Solar for automatic battery maintenance

[ScottBrownstein]

After installing my Trimetric I now probably know too much about my batteries. I have 4 Group 27 12 volt batteries, a PD9270 converter and two inverters. One is a dedicated unit for the residential reefer and is a 2000 watt Xantrex and the second is a 1000 watt Xantrex that I installed with an automatic transfer switch that powers all of my TVs and all of the plugs on the driver’s side of my 335DS. The second Xantrex is in the power bay and piggybacks on the converter feed for power. Figured that if the converter would put out 70 amps when on shore power, the inverter could use the same cables when on battery power with no converter running. The auto transfer switch makes this certain since it disconnects the output of the inverter whenever 120 volts is detected in the coach. It is a slick installation on any rear power bay Forest River coach since everything is right there and the main power panel is very close as well.

We never spend endless days hooked up to shore power and generally none at all. My batteries actually haven’t been equalized now for 38 days according to the Trimetric…which is correct. Sure I can run the generator and we have driven for 10 to 12 hours on multiple days but never long enough for the PD to do it’s thing and it certainly won’t happen since my coach is stored for months without shore power.

This concerns me for a number of reasons. First is that I have become a state of charge miser with the Trimetric. I want that 100% and imagine my devices sucking the life out of the battery bank. Normally I am not obsessive compulsive, but I guess I am in this case. Besides that, I am concerned that without being hooked up to shore power for a solid day, my batteries will never get a de-stratification operation from the converter. This means that the acid in the battery will migrate to the bottom of the cells and the water will end up concentrated at the top. Without the mixing motion of bubbling, they will appear fully charged but since a large portion of the plate has the wrong specific gravity electrolyte, they will have reduced capacity. Besides that, when stratified they will be more prone to plate sulfation at the top and significant corrosion at the bottom. Besides that, it is questionable if the 14.4 volt 15 minute cycle from my 9270 will be at a high enough voltage or for long enough to ever perform successful equalization. (Trojan recommends an equalization cycle of 15.3 volts for 1 to 3 hours every 30 days.)

It seems that the solution to all of this is to install a small solar solution. I am currently looking at using a single Kyocera 140 watt panel on the roof, connected to a Bogart SC-2030 PWM controller and tapping to the output terminals of my converter. The cool thing about the SC-2030 is that it connects to the Trimetric, remotely senses actual battery voltage and understands SOC and all of the other Trimetric data and uses it to optimize performance. It also has adjustable voltage levels so that I can get the soak at 15 volts or more. The 140 watt panels are a little more expensive but if I am going to only install one, it seems like a good compromise. 10 AWG PV wiring for a run length of around 12 feet to the controller. The wiring from there is the 6 AWG from the converter and since the solution has remote sensing, voltage drop between the controller and batteries doesn't matter as long as the controller has enough voltage available, which the panel will put out at low current anyway.

On a rear power bay coach, a ¾” PVC conduit can go directly from roof to power bay through the bedroom cabinetry and won’t show at all. The ¾“is to allow an optional upgrade to a second 140 watt panel by fishing another pair of 10 AWG conductors at some future time. The conduit will penetrate the fiberglass roof and stick up maybe ¼” into a PVC junction box which will prevent any possible leakage.

When boondocking I can run the generator to get me back to a reasonable 85% SOC or so (and boost the charge rate with the pendant on my 9260,) but there are a lot of hours in the day and I would have complete confidence that after a while (hours or days) my batteries will again be at 100%, destratified and equalized…and I would need to do nothing!

I think that’s it. The whole thing should come in under $500 and is eligible for the 30% energy credit. An added benefit is that it would make the Trimetric installation also eligible for the 30% credit!

Wonder if any of you guys with solar have suggestions or comments. Seems like the kind of thing that FR should include as a standard or option for their coaches and TTs.

