Connect solar panels

[mgermasi]

Hi Guys
Hope you all had a great Xmas break!

I have a projecta DBC 150 electronic isolator to charge 2 x 55Ah auxiliary batteries.
I'm planning to buy a set projecta 120w folding solar panels for my next trip BUT where should I connect them?
1)- Directly to the main battery so that the isolator will take care of charging the auxliary batteries?
or
2)- Directly to the auxliary batteries?

Thanks a lot
Maximus

 

[Old.Tony]

It depends on where the regulator is.

Unregulated 12V solar panels produce between 18 and 20V roughly, and that'll fry the battery regardless of what it is (it's one way to cook a spiral wound AGM, other alternatives are squashing it, shooting it, setting it on fire or using a dwarven battleaxe).

If the panel has a regulator you should probably hook it straight up to the battery. The isolator doesn't look like it has a battery management module - if you were using something like a C-Tek D250S then you'd disable the regulator and let the charger manage the input power.

If your panel does NOT have a regulator (and you can tell, put a multimeter on the leads when the panel has sunlight on it, 14-15V = regulated, 18V+ = unregulated) then you will NEED a regulator of sorts. A decent 20A regulator will cost you $149 from Jaycar and the Ctek D250S is about $250.

 

[Tappet]

Yeah be carefull on that one as Old tony points out unregulated you can fry the bat although the 18-20 volts is usually a full sun, at midday open circuit voltage and once connect to a discharged bat it will not be that high, however if the bat is at full charge it will be and fry it. Regulation is the way to go.

 

[mgermasi]

The panels come with a regulator. http://www.projecta.com.au/Products/TravelFriendlySolarPanelKits
If I connect the panels to the main battery would the DBC 150 electronic isolator (http://www.projecta.com.au/Products/PowerManagement/DualBatterySystems.aspx#!prettyPhoto ) start charging the auxiliary batteries once the main battery is fully charged?
Or will it work better to connect the panels to the auxiliary batteries?

Thanks

 

[gunning1987]

I'd connect it to the one with the most current being drawn, if you connect to the main it'll feed back to the aux from the isolator but I think you'd loose some of the efficiency of the panel.

 

[Old.Tony]

You could connect it to the main battery but I don't know how the panel will fair with the alternator jamming power into it directly.

This is the perfect scenario to introduce a C-Tek D250S, and allow it to decide between isolator-guided alternator power and the solar input.

However, without that device, I'd probably hook the solar panel in to the aux battery (so it sits on the "south side" of the isolator). I might even put a low-cost VSR in the solar panel output and use the relay to disconnect the isolator, so if the sun's shining bright while you're driving along, the solar panel does the work and leaves the alternator alone.