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monkey44's avatar
monkey44
Nomad II
Oct 03, 2016

Battery test ?

I believe I have a battery that is not charging - at least it's not holding a charge (Interstate 27 - five years old) ...

I need to see if the truck is charging the battery before I spend the money on a battery. If I charge it at the 110v pedestal, it charges and holds a charge for a couple days with very minimal use once we disconnect... That tells me the camper charger is working?

A few lights, fridge ignite, no heater ... use no electronics, very careful with battery use, bed early, up early. But it discharges pretty quickly, two / three days. We normally get a least a week out of a full battery boon-docking when we limit the use.

How can I test if the truck is charging the battery on the road tho?
It seems to be charging very slowly, if at all when driving. And when we stop overnight after driving all day, it discharges overnight.

I have a line tester - so, if I run the truck, remove the cables, and link one pin to each cable connector, what should it read if it's charging properly -- if that even works? Seems the cable should read power if it's charging, even if the battery is not attached.

It's inconvenient to bring battery in to station for test, but if that's the answer, I'll make that happen.

One more thing: I have a truck camper, so battery raises and lowers the legs. When I tried to raise legs to slide under camper to load it, it tries, but fails and just groans a few seconds and quits. BUT, if I attach jumpers from truck battery to Camper battery, then it will raise the camper easily - I expect that's using the truck charging system and jump power tho, and tells us nothing about the truck charging the battery thru the internal lines??

Any thoughts??
  • when I have that kind of challenge i just take it to town and have it tested for free.
  • 1. Read the voltage of the RV battery.
    2. Connect the tow vehicle and start the engine.
    3. Read the voltage of the RV battery, if charging it will be 13.2 or more.
  • Charging system from truck is better at maintaining a camper battery vs recharging a camper battery especially one that is low.

    Charge line wire size is limiting and truck alternator is limited due to voltage regulator

    Volt meter connected to batter cables========note voltage at battery
    Turn truck on--------note voltage at battery
    Increase truck RPMs....note voltage at battery


    Then go buy a new battery :B

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