Retrofitting a battery pack into an ebike.

Ok I was just looking at this ible. And noticed the type of battery the guy used.  So I did some googling and ended up here. Wondering to myself about trying to retrofit this type of battery into a veloteq challenger from 2008 or so. Remembering that its a 48 volt pack built from 4x 12volt lead acid 20amp batteries(cells) wired in series thus to stack the voltage and not the amperage.  

Now I know amperage is simply a measurement of consumption so I'm guessing that these Yellowtops are way above the usual 20amp's that the veloteq asks for but I'd imagine that shouldn't make much of a difference.  Seeing as I only want to throw on two of these as to not blow way past  the weight restriction on the ebike itself by hitting 48 volts with four of these also to avoid breaking the bank with an 800$ purchase.  Could I not add some sort of transformer to step up the voltage to 48 volts or something like this?

Any suggestions are welcome but I can't imagine this would really be all that bad of an idea.  I'd imagine it should boost the range somewhat if not a fair bit.  I'd imagine that my assumptions here are not far off but I'm here to either be validated or corrected. Or even educated if someone has any suggestions or advice.

sort by: active | newest | oldest
chamunks (author) 4 years ago
Would I not be able to use a 12 volt to 24 volt step up transformer on each of the two Yellowtops?
jbrown794 years ago
of course there's a way. but why?

you have an electric scooter powered by 4 12V 14 amp hour batteries ran in series for 48V.
you wish to increase battery storage presumably for range.
you're main concern is weight.
the chosen Yellow top® lead acid batteries give double life for double weight.

the answer to me seems simpe. Drop the lead. you can source Nickel Cadmium or even lithium ion rechargeable easily enough. every cordless power tool has a battery pack that consists of multiple 1.5V 3000mAh ran in series to get desired voltage. every junk cell phone has a Li battery most 3.7v i think. i would build me a number of battery packs that push out 12v probably get 4 in series in the space of 1, def in weight.
definately keep NiCd and Li in seperate battery packs.
also adding a solar panel if your needs are something like enough range to destination, no place to charge, extended time at the location, not enough rang for home. or also maybe carrying an extra 12v power source, like a car jump starter to resupply your batteries.
chamunks (author)  jbrown794 years ago
I had a friend who wanted to tote around an portable jump kit on his bike too.
A solar panel adds an entirely new level of complexity again though if ultracapacitors were a bit more economical it would be a very good solution.

If we were going to re engineer this from the ground up I'd like to talk to someone who does free design work in 3d cad software so we can build something awesome but thats an entirely different story.
chamunks (author)  jbrown794 years ago
I've been conciddering this building a pack from used batteries but I feel like it would be much more difficult to charge going this route. I wouldnt be going for 4 of the yellow tops in my suggested configuration above though I'd just go for two equaling 52lbs of battery weight and than attempting to add a step up transformer. I would imagine that shouldn't be too unreasonable?

But you're likely right I could get in touch with some scrap dealers for battery packs.
chamunks (author) 4 years ago
Heading to bed I'll check this in the morning before I head out again. :)
lemonie4 years ago
You want more range by adding more capacity?
You'd probably do best to replace the motor as well, rather than try to assemble a 48V supply.

chamunks (author)  lemonie4 years ago
Replacing the motor goes from attatching some wire and soldering some pcb stuff to custom fabrication of metals and sourcing an appropriate motor.