Upgrade Heinzmann to lithium

[gregh3269]

Hi,

I am trying to change my classic ebike Heinzmann 36v 9ah nimh to use a lithium ion battery. I have chosen a 10s 3p lithium 7.5ah battery using Samsung INR18650-25R cells. My motor is 500w imax 30A and controller imax 25A. I have disabled the half voltage on the control board.

The main problem now is the throttle action is very different. Before it had a smooth acceleration, but now it lurches/surges and blows a 25Amp fuse I have on the battery. I think the battery is delivering too much current. I could increase the fuse to 30A but I think it may just damage the motor/controller due to the current surging.

I have read here other conversions seemed to have worked with a much larger battery and was wondering have I now got the wrong controller imax. Maybe I need a higher imax controller or a possibly different battery chemistry.

For the controller, I think there is a resistor that sets the imax current, does anyone know the resistor values for 30amps? (or 33amps) this would then match the motor and may be work better??

Any advice would be greatly appreciated.

Cheers Greg

 

[gregh3269]

Increasing the fuse size would only make it surge more? If I spin up the motor with no load it surges rather than a slight delay then slowly accelerating (with the old nimh battery) which is my main issue. I cycle in London traffic so don't want it to suddenly accelerate!

I think the max rating Heinzmann use is 30A, which I might try as the controller can handle up to 33A (since they all the same except for the imax resistor). I did look a at small resettable fuse but they seem to only be rated to 20A.

I might try and discharge the lithium battery (to 36v) and see if the controller would work with the lower voltages.

There are some notes on the kinetics website http://www.kinetics-online.co.uk/technical-info/heinzmann-technical-info/ which show the 32a imax resistor value 4.61 k :

4.86 k 22A
4.64 k 28A
4.61 k 33A

My 25a has a 4.74kohm (measured with my meterman).

The resistor colours on my 25A are something like (as its difficult to see):
brown, red, violet, gold, gold (== 120MΩ 5%) ??

4.74k is:
yellow, violet, yellow, silver, red (2%)

If anyone has a 30/33a controller and could let me know what the resistor actually is I would be most grateful.

Cheers Greg

 

[gregh3269]

I think I have resolve this, and seems to be down to the half voltage modification. I was following the notes on the kinetics website where you bridge the diode above the IC. There seems to be different controllers and on mine there is a diode left of the pedal sensor (below the IC). I removed this (and also the previous mod to bride the diode) and now its back to normal. Smooth acceleration and no fuses blowing. Credit for this goes to this link http://www.pedelecforum.de/forum/index.php?threads/hier-eine-anleitung-um-einen-heinzmann-nimh-controller-auf-nc-oder-lifepo4-umzubauen.19285/.

I would still like to up the power if anyone has a 30amp/resistor value!