Jump Starter Battery Pack

Solcar

10 kW
Joined
Jan 7, 2010
Messages
508
Location
Ohio River Valley
Things have been pressing for the last several years. The ebike project had been sidelined for a long time.

I had mostly finished a controller/charger device and was hoping to try it out on my custom friction drive that had drawn upon ideas from the community here.

But then the floor of a third of the house collapsed last summer. Now, I am looking into a simplified electronics system for the ebike project. I am reluctant to put the same level of mental focus on it now.

I see three options to consider now. I don't plan to ride very fast or far, so a lower power set up is okay. That is a reason why I put extra down-gearing in the friction drive assembly at the rear bike wheel.

One option I have is a $15 lead AGM battery. That is about the max weight I want to carry in a battery. That would only give about a 7ah capacity @12v. I would have to make a voltage booster as part of the controller, since 12v won't give enough power or speed from my 2 pound Pittman brush motor, even for my relatively light requirements. My last working ebike did that and I know how to do that type of thing. But a downside of that idea besides low capacity, is disposing of the agm battery after it's relatively short lifespan.

The next ebike power idea I was considering was a power tool battery set-up. Some concerns with that idea include relatively high cost per watt hour, having to have a receptacle on the ebike to plug the battery into, and, and relatively low energy storage in such a battery pack. The advantage is plug and play charge and power. That would allow me to eliminate having to worry about making my own charge circuit or fussing with various plugs and monitoring of balancing and voltages on individual battery cells. Another upside is that 60v batteries are available, eliminating the need for me to have to build voltage boost in my motor controller.

I been mulling over a third battery option lately. I have been looking into some vehicle jump starter devices. They have relatively low capacity, but that isn't too much of a problem since I don't plan to ride more than several miles. The upside is they have easy power output access in the alligator clips, and they supply relatively high peak amperage. 24v ones are available, which would simplify the boosting circuit I would need in my controller, since voltage doubling tends to be easy and efficient. I could double that 24v to 48v, which would be a fine upper limit to drive my Pittman 12v motor with. The control will have current limiting, like I did on the last controller in the now defunct last ebike project, to protect the motor when being overvolted.

It would be kind of nice to be able to take it more easy riding this summer. There are a few hills that tend to put a strain on my joints, and I would like to stay cooler as well.

5/4/17: I have changed the basic approach of the controller a bit. Instead of push pull transformer drive supplying voltage boost to the motor, I have redesigned it to use two interleaved boost circuits, 180° out of phase (the easiest interleaving timing by default). This way simulates much more smoothly and with a quite fewer number of parts. (I am using either the SG3525 or the KA3525 pwm IC as the controller IC.)
 
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