[PokerDealer]

I can see from having 4 group 27's the chart showed me 85 to 105 so how are they wired? What is the total Amps 340 to 420? My only question is with only 140 watts of solar, how many hours of good sun hours will it take to push in the last 10%. I've decided on my equalizing days, I'll just run my battery charger directly to my batteries. I too always ended up wondering how much solar would be needed and what happens if I'm in Montana with short good sun days or anywhere North. If I know I was going to be South, that helps but ends up being part of the equation. Your SC 2030 will help and I wish you the best. I'll be very interested to know how it works and geographically where you are. :-)

[Blackhat6mike]

From my personal experience, I would seriously consider a MPPT controller rather than a PWM unit. I've used both and the MPPT unit is hands down more efficient than the much cheaper PWM.
I'm running 600 watts of panels into a 40 amp controller and about 550 amp hrs of AGM bats. Also have an auto transfer switch and a 5,000/10,000 surge inverter that will run anything in the unit.
I originally started with 2 x 100 watt panels and a 20 amp PWM controller just to keep the batteries up. A friend talked me into the MPPT controller and I just kept adding panels. Still have two new 100 watt panels in garage, but they will go into another solar project I am putting together. I also have a 60 amp MPPT controller that is part of the home project.

[spock123]

Originally Posted by Blackhat6mike

From my personal experience, I would seriously consider a MPPT controller rather than a PWM unit. I've used both and the MPPT unit is hands down more efficient than the much cheaper PWM.

I'm running 600 watts of panels into a 40 amp controller and about 550 amp hrs of AGM bats. Also have an auto transfer switch and a 5,000/10,000 surge inverter that will run anything in the unit.

I originally started with 2 x 100 watt panels and a 20 amp PWM controller just to keep the batteries up. A friend talked me into the MPPT controller and I just kept adding panels. Still have two new 100 watt panels in garage, but they will go into another solar project I am putting together. I also have a 60 amp MPPT controller that is part of the home project.

I have question, I want to eventually install solar on camper, I want to start out with the battery bank first as I have a 40amp charger and a 3,000 watt inverter, I plan to have 4 6 volt Trojans in this battery bank. This is the question, I already have a bank of cheap batteries that I use for the electric refrigerator and a 1,000 watt inverter, how do I keep the converter from trying to charge the cheap batteries up when I plug into the 3,000 watt inverter?


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[doc73]

Flip the breaker off for the converter? All your 12v stuff will work, just will not charge any mo.

[spock123]

Thanks


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[ScottBrownstein]

Originally Posted by spock123

I have question, I want to eventually install solar on camper, I want to start out with the battery bank first as I have a 40amp charger and a 3,000 watt inverter, I plan to have 4 6 volt Trojans in this battery bank. This is the question, I already have a bank of cheap batteries that I use for the electric refrigerator and a 1,000 watt inverter, how do I keep the converter from trying to charge the cheap batteries up when I plug into the 3,000 watt inverter?


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In my opinion you should remove the old batteries and replace them with 6 volt deep cycle units, probably Trojans or equivalent. Why make your system so complicated. One bank, well tended and backed up by a solar solution is best.

This way your converter will supply boost charging with shore power or a generator and your solar will make up the rest, equalize them and keep them topped off.

[ScottBrownstein]

Originally Posted by PokerDealer

I can see from having 4 group 27's the chart showed me 85 to 105 so how are they wired? What is the total Amps 340 to 420? My only question is with only 140 watts of solar, how many hours of good sun hours will it take to push in the last 10%. I've decided on my equalizing days, I'll just run my battery charger directly to my batteries. I too always ended up wondering how much solar would be needed and what happens if I'm in Montana with short good sun days or anywhere North. If I know I was going to be South, that helps but ends up being part of the equation. Your SC 2030 will help and I wish you the best. I'll be very interested to know how it works and geographically where you are. :-)

They are installed in parallel and I have told my Trimetric that I have 400 Amp hours of capacity, which is conservative. I spend 7 months in south Florida in the winter so if I don't get there in one day...there are plenty more days after that. As I said, we don't use the RV in the winter and I just want to get everything up to 100% SOC as well as equalize periodically.

