Solar self-install on MB December 28, 2004, 10:19:39 am Yahoo Message Number: 48395Hi all,I'm gathering the parts for my solar install and have a question about the factory solar wiring on a 26 MB. While it's tempting to run the wires from the roof panels down the refrig vent, there's not a lot of room to mount the charge controller near the fridge.I'm pretty sure the factory runs the wires down inside the closet for this reason, and mounts the charge controller on the closet wall - - lots of room. This route means more wire length to get to the batteries. The question . . .Does the factory run the wires from the charge controller to the batteries as a seperate run, or do they instead run them to the generator located just forward on the right side? The starter cable going to the generator is large, so going to this terminal would provide a low resistance way to tie in to the house battery positive. Tempting (g), and one less large wire going to the battery compartment. Thoughts?all the best,bumper
Re: Solar self-install on MB Reply #1 – December 28, 2004, 10:56:37 am Yahoo Message Number: 48396Bumper You might want to relook at the refrig vent.
Re: Solar self-install on MB Reply #2 – December 28, 2004, 11:37:42 am Yahoo Message Number: 48397Dan,Thanks for the input, I'll check that location above the microwave to see if it'll fit. The RV Power Systems (now Blue Sky) MPPT charge controller is (guessing) 4 X 6 for the panel, and 2" deep.Having a slightly longer wire run shouldn't be a problem (though, for a change, shorter *is* better), as I bought some bodacious cable (4 ga) from www.weldingdepot.com - - cheapest place I could find. I also bought some in-line quick disconnects for this size cable as my under frame mounted, swing down battery box will need to be unplugged to easily remove.As it won't be very convenient to check fluid levels, I'll be using a Pro-fill too.
Re: Solar self-install on MB Reply #3 – December 28, 2004, 12:09:25 pm Yahoo Message Number: 48400Quote Dan,"Thanks for the input... The RV Power Systems (now Blue Sky) MPPT charge controller is (guessing) 4 X 6 for the panel, and 2" deep..."Quote "I'd rather do the filling from the upper battery box, but am concerned that ... may slowly overfill the physically lower add-on battery bank..."Quote bumper Bumper The Solar Boost 2000e measures 4 5/8" X 6 3/8" X 1 7/8". The company also offeres a "Optional conduit ready surface mount box" if you were inclined to got that way.On the Flow-Rite systems, specifically the Pro-Fill, I think you will find that the magic component that will not permit overfill is a valve which is integral to each cell which, when the water level rises to a pre-determined point, shuts off the flow, preventing further input. That should work equally well no matter the physical orientation of the battery bank.Steve S. Lazy Bones
Re: Solar self-install on MB Reply #4 – December 28, 2004, 12:09:44 pm Yahoo Message Number: 48401I'm not going to tell you that cable length and gauge don't matter...but with your solar system putting out an maximum of 240W under ideal conditions and probably about half that most of the time, the wiring from your panels to your controller is not nearly as critical as the wiring from your batteries to that 2KW inverter. I wouldn't think twice about running the cable down the fridge vent if that were more convenient, even if it meant the run would be a few feet longer. In fact, that is exactly how Gertie was wired by the previous owner, a perfectionist software engineer, and his brother, an electrical engineer. There's a not-too-heavy cable (I'd guess AWG 14) leading from the 204W worth of solar panels down the fridge vent to the controller...but there are cables the size of your thumb (and very short runs) connecting the four house batteries to the 2KW inverter. Those guys knew exactly what they were doing. Even multiple solar panels don't put out enough juice that you need to go crazy with 4-gauge cable...save it for the battery-to- inverter run, where you really need it.Andy Baird
Re: Solar self-install on MB Reply #5 – December 28, 2004, 03:40:19 pm Yahoo Message Number: 48417Bumper The controller I installed was the Solar Boost 2000. It just fit nicely above the Microwave and the ceiling. I had to trim a bit off the top and bottom 1X2's frame of the compartment to make it fit. Dan Zoll
