LVC

[Ozzzz]

Hi ES, I was searching for a Low Voltage Cut-off... regulator/'device'
Still setting up, or gathering bits for a 36v 250w Xiongda Hub build, for the rear of a 27.5+ bike, this time with only PAS and e-brake, no HAL, no throttle, no display.

Battery- Circuit breaker- LVC(?) - Controller

Rather than rely on the BMS LVC in the shark pack, can I simply wire in an additional LVC (as a first line 'empty')?

If so, how so? Anyhow, thanks in advance for any advice?

 

[dustNbone]

Most (all that I've ever seen) ebike controllers have an LVC built in. If your kit comes with a 36V controller and you use a 36V battery the controller should have an LVC set to the appropriate voltage.

 

[Ozzzz]

I haven't used this controller, Ok, thanks, I was under the impression the BMS managed LVC. So if it's not considered safe to rely on the 'LVC', my query still stands abt adding a second LVC 'switch'.

 

[wesnewell]

Be aware that you should have different LVC voltages depending on the battery type used. Many controllers are set for SLA batteries with a LVC of ~31V. That's fine for SLA, but it should be 33-35V for rc lipo, and 27-30V for an 18650 or lifepo4 pack. Let me put it this way.
LVC per cell.
SLA RC lipo 18650 li-ion lifepo4
1.75V 3.3-3.5V 2.75-3.0V 2.5-2.7V
With the higher value giving you the longer life.

 

[Ozzzz]

Thanks, appreciated. In short i'm chasing a stand alone LVC device (similar to https://www.baintech.com.au/business-products/battery-protection/product/1403-baintech-low-voltage-cutout-12-24v _ ... with the appropriate, settable, voltage.

I ran my 48v battery by the LVC in the controller without an issue, just trying to make the new 36v built fool proof (amap).

 

[fechter]

Normally you want the controller to hit it's LVC before the BMS does. The BMS should only be a backup if the primary fails. Most controllers can be programmed to change the LVC or there is a way to do it with resistors.

Something like a Cycle Analyst can be used as a programmable LVC. When you reach cutoff, it clamps the throttle line.

There are some Chinese volt/amp meters with a relay that can cut the load, but those are not made to survive being on a bike.