While designing my system I have now discovered that my 70 amp converter is connected to the bank on 22 feet of number 6 wire. That is a long run and explains why my Trimetric never shows a good boost voltage. I will change that immediately, at least using the chassis for the return, which will effectively cut the voltage drop in half.

Right now I am going to install a Kyocera 140 watt panel (if installing one panel, might as well make it as big as possible) and have capacity to double that for 280 watts. I have tons of unobstructed room where no shadows will fall...ever! On your rig you probably don't have room for more that two panels anyway.

[spock123]

Originally Posted by ScottBrownstein

In my opinion you should remove the old batteries and replace them with 6 volt deep cycle units, probably Trojans or equivalent. Why make your system so complicated. One bank, well tended and backed up by a solar solution is best.



This way your converter will supply boost charging with shore power or a generator and your solar will make up the rest, equalize them and keep them topped off.

The four batteries that came with the camper are only one year old, maybe next year change them out. I want to get some more use out of what I have


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[ScottBrownstein]

Originally Posted by spock123

The four batteries that came with the camper are only one year old, maybe next year change them out. I want to get some more use out of what I have


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Me too. Otherwise the existing 1 year old 12v batteries would be out already!

[prairiecamper]

[QUOTE= On a rear power bay coach, a ¾” PVC conduit can go directly from roof to power bay through the bedroom cabinetry and won’t show at all. The ¾“is to allow an optional upgrade to a second 140 watt panel by fishing another pair of 10 AWG conductors at some future time. The conduit will penetrate the fiberglass roof and stick up maybe ¼” into a PVC junction box which will prevent any possible leakage. [/QUOTE]

Did you put in that conduit or did it come from the factory?? I often wondered why this isn't done at the time of build, just a few dollars extra but ton's of convenience, our 29 RE doesn't have one!!

[ScottBrownstein]

Originally Posted by prairiecamper

Did you put in that conduit or did it come from the factory?? I often wondered why this isn't done at the time of build, just a few dollars extra but ton's of convenience, our 29 RE doesn't have one!!

Don't be jealous...neither does mine. However, on a 335 or really any Georgetown and other design like it, it is an easy mod. Bedroom floor to ceiling storage is a straight shot to the lower power bay...which also happens to be a pass through. eventually when you put in a lot of slides it becomes virtually impossible.

They could do this and then it could be used for solar, satellite, satellite radio...whole bunch of things. On a design like mine it would probably cost maybe $10.00 in PVC and the resulting labor. However, not sure how many people would appreciate it enough. i am sure we all can come up with a bunch of relatively low cost mods that would go unused in most units.

But a single 1" PVC conduit to a conventional PVC junction box on the roof would solve a lot of problems. Maybe they should call it the "DIY option."

[Blackhat6mike]

Originally Posted by spock123

I have question, I want to eventually install solar on camper, I want to start out with the battery bank first as I have a 40amp charger and a 3,000 watt inverter, I plan to have 4 6 volt Trojans in this battery bank. This is the question, I already have a bank of cheap batteries that I use for the electric refrigerator and a 1,000 watt inverter, how do I keep the converter from trying to charge the cheap batteries up when I plug into the 3,000 watt inverter?


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I doubt you will need your converter after you get your solar installed. I haven't turned mine on in 6 months except to make sure it still works. Even when on shore power, the solar system keeps the bank fully charged. [600 watts]. We get a lot of sun here in the deep South.
When the temps get at or near freezing, I turn the gas furnace to 40* and the batteries provide more than enough juice to run the furnace. The unit is in storage and I only check on it once a week unless a deep freeze comes and that is only for a few hours at night. That hasn't happened in several years here, so no problem. I also open any and all cabinets that water lines go through so heat can get in.