Re: [Life With A Lazy Daze RV] Re: Solar self-install on MB Reply #6 – December 28, 2004, 04:12:12 pm Yahoo Message Number: 48418Andy's right on the wire size, since you should never see more than 20 amps from the 240 W panels, 14 awg wire should be sufficient, but I'd probably use 12 awg to be sure. 4 awg is definitely overkill but won't hurt anything. Just be sure to fuse whatever wire you use with a fuse size matched to the wire size used where it connects to a larger size (lower awg number) wire or the battery. 14 awg is normally OK with a 20 A fuse, 12 awg is normally OK with a 30.Rich 2000 MB Lake Stevens & Birch Bay, WA
Re: Solar self-install on MB Reply #7 – December 28, 2004, 07:39:55 pm Yahoo Message Number: 48423Steve,Thanks for your help.I looked at Yonder today and shur'nuff, there's plenty of room over the microwave for panels and meters (g).I agree, having the Pro-fill filler tube uphill from the lowest battery bank wouldn't be a problem *if* all the individual valves close completely and don't leak even a teensy little bit. But if one should leak, then the water
Re: Solar self-install on MB Reply #8 – December 28, 2004, 08:37:03 pm Yahoo Message Number: 48428Quote I'm not going to tell you that cable length and gauge don't matter...but with your solar Quotesystem putting out an maximum of 240W under ideal conditions and probably about halfQuotethat most of the time, the wiring from your panels to your controller is not nearly as Quotecritical as the wiring from your batteries to that 2KW inverter. I wouldn't think twice aboutQuoterunning the cable down the fridge vent if that were more convenient, even if it meant theQuoterun would be a few feet longer. Andy,I agree, but I'm also mindful that wiring voltage drop is wasted power, and heavier wiring is cheap. One of the reasons to use welding cable, is that due to the very fine strand size, it's remains flexible and easy to work with. I'm aware that the battery to inverter run is far more important, as current will be high when running heavy loads like the microwave. This run will be short and will use #4/0 AWG, NEC rated in conduit for 230 amps, much heavier than the 4 gauge welding cable from the solar array.bumper (who actually has a California electrical contractor's license - - though I sure wouldn't want to live in a house I wired! I was forced by silly CA law to get the C-10 license to continue to install and service fire alarm systems back when I used to work [harder] for a living.:c)
Re: Solar self-install on MB Reply #9 – January 01, 2005, 08:51:42 am Yahoo Message Number: 48534QuoteI agree, but I'm also mindful that wiring voltage drop is wasted power, and heavier wiring is cheap. One of the reasons to use welding cable, is that due to the very fine strand size, it's remains flexible and easy to work with. Since 240W @ 17V corresponds to 14 Amps, gauge is of small importance - particularly for the run from the panels to the charge controller. Check resistivity of the wires and add the combined pos/neg run lengths as a multiplier to get your voltage drop. Anything of 1V or less is not significant to your daily A-hr charge total. Where problems arise is nearly always in the quality of the connections. Mind your P's and Q's there above all.Bear in mind that your battery bank will determine the voltage it sees, which will be in the range of 12V to 14.3V or so - the rest of your voltage compliance is lost as dissipated power either in the solar cells or your wiring, and it doesn't matter which. Only in conditions of low voltage from the array do you need to consider the issue:-early morning, late evening: current output in these conditions is low, so power dissipated is not an issue. -high heat due to high ambient temps: this is the only condition need be of concern, but since power dissipated in the wiring is NOT then contributing to IR heating of the solar array, I suspect the situation is almost a wash.Steve
Re: Solar self-install on MB Reply #10 – January 01, 2005, 11:05:28 am Yahoo Message Number: 48536QuoteSince 240W @ 17V corresponds to 14 Amps, gauge is of small importance - particularly for the run from the panels to the charge controller. QuoteCheck resistivity of the wires and add the combined pos/neg run lengths as a multiplier to get your voltage drop. Anything of 1V or less is not significant to your daily A-hr charge total. Where problems arise is nearly always in the quality of the connections. Mind your P's and Q's there above all.Bear in mind that your battery bank will determine the voltage it sees, which will be in the range of 12V to 14.3V or so - the rest of your voltage compliance is lost as dissipated power either in the solar cells or your wiring, and it doesn't matter which. Only in conditions of low voltage from the array do you need to consider the issue:-early morning, late evening: current output in these conditions is low, so power dissipated is not an issue.