controler power mod

[dylan]

hi guys
I want a bit more oomph from my 2nd (backup) electric bike
Its a Thompson K2 MTB 250W originally 24V
I normally run it with my 48V pack from my main electric bike
I have pulled the little 6 FET controller apart to look at possible doing a shunt mod to up the amps a little
1st problem is I can't find the shunt
2nd problem is the capacitors in the controller are rated at 50V (possibly to low for my 48V pack?)
I would ideally like to just put a KU123 controller on it but this would be a physically bigger controller & not fit the original frame slot on the bike
the original controller is 85L x 68W x 34H , (KU123 is150 x 88 x 44)
I know I could mount the controller in another place but I currently have it hidden under a water bottle for stealth reasons
so I guess my main question is how much current can I squeeze through this little controller?
if I can't get 20A it's not worth messing around with it & I will go with a relocation on a KU123
or is there a physically small controller with equivalent power of the KU 123?
I have uploaded some controller pictures

 

[d8veh]

There's the shunt grinning at you between the large capacitors and the CPU. 20 amps should just about be doable. Start with soldering about 20% of the shunt. Use a wattmeter or voltmeter to measure the current before and after so that you know what you've done.

 

[dylan]

Thanks d8veh i'll give it a try

 

[Punx0r]

I'd check the part number on the FETs and see what their ratings are. I would also seriously consider replacing the electrolytic capacitors with 63V rated ones. Just check there's room inside the case as they will mostly likely be a little larger.

FWIW you should have no problem running 20A on a 6 FET controller. My kit came with a 6 FET controller running 22A continuous (1000W). I turned that up to 50A peak, then to 70A after replacing the FETs as a precautionary measure.

 

[dylan]

Thanks for all your help guys
I have soldered a copper wire along approx 50% of the shunt
I haven't changed the capacitors or measured the current, I have just 'winged it'
The result - much better acceleration & around 21 mph - that will do nicely...!
I have a KU123 controller on order anyway, so if this little controller goes up in smoke I have a spare