Quote:
Originally Posted by ATrain
Ah I see what you're saying now. In layman's terms, when the BMS cuts power, it's basically pulling the negative terminal off the pack. And you're suggesting connecting the EMB somewhere inline where I pictured below so that it will remain powered in the event of a BMS issue. Right?
Doesn't that make the EMB always on?
It seems like the best solution would be just hooking only the motor and charger somehow but keeping power to the controller. So when the BMS shuts down the primary load (motor) is disconnected. |
Yes, it cuts the ground.
My initial thought was to isolate that circuit so only the ground to the relay / run/tow switch bypassed the BMS (as pictured in red), or to bypass the entire chassis wiring as you suggest since the load is still relatively small (shown in blue). So, not wiring the EMB to be constantly on, but providing an uninterruptible ground to the circuit one way or another. Trouble is, the more I look at this, the more it looks like the signal to the relay from the controller will still drop if the BMS cuts power to the the big cables as the controller ground will drop.
I plan to work on mine this weekend in sort of the opposite fashion (I would like to get my chassis wiring (sans the EMB of course) on my BMS because the Daly Smart bluetooth functionality only activates when it detects load or charging) so, I will confirm that is the case.
Otherwise, I think there are two ways around it for sure.
1 - Parking brake switch. Not as convenient for sure as the auto brake feature, but as long as you wire it to a pre-BMS ground, it would be an easy way to solve the problem (I would use a relay for good measure). The right switch, wouldn't even look too bad.
2 - Auxiliary relay. One that works in some set of conditions. So, if you say move the chassis wiring to be pre-BMS, you could have a relay wired so that if the power is on to the chassis the EMB is off. Or, if you added a speed sensor to the mix, it would be possible to simply not allow the EMB to engage if the cart is moving, but that one would require a bit of extra hardware.