Hi Hilo friends! I'm the proud owner of a 1999 21TD hilo. I'm in the process of adding solar panels (100w total) and hoping to get some feedback - my main concern is whether there could be any issues over-charging the battery driving over the road when both the solar panels and car alternator are charging the battery at the same time? (I'm assuming the car alternator chargers the battery when driving based on general info I've read online, but not 100% certain on that detail either - trying to find my owner's manual to confirm.) I've read some info online that says charging from both sources isn't too bad, it may just cause the solar charge controller to artificially 'see' a higher voltage on the battery than reality due to the alternator trying to charge the battery at the same time. If this will be an issue I've been researching how to put some type of switch/breaker to cutoff the solar charging when I'm on the road. Then once I reach my destination I'd turn the switch back to allow solar to charge the battery. Still working out those details, but wanted to get feedback first if I need to go that route or not. Anybody with solar panels installed have to deal with this? Or am I making a big deal out of nothing? Thanks! -HiloDrew

Hello, Drew, and welcome!

I think you MAY be making a "big deal out of nothing". I have 300 Watts of solar power on the roof of my trailer and it constantly sends charging power to the trailer batteries along with power from my truck's alternator when I'm on the road. I'm also running the refrigerator on DC power during these trips. About the only difference I've seen from before, when I didn't have the solar input is that now, when we arrive at our destination, the trailer batteries are nearly fully charged. Before, they were always low.

There should be no "interference" caused by the 2-source charging. The voltage regulator on your alternator and the charge controller on your solar will keep the charging voltage at a proper level and the battery(s) will not be overpowered. There's no danger of say, power from the solar traveling back up to the tow vehicle's alternator and damaging it (or vice-versa). Both will "see" the same voltage at the battery terminals, and if it is in the neighborhood of 13+ volts, both will reduce the charging current accordingly. But if the voltage is below that, both will supply charging current as needed.

One of the big advantages of having the solar is that if you stop, say for lunch, the solar will continue to supply power to the battery and that will help support any draw from your refrigerator.

My only advice to you would be to seriously consider increasing your solar wattage to at least 200 Watts. Solar is not particularly efficient and you will find that under ideal conditions you will not see more than half the "rated" output from it.

I've had my panels operational for four years now, with no problems. Here's the link to the thread I posted on their installation: http://www.hilotrailerforum.com/f28/...allation-4354/

- Jack

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Hi-Lo 1707T - Tire Minder TPMS on Tow Vehicle and Trailer, 300W Solar Battery Charger, Equal-i-zer WDH, Progressive Dynamics Converter, Fan-Tastic Fan, LiFePO4 battery 12V DC Electrical System, SoftStartRV mounted on A/C
2024 F150 Platinum FX4 3.5L PowerBoost SCrew

Thanks Jack! I was hoping you'd chime in with your expertise on this. That's reassuring you haven't had any problems charging over the road, I'm not stressing out on it much now. I saw your post previously and really like the route you went with the flexible panels, it'd make install much easier/cleaner with not having to poke holes in the roof. I'm now re-thinking my plan and going to look into adding 200w with flexible panels. Thanks again! -Drew

I have a similar question. I have only one battery, I would like to add solar to my HiLo. I was looking at a 120-watt or a 200-watt one. We only use the camper several times a year and probably only once dry camping. Would this be enough to charge the battery? I know I have gone three days with only a small 1.2watt panel and all LEDs. We was careful how much we used. But we did not use the furnace. The refrigerator was on gas.

Thanks

tcongdon - I'm finding it hard to believe that a 1.2 Watt panel did ANYTHING to help your battery state of charge! I know a previous "portable" 60 Watt setup I used was able to just manage to keep the battery sort of charged over a long, 1 week+ period. I'm guessing after 3 days, your battery was probably pretty low.

But, if you have converted to all LED lighting and aren't going to use the furnace (it has a DC powered fan), won't use a ventilating fan (much) and minimize use of the water pump, then I suspect a 120 Watt or definitely a 200 Watt setup would work for you in a dry camping environment with ONE caveat, the panel(s) cannot be in "heavy" shade. I found that my roof panels did not work for us in the campground on the North Rim of the Grand Canyon because we were under a very dense tree canopy and got almost no direct sun. There were some clouds too. This actually surprised me, because I thought there was enough light, but I had to supplement the panels with my generator.

This was the ONLY time they let me down. They've been flawless otherwise.

- Jack

Drew, if you decide to go the flexible panel route and fasten them down with EternaBond tape like I did, I recommend you do this:

Get some double-stick EternaBond tape too. Apply it all around the perimeter of the underside of the panels and use that to add additional mounting security as a first step. Then, you can apply the regular EternaBond around the top edges like I did.

I discovered, when I added the third panel to my setup, that the top-only tape was not holding that panel properly, so I went the "double-stick" route on it that I just described. This has proven to be very secure. I used 3-in wide double-stick.

- Jack

Could you add this info to your main solar panel thread - or is it somewhere there and I am just blind....

No, you're not blind. I SHOULD have added this bit of information. I'll do it now.

- Jack