Connecting solar converter to batteries - Fiberglass RV


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Old 11-08-2014, 03:00 PM   #1
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Connecting solar converter to batteries

I have two 40W solar panels running into an MPPT15 Charge Controller. Can I connect the controller directly to the batteries (two 6V in series) or should it be run through the Progressive controller/charger? If it's the latter, is connecting to the converter straightforward?
Thanks,
David
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Old 11-08-2014, 04:24 PM   #2
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Originally Posted by Stretcher View Post
I have two 40W solar panels running into an MPPT15 Charge Controller. Can I connect the controller directly to the batteries (two 6V in series) or should it be run through the Progressive controller/charger? If it's the latter, is connecting to the converter straightforward?
Thanks,
David
Key words "Charge Controller"..... Yes connect the "Charge Controller" directly to the battery.
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Old 11-08-2014, 08:51 PM   #3
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Not only should you connect the charge controller directly to the batteries but you should use as short a run of wire as possible between that controller and the batteries and use the heaviest gauge wire (8-10) as possible. The maximum wire gauge maybe determined by what the charge controller will accept. I would try to keep the controller within 3 feet of the batteries.

General practice calls for a fuse or fuses between the panel and the controller and again between the controller and the battery. If the panels are mounted on the roof a "kill switch" should be installed to facilitate maintenance. If they are portable it is not as critical.

Check the manufacturer specifications for your dual 6 volt batteries to see what charge voltage they recommend, then configure your controller accordingly.

Though not as critical as the wire between the controller and battery, the wire from the panel to the controller needs a proper gauge depending on the length of that run. Using 10 gauge here can help but becomes unwieldy and expensive, 12 maybe the best here.
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Old 11-08-2014, 10:26 PM   #4
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[FONT=Georgia][SIZE=3]

General practice calls for a fuse or fuses between the panel and the controller and again between the controller and the battery.
Really? Not sure I have ever seen that mentioned before.

What size fuses should the solar systems have? I know mine doesnt have an inline fuse from the solar controller to the battery (unless the controller itself has one built in that I can't see) and I know there is none in the connection from the controller to the panel (which is portable) and the quick connection - all came together as a package from the same manufacture. I do though have the standard inline fuse right of the battery to the trailer though.... along with another inline fuse on the line going to the trailers converter. I have helped a couple of others with there installs as well and I don't recall seeing any inline fuses on their controllers of panels either. Is this something that is only put on high wattage panels perhaps? 200W or more maybe?
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Old 11-09-2014, 07:20 AM   #5
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Really? Not sure I have ever seen that mentioned before.

What size fuses should the solar systems have? I know mine doesnt have an inline fuse from the solar controller to the battery (unless the controller itself has one built in that I can't see) and I know there is none in the connection from the controller to the panel (which is portable) and the quick connection - all came together as a package from the same manufacture. I do though have the standard inline fuse right of the battery to the trailer though.... along with another inline fuse on the line going to the trailers converter. I have helped a couple of others with there installs as well and I don't recall seeing any inline fuses on their controllers of panels either. Is this something that is only put on high wattage panels perhaps? 200W or more maybe?

My internet study on this subject is just that, study as I have not burnt anything up yet testing. But this research indicates no fuse is necessary between the panels and controller. The panels are the power source and can only put out so much energy which the wire and controller are, by design, capable of handling under any scenario. This does not apply past the controller however and BOTH sides of the battery-involved circuit should be fused, in AND out. I think this is a MAJOR failing of the solar "kits". I bought one too and even though their own diagram that came with the kit showed fuses none came with the kit nor did the company sell any! When I e-mailed the company asking about this they said to get some from ebay or Amazon. I thought that was pretty dadgum lame but did end up getting some from Amazon. Remember, fuse size is determined on protecting the circuit and is usually based on the wire size protected.
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Old 11-09-2014, 10:42 AM   #6
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The panels are the power source and can only put out so much energy which the wire and controller are, by design, capable of handling under any scenario. This does not apply past the controller however and BOTH sides of the battery-involved circuit should be fused, in AND out. I think this is a MAJOR failing of the solar "kits". I bought one too and even though their own diagram that came with the kit showed fuses none came with the kit nor did the company sell any! .
Thanks Tim you at least have seen a solar manufacture suggest a fuse be used in line between the controller and the battery in the documentation that came with a panel. I had just assumed apparently incorrectly that the controller was actually the protection system and had its own built in fuse.

What size fuse did the company suggest and what size was the panel?


I just did a google search on solar wiring diagrams and sure enough there were a small number of solar wiring diagrams showing a fuse between the panel and the controller. Mostly on multi panel systems. I did find a fair number more wiring diagrams with the fuse between the controller and the battery though but nothing between the panels and the controller.... even more with no fuses at all on the solar side ...interesting.

Now wondering if there is a certain panel wattage size that one need not to worry about adding an in line fuse?
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Old 11-09-2014, 11:13 AM   #7
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Carol, they did not show a size just that there was one. In any event it is not that difficult. You size a wire to carry a load and a fuse to protect the wire. The Electrical code and usual practice have fairly well established the norms of fuse/breaker protection within certain conditions. As a usual practice 14 gauge wire is protected by 15 amp fuses/breakers, 12 gauge 20 amp, 10 gauge 30 amp, etc. Nothing wrong with over protecting too. And one other point, DC rated fuses and breakers should be used. They may be more robust than their AC equivalents. You may have an 8 gauge wire from the controller to the battery protected by a 40 amp fuse but only a 12 gauge wire from the battery into the trailer protected by a 20 amp fuse and that is fine.

