Izip Trialz double battery pack.

[Graygray]

I have an Izip Trialz Al with 2 battery packs, I have seen a chap in USA use a different controller and use both battery packs together at 48 volts giving his bike a better top speed. I have no idea about electrics but I would like to know how to increase the speed of mine, I'm not looking to go mega fast but the bike struggles to pull me and only does 11mph on the flat, I would like to go at least the 15 mph the law allows and of course a little faster off road. can anyone advise me, in laymans terms please?

 

[Andrew Hodson]

I'm thinking of doing this + mine Izip, I'd bought 48 volt 1kw rear wheel kit sans battery 1st.
In theory voltage ~ speed of motor, but too much could over-heat it.
& even +2 times power, you'd only get 13 mph, if it needed all its power to do 10.