Charging aux battery in camper trailer

Submitted: Wednesday, Sep 23, 2015 at 19:56
ThreadID: 130383 Views:2385 Replies:9 FollowUps:2
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I am trying to get my battery in my camper trailer charged from my car. I have an anderson plug on the trailer and car both connected directly to the batteries but there is no charge getting through.

No I haven't installed a battery isolator or dc/dc charger. Just connected both batteries directly together. I figured I wouldn't need either as it is only to prevent the aux battery draining while driving then disconnected at the end of the day and the solar panel connected.

I'm not that technically or electrically minded but I don't see why it wouldn't work but it's not working as I want it to. My understanding on how it will work is that the lower charged battery will draw from the higher.

I don't have a second battery installed in my car. No real need given we always head out with the camper.

Any thoughts or advice would be appreciated
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Reply By: Robin Miller - Wednesday, Sep 23, 2015 at 20:29

Wednesday, Sep 23, 2015 at 20:29
It may not be Optimum Slats but it will work.

But what test have you done to determine it isn't charging ?

First thing would be to disconnect the second battery at the terminals and measuring the volts at the terminals.

They should be same as under the bonnet , which tells you you have good connections.

Then measure the 2nd and disconnected batteries voltage, if its lower a current will flow and charge it.

Maybe your solar is already charging the 2nd battery to higher than the cars battery voltage and if so no current will flow (into it).
Robin Miller

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Reply By: Notso - Wednesday, Sep 23, 2015 at 20:47

Wednesday, Sep 23, 2015 at 20:47
It will also depend on the size of the wire you are using. The voltage drop in thinner wiring can be very dramatic over 6 or 7 metres.

You may well measure the same voltage at the camper trailer as in the tow vehicle but as soon as you apply a load, eg. charging a battery then the voltage can drop to a level where you will get virtually no charge going into the camper battery.

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Reply By: Whirlwinder - Wednesday, Sep 23, 2015 at 21:08

Wednesday, Sep 23, 2015 at 21:08
And of course, it depends on what car you have and if it has a smart alternator.
A bit more detail might help.
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Reply By: Member - Robert1660 - Wednesday, Sep 23, 2015 at 22:20

Wednesday, Sep 23, 2015 at 22:20
Hi Slats,
Just a thought but it might be worth checking the Anderson Plug. Although you may be able to get a voltage output with a multimeter make sure that the pins in the plug are actually making a connection. We had this problem and it took some time to work out that the pins in the Anderson Plug were not installed in the plastic surrounds correctly.
Robert
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Reply By: HKB Electronics - Thursday, Sep 24, 2015 at 10:34

Thursday, Sep 24, 2015 at 10:34
Car make, model and year?

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Follow Up By: slats - Thursday, Sep 24, 2015 at 11:55

Thursday, Sep 24, 2015 at 11:55
I have a 2015 Colorado 7
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Follow Up By: HKB Electronics - Thursday, Sep 24, 2015 at 12:03

Thursday, Sep 24, 2015 at 12:03
I believe they have an ECU controlled alternator but I may be wrong, ask the dealer and if it has, if it is ECU controlled ask him if they can turn off the smart charge function for you?

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Reply By: Gronk - Thursday, Sep 24, 2015 at 10:57

Thursday, Sep 24, 2015 at 10:57
You need access to a digital multimeter....$10 if you can't get a hold of one .

Disconnect the camper from the car ( at the anderson plug )....start the car and check at the anderson what the voltage is ?
Check at the campers anderson what the camper voltage is ?
Reconnect the anderson plugs and check voltage again at the camper battery ?
If the voltage at the camper went up and is reading similar to the car voltage ( car still running ), then the charging circuit is OK.
If the camper voltage didn't change, then you have a break somewhere in the circuit ( as said, 1st place to look is the pins in the anderson plugs )

These tests will take all of 5 mins, so let us know how you go ?
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Reply By: Batt's - Thursday, Sep 24, 2015 at 11:36

Thursday, Sep 24, 2015 at 11:36
Take it to an auto elec and get it set up correctly or you may end up with 2 buggered batteries if one goes bad it may ruin the other. You may not need to spend much to set it up, you will have trouble free camping, a charged camper battery you can rely on and it will also be in your best interest to learn the basics about how long your battery will last running your camper so you can avoid ruining the battery.
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Reply By: TomH - Thursday, Sep 24, 2015 at 12:30

Thursday, Sep 24, 2015 at 12:30
What gauge cables are you using. Would suggest 6 B & S would be the correct size. anything under 8 B&S is too small
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Reply By: slats - Saturday, Oct 24, 2015 at 09:29

Saturday, Oct 24, 2015 at 09:29
So after finally getting my multi metre unpacked I've tested both connectors on the anderson plug. Carsideis a solid 12.7 volts withouth the engine running. Nothing on the camper trailer side. So seems to be a connection problem to the camper battery.

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