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Old 03-23-2015, 10:18 PM   #1
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Wiring solar charger to factory separated 12v batteries?

We have a 2003 30' Classic and are looking to add maybe three 100w solar panels to the roof to aid in keeping batteries charging during prolonged boondocking. After much research, I understand just enough to be dangerous. After installing the panels and connecting them to a combiner box in the fridge vent, they will connect with the charge controller. At that point, the cables should run to my two 12v batteries. However, the two batteries are located in the separate factory battery boxes under the front lounge (externally vented, externally accessible only). So, in this case, am I not connecting the cables from the solar charge controller directly to the batteries? The batteries must be factory wired in series or parallel under the lounge, but the batteries themselves are only accessible externally in individual bays on either side of the A frame. So where do I actually connect these wires? What exactly am I looking for under the lounge? And how do I make sure to maintain the integrity of the current 12v and 110v electrical systems? For additional consideration- I have upgraded the factory two stage converter to a newer 4 stage Powermax converter after emailing Randy at best converter (learned a tough lesson after frying the original batteries on shore power). I also will probably be installing new lifeline AGM batteries at some point, although the battery boxes are fairly restrictive in terms of size/ capacity. I really would rather not rebuild a new battery compartment inside the A frame or under the lounge if I can avoid it. So, am I looking for a similar combiner box/terminal for the batteries under the lounge to connect these solar cables to?
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Old 03-24-2015, 08:29 AM   #2
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Mastermarx,

I have a setup almost exactly as you describe except that I have 3-120 watt flexible panels. They are combined at the refrigerator roof vent and a #6 AWG leads to my MPPT controller located about 18" from my two 12v batteries wired in parallel. I've used #2 AWG between my controller and batteries and also between my batteries and 1000 watt inverter. As to how I penetrated my battery box, I simply drilled holes near the top the size for the #2 wires.

I am currently using the lead acid batteries installed by the dealer, but I plan to replace them with AGM batteries when these start to go. I will add a third AGM battery, but since these are sealed, I will locate one of them in an interior cabinet near the two others in their battery boxes.

That's it in a nutshell.
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Old 03-24-2015, 08:42 AM   #3
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Thanks AC! I'm concerned about drilling holes in the battery boxes. For one thing, after experiencing the original batteries' venting episode, I'm not sure I'd seal that box well enough that it wouldn't vent back into the trailer where someone in sleeping. I do get that the AGM batts would be sealed, but for now it's lead acid.
As for the cables, you must have split the return on the pos/neg wires at some point to connect to each battery, right?
Thanks for the response!
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Old 03-24-2015, 08:50 AM   #4
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I caulked around the holes to seal them. Rubber grommets would have been better, but I forgot to put them around the wire before I applied the lugs to the wires ends.

I used terminal blocks to connect the wires. Most of the connectors I used were for marine application, including the wire. Marine wire (i.e. West Marine rather than Home Depot) has more strands and is more flexible which makes pulling and connecting easier.
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Old 03-24-2015, 09:16 AM   #5
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Thanks AC, I'll check it out and see what that looks like here. The rubber grommets do sound like a good idea, too.
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Old 03-24-2015, 01:36 PM   #6
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You do not have to access the batteries. Just connect the Solar regulator output to the Converter battery input cables. You are not running high currents through these wires. If you have junction posts for the connection to the Converter you can use them. Or just wire directly to the posts on the Converter.
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Old 03-24-2015, 07:14 PM   #7
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Quote:
You do not have to access the batteries. Just connect the Solar regulator output to the Converter battery input cables.
I beg to differ. Solar controller wiring should always run directly to/from the batteries and not be connected through busbars or converter as you suggest.
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Old 03-24-2015, 07:33 PM   #8
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i beg to differ. Solar controller wiring should always run directly to/from the batteries and not be connected through busbars or converter as you suggest.
right on!!!! :d
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Old 03-24-2015, 09:50 PM   #9
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There are several busbars leading from the batteries to the converter. I truly think it's unwise to drill through the battery boxes, however I see no other choice if the busbars are out. And I'm assuming I'll lose a considerable amount of voltage by using the busbars?

