Help With Accessing BMS Amperage Cap

Thorsaw

1 mW
Joined
Jan 2, 2020
Messages
10
Hello all,

I was hoping someone could provide me a little insight into some limitations I am having. I have a 72v 48AH Battery paired with a Sabvoton 72150 (software unlocked) controller, Cycle analyst V3 and a Qs273 Motor. I am unable to pull more than 80 amps from the Battery (it seems). I have checked all of the parameter settings to make sure nothing was limiting the current on the controller software and the cycle analyst. Because I am capped at 80 amps current it makes my think that the BMS is the limiting factor. The bike was sold to me as something that could Phase at 12kw power. Given my voltage I would need to pull closer to 150 amps to achieve those numbers. Is there a way to check the BMS limitations without opening up the battery so I can make sure that isn't the issue? I highly doubt the BMS is capped at 80Amps current but I wanted to rule it out as the suspect. I am able to travel at 55mph on dead flat but the CA3 is reading correctly at just above 5KW

If there is something you think that is limiting me other than the BMS by all means call me out on my Noobness.

In advance I appreciate you and this forum very much.
 
Thorsaw said:
a Sabvoton 72150 (software unlocked) controller,
Based on ohter Sabvoton posts, this is probably your limiting factor--it's probably either not "unlocked" or it's simply incapable of as high a current as advertised.

But another possibilty is that you simply aren't putting enough of a load on the motor to cause it to draw as much current as you think it should.

What kind of situation are you putting it thru at worst case, to cause it to draw the most power?


Cycle analyst V3 and a Qs273 Motor. I am unable to pull more than 80 amps from the Battery (it seems). I have checked all of the parameter settings to make sure nothing was limiting the current on the controller software and the cycle analyst.
First, are you sure your shunt resistance is set correctly in the CA, to show the correct current and power?

Next, connect your throttle directly to your controller, and not to the CA. This will completely bypass the CA and all it's limiting. If there is no change then the CA is not limiting it. If you cannot physically wire it this wya, set the CA to Bypass mode in the throttle menu, which does the same thing but electroncally instead of electrically.


Because I am capped at 80 amps current it makes my think that the BMS is the limiting factor.
If it is, then the bike wil shut off, no power of any kind, whenever you hit the BMS current limit.

The BMS *cannot* limit power the way your controller or the CA can, it can *only* shut off when any BMS limit is reached (overcurrent, overvoltage, undervoltage).
 
I see you all around the site. This is all exceptional advice. I will use the bypass mode on the throttle CA menu.

Worst abuse on bike is full throttle up slightly steep hills (where I found the bike limited at a bit over 5 KW and 80amps

I do think the shunt resistance is off as I doubt highly 5 KW would achieve 55mph on a GPS on anything except a much lighter dual hub e scooter.

You assisted my brain. I will try this, thank you.
 
Thorsaw said:
Worst abuse on bike is full throttle up slightly steep hills (where I found the bike limited at a bit over 5 KW and 80amps
What slope were they, how much does the whole setup including rider weigh, and what speed did you maintain?

Knowing those, then using various internet power calculators you can determine how much power it *should* take to do that, to know if the reading is correct. the lower the speed was, the less aero matters, and the simpler the calculation is.


I do think the shunt resistance is off as I doubt highly 5 KW would achieve 55mph on a GPS on anything except a much lighter dual hub e scooter.

Is it an external shunt? If so, just input the resistance marked on it into the CA; you'll probably need to use High Range mode if its a high current shunt, as they're usually less than 0.750mohms.

If it's the internal controller shunt, you'll need to measure it to find out what to put in CA's setup.
 
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