Camper Battery Charging

[mudski]

Dont quote me Paul but the ctek works on lower volts but higher amps. I think thats correct???? Maybe why your seeing a lower voltage. ..

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[the evil twin]

Nah, thats the DC/DC conversion happening on the Alt +ve input.
IE the Ctek will take a voltage too low for efficient charging due to losses (say 12.5) and raise it to 13.8 at the cost of amperage

The Solar is opposite
IE it will take a voltage that is too high for efficient charging (17 volts) and use it to make more amperage at 13.8

[mudski]

Nah, thats the DC/DC conversion happening on the Alt +ve input.
IE the Ctek will take a voltage too low for efficient charging due to losses (say 12.5) and raise it to 13.8 at the cost of amperage

The Solar is opposite
IE it will take a voltage that is too high for efficient charging (17 volts) and use it to make more amperage at 13.8

Yeah i thought about that after i posted...

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[Cuppa]

Hi Paul,
Just read this thread. I too suspect that ET is correct.

I don’t believe there should be any need for a relay set up, & the Ctek should do a way better job than any cheapie reg stuck on the back of a panel. I have a relay set up with my Redarc BCDC, but this is only because the Redarc requires this for ‘auto’ switching between fixed solar panels & alternator. (Ignition controlled). I believe as Mudski has said that the Ctek automatically chooses the best source itself (different to the Redarc).

As per ET’s post (post #10) I reckon all is probably working as it should be. You could roughly check this by measuring the voltage of the Patrol’s aux battery & the camper battery bank after each has ‘rested’ for 20 to 30 minutes (i.e. ignition off & nothing running off the aux or camper batteries). I think you will find the camper batteries at a lower voltage than the Patrol’s aux battery, confirming what ET has suggested. You can check solar operation by then connecting the solar panel to the solar in terminals on the Ctek (still with nothing running off the camper batteries) you should observe a slow rise in camper battery voltage until they reach float voltage. Of course there will be less amps available than via the alternator so the charge rate will be lower & take longer.

I note that you said (in post #3) “I had been camping for a few days, so i moved the lead over to the solar input terminal, so i could use the solar panel to charge the battery’s."
If I’ve understood this correctly, you had used the camper batteries for a few days with no charge before connecting the solar to give them a charge. It is most likely that this is an unreasonable expectation of the solar panel. The best way to utilise the panel’s charging ability would be to connect the panel as soon as you can after arriving at camp, that way it will assist in keeping the level of charge as high as possible from the outset. Of course it you take out more than you put in to the batteries, they will still discharge, but by having the solar connected from the outset this will help to slow that discharge rate.

Also if when you measured the voltage on the camper batteries you had anything in the camper using power this too would show a lower voltage. (Eg. if a fridge was running voltage would be lower, with it switched/cycled off battery voltage would rise again after a short time (the reason for checking ‘rested’ batteries).

The reason the voltage would have been higher in the Patrol’s aux battery is that the Ctek also acts as a battery isolator, so any loads in the camper would not be drawing from the aux.

I reckon two leads/two anderson plugs is a better solution than a relay set up, but if running the additional lead is impractical an alternative would be a manual switch somewhere close to the Ctek to change between alternator & solar. A three position switch (On/Off/On) will suffice.

[paulyg]

Hi Ian, I should have made post 3 a bit clearer, I did connect the solar panels to the Ctek as soon as we got to camp.
Thank you to everyone who replied, as usual lots of good advice,