When people come and test-ride electric bikes. The first reaction is usually an expression
of a pleasant surprise. Frequently,
customers will ask if the bike can be boosted to make it go faster. I thought I’d touch briefly on this topic.
Of course as soon as we discuss boosting the e-bike, we are
talking about increasing its power, which means it will no longer be street
legal. The ramifications of riding an
e-bike that is not street legal are:
stopped and tested, the police can give you a fine, and confiscate your
bike. This might not be very likely
if your bike has only been slightly boosted. But it becomes more and more likely if
you have some direct drive on steroids, sporting a 72V battery and 40A
you are involved in an accident, particularly with a pedestrian. Then the legal ramifications of being on
an illegal vehicle can be daunting.
So how do you boost your power output? There is no cheap way of doing this. Essentially, you need your electric bike motor
to have more input power, so your power output increases respectively. This can be done by changing your battery to
one with higher voltage (eg from 24 V to 36 V, or from 36 V to 48 V), and
change your e-bike controller Current rating to match (eg from 14 A to 17
A). Note, if you change only one, then
the result will be less than desirable.
In most cases your motor should be able to handle the extra input power.
The e-bike Controller has a Battery Management system (BMS)
embedded in it. The BMS will cut the
circuit if the voltage drops below a certain level (Min Voltage cut-off) in
order to protect the battery cells. It
will also cut off if the current exceeds a certain level (Max Current cut-off).
You could possibly just change the controller alone to a
higher rated controller. This will give
you an increased peak current. The top
speed will still be the same, but you’ll get to it quicker. The problem is that if it doesn’t match the
battery’s Max current cut-off, your battery will start switching off in the
middle of accelerating. Which could be
very unpleasant, and possibly dangerous.
The clean way is to change your battery so that the BMS Max Current
cut-off is about double the average current.
For instance for a 9 Continents motor, that is expected to deliver 800W
at 48V, the operating current will be 16.6 A, so the maximum Current cut-off
should be around 32A.