Using a 48V battery pack with 36V motor/controller

[rw3iss]

Is this possible?
I was told I can use the larger voltage battery pack without any issue, but it will make the bike "considerably faster".
Do I risk frying the controller or the motor? It's a 500W geared rear wheel motor.
I'm doing this because in the future I may build a custom 48V higher power bike and don't want to have to buy another battery pack.

 

[wesnewell]

Most 36V controllers will support a 48V pack, but the LVC will still be set for a 36V pack, so you'll need to monitor pack voltage and not let it get too low. You can verify this by opening the controller and checking the caps and fets. If it has 63V main caps it should be fine. If they're 50V caps it won't support a full 48V pack.

 

[rw3iss]

OK, thanks.
Couple more questions...
If I buy this 48V 20AH battery pack:
http://www.ebay.com/itm/NEW-48v-20ah-LiFePO4-Battery-5A-Charger-BMS-For-Ebike-Powerful-Sea-8-Weeks-Gift-/141296286054
It has nominal output voltage as 30AH.
Would this still be fine if the controller's output is only 15AH or 20AH? Does it matter?
Also, if the caps happen to only be 50V, can I just swap them with 63V caps?

 

[USAEBIKECO]

You will notice a boost in speed. But make sure to keep an eye on the heat coming from the controller box. Too much heat could burn it out. It needs to be air cooled.

 

[rw3iss]

Great, thank you.
I will design some controller housing with a duct to allow airflow through it.

 

[rw3iss]

Does the AH matter at all as far as power output, or is it just a number for the battery's capacity?
20AH has the POTENTIAL to delivery more power, but at any given speed (let's say 20mph), will the power draw/provided power from a 48V@15AH battery vs. a 48V@20AH battery be the same?

 

[wesnewell]

OK, thanks.
Couple more questions...
If I buy this 48V 20AH battery pack:
http://www.ebay.com/itm/NEW-48v-20ah-LiFePO4-Battery-5A-Charger-BMS-For-Ebike-Powerful-Sea-8-Weeks-Gift-/141296286054
It has nominal output voltage as 30AH.
Would this still be fine if the controller's output is only 15AH or 20AH? Does it matter?
Also, if the caps happen to only be 50V, can I just swap them with 63V caps?

You've got AH (Anp Hours) confused with A (Amps). Two totally different measurements. The 20AH battery pack is rated for a 30A continuous output with a 50A burst. As long as the controllers max amps is 30A or less, you'll be fine.

 

[rw3iss]

Thank you for clarifying. Phew, now I can spend $400 on a battery with confidence. Yeeha!!

 

[d8veh]

Controllers don't cost much compared with a battery. In my experience, most 36v controllers can handle 12S (44v), but 13S (48v) is risky. If you don't want to be off the road, order your 48v controller now. At least you won't get any problems with lvc/hvc.

 

[rw3iss]

OK... if I use a 48V controller with the 48V battery pack, but on a 500w geared motor, what are the risks? If I throttle up and the controller starts putting 30A into the motor (close to 1500w), wouldn't it burn the motor out?

 

[wesnewell]

A 500W motor is rated to run at 500W continuous. It can run at 1500W or more for shorter periods of time. Generally you can safely put 5-10 times the max W rating in a motor for shorter periods of time without doing damage to it

 

[rw3iss]

Wow, good to know. Wouldn't have thought.... Thanks.

 

[999zip999]

What kit do you have ?

 

[d8veh]

There's hardly any risk to the motor as long as you're sensible. Try not to let it labour at liw speed for a long time when climbing hills. You can check the temperature of the motor with your hand after climbing hills, so you get an idea of how hot it gets. Warm is OK. If you can't hold your hand on it, your in the danger zone.

 

[rw3iss]

Gotcha...
Yeah I was only under the assumption that battery usage/requirements can directly from the load requirements at a specific moment in time/work, so it makes sense that less throttle/taking it a little easier will be better on the battery pack.
Thanks!