transformer, 15lbs is quite heavy, but it's not moving anywhere, who cares I guess. IF this were to be used I might want to get the BMS then as I takes care of balancing while being charged. 10amp charge sounds really nice, as it will be charged on a 720i at about 9amps, each side, so you have to do that twice. Looking for a dual output charger that can charge 7 cell packs... why not a 710i DUO, Hyperion?


Also, for another idea for emergency charging, say you are away from your charger and don't want to use your own effort to bike back (far away), I was thinking a small charging circuit built into the battery case. I was thinking just a couple amps at the most with a built in AC socket with protective rubber plug with a PC AC cord somewhere on the bike stored away.