CA v3.12 Watts indicator -8 watts at rest

99t4

100 kW
Joined
May 10, 2020
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This is for a secondhand e-bike I recently bought. Good quality components, CA v3.12, 16s7p Samsung 30Q triangle battery pack, 12x3077 1500 watts nominal/3500 max. controller.

I noticed the watts reading on the CA main screen starts at 0 at power up, then after several minutes at rest will creep to -8w. I figured out how to zero out the calibration via [ Cal->Zero Amps ] setting, but it must have been calibrated correctly at some time in the past.

Does the -8 watts reading at rest indicate battery deterioration? If not, what could cause the CA watts display to drift?
 
Thank You. So I take it that minor swings in the at-rest watt readout are to be expected?
 
Not usually, but those things above could cause it to happen.

I have seen it most often when there is a poor connection somewhere, usually at the CA-DP connector, where it plugs into either the SA shunt or the controller DP connection.

Also, its' easily possible that whoever built the bike originally never did zero it.

Another possibility is that they had something like a bike light plugged into the CA's light output, or some other ocnnector that is "post-shunt" so it's idle power draw was read by the CA, and then they removed it when selling the bike, but did not re-zero amps.
 
Makes sense. I did zero out the setting before my last ride, and now the watts readout ranges from 0 to +8w at rest, possibly related to (controller?) temperatures. I have not studied it closely enough to find a direct correlation to temps yet.

Next step is to examine and clean the connections.
The CA v3 connects to the controller via the 6-pin CA-DP plug
The throttle, ebrake, speed switch, ignition are connected to the controller via JST-SM connectors
Battery connects via XT90.

The JST connectors are difficult to clean. Probably the best I can do is to disconnect/reconnect them several times in an attempt to "wipe clean" the contacts.

Presuming I can use dielectric grease on all the connections except for the XT90?

Amberwolf, is the SA shunt you mention inside the CA or controller?
 
99t4 said:
The JST connectors are difficult to clean. Probably the best I can do is to disconnect/reconnect them several times in an attempt to "wipe clean" the contacts.
That should work, if its' just contact oxidation.

Presuming I can use dielectric grease on all the connections except for the XT90?
Fine all connections. (it's used on battery terminals whcih are alos high current).

Amberwolf, is the SA shunt you mention inside the CA or controller?
This:
The CA v3 connects to the controller via the 6-pin CA-DP plug
means it is in the controller. So as the controller heats up, so does the shunt, which could (but usually odesn't) change the shunt resistnace teh tiny bit needed to offset by that much current.
 
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