Solar Update

[Caver]

This is the second season to use solar panels on our 3023 TM. I’m pleased with the capability and it has met my expectations but it may not be the solution for everyone.

A quick summary: Two 90 watt solar panels mounted on the rear shell with a BZ Products charge controller mounted next to the converter. The other component is a Bogart Trimetric battery monitor. The Trimetric allows monitoring current, voltage, AH used, and % battery capacity.

I mounted the panels on the rear shell using the adhesive technique that RockyMtnRay described. I did fabricate custom mounting brackets from aluminum. The combination worked well and I didn’t have to penetrate the TM roof. Thanks Ray! The aluminum mounts are still solid on the TM roof with the Loctite Depend adhesive. These appear as strong now as when initially installed. The panels are mounted flat. I didn’t make any provisions for tilting the panels since I will primarily use them during the summer months.

Last winter I left the batteries in the TM. Since the TM is stored in the driveway and gets a few hours of sunlight per day in the winter this is more than adequate to keep the cells charged. It would be safer to remove the batteries and store them charged in a warm location.

Since I use flooded lead-acid batteries, it’s absolutely essential to water the batteries every few months. I try to check them once a month but they seem to go for at least two months in the summer. They didn’t use much water over the entire winter. I use one of those auto-fill devices for the distilled water. This makes quick work of filling the batteries to the proper level.

The biggest thing I would do differently is to install the charge controller closer to the battery and use a larger gauge wire between the charge controller and the batteries. The relatively long run of 10 gauge wire is limiting the maximum charge current.

For my next installation I would prefer to use AGM batteries so I don’t have to keep checking the water level but this will require some changes in the solar charge controller and also the converter. The ability to rapidly charge batteries is inconsistent with automated techniques to sense battery condition and prevent overcharging. I’ve spoken to several manufacturers of RV converters and charge controllers and most recommend using flooded batteries and adding water as required.

During a four day boondock campout over Labor Day weekend, by the first morning I had used 40 AH of battery capacity. This was a record for me and was due to running the refrigerator on battery while en-route. That was about 10 AH. I left an outside light on all night for my kids and over a thousand fellow tent campers. I also made two pots of coffee with an electric drip coffee maker that uses 4 AH per pot. The batteries were back at 99% capacity by the end of the day due to clear skies and full sun exposure. In fact over the four days there was no reason to try to conserve battery power and the batteries were fully charged by the end of the day. We even ran the electric ceiling fan for part of each day. Multiple days of cloudy weather would have required more of the available AH capacity. You don’t want to regularly use more than 50% of your battery capacity or it will reduce the number of available charge cycles.

Solar may be right for you if:

- You do a lot of boondock camping

- Camp in a place where there is direct sun exposure

- Can’t or aren’t interested in running a carbon fuel based electric generator

I’ll be interested in updates from other solar users. For those interested in solar there is a wealth of information at this forum:

http://www.wind-sun.com/smf/index.php

Ray

[RockyMtnRay]

Originally Posted by Caver

This is the second season to use solar panels on our 3023 TM. I’m pleased with the capability and it has met my expectations but it may not be the solution for everyone.

Completely agree. The solar panels on my TMs roof are definitely the best mods I've done to the trailer. They've more than met my expectations.

A quick summary: Two 90 watt solar panels mounted on the rear shell with a BZ Products charge controller mounted next to the converter. The other component is a Bogart Trimetric battery monitor. The Trimetric allows monitoring current, voltage, AH used, and % battery capacity.

Mine are are a 120 watt and a 50 watt panel (170 watts total). Generate about 11 amps in full mid day sunshine. Basic controller, use just a digital voltmeter for monitoring battery voltage.

I mounted the panels on the rear shell using the adhesive technique that RockyMtnRay described. I did fabricate custom mounting brackets from aluminum. The combination worked well and I didn’t have to penetrate the TM roof. Thanks Ray! The aluminum mounts are still solid on the TM roof with the DuPont adhesive. These appear as strong now as when initially installed. The panels are mounted flat. I didn’t make any provisions for tilting the panels since I will primarily use them during the summer months.

Welcome. Yes, the Loctite "Depend" adhesive is superb. Mine are also still firmly attached to the roof after 2 1/2 seasons...despite much wind, rain, and even some snow.

Last winter I left the batteries in the TM. Since the TM is stored in the driveway and gets a few hours of sunlight per day in the winter this is more than adequate to keep the cells charged. It would be safer to remove the batteries and store them charged in a warm location.

My TM is stored inside my garage so little to no sun on the panels. I use a 3 stage charger to keep the batteries fully charged (but not overcharged) during the winter.

Since I use flooded lead-acid batteries, it’s absolutely essential to water the batteries every few months. I try to check them once a month but they seem to go for at least two months in the summer. They didn’t use much water over the entire winter. I use one of those auto-fill devices for the distilled water. This makes quick work of filling the batteries to the proper level.

Also use flooded cells (a pair of Trojan T-105 6V Golf Cart batteries). After two seasons of use, I find they need a water top off only twice a year...once when the trailer is brought out of storage in April/May and once when it's put back into winter storage in September. So far the electrolyte has stayed above the bottom of the slot in each cell's fill opening.

The biggest thing I would do differently is to install the charge controller closer to the battery and use a larger gauge wire between the charge controller and the batteries. The relatively long run of 10 gauge wire is limiting the maximum charge current.

Agree. My controller is about 18 inches from the battery and connected with 10 gauge wire. No limit being put on charge current.

