Electric Bikes - adding extra battery for boost help please.

hi is their anyone with a good knowledge of wiring that could help me please ? i have a 48v 1000watt system on my bike the other day i added an extra batt to my pack to make 60v wired in series. worked lovely extra speed. i would like to keep the extra 12v but not all the time as i dont want to over volt motor all the time.i wish to use it as extra boost. is their a way i can wire it into system with a switch to switch it on when i wish ? any ideas ? diagrams etc. many thanks in advance.

What you need is a single pole, double throw (SPDT) switch with enough current-carrying ability to handle your system.

See the wiki link here: http://en.wikipedia.org/wiki/Switch#Contact_arrangements

You would use the second one down in the matrix.

Your common wire would go to your controller. Connect your batteries in series, +ve of the 48V battery to -ve of the 24V. Connect the +ve wire from the 12V battery to terminal L1. Connect a wire from the junction of the series connected batteries (where the +ve of the 48V battery connects to the -ve of the 12V battery) to terminal L2.

When terminal L1 is active you have 60V on the common terminal, when L2 is active you have 48V.

ps. If you have trouble finding a SPDT switch with sufficient current ability, try finding a double pole, double throw with at least half the capacity you need, then wire the terminals together in parallel, this will effectively double the current carrying ability.

hi thanks for that info. with this arrangment would i be able to charge the single 12v separate to the 48v as i only have a 48v charger thanks again rob

Charging is a different story. What is the battery chemistry (LiFePO4, SLA etc.)?