performance

Panasonic have designed these as sealed repair-by-replacement units and have never issued full technical information or circuit diagrams. However, there are some ways in which the performance of e-bikes using these units can be increased as detailed below:

36 volt units

This is is the only mention of these in this site. There is a dongle available from mid 2013 which enables the road speed power cut off point to be nearly doubled from 15 mph/25 kph to circa 28 mph/45 kph. These are sold by the e-bikeshop.co.uk and further information on them is in a thread on this link in the pedelecs.co.uk website. For any queries on these, please phone 01420 544999 and ask for Martin.

Another method of increasing the assist speed is to alter the position of the speed sensor and magnet. As standard the magnet is on a rear wheel spoke with the sensor on the rear frame reading the wheel rotation speed. Sensing the slower rotating speed of the crank in top gear instead enables the cut-off to be increased.

26 volt new units

The performance with these can be enhanced in two ways. First the cut-off speed can be increased by simply changing the gearing which is not possible on the 36 volt units, therefore no dongle is needed Full information on changing the gearing is given within this site on this link.

Second, the power can be increased by altering the resistance of a shunt within the unit. Be aware that this will breach the warranty conditions and no guarantee can be given about the consequences in terms of wear and overheating of the unit and excess bike transmission wear.

To carry out this modification you'll need to remove the unit from the bike and open it up. The photos on this page will help with the removal and this page for the old unit will help with the opening up procedure.

Within the unit you will see this goal shaped shunt arrowed on the right. Normally shunt resistance can be reduced by soldering up from the base of one upright to thicken it, but the encapsulation of the board prevents this. Strapping across the uprights with wire binding works though, and this can increase the output on the pedal torque sensed peaks from circa 400 watts to as much as 900 watts. The wire can be soldered to the uprights to ensure secure connection.

The graph on the right shows the standard power outup of circa 400 watts on the pedal thrust peaks. These can be more than doubled, but I personally don't like the result due to the jerkyness of the power increase output. In my experience the Panasonic units smoothness of operation was best of all on the earlier low powered unit, and each power increase since makes the power delivery less smooth. That's probably inevitable, given the way the torque sensor operates the motor in a servo motor fashion. Again I stress that I have no idea how long the unit will last with this modification.

24 volt old unit

These units do not have a shunt which can be modified and no dongle is available. Therefore only the road speed power cut-off point can be changed in the same fashion as for the 26 volt units, details on this link.

It may be that the 36 volt unit also uses a shunt like the 26 volt one, if so it may be possible to increase the motor power input as well. For more details on that method see the 26 volt unit information below.

This photo of the modification on his BH Emotion bike kindly supplied by pedelecs member d8ve shows the details. My captions show the sensing pickup is repositioned outside the chainstay and near to the left hand crank end, surplus lead being stowed under the cowling. A suitable rod or bar magnet is fastened with araldite or similar to the crank arm end. To ensure the magnet polarity is correct it should first be tried fastened with PVC tape before permanently fixing in place.

This quick and simple modification makes the bike much faster and easily able to cruise at 20 mph with motor assistance. And of course it's easily reversible if required at any time.