During a four day boondock campout over Labor Day weekend, by the first morning I had used 40 AH of battery capacity. This was a record for me and was due to running the refrigerator on battery while en-route. That was about 10 AH. I left an outside light on all night for my kids and over a thousand fellow tent campers. I also made two pots of coffee with an electric drip coffee maker that uses 4 AH per pot. The batteries were back at 99% capacity by the end of the day due to clear skies and full sun exposure. In fact over the four days there was no reason to try to conserve battery power and the batteries were fully charged by the end of the day. We even ran the electric ceiling fan for part of each day. Multiple days of cloudy weather would have required more of the available AH capacity. You don’t want to regularly use more than 50% of your battery capacity or it will reduce the number of available charge cycles.

Solar may be right for you if:

- You do a lot of boondock camping

- Camp in a place where there is direct sun exposure

- Can’t or aren’t interested in running a carbon based electric generator

I’ll be interested in updates from other solar users. For those interested in solar there is a wealth of information at this forum:

Ray

Internal lights and the furnace are my biggest electrical power users. Last summer was downright cold and raining in the mountains and I used the furnace a lot...yet the battery state never dropped below about 50%. This year was much warmer & drier...and I replaced 3 light fixtures with fluorescents (roughly 2/3 the electrical load, yet much brighter)...so battery state never went much below 85% even if I used the lights for extended periods.

This year I needed to recharge/run my laptop computer from the TM's battery a number of times and the solar panels easily provided all the needed energy. On two occasions, I also had to leave the trailer parked in a parking lot for an extended period with the refer running on DC. Once was all day (8 am to 4 pm), once was almost an entire morning (9 am to noon). Fortunately both days were very sunny with almost no cloudiness and the panels came very close to meeting the electrical demand of the refer...battery state was down only about 10% when I arrived at my destination.

I'm fortunate that I camp in the mostly sunny West...and I've gotten pretty good at reserving campsites through reserveusa.com that get at least 3 to 5 hours of full, unshaded sunshine per day. As long as I can get 3 to 4 hours of good sunshine on the panels every day or so, having sufficient electrical power is simply no longer a factor in determining how long I go without needing to have an electrical hookup. For me having an electrical hookup is now purely a nicety and not anywhere close to being a necessity.

I am very interested in following this thread. I have a fascination for gadgets.

However, having used my TM on 5 trips this years since I took delivery in March I am wondering just how worthwhile soar really is.

I have a Honda 2000 generator. I haven't made any real measurements, but it appears that I need to use about a pint of gasoline per day to keep my batteries charged. For any trip less than 4 days I don't even take the generator any more.

Fridge is on propane. I don't use the furnace. I don't use any electrical appliances like coffee pots. No television. Some radio. Mostly the lights and the toilet.

It looks like solar would not help me very much.

My only real dislike for the generator is having to hide it in the TM while we go sight seeing. The biggest advantage I think I would get from solar is security and ease of use.

I have a question for owners of the Trimetric or the Xantrex. You are given a % capacity remaining and strive to stay above 50%. How do you know the capacity of your battery? As a battery ages or if is over-discharged, its capacity decreases. Are these meters in some way able to sense this changing value? A similar question is "how does it determine capacity of a new battery?"

[Caver]

Bob,

With the Bogart Trimetric you can set the AH capacity of your battery. I set mine at 100 AH which is roughly half my AH capacity so it's actually reading AH available. Using the 100 amp shunt gives me resolution to 0.01 amps. Both the Xantrex manuals and Trimetric manuals are on-line. The Xantrex is smaller and can be more easily mounted. I've setup the Trimetric to plug in so I can remote it outside the trailer if I wanted to monitor the battery with the TM closed. I just set it behind the refrigerator or Velcro it to the wall for easier eye level viewing. Having it visible makes everyone aware of how much battery capacity they are using.

PopBeavers, I agree the Honda generator is more cost effective and you certainly can't operate the AC on solar. I have some of these at work and they are great. I just like the idea of using solar for an RV. I think if I even had a generator I would have at least 50 watts of solar panels.


Ray,

I've only seen a sustained 8 amps into the batteries from the solar panels. I had expected over 10 with the MPPT charge controller. I wanted to mount it where I could see it and also I was concerned that it be mounted where some air could flow over the front panel. In fact the charge controller barely gets above ambient temperature and I don't really need to refer to the LEDs on the front panel since there is more info on the Trimetric. I may move it to below the sofa in the 3023 adjacent to the front wall of the TM. It would be only a foot away from the batteries.

Ray

Thanks, Ray. Very nice work on the solar setup.

[Bill]

Originally Posted by Caver

The biggest thing I would do differently is to install the charge controller closer to the battery and use a larger gauge wire between the charge controller and the batteries. The relatively long run of 10 gauge wire is limiting the maximum charge current. Ray

Caver Ray -

That is a great update, and I'm glad to see this discussion area come to life again.

Let me make a minor comment in response to your "wire size" comment. Any wire larger than number 10 is hard to work with, so you would like to stay with #10. And there is an alternative to using heavier wire. This alternative is to choose a charge controller that has "remote sensing" capability, which is fairly common. With such a controller, you run the charge lines as you normally would, but you also run a separate pair of small wires from the controller to the battery. These small wires don't carry the charging current, so there is no voltage drop in these wires. The controller bases its charge rate on the voltage at the battery as seen by the small wires, rather than the voltage at the controller as seen by the large wires. As a result, you can use #10 wire for the charge lines over almost any needed distance, and mount the controller wherever it is most convenient.

Bill