Basic Question: Looking for wiring diagram, Solar + DC to DC charger

[ADDvanced]

This is super common, idk why I can't find a basic diagram like this, but I have a van, 12v start, 12v house battery, and I want to do solar AND a renogy 20a dc to dc charger..... not sure how to incorporate both at the same time?

Thanks in advance!

 

[ADDvanced]

That's it? What about when driving, on a sunny day with dc to dc going? No issues? Huh. That's easy enough.

 

[john61ct]

If you want both batteries charged off solar

say you leave the vehicle stored outdoors without shore power available

then the SC can go to Starter and the DCDC will pass it through to House

assuming it has a VSR/ACR type switch built in, as the good ones do.

 

[Martinjmpr]

Simply connect the output from the DC to DC charger to your house battery.
Connect output from your solar controller to your house battery also.

That's literally exactly what I did with mine.

DC-DC charger connects to my battery box using a large Anderson connector.

Solar connects with an SAE cable. I use an SAE cable because when I'm at home the battery box sits on a .75a Battery tender to keep it charged. The Battery Tender harness has (I think) a 10a or maybe even a 7.5a fuse. My solar panels are 100W so there will never be more than maybe 5-6a going through them.

Our travel trailer has an SAE harness on the battery as well as one on the rear body of the camper that goes directly to the battery, so with a 25' SAE extension cable, I can position the solar panels wherever they need to be for maximum sunlight. Sometimes if we are sitting at a campsite for a few days, once the camper batteries are topped off, I'll switch the solar panel to keep the battery box in the truck charged. However, I'm now thinking of maybe buying a 2nd 100W panel to dedicate to just the truck.

I don't see any actual value in having the solar pass "through" the DC-DC charger, and I don't see any harm in having two separate harnesses on the battery to provide power.

I'm a simple guy and I like to keep things simple. Having two harnesses, one for the Renogy DC-DC charger and one for the solar panels, is simple.

EDITED TO ADD: The solar panel has the charge controller on the back of the panel, so the wiring goes solar panel ----> charge controller -----> battery. I suppose if the DC-DC charger could also function as a charge controller, you might want to run it through there just so you don't have to have a separate charge controller, but I need to have the charge controller on the panel anyway for the camper (which does not have a charge controller.) So, my system works and that's all I really care about.

 

[DiploStrat]

I simply connect the DC-DC charger and the solar controller to the camper battery. This way, the output of both chargers is added together.

BUT, jon61ct is actually being VERY clever here. By connecting the solar controller to the starter battery (and setting the profile appropriately) he is providing an elegant solution to the problem of solar charge to the starter battery when in storage. I use a second DC-DC charger and a ton of relays to do this. Others may use something like the AMP-L-START, etc.

The only drawbacks to john's solutions are:

-- Your total charge is limited to the charge of your DC-DC charger. The charge from the solar controller is not added on top of the DC-DC charger.
-- Assuming that your shore power charger is connected to the camper battery, that charge is not shared back with the starter battery.

So, depending on the size of your battery and the size of your DC-DC charger, this could be a really slick solution. Especially as I have seen some unconfirmed indications of interaction between chargers. (Never a problem with lead acid, but may be an artifact of the very flat voltage curve of a lithium battery bank.)