OK, I'm a bit of a duffer when it comes to electrics. I've acquired a couple of 24v NiMH battery packs off ebay, and I want to hide them in my panniers and use them to extend the range of my bike. My Currie Electrodrive has the Motor controller built into the bottom of the standard lead acid battery pack.

 

Do I need to use diodes to prevent battery current from the spare pack getting soaked into the lead acid batteries when I splice a new cable in to the wires going to the motor controller from them, and vice versa? Or should I arrange a 4 pole switch to make sure the current is always discreet in a more obvious mechanical way?

 

Thanks in advance for any advice. :o

I would go for the switch option. At least you'll know that only one battery is powering the bike at any moment. Plus when you are out on the road you'll know when it is time to swap over to a different battery and this will help you guage your remaining range to ensure you get home on power !

Switch is not only safer but more efficient, since diodes involve losses. Not only that, the currents taken by these motors peak at levels which would mean the diodes would need to be mounted on a heatsink somewhere.