48V in a 36v system

[Electric_Bike_2007]

Hi all.

Is it possible to use 48v in a 36v system without damage  it?

If not,The problem will be the electronic control or the motor?

Thank you!

[myelectricbike]

At your own risk only and voids warranty.

[Bassbiker]

Here are the things to consider.
1. 48 v vs 36 is 33% increase in voltage and will cause a similar increase in current draw.
2. You will saturate the magnetic structure of the motor and the additional magnetic force will be wasted, with the waste being turned into heat.
3. Generally a motor can take an overvoltage/current situation for a short time. If the motor is already hot then  the additional heat from too much power will likely start to burn the insulation on the windings.
4. If it is a brushless design you may exceed the semiconductor ratings in the electronic commutator.

This Tim-the-Toolman approach is not a good idea.

[Dalecv]

BsBiker



I think you may be gaussing about saturating the magnetic structure.

[29a]

If you where to go 48V
The safest way to go would be open the controller and take the part numbers off the mosfets and check the specs on digikey to see max volts/Amps to prevent you damaging the controller.
Then to prevent overheating the motor you could replace the hall throttle with a pot to lower amps available to the controller output so you could run same watts through the motor.
The effect would be less torque (slower speed increase) but higher eventual top speed.

and see here http://goldenmotor.com/SMF/index.php?topic=34.0

[Electric_Bike_2007]

  Hello.

Thank you very much for your answers..

I like the idea to check the mosfets max voltage.

another possibility is to use 3 -12v batteries and 1 -6 volts batteries.(36+6v)

In this case I will get 42v...

Using high voltage I will get less torque and more speed?

Thank you all!!

I will mont the bike tomorow... the kit just arrive today

Regards

[myelectricbike]

What you may do as I just did is to melt the insulation. If you are going to void the warranty then as least do yourself a favor and replace the power phase leads with AWG 16 high temp appliance wire - the stuff they use to light the burners on top of the stove. If you want to also replace the windings then use AWG 14 if you can get it through the axle hole. Also be sure to carry a fire extinguisher with you.

[ricel]

i would suggest to put dpdt switch to harness your 6 volt battery when the 36v battery pack dropped to cutoff voltage. when your 36v battery pack is fully charge you will safeguard your controller with max tourque/speed and when it dropped close to cutoff voltage then use the dpdt switch wired in series with your back-up 6volt resulting to the desired 36volts at least. this will give you a turbo boost safely.

[myelectricbike]

In the future the dual voltage controller I have suggested may include a battery management chip which will adjust voltage according to throttle demand and maximum limits. Currently the 36 volt regenerative controller gets very confused if you supply it with more than 41 volts but I do not yet have an explanation.

[Mordaz]

i would suggest to put dpdt switch to harness your 6 volt battery when the 36v battery pack dropped to cutoff voltage. when your 36v battery pack is fully charge you will safeguard your controller with max tourque/speed and when it dropped close to cutoff voltage then use the dpdt switch wired in series with your back-up 6volt resulting to the desired 36volts at least. this will give you a turbo boost safely.

No good for the batteries.  The point of this low-voltage cutoff is to prevent deep discharge. 

[ricel]

that's the intent of the dpdt switch. flip the switch when needed, don't wait to drop to cutoff voltage. the 6 volt pack is only for turbo boost when needed. when you get home, then recharge your 36volt packs

[myelectricbike]

I forgot about deep discharge when I did a similar setup with my 36 volt pack and a 12 volt battery with a bad cell. Although total voltage stayed above 38 volts (assuming 10 volts from the bad battery) that means at some point I had to be in deep discharge range although when I got home the meter showed the batteries at 12.9 volts. I'll connect meters to each battery if I run this setup again.

[pdonahue]

I'm trying out running at 48V SLA on a 36V controller.  It starts out fine and rides OK while under load.  The battery voltage is around 47V while I'm riding.  When I release the throttle, the voltage goes back up to around 50V and the controller cuts out.  I have to disconnect the battery, wait 10 seconds, and reconnect to get it working again.

[myelectricbike]

The 36 volt controller is not designed to handle 48 volts. The only reason it appears to is because of the 58 volt specs on the mosfets and the TTL voltage regulator. Use a 48 volt controller if you want to run with 48 volts and be prepared to upgrade you motor wiring to Teflon.

[pdonahue]

I've taken my bike to work and back running 48V for the past few days.  I'm still trying to find a way to avoid the controller needing to be reset when I come to a stop. 

Pete