Issue with new AGM upgrade

[Bartyczak]

Update: Today I did a thorough checkout of my wiring. No shorts found (continuity check between the frame and the positive battery cable), checked all my fuses at the converter, and disconnected the inverter. After disconnecting everything from the positive bus, and reconnecting 1 by 1, I found that the voltage drops when I connect the 10” cable from the positive bus to the battery disconnect solenoid. The solenoid is brand new and so is the converter that it connects to so I know they aren’t the issue. I thought maybe the cable is bad so I disconnected both ends and measured resistance. It fluctuated between 0 and .5 ohms. Wondering if this is the culprit. I reconnected it and now the voltage drop has reduced from 1V to .5V. So problem is not solved but improved. Is the cable the issue? I’m going to replace it and see.

[Bartyczak]

Originally Posted by John Ware

You have to hope you don't get an RV tech who is a parts swapper too. Some parts aren't refundable.

That is my backup plan but they couldn’t give me an appointment until October. Figured I might as well try an troubleshoot myself in the meantime. Maybe I’ll learn something 😜

[uncle_bob]

Originally Posted by Bartyczak

Update: Today I did a thorough checkout of my wiring. No shorts found (continuity check between the frame and the positive battery cable), checked all my fuses at the converter, and disconnected the inverter. After disconnecting everything from the positive bus, and reconnecting 1 by 1, I found that the voltage drops when I connect the 10” cable from the positive bus to the battery disconnect solenoid. The solenoid is brand new and so is the converter that it connects to so I know they aren’t the issue. I thought maybe the cable is bad so I disconnected both ends and measured resistance. It fluctuated between 0 and .5 ohms. Wondering if this is the culprit. I reconnected it and now the voltage drop has reduced from 1V to .5V. So problem is not solved but improved. Is the cable the issue? I’m going to replace it and see.

Hi

Unless you have a 4 wire ohm meter setup, measuring anything below an ohm is suspect. If indeed you had a 1 ohm cable resistance, you would get a 10V drop at 10A. That's ... umm ... a lot of drop.

If you want to do a DIY test of the cable, set up a load and hook it to the battery. See how much current the load is pulling. See what the voltage drop is on the cable. From that you can divide the voltage by the current to get the resistance. When doing this, the battery and load "contacts" need to be separate from the contacts used to measure the voltage. Otherwise contact resistance will mess you up a lot.

Unless the cable is obviously damaged it is unlikely to be defective "in the wire". The connectors on the ends should be crimped on. A quick test there is to give them a good tug. If they come off, the crimp was badly done. Yes, this assumes you are dealing with nice hearty battery cables and not some small gauge stuff.

Bob

[John Ware]

If the cable is suspect, as Bob stated it would more than likely be the connectors not making good contact with the cable. The cable could be corroded inside the insulation but usually when that happens the cable will have a bulge in it. Try bending the cable back and forth while testing it. Sometimes a new part can be defective too and that will throw you off.