DC to DC converter for 60v battery

[jpogge]

I have an DIY build with a 48v Bafang mid drive. I recently acquired a battery that I thought was 48v, but turns out it is 60v. Is it possible to use a DC-DC converter to step down to 48v? If so, then what sort of amperage should the converter be able to handle? I have found some that are 10a and others that are around 30a.

 

[HumanPerson]

Welcome to the forums!

 

[addertooth]

The answer is: The number of Watts your motor is, divided by 48. Actually, a bit more to allow for headroom.

Example, 500 watt motor, divided by 48 volts, roughly 10 amps.. but go with twice that for safety as some bikes feed the motor more power than it is rated for to get more "ooomph". (500 / 48 = 10.416 amps).

I have seen some bikes where the 750 Watt motor is driven at 1200 watts for short bursts.

 

[jpogge]

thanks, that is exactly the information I was looking for.

 

[addertooth]

Not a problem, we are all here to share.

 

[jpogge]

Now I just need to find one. the current motor is a 750w, so I am looking for a 60v-48v with at least 15a. best I can find is 10 amps

 

[addertooth]

Now I just need to find one. the current motor is a 750w, so I am looking for a 60v-48v with at least 15a. best I can find is 10 amps

Once again, I remind you it may need a little "extra headroom". I wouldn't consider anything smaller than 22 amps.

 

[jpogge]

Once again, I remind you it may need a little "extra headroom". I wouldn't consider anything smaller than 22 amps.

thanks again, I was hoping to find something around 25a, but I am having a hard time finding anything that steps 60v down to 48v. Most of the buck converters I am finding are used to drop to 12v

 

[addertooth]

Yes, most buck converters have a "range" of input voltages. They normally aren't designed for a narrow and specific supplied voltage when they get this big. i.e. 55 to 90 volts in, 48 volts out. Anything with an output voltage of 48 to 54 Volts will work, just be certain to use a "battery combiner". to tie together the output of the buck converter with your existing battery to prevent backflow of power from one power source to the other. They are also known as a "battery blender".

An example would be the "Polar Bear" battery blender. Also, you may have to hit a hobby shop to find the right connectors to link everything together. Pretty typically they use an XT60 connector on a lot of eBikes.

 

[TwoTired]

A PWM solar charge controller is essentially a DC to DC converter. The 60 volt battery connected to the solar panel input and battery output connected to the existing 48 volt battery might do the job.
I haven't tried this so I can't say it will work.