Tow Vehicle Charging PUP when in tow... Need help

[bryankloos]

Hi All,

I've recently upgraded some components on the PUP, adding a BVM712, MPPT charge controller for solar suitcase, small inverter, upgraded converter and moved most wiring into the PUP.

I was always under the impression that when towing, my truck was supplying power to the PUP. I had things hitched up for the first time yesterday to move the PUP into the garage for winter storage and when all hooked up I noticed that the BVM was reading -0.20a. I would have thought it would be charging, not drawing when hooked up to the TV.

Any thoughts and how should I troubleshoot?

Thanks,

Bryan

[NavyLCDR]

With you trailer 7-pin cable disconnected from the vehicle, do you get trailer battery voltage between pins 1 and 4?

[Thomas ho]

put volt meter between pos. terminal on pup battery , and frame . 12v ,,yea ,, no 12 sad. turn on head lights ,check results .

[bryankloos]

I can confirm 13.4 v between pins 1 and 4 on the trailer side connection.

[NavyLCDR]

Originally Posted by bryankloos

I can confirm 13.4 v between pins 1 and 4 on the trailer side connection.

Then the trailer side wiring is OK and time to start measuring for voltage back from the connector on the vehicle. The problem is on the vehicle side.

[ependydad]

Are you sure you have the shunt hooked up correctly? I had mine backwards for a spell- power coming in looked negative and power being used looked positive.

[Aussieguy]

what is your truck battery voltage
use a multi meter at idle and around 2000rpm

if you got a lifepo4 trailer battery 13.4v
it may feed the truck..... if truck battery and alternator are weak

increase the revs on the truck see if that makes a difference to trailer battery voltage

[2WheelJon]

13.4 volts from the trailer battery can only come from a LiFePO4 batter(ies). This could be higher than the voltage coming from the truck when it’s hooked up (idling) and therefore the trailer battery is feeding the truck and therefore showing a drain and not charge. Also, not all TV trailer plugs charge lines are live when disconnected. On my Ranger the 12 VDC charge line is off until its plugged in. Lastly, to keep my LiFePO4 batteries charged when towing I installed a Victron DC-DC charger. Hope this helps.