Second Battery Gremlins

luthj

Engineer In Residence
That 3V you were seeing was probably from the ACR. The ACR is monitoring both batteries voltage constantly, probably by applying a few mA of current. With the ground disconnected, and your meter inserted into the circuit, you were seeing this sensing function as a low DC voltage. I bet if you disconnected the ACRs ground wire, the voltage would disappear.
 

another_mike

Adventurer
A few thoughts.
You are going about this the wrong way. Measuring voltage with stuff disconnected won't do you much of anything. You want to measure current. Generally most multi meters can measure up to 10A. So set the meter to the current/amp setting, move the leads to the right plugs if needed. Disconnect the load you think is parasitic, and use the meter to complete the circuit. This could be at the ground/negative, or at the positive side of the loads supply wires.

Agreed. Never heard of parasitic draw being tested in volts. Use a fused multimeter in amps with the key off and doors closed, measure amp draw in series on the positive 15-20 minutes after turning off the ignition or isolation of that bank to let everything power down and sleep. A good generic value for draw is about 50mA. If you have one positive running to a fuse block it’s easier. If you have a large draw then you can pull individual fuses at the same location to determine which device it is.

Remember that with the meter hooked in series, that all power is flowing through that meter. If you turn on any accessory (which can include opening a door - dome lighs, courtesy lighting, chimes, etc) that exceeds the meter’s maximum load capacity, you’ll either fry the meter or if it’s a good meter, it’s fuse. Wouldn’t be hard to place a fused jumper in line if you have a meter that isn’t fused.
 

SameGuy

Observer
I wasn't testing parasitic draw with volts. I was just testing different things to see what was going on with the ACR. I still don't understand where the fantom voltage between the house ground and starting battery ground is coming from but assuming the ACR is causing it seems the most plausible. The parasitic drain is coming from my remote start, can't remember what its pulling but its not enough to be too worried about. I'm installing a switch to turn it off if its going to be parked for weeks, but I haven't had it parked that long since I bought it so the issue is moot as far as i'm concerned. I bought an Optima digital 400 charger to maintain the starting battery every few weeks if I don't drive very much, I think that will keep everything happy and hopefully extend the life of the batteries.
 

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