-high heat due to high ambient temps: this is the only condition need be of concern, but since power dissipated in the wiring is NOT then contributing to IR heating of the solar array, I suspect the situation is almost a wash.Steve Hi Steve,I agree with most of what you are saying. My array is 360 watts, though I know I won't see that in the real world due to mounting angle etc.Unless I'm misunderstood, I respectfully don't agree with what you say regarding battery voltage "clamping" (my wording) panel voltage so any excess voltage is wasted - - at least not always. While this is the case with simple switching (on-off) type solar charge regulators, and also with higher tech PWM (pulse width modulator) types, it does not occur with Maximum Power Point Tracking (MPPT) regulators.MPPT solar charge controllers allow the PV panel voltage to stay high, not clamped by battery voltage. This is especially important with cold temps which increase PV voltage or when battery voltage is low due to discharge. Then the MPPT uses a DC to DC inverter to trade the extra panel voltage, above battery voltage, for more charging current. So as long as the batteries still require charging, there is little wasted power and the MPPT can deliver as much as 30% more power to the batteries compared to lower tech controllers.I do concur that with the short runs and relatively low current we have from PV to battery bank, 10 or 12 GA would do just fine. But 4 GA welding cable is better yet (and I've always been a sucker for "better"). After investing all that money in solar panels, it seems worthwhile to optimize the power they generate. If it doesn't cost all that much to do - - even a percent or two is worthwhile if it can be easily had. At about 50 cents a foot, the wiring cost isn't a big deal compared to other components (Prosign 2000 inverter was $1200). It *is* more difficult to terminate larger cable properly, no question, but I'm up to it!!all the best,bumper
Re: [Life With A Lazy Daze RV] Re: Solar self-install on MB Reply #11 – January 02, 2005, 11:29:23 am Yahoo Message Number: 48565Maybe your being amp wise and pound foolish?John Morgan bumperm@...> wrote:
[Life With A Lazy Daze RV] Re: Solar self-install on MB Reply #12 – January 02, 2005, 12:40:30 pm Yahoo Message Number: 48568QuoteMaybe your being amp wise and pound foolish? Well, maybe!Though if we are talking about weight (and not good ol' English pounds), then the increase in using 4 GA vs 10 GA wire is inconsequencial. Guessing it would be on the order of a pound or two. Of far more impact will be the extra bank of batteries I'm adding between chassis frame rails to store the energy from the four 80 watt panels. BTW, since I was born a "limey" (came to the US [legally!] in '52 on the Queen Mary), I reserve the right to be pound foolish if I wish (g).all the best,bumper
Re: [Life With A Lazy Daze RV] Re: Solar self-install on MB Reply #13 – January 02, 2005, 03:43:37 pm Yahoo Message Number: 48573Bumper My GGGGGGrandfather came to America
[Life With A Lazy Daze RV] Re: Solar self-install on MB Reply #14 – January 02, 2005, 09:31:17 pm Yahoo Message Number: 48592QuoteUnless I'm misunderstood, I respectfully don't agree with what you say regarding battery voltage "clamping" (my wording) panel voltage so any excess voltage is wasted - - at least not always. While this is the case with simple switching (on-off) type solar charge regulators, and also with higher tech PWM (pulse width modulator) types, it does not occur with Maximum Power Point Tracking (MPPT) regulators. You're right - this type of regulator will recapture some of that power, although if yours are 17V panels, it will not make a large difference. The method also comes with conversion inefficiencies, not always noted by the manufacturer. If you stay in one spot for extended periods this time of year, then careful siting and solar tracking would make a much bigger difference - nearly twice the maximum charge current at noon, say (vs. flat on the roof).Still, that small extra charge rate to the batteries using the MPPT comes without having to fine-tune siting, which is nice.Steve
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