I hadn't thought about using the poles from the converter... I thought that may interfere with the function of the converter overall.
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Old 03-25-2015, 06:09 AM   #10
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Your battery boxes are ABS plastic, easily drilled and easily filled and sealed after you run the solar charge lines to the batteries.

Some of the MOST important installation details of RV solar are to minimize all connections in the cable runs, use appropriate gauge cable for your system, keep the solar charge controller as close to the batteries as is practical and connect the solar charge controller DIRECTLY to the batteries.

It's your system and of course, you can place the wiring any where you like, but you WILL see measurable voltage drop with any other connection method other that what is stated above.
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Old 03-25-2015, 10:49 AM   #11
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I beg to differ. Solar controller wiring should always run directly to/from the batteries and not be connected through busbars or converter as you suggest.
I beg to differ with your 'beg to differ'. There is nothing magical about solar regulators and how to hook there output to the batteries. The amount of voltage loss is determined by the current output, the wire size and the wire length (times 2 for the plus and minus). Ohm's Law should work fine for this calculation.

The cables use to connect your batteries to the Converter are probably the largest size used in the trailer. You can easily determine what the voltage loss will be by measuring the voltage on the battery and then comparing it to the voltage at the converter input terminal. Turn on several fans including the heater and ventilation units so you get some current draw. I seriously doubt that you will be able to measure any voltage loss.

I have connected many solar regulator outputs to the Converter terminals with no problems and virtually no voltage loss. This negates the need for drilling through the body, running separate cables and then rigging up an attachment connector to go directly to the battery terminal.

Several times, with just a single solar panel, I have connected the regulator to the refrigerator 12 volt supply. This made the installation quite easy. This works best with a 3-way fridge which has a heavy duty wire size for 12 volt operation. The primary purpose of the Solar was to provide a trickle charge for the batteries to keep them from freezing.

Unfortunately many of these 'so called' rules have been hanging around for years and have become accepted facts.
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Old 03-25-2015, 12:26 PM   #12
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Wiring solar charger to factory separated 12v batteries?

Providing a trickle charge is quite different than boondocking where you're trying to maximize current to your battery bank so you can get through another day or two of cloudy days!




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Old 03-25-2015, 01:20 PM   #13
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Any type of wire sending a 'trickle charge' thru numerous connectors and wire lengths will 'work'. How well it works is the ultimate question.

The 'rules' you speak of are actually well researched results from 28 years of research and experimentation specifically on RVs and their solar charging systems.

Greg Holder of AM Solar is one of the true experts in the RV Solar field. His systems and installation methods work to maximum efficiency due to his years of practical research in the field on real RVs.

Call it what you like and do as you will. I'll stick with the experts (and so do my clients). Thanks!


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Old 03-25-2015, 03:04 PM   #14
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Any type of wire sending a 'trickle charge' thru numerous connectors and wire lengths will 'work'. How well it works is the ultimate question.

The 'rules' you speak of are actually well researched results from 28 years of research and experimentation specifically on RVs and their solar charging systems.

Greg Holder of AM Solar is one of the true experts in the RV Solar field. His systems and installation methods work to maximum efficiency due to his years of practical research in the field on real RVs.

Call it what you like and do as you will. I'll stick with the experts (and so do my clients). Thanks!



Lew Farber
RVIA/RVDA Nationally Certified Master Tech
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center
Lifeline Batteries**Magnum Inverters
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That is exactly what I am talking about. Show me the technical article that says Solar systems must be attached directly to the battery. Unfortunately I find these so called rules all over our Camping community. They result in thousands of campers towing unsafe rigs, filling there tires to the pressure number stamped on the tire instead of the correct level based upon weight, etc., etc. Attaching the regulator for three 100 watt solar panels to the main battery bus in a trailer is perfectly acceptable and will not result in any significant voltage loss or degradation in performance.

The 'experts' or old timers who are referred too that have been doing it this way for 25 years do not impress me. Since I have been camping for over 70 years when I ask why is this correct I expect an article, a manufacturers specification or a calculation.
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