2008 E350 Ford Van, Battery Drain

This 2008 Ford E350 van belongs to one of the local utility companies and the battery will go completely dead if it sits for more that two days. The standard routine, I connected my trusty Fluke meter in series with the battery negative post and terminal. There is a significant drain present as you can see in the next picture.

I had already looked under the vehicle for a second battery. It is common for a auxiliary battery to be installed at frame rail under the van. There was no second battery. I started isolating the varying systems and had located three separate drains. Only one significant drain though. It was located on an added cable system that went to the rear of the vehicle. Initially I thought it went to an inverter but Low and behold there was a second battery. It was buried under boxed and stuff. It was also located behind the boom assembly.

I needed to find out of the drain was from the battery or from something else in the rear of the vehicle. There were two cables attached to the negative post. I removed the cables and bolted them together.

I connected a small jumper wire from the cable connection to the battery post.

With the jumper wire in place the drain was present. With the jumper  removed the drain went down to a manageable .08 amp draw.

Just for fun I decided to connect my Fluke meter to the second battery. Between the post and the two cables that I had bolted together. I have to admit that a few hours went by before I got to this point but as you can see there is now a 4 amp drain.

I let it sit for another hour and it went to 4.29 amps. The diagnosis was a faulty rear battery that was draining the vehicles primary battery.

A new rear battery and a recharge of the primary battery and this one was fixed. As a quick side not the front battery is an AGM design and when recharging you have to make sure the voltage never goes over 15 volts or the battery will be damaged. There are special chargers just for these batteries but I just connect a meter to the battery terminals while charging and set the charger to a low to medium charge. I glance at the meter as I walk past doing other jobs and adjust the charge rate accordingly.

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