I forgot to say in case it is not clear that the protection (fuse) should be as close to the source (battery) as practical.
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Old 11-09-2014, 01:33 PM   #8
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Originally Posted by Timber Wolf View Post
Carol, they did not show a size just that there was one. In any event it is not that difficult. You size a wire to carry a load and a fuse to protect the wire. The Electrical code and usual practice have fairly well established the norms of fuse/breaker protection within certain conditions. As a usual practice 14 gauge wire is protected by 15 amp fuses/breakers, 12 gauge 20 amp, 10 gauge 30 amp, etc. Nothing wrong with over protecting too. And one other point, DC rated fuses and breakers should be used. They may be more robust than their AC equivalents. You may have an 8 gauge wire from the controller to the battery protected by a 40 amp fuse but only a 12 gauge wire from the battery into the trailer protected by a 20 amp fuse and that is fine.

I forgot to say in case it is not clear that the protection (fuse) should be as close to the source (battery) as practical.
Thanks Tim appreciate that adding an inline fuse is not difficult but as I indicated just surprised for the need for one on the controller. As I indicated I had not seen that specified in the system wiring directions received from the solar manufactures equipment that I have helped install in the past - including my own. In looking at the various solar equipment suppliers online it also does not appear that they routinely include an inline fuse holder on wire for the battery to controller connection even if you order one custom made from them complete with connections .... just seems odd.

I guess I was simple silly to think that that the world "Controller" meant it was actually controlling the output to the battery and would have its own built in mechanism for preventing more amps being pushed to the trailer battery than it could safely handle - would have thought the Controller would have its own built in fuse. Or at least I would have expected some of the pricer controllers would.

Just goes to show you learn something new every day!!
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Old 11-09-2014, 03:19 PM   #9
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While a fuse between the controller & panel is not required in many small systems since the short circuit current is fairly low compared to the wire sizes likely to be used, the wiring between the controller & battery is likely to be far smaller than the short circuit current the battery can provide. Because of that, it is important to fuse for the wire size on the battery side. If something fails in the controller causing a short to ground, it would be possible for the hot wire to attempt to carry the short circuit current of the battery, i.e. hundreds of amps.

In my case the factory installed GoPower system has a 30 amp circuit breaker protecting the #10 wire between the controller & battery. While there is no fuse or breaker between the built in panels and the controller, I did add one for the connection of my portable panel.
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Old 11-09-2014, 04:14 PM   #10
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Thanks for adding that Jon. You are correct that there is no requirement for a fuse between the panels and the controller. However, like you, there are some installers that do recommend them. Here is a link to one. This is one of those nebulous practices that some installers do and others do not.

I like the idea that if I have a wire carrying a current there should be some protection on it. My panels are portable, thus outside and potentially in the rain. A heavy rain, water puddles and a frayed wire could be a nasty surprise. I can envision some similar scenarios.

The link I provided is for ChromolyWally and is one chapter of an eight part book he has published on line. I find it an easy read and full of down to earth advice. However, I am not a solar expert so I have no idea how accurate Wally's advice is.
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Old 11-09-2014, 04:22 PM   #11
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Fuses are an interesting item. There's a saying in the electronics industry that when put a fuse in the circuit, the electronics protects the fuse. So don't be surprised even with fuses on both the input and output of your solar charge controller it goes away and fuses are still good.
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Old 11-09-2014, 05:36 PM   #12
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I guess I was simple silly to think that that the world "Controller" meant it was actually controlling the output to the battery and would have its own built in mechanism for preventing more amps being pushed to the trailer battery than it could safely handle - would have thought the Controller would have its own built in fuse. Or at least I would have expected some of the pricer controllers would.
As indicated in other posts a fuse between the battery and controller is not protecting the battery from the controller, it is protecting the controller (maybe) and the wire running between them. Dead short a wire between the positive and negative posts of a battery and see how hot it gets (do not really do this). I can tell you from first hand experience, at least hot enough to melt lead! In any event a fuse is at least a disconnecting means if nothing else and why, I suspect, it is sometimes shown between the panels and controller on wiring diagrams.
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Old 11-09-2014, 06:05 PM   #13
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Dead short a wire between the positive and negative posts of a battery and see how hot it gets (do not really do this). I can tell you from first hand experience, at least hot enough to melt lead!
Oh but I got to try it now you have said it!

THANKS everyone for clearing up my confusion as to why a fuse should be between the controller and the batter.

Still wonder though why the folks who will make up custom connections or the companies that sell the complete solar kits do not include an inline fuse holder as a matter good practise.
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Old 11-10-2014, 02:13 PM   #14
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Still wonder though why the folks who will make up custom connections or the companies that sell the complete solar kits do not include an inline fuse holder as a matter good practise.
That is a puzzler. Here is a pretty clear diagram that shows fuses everywhere: http://www.renogy-store.com/v/vspfiles/photos/RNG-100D-5.jpg One point; modern automotive blade fuse holders are readily available and I have found both 12 gauge and 10 gauge wire models. My local NAPA store had the 10 gauge variety fairly cheaply. The blade fuses are convenient and can be easily tailored to the desired protection just by changing the fuse. But, just like with the old screw in glass fuses one can easily put too much fuse in and have little or no protection.
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