Dual Battery Quick Sanity Check

[Infidel_XJ]

Howdy... Just a quick sanity check on the below please.

I currently have an 06 Tundra with a dual battery set up. Both my starter and house batteries are AGM. I have an Keyline Chargers Smart Isolator between them. Starter battery charges first through the alternator, then charging the house battery after the starter battery is "topped off". Even if my house battery gets drawn low, it won't pull from my starter battery due to the isolator. Nice and simple...seemed to work well for running my fridge and a few small 12v items during my last trip.

I have a hood solar panel (and a briefcase panel) I'd like to add to the mix. Since the truck won't always be running when camped, this would help topping it off. I'm assuming I'll need an MPPT solar controller now as well for this. Am I correct to assume that, since solar and alternator charging should play well together, I can leave the current set up (alternator - starter battery - isolator - house battery) and simply add the solar controller between the house battery and solar panels? Or will there be an issue with the alternator/starter battery charging the house battery at the same time the hood solar panel is?

I'd looked into upgrading the house to a LiPo, but then I'd need a DC to DC charger and for the low draw requirements I have for items in the truck...I decided just to stick with the AGM...possibly upgrading it to a Renogy 100ah AGM for a bit more storage. My small travel trailer has a Lithium set up for it's more robust demand.

Thanks in advance

 

[jonyjoe101]

You only need a mppt controller if you have a large solar panel 200 watts or more (40 volt panel), if you have a smaller 120 watt panel or similar (24 volt panel) you only need a pwm controller. On the back of the panel it'll give the max panel voltage.
You can use either the mppt or pwm on either panel but on a low voltage panel the more expensive mppt controller won't extract more amps out of it.
Example on a 120 watt (24 volt panel) pwm will give you 6 amps of output, the mppt will also give you 6 amps output power.
You connect the controller between the panel and house battery, there should be no issue between anything.
I recommend you get a a 90 volt 30 amp combometer (you can find on ebay for 20 dollars) and connect between the controller and house battery so you can see if the controller is charging at max voltage (14.4 volts).
Most controllers pwm/mppt dont have LCD screens, if they have them they are inaccurate, having a combometer you can make sure the battery is getting charged to full capacity.

 

[Verkstad]

Fwiw,
You mention you have a hood solar array and a briefcase array.
Unless their outputs are identical, which is most unlikely. And you plan to use them on the same battery at same time.
You will be better off using individual controllers for each array.
Total energy captured on mismatched solar array is less than the total if each array uses its own controller.

 

[Infidel_XJ]

Thanks to you both.

I should have clarified.... The hood panel will be connected normally and if I decide to use a briefcase panel, I'd undo the hood connection. There would only be 1 panel connected at the same time...either briefcase or hood.