What controls the LVC the BMS or controller ?

[Deus]

What controls the LVC the BMS or controller which takes precedence ? i am using an ANT BMS and a BBSHD controller .

 

[wheeliepete]

What controls the LVC the BMS or controller which takes precedence ? i am using an ANT BMS and a BBSHD controller .

Which ever one has the highest cut off voltage. The LVC on the BBS controller is adjustable. I can't see any specs for the ANT BMS, but being a smart one, it's possibly the same.

 

[Deus]

Which ever one has the highest cut off voltage. The LVC on the BBS controller is adjustable. I can't see any specs for the ANT BMS, but being a smart one, it's possibly the same.

Thanks for that i could not find an answer anywhere i looked Endless Sphere, Ebike forums etc the ANT BMS is adjustable via bluetooth.

 

[Nealh]

The LVC with any smart programmable BMS like the ANT is set at what ever the end user chooses in the settings, as are all the other parameters. It is best for the battery BMS to determine the cut off value.

 

[vfr400]

What controls the LVC the BMS or controller which takes precedence ? i am using an ANT BMS and a BBSHD controller .

The controller is always set higher than the BMS, so it's the controller that controls the LVC cut-off.

 

[StuartsProjects]

Out of interest at what voltage are the controllers normally set to cut off ?

 

[Nealh]

The KT controllers are typically set at 30v/40v for 36v/48v operation, my 36v/48v BMS all cut off at a higher voltage typically 32v min and 41.6/42v min.

 

[StuartsProjects]

The KT controllers are typically set at 30v/40v for 36v/48v operation, my 36v/48v BMS all cut off at a higher voltage typically 32v min and 41.6/42v min.

OK thanks.

3.0V per cell is a bit on the low side.

3.2V or higher makes more sense if you want long battery life.

 

[vfr400]

Most 36v controllers are set to 30v to 31v and BMSs to 29v ot therabouts.

 

[Nealh]

None of my BMS go as low as 29v, most of mine are at about 32v.

 

[vfr400]

The controller uses a overall battery voltage for LVC. The BMS uses individual cell voltages often as low as 2.5v.

When the cells get down as low as 3.1v, they can't keep up with the bike's demand for current, and they go crashing down. The BMS will switch off when the first cell reaches LVC.

The more out of balance your cells are, the higher the voltage you would see for the whole battery pack when it cuts off. You could cut off at any voltage if you have any dodgy or unbalanced cells.

I've tested many batteries with a proper ebike battery tester. Good healthy batteries usually cut off at around 29v when discharging at 5A, which is what I use for capacity testing. If you discharge at 10A, the cut-off voltage would probably be higher. The return testing voltage would definitely be higher.

The battery voltage is very dynamic. It can change by several volts, depending on the amount of power you're taking from it and its state of charge, so none of these numbers are fixed as far as the rider is concerned.