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Replacing controller on rad2go sunbird

 I think my original controller is burnt out so I bought new controller (36V/500W) :

However my original controller (check attached pic) don't have so many connections and names are also different than the ones referred in link.

I can't decide which connections should I do from new controller. I would appreciate any help



If the wires between the battery pack and controller are not visible because of where they are routed and you can not determine which wires are coming from the battery pack then you might want to consider running new wires from the battery pack to the controller. If you do run new wires make sure to install a fuse or circuit breaker, or reuse the existing fuse or circuit breaker, between the battery pack and controller for short circuit protection.

Please let me know if you have any questions.

I should look in to fuse/circuit breakers. Don't want to try running bunch of wires around. Can you recommend fuse or circuit breakers?
I need to check current requirement for this.


For a 36 Volt 500 Watt controller like you are installing a 30 Amp fuse or circuit breaker is the recommended size. The most popular fuse is the ATO fuse which I recommend if you are going to use a fuse. If you prefer to use a circuit breaker then any style of circuit breaker that we sell will work.

A fuse with inline fuse holder will be easier than a circuit breaker to install unless there is already a hole for a circuit breaker drilled into the scooter.

Here are links to our fuses, fuse holders, and circuit breakers:
Thanks I think I'll go with bunch of fuses.
I'll update few days later again


the A,B,Off usually meant that there was an extended range battery pack under the seat like the Electra had. Battery pack A was the floor board and battery pack B was under the seat.

Yes there are wires / connections present for extra battery pack.
So that would mean I still can use 2 wire switch, is that correct? as long as I leave battery pack B (nothing under the seat) disconnected. If I can successfully get it running I will think of second battery pack.


Since you mentioned that your new key switch has really thin wires compared to the original key switch, the new key switch should probably not be used in the same circuit that the original key switch was used in because it will not be able to handle the full power load of the battery pack. If you use the new key switch with thin wires it should be wired directly to the new speed controller's connector with blue and red wires (the key switch connector). Doing this would require bypassing the original wiring harness and running new wires directly from the battery pack to the controller (with a fuse or circuit breaker in between).

However if you want the lights to work then the original key switch may need to be replaced with an identical key switch that has thick wires. I recommend replacing the original key switch with the same or similar key switch that has thick wires and using the power input wires that were cut off of the original speed controller to provide power to the new controller. This way the original wiring circuit will remain in use.

you can use a 2 wire switch. the switch only turns on the controller when hooked up correctly

Hi Darrell, thanks for letting us know that the key switch only turns on the controller. I have never owned or worked on a Rad2Go Sunbird scooter so I can only guess as to how it is wired. It is great to have your expertise on this forum. Thank you for joining and participating in this forum - your replies are always welcome here.
I also have a Rad2go SunBird. The key switch for battery A works fine but when I turn key switch to battery B, there is no power. I've charged and checked both batteries and both are fully charged just under 36volts. I've also verified key switch work both A and B. This makes me think the controller is the problem. Is there a way put to power controller to test the controller when it's off the the scooter? I called Electric Scooter Support yesterday and was told they had no controller that would work with SunBird, yet is appears from the forum above the 36500B will work with some modifications and a new throttle.
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The Rad2Go Sunbird key switch simply switches between the positive leads of the battery packs to the controller. So if the scooter runs when the switch is on battery A then the controller is good and does not need to be replaced. The problem would have to be in battery pack, wiring, or switch.

36 Volt battery packs should be at around 41 Volts when fully charged. A Voltage reading that is just under 36 Volts indicates that that the battery packs are not able to take a full charge, or that the charger is not able to fully charge the battery packs. The sealed lead acid batteries found in most electric scooters only have a 200-300 cycle lifespan, or a 2-3 year lifespan whether they are being used or not.

The first thing I would test is the input power leads of the controller when the key switch is on battery B to maker sure that power from battery B is reaching the controller, this will confirm that the switch and wiring are good between battery B and the controller.

If the key switch and wiring are determined to be good then the next test I would perform would be a load test on battery B. To load test battery pack B place your multimeter leads where the Voltage of the pack can be read, and then turn the key switch to battery B and fully engage the throttle, or pedal the bike if that is how the motor is activated. The Voltage of the battery pack should only drop around 1 Volt if the battery pack is good, if its Voltage drops under 33 Volts then it fails the load test and needs to be replaced. The controller will not operate the motor when a battery pack is under 33 Volts, which is a safety feature to protect the battery pack from being over discharged.

Please let us know if you have any questions and how the testing goes.

you can always hook up the charger with the bike on the stand and retest to see if b powers up. if it does then you need new batteries. but I think there should also be a fuse somewhere in both battery packs also start with the easiest things first before tracing down wires 

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