Increasing controller power to my 1000W DD hub motor

[Yungyakz]

I have some generic "48v" 15FET controller that was "rated" for around 30A, got peaks of around 33-35A ish. It had two shunts in it. I added a third shunt (from some random dead controller) in parallel with the first two , and that upped it's limit to around 80A. I have no idea what the original shunt or new shunt values are, it was just an experiment to get more oomf from a cheap controller with as close to zero effort and cost as possible.

So far, it's still working on SB Cruiser, and it sees that 80A ish peak every day dozens of times during my work commute in traffic, for seconds at a time. I have no idea if it would last if I kept pushing that limit up a hill, at least not any longer than it takes to go up some of the canal-path road-underpasses, which is under 30 seconds.

Some time back, I had an 18FET controller from someone that had been shuntmodded by addng solder to the shunts, and again I don't know the before/after values, but the contorller itself failed when used on CrazyBike2 for acceleration testing...something that works fine with the 15FET modded controller with a more power-hungry motor on the much heaver SB Cruiser trike.

So...a shunt mod may get you quite a bit more power, but it might also destroy the controller, if it heats too much inside. (it's also not just up to the FET specs, but also how the controller drives them; sometimes it's done well, and sometimes nto so much...the latter can result in more heating for the same conditions otherwise, and earlier failure under "overclocking" conditions).


If you're planning on replacing the controller anyway, if it doesn't do the power you want once modded, it won't hurt to try a shunt mod.

80a thats some current on generic 1500w controllers. what motor did you dump it on and did you beef up traces replace motor phase wires etc.

 

[amberwolf]

80a thats some current on generic 1500w controllers. what motor did you dump it on and did you beef up traces replace motor phase wires etc.

No, I didn't change anything except adding that shunt. I didn't really expect it to survive very long, but it has.

It's on an MXUS 4504 in a 20" wheel (closer to 22" actual diameter with the Shinko SR714 tire on there, IIRC).

The peak current is only for a few seconds at most, and the controller is in airflow under the trike bed, as are the phase wires...but those wires do get warm during repeated acceleration and braking.

I doubt I could do a hillclimb with it, by itself. :lol:

 

[Jan-Erik-86]

I've now been pedaling around for about 500 km since the shunt mod, and everything works perfectly as it should.
After a 1.5 hour trip today, also with some hills and several start and stops, the controller FETs never got above 35c.

So, just curious, as it appears the FETs are able to stay really cold, even for longer rides and occasional hill climbs, does that mean that it would probably be safe to go even a bit further with the shunt and up the current to maybe 45-50A or so (as long as i keep an eye on the temp)?

 

[fechter]

On one of my bikes I'm running a 12 FET with IRFB4110s. 40A is no problem. I can get it up to near 60A for short bursts.
I think yours would be fine up to 45A or so as long as you watch the temps. Climbing a long steep hill is where you get a lot of heating.