Designing the smallest charger, starting with the batteries

[hillyterrain]

It would be really nice if the charger would be so small that it can be a natural part of the battery pack so you can just plug in wherever, so in order to design the smallest charger possible, the charger should do as little as needed, e.g. no voltage transformation. In the US with a lucky 110V AC, the negative half inverted and the whole sine averaged should give 110V/0.636 ~ a 70V battery pack. If you don't need a system with that high of a voltage I can imagine having a split 36V parallel system that gets reconfigured in series for 72V while charging ..

Am I on the right track here or is this pure fantasy? Can you think of other tricks to bring down the charger size?

 

[999zip999]

To power what ? And how far ? At what speed ?

 

[hillyterrain]

Totally independent of any other design parameters, what is the smallest charger that can be built? I think it's the one that only inverts the mains voltage without transforming it..

 

[knighty]

google capacitor battery charger

basically your rectifier system, but with a capacitor too, which is much better because it limits the amp output of the charger

often called a constant current charger... but they're actually a constant power charger... so you'll get the same watts out no matter the voltage (within reason)

then all you need is something to trip/turn it off when the battery is full

 

[spinningmagnets]

http://endless-sphere.com/forums/viewtopic.php?f=14&t=42169

$130 each, They are out of the box adjustable in voltage and current, available from many suppliers, and come with a 5 year warranty. They are silent, potted and very efficient. They just get warm when silently putting out 25 volts at 12 amps into a 6S Lipo bank. You can set the voltage and current and plug one of these into your 6S pack, or series two or three of them and plug them into your 12S or 18S pack and they will bulk charge them nicely

 

[dogman dan]

Looks like a robust solution for a bike mounted charger, when combined with the lipo protection boards. Potted, they could be mounted in horrible locations like the bottom of the downtube.

 

[velias]

Theres usually a reason why chargers are not put on the bike,
Its so bouncy and exposed to elements. The components in the charger are big and heavy and usually end up breaking off the circuitboard.
its hard enough to keep the caps from a cheap chinese motor controller from breaking off.