Parasitic Current Drain?

[JDKub]

Hi all. I have a 2014 Interstate EXT. I had it in the shop for the last 3 days. I turned the battery switch off when I dropped it off, and confirmed everything was shut down. My batteries are 6 week old 90 AH 12 V AGM. They were fully charged when I dropped off the rig. I picked it up today, turned on the batteries, and they were nearly dead, 10.8 V. I have always suspected that something was discharging the batteries faster than they should. One night of boon docking drops them from fully charged to about 12.2V. It's not just the new batteries, but my old ones as well.

Anyone have any ideas or suggestions?

edit: to be clear, it was in the shop for engine servicing, nothing to do with the RV side of the house. The mechanic never touched the battery switch.

[BayouBiker]

I would begin by directly measuring current draw when the battery switch is off. Three days down to 10.8 Volts indicates all 180 AH. Adjusting for resistive losses and whatnot, that is at least 3 amp continuous draw. Your overnight experience is similar with 4-5 amps minimum draw unless the batteries are weak.

So get digital multimeter capable of measuring DC current. the ones with inductive pickup are nicer since you don't have to disconnect wires. You don't need an expensive one. $35-50 will do it.

If you get more than 3 amps then the task is to find where it is going. If you get much less, next is to test the batteries condition.

[JDKub]

Where would I measure that? From the battery terminals?

[BayouBiker]

Yes start at or near the batteries, you may have to measure more than one lead. Sum them together. Measure and sum all positive or all negative wires.