Simultaneous Alternator And Solar Charging?

Our TV is a 2017 Outback with (undoubtedly) a "Smart" alternator which should provide slightly less than full a trailer battery charge. I can't confirm this as we occasionally do seem to be able to get the trailer battery back up to 12.8V after a very long drive.

With the objective of attaining with certainty a full trailer battery charge between sites, I am considering connecting the 100W solar panel which is mounted on top to charge while we on the road. Essentially hard-wiring it. Typically, I have only connected the panel and used it while stationary and while disconnected from both shore power and the TV. The success of this solar strategy to this point has been very much hit and miss, given the time of day I'm connecting it, weather and site selection.

Unlike the CI solar install which is hardwired through the CTEK (I presume), and which can sort out multiple charging sources and chooses (and/or optimally boosts the voltage of) the best, my battery would be receiving charging from two sources with different set points for cut-in, cut-out, bulk, absorption, float etc... with no referee to prioritize or optimize the multiple inputs.

Does anyone have any experience in how these may play well together, or not at all? Would the system automatically default to the charger with higher voltage set points while the other charging source "goes to sleep"?

This is the best source of information that I could come up with: RV / Marine Battery Charging - Solar & Shore Power Combined! but it doesn't speak specifically as to how a solar charge controller with a 13.2V cut-in and a 14.2V cut-out will perform with the Outback's alternator, the specs and behaviour of which I am severely ignorant. All I know is that I'm probably not going to blow anything up or double-cook a battery by having multiple charging sources. Marine set-ups occasionally have all three sources (shore, alternator and solar) connected and operating at the same time with no ill consequences.

Any insight, particularly with the performance and idiosyncrasies of the Outback alternator, and how it may perform with a quality solar charger, would be welcome. Thanks.

 

Steve,

Your CTEK has a "Smart Alternator mode" built in. It activate it simply turn your running lights on while driving. The sense lead for turning on the Smart Alternator mode is connected to the running lights and that signal will tell it to turn on. When not in Smart Alternator mode the alternator will fold back back to save fuel and the resistance of the wire going back to the camper will prevent it from providing much of a useful charge to the camper's battery. When Smart Alternator mode is enabled it drops a half amp load on the line that forces the alternator to kick up enough to provide a useful amount of current to the charge line to allow the CTEK to provide it's full charging to the battery.

Prioritizing. The CTEK prioritizes to the solar input when source input is available on that line. For a camper with a roof top solar system driving down the road during the day the roof top solar panels will be providing the power source to the CTEK charging system and the tow vehicle charging will be turned off until the sunlight goes away. That should be the most efficient way.

Cary

 

Thanks Cary. That explains it way better than anything I’ve come across.

Its looking like a CTEK install, which I was kinda trying to avoid, may be the best solution.

If it has the added benefit of “turning off” the car alternator, at least while the sun is shining, then it may help (ever so minimally) pay for itself in added fuel economy. And added overall battery efficiency and certainty.

You bring up an interesting method of CTEK operation: I’m wondering if in the past I similarly may have been able to fool the smart alternator and its ECU into putting out more voltage to the trailer by driving with headlights on. That has been suggested on some other Outback-towing forums as a work-around to an undercharged trailer battery from a smart alternator. Is this why I may have experienced a battery charged back up to 12.8V after driving a distance?

 

Steve,

I suspect running the headlights with a smart alternator has a similar effect by the load of the lights kicking up the alternator which would give more charging available to the car's battery also. It would be a similar effect as the load the smart alternator mode in the CTEK.

Cary

 

Cary: Thanks. It sorta made sense. But I take that sort of info on third party non-trailer forums with a big grain of salt. Thanks for semi-confirming my suspicions.

Whether it does fool the smart alternator, or not, I pulled the plug 10 minutes ago on a Renogy DC-DC. Which was on sale for $200 (CDN.) I believe that it has many of the same functions and characteristics of the CTEK, as a dual-source (solar-alternator) device, and has a similar install procedure.

My only Q? would be can the "ignition wire" be connected in the same manner, to the trailer running lights, as you have guided others with their CTEK install? This is simply an on-off switch for the device, and doesn't necessarily need a specific voltage taken from a wire close at the ignition wires, correct?

 

Steve,

Correct, ignition trigger wire just needs to be a voltage source that the operator can power on and off. That is why we use the running lights. Turning on the running lights powers up the smart alternator circuit.

Cary

 

Thanks. 80% of the way there. Just need to find a decent place to put it. And some weather that is above freezing.

 

Steve the Nest upgraded my used/new to me 560 with the AutoW and Ctek in the right hand galley bin.

( I later added the NOCO5 to same area when came time to replace the shore battery charger when it failed as it was just too hard to get at below especially with the added CI trailer hitch blocking access to the original location between water tanks spot).

I just store soft stuff on that right side and heavy hard stuff in the left bin.

 

Kevin: I was just looking at the right side bin. The Renogy is 9 1/2" x 6 x 3, plus holes for the cables. That's pretty much the only place to mount it, with cables going to and from it entering the cabin at the foot of the mattress (hopefully out of sight) and being fed into the battery compartment at the same height.

I just ordered yesterday a set of Magma nesting cookware to increase space in that bin (to replace my rag-tag collection of camping cookware) but that may not be enough. Further, I wouldn't want something like the Renogy taking a hit from something hard and heavy like my Dutch oven; I'll have to go with "soft" stuff as you suggest. I'm not hurting for gear space overall; just need to reimagine where everything goes now.