I am looking to use a 36 volt electric motor to use as an alternator to charge three 12v batteries. I am looking for some advise to see if it would work and some options on diodes to keep the current from going backwards. Thanks
We have had several customers use our motors as generators to recharge battery packs. Our motors output pure DC power so they are considered to be a generator instead of an alternator.
One thing to keep in mind is that a DC motor will need to be spinning at a slightly higher RPM than it is rated for in order to output its rated Voltage. If the RPM will be lower than the motor is rated for then a motor with higher Voltage rating can be used to output the desired Voltage - for example a 48V 3000 RPM motor could be used to produce 36 Volts at around 2000 RPM.
As far as diodes go only one will be needed. A single large diode should be used instead of several small diodes wired together to make a big diode otherwise the smaller diodes will most likely burn out. The diode will need to be rated above the Amp load that will be placed on the circuit by the generator.
If you are recharging three 12V lead acid batteries then they will need to be charged up to around 42 Volts in order to fully charge them, that is something to keep in mind when designing the system.