22,2 volt lipo with 24 volt brushed controller

[bentech]

I'd like to know if a 6s 22,2V lipo battery can be use with a 24V brushed controller ??
The cut off voltage of the controller is rating at 20V +/- 0.5V
So this mean ''in theory'' that the controller will turn off the power to the motor when the battery cell will get at 3.3V. (3.3volt x 6s = 20V)

that should be perfect, like i said, in theory. But is this really what gone a happen ??
Is those controllers specs are right ??

http://www.ebay.ca/itm/e-bike-Motor-Brush-Speed-Controller-for-Electric-Bike-Bicycle-Scooter-24V-500W-/171271528995?hash=item27e0942223&vxp=mtr

 

[Hillhater]

It depends a lot on how "Stiff" your battery is ( how much it sags voltage under load) and that is affected by how much current your motor/controller will draw.
So, if you have a "weak" ( 4 Ahr) 5C rated battery and a motor/controller that draws 40+ amps, then you may expect the controller LVC to cut out under load.
But if you have a "stiff" 65C (20Ahr) pack and a motor/controller that only draws 20 amps max, they you probably will not see any LVC load problems.
The above are obviously extreme examples, but you get the idea ? .... more details are needed to offer a judgement.

That controller should limit amp draw to ~30 A max, but without knowing the type, capacity and "C" rating of your pack, it hard to say for sure !

 

[skeetab5780]

Yes it will work fine

 

[bentech]

I'd like to know if a 6s 22,2V lipo battery can be use with a 24V brushed controller ??
The cut off voltage of the controller is rating at 20V +/- 0.5V
So this mean ''in theory'' that the controller will turn off the power to the motor when the battery cell will get at 3.3V. (3.3volt x 6s = 20V)

that should be perfect, like i said, in theory. But is this really what gone a happen ??
Is those controllers specs are right ??

http://www.cafr.ebay.ca/itm/e-bike-Motor-Brush-Speed-Controller-for-Electric-Bike-Bicycle-Scooter-24V-500W-/171271528995?hash=item27e0942223&vxp=mtr

 

[bentech]

The battery i want to use is (2) Zippy Flightmax 6S 30C 8000 mah plug togheter for a total of 16000 mah.

 

[dogman dan]

That should work ok, BUT. I don't think it's a great idea to rely on the lvc. You want to at least monitor the whole pack voltage and stop closer to 3.5, or better still for staying balanced, 3.65-3.7v per cell.

If you drive the cells all the way to 3.3v, it will force them out of balance, and once out of balance, you will find when you hit the cutoff that one cell might be at 3.5v, and another at or below 2.7v. This is fine if you just want to race this pack a few times, but if you want two years use for it, stop at a much higher voltage. This may happen anyway, since it will cut out under load. So your real world cutoff might be close to 3.5v average.

6s will charge to 25v.

For 24v, 7s is not a bad way to go. You could add 1s later, or go for 3s + 4s now. This would mean that the cutoff would be much lower, close to 2.8v per cell. But again, once below 3v, that pack is going to voltage sag like hell under load. So once cutoff happens, it might be still near 3v resting voltage. Not good, but not past the throw it away voltage. Using a voltage monitor while you ride, you will have a much nicer run starting at 29v, vs 25v. It depends on if you'd like a perkier, slightly faster run.

 

[bentech]

That should work ok, BUT. I don't think it's a great idea to rely on the lvc. You want to at least monitor the whole pack voltage and stop closer to 3.5, or better still for staying balanced, 3.65-3.7v per cell.

If you drive the cells all the way to 3.3v, it will force them out of balance, and once out of balance, you will find when you hit the cutoff that one cell might be at 3.5v, and another at or below 2.7v. This is fine if you just want to race this pack a few times, but if you want two years use for it, stop at a much higher voltage. This may happen anyway, since it will cut out under load. So your real world cutoff might be close to 3.5v average.

6s will charge to 25v.

For 24v, 7s is not a bad way to go. You could add 1s later, or go for 3s + 4s now. This would mean that the cutoff would be much lower, close to 2.8v per cell. But again, once below 3v, that pack is going to voltage sag like hell under load. So once cutoff happens, it might be still near 3v resting voltage. Not good, but not past the throw it away voltage. Using a voltage monitor while you ride, you will have a much nicer run starting at 29v, vs 25v. It depends on if you'd like a perkier, slightly faster run.

Thanks !!
I dont want to use the controller LVC as a system to control my battery low voltage cut off.
I will use a real Lipo battery monitor power by the balance plug and i dont want to go under 3.5V per cell.

I was asking the question because i dont know if thoses chinese controller are acurate. I just dont want to
have 40% of power remaining in the battery but have to stop because of the controller LVC.