How to measure voltage on the CAN bus battery connector

[Chuck E. Cheese]

I bought a used gold 814Wh battery on ebay as a secondary battery for my ST2. While it doesn't have the capacity of the new one that came with the bike, it seems to be somewhere around 80% of the fresh one. According to the Omni App, the health of both batteries is described as "Very Good". I've tried putting a multimeter across the two large pins on the battery to see what the voltage at full charge is, but I can't get a reading, and I don't want to risk shorting the battery. Is there a way to see what the actual voltage is? I haven't been able to find anything here or on Endless Sphere.

 

[Calicoskies]

Not that familiar with this pack but thought I would make a couple of statements. First, the two main connectors should be correct for measuring the DC voltage so not sure why that did not work for you. As long as you do not short the two leads from volt meter together you should be safe. Second, some BMS system only allow you to charge to 80% to make the battery last twice or three times as long. Sorry if this is to basic.

 

[Chuck E. Cheese]

Not that familiar with this pack but thought I would make a couple of statements. First, the two main connectors should be correct for measuring the DC voltage so not sure why that did not work for you. As long as you do not short the two leads from volt meter together you should be safe. Second, some BMS system only allow you to charge to 80% to make the battery last twice or three times as long. Sorry if this is to basic.

Thanks for the response. My guess is that CAN bus, which is the standard used in larger EVs including cars and trucks, is a more robust protocol involving some kind of BMS that requires a connection to all 6 pins in order to pass current. I don't know. It's just a guess. As soon as I put the meter leads on the pins I see a small spike that immediately cuts off- almost like a fault cutoff or something. I'm wondering if maybe an automobile garage that services electric cars might have a diagnostic tool that could measure the battery parameters.

 

[bluecat]

According to the Omni App, the health of both batteries is described as "Very Good"

No clue, on what such OMNI statements are based.

EndlessSphere is a good source for expert tech stuff; Stromer uses the EnergyBus protocol, which might not be known in the US. The EB is a CAN bus protocol with (many) public specs. If you dig in the swiss stromerforum, you'll find some people which are familiar with the EB.