[zapyourrideguy]

Has anybody dealt with discharge limiting a zilla?
I have sent Orion a snapshot waiting to hear back.

 

[EVfun]

If you want an external system to cut power then all you have to do is short out the pot box. Zero ohms is zero throttle. You can insert other resistance values to limit the throttle (for example, 5000 ohms in parallel with the pot box will limit resistance 2500 ohms full throttle and cut peak motor voltage down by half. This doesn't work with Hall effect throttles.

Another option is to have a BMS output switch the zilla into valet mode and program those settings to a desired lower power level. That is how I would make a BMS cut back power, if I was inclined to do such a thing (and I'm not.)

The Zilla is not designed for you to externally control the current limit on the fly (except with valet mode and reverse mode inputs on the hairball.) I know its an ethernet cable between the hairball and the zilla, but is NOT an ethernet network between them.

 

[zapyourrideguy]

Thanks for the reply, I always wonder whether my questions are too stupid or too hard.
Can you elaborate on why you wouldn't be inclined to have the bms do this?

My thinking was for greater foolproofing of the car from over discharge. The other 2 ooptions were a buzzer that can be ignored, or complete shutdown which seems could be dangerous.

In my testing and correspondence with Ewert Energy, the BMS shuts down car when the current sensor is pulled. The BMS was also able to force a limp mode when I discharged my pack below 80% and my low cell was being pulled to the set threshold. I just thought the BMS should continuously enforce a current limit.

 

[EVfun]

If I want my BMS to cut power I vote for a complete shutdown. It has worked that way with gas powered cars for 100 years and no one seems to be claiming it makes them unsafe. Many gas cars have horrible fuel gauges that are often little better than "guess gauges." We can do better counting amp hours in our EVs. I don't think that running the cells down more is a good idea just because we do it slow. There is little capacity between the time when sag starts to sharply increase and when the pack is dead.

If you want BMS control you should use the BMS to set valet mode which you can program with alternate current and voltage limits. Throttle control doesn't actually limit current, you can easily be at current limit at 50% throttle if the motor rpm is low enough. If you take off with a Zilla in 3rd gear you can feel this, a condition where full throttle is no more power than about 1/2 throttle. There seems to be some algorithm to minimizes the effect (otherwise there would be situation where 20% throttle would be full current) but the throttle doesn't set amps so much as voltage (duty cycle.)

 

[dougingraham]

Can you elaborate on why you wouldn't be inclined to have the bms do this?

My thinking was for greater foolproofing of the car from over discharge. The other 2 ooptions were a buzzer that can be ignored, or complete shutdown which seems could be dangerous.

Do the buzzer. That way you can elect to still drive the car when the BMS falses on you when it is cold.

Why not ask Orion how to do this?

 

[zapyourrideguy]

That maybe best but I still fear the wife or daughter ignoring it for too long, I guess it would have to be LOUD. I do have the wiring diagram for that also from Orion.
Thanks

 

[EVfun]

Perhaps a timer and buzzer? Something like when hitting the lower limit it starts an annoying 60 second buzzer and puts the car in 1/2 power mode through the valet mode input. After that is shuts the controller down and locks it out by refusing to apply power to the ignition input. That's a whole minute more warning than a gas car gives.