How to use victron smart shunt for capacity testing?

blutow

Solar Addict
I've got 16 lishen cells hopefully arriving next week (they arrived in the states last Friday). I'm working to get everything ready for charging and testing.

I think I'm all set on charging.

I was planning to to use my inverter with a load to run the capacity test and capture statistics with my victron smart shunt.

I did a quick test last night and it looks like the smart shunt loses it's history when the power is cut. So, I can watch the ah's tick away during the test, but as soon as my the bms cuts out during a capacity test, it looks like there is no way to see where it finished.

So, does anyone know if there is a way to use the victron smart shunt for a capacity test and see the final ah's consumed? I don't think so since the only negative connection is the actual load. I was thinking maybe I could connect a power supply to maintain a small current so it would keep the shunt running even after the BMS cut out. That could slightly skew the test and I'm not sure how that would work when the BMS cuts out and my inverter is still trying to pull a bunch of amps.

My backup plan - try to catch the pack before it gets too low and record the Ah's and then switch to a small capacity tester to finish the test (I've got one of those cheap fan-based testers). Then, I could just add the values together to get total capacity. I think that plan will work, but there is a risk I miss the cutover and lose my data and have to start over again.

The other alternative is to just test the battery using the fan-based tester, but that's going to take forever and I'm afraid I'll kill the tester unless I run it really conservative. If I run it at 100 watts, I think I'm looking at ~35 hours to test each battery. The only reason I got the fan tester is to capacity test single cells if needed.
 

codfish

Solar Enthusiast
I've got 16 lishen cells hopefully arriving next week (they arrived in the states last Friday). I'm working to get everything ready for charging and testing.

I think I'm all set on charging.

I was planning to to use my inverter with a load to run the capacity test and capture statistics with my victron smart shunt.

I did a quick test last night and it looks like the smart shunt loses it's history when the power is cut. So, I can watch the ah's tick away during the test, but as soon as my the bms cuts out during a capacity test, it looks like there is no way to see where it finished.

So, does anyone know if there is a way to use the victron smart shunt for a capacity test and see the final ah's consumed? I don't think so since the only negative connection is the actual load. I was thinking maybe I could connect a power supply to maintain a small current so it would keep the shunt running even after the BMS cut out. That could slightly skew the test and I'm not sure how that would work when the BMS cuts out and my inverter is still trying to pull a bunch of amps.

My backup plan - try to catch the pack before it gets too low and record the Ah's and then switch to a small capacity tester to finish the test (I've got one of those cheap fan-based testers). Then, I could just add the values together to get total capacity. I think that plan will work, but there is a risk I miss the cutover and lose my data and have to start over again.

The other alternative is to just test the battery using the fan-based tester, but that's going to take forever and I'm afraid I'll kill the tester unless I run it really conservative. If I run it at 100 watts, I think I'm looking at ~35 hours to test each battery. The only reason I got the fan tester is to capacity test single cells if needed.
How about putting the shunt between the battery and the BMS ( just for the test). Shunt stays connected when BMS shuts down the negative path.
 

blutow

Solar Addict
How about putting the shunt between the battery and the BMS ( just for the test). Shunt stays connected when BMS shuts down the negative path.
Thanks, I can't believe I didn't think about that option. It will make my wiring a little messier for the test, but should work great.
 

blutow

Solar Addict
I found another way without messing with the wiring - As long as my Cerbo GX is connected to wifi, it will log the ah's consumed to the cloud and I can still view it in VRM once I get the BMS disconnect. It looks like the cerbo and VRM basically hold the last Ah consumed number from the shunt until you wake the shunt back up (and then it resets to zero). I was already planning to run the cerbo during the test so I can check in remotely and set up alerts, so this should work well. I also plan to power the cerbo and color GX from another 12v source so it stays live after the BMS cutoff.

Putting the shunt between the battery and the BMS would technically make the capacity test a little more accurate, but I'm probably not going to mess with it. I figure the more I can keep clean simple wiring during my test, the less chance I will do something stupid and melt something.
 
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