UPDATE! need recomendation for 200 watt solar and batteries

I have the same requirements in our TT, the first thing I will be doing will upgrading the converter/charger. I gather the output of the camper chargers is low. The running a generator all day gets old fast.

Mentioning your batteries are shot probably is from the constant running them down below the 50% charge state and not getting them back up to their at least 90% charge state to burn off the bad deposits built up on the battery cores.

We camp off the grid alot here but did plan out how big of a battery bank we needed to run the things we wanted to have. We watch our batteries real close and will not ever let them get discharged below the 50% charge state (around 12.0VDC level). Then we re-charge them using our smart mode converter/charger being powered by our 2KW generator to get the batteries back up to their 90% charge before using them again. Just running a charge for a couple of short charge cycles may do additional harm to the batteries. We found we need to get to the 90% charge state before start using them again...

I have been doing this 50% to 90% charge cycles since 2009 and my 255AH battery bank is still doing ok. They are just now starting to fall off on performance now.

Just keep in mind a typical 120WATT Solar panel will only give you 5-6 usable DC AMPS to trickle charge your battery bank. Depending where you are you can only expect 5-6 hours of high sun...

I am just now planning to use solar panels to help out in the re-charge of my batteries and want to produce around 20AMPS of usable DC Current while in the high sun. To get my 255AH capacity battery bank started off I will still use the 2KW generator for the first hour of charging and then let the rest of the high sun day do its thing to get my battery bank to its 90% charge state before i loose the high sun. My 255Ah battery bank wants to see around 52-53 AMPS DC Current when first hit with 14.4VDC when recharging... Only my on-board converter/charger can give me this much DC Current being run by my generator.

I like to be able to run a good 20AMPS DC CURRENT load off my battery bank from 6PM to around 11PM each evening when camping off the power grid... Then of course there is also a good 1-2 AMPS being drawn by parasitic drains 24/7...

If we were just running a light or two and living off of candles and flashlights it wouldn't be much of a big deal haha..

Even with my bigger capacity battery bank I still don't have enough available power to run air conditioners, microwaves or long term runs just using the trailer furnace and 12VDC blower.

We actually know not to expect all those lovely things to have when camping off the power grid anyway...

lots to think about for me to make it all successful...
Roy Ken

Moved to Tech Issues

Wayne
Moderator

Measure twice before buying a panel. Make sure that it will fit with your limited space on the roof, without going so close to the front that poor fuel mileage will offset any added benefit of saving generator gas. .

Also avoid the AC and TV antenna shade.

SUnEle.com has some fantastic prices. Look for 12 volt nominal, and aluminum frames, so that you will have something to attach to.

Good luck,

Fred.

How about a pair of the flex panels on the front slope of the cabover?

In a nutshell unless you are a reasonably frugal camper 200 watts will not be enough.

Make room for more panels when needed.

Hemi Joel wrote:
How about a pair of the flex panels on the front slope of the cabover?

I think you would have so many bugs on the panels, it would be a waste of time. The angle is wrong, and you would always have to park your camper with the front facing south.

Wayne

It does sound like you need more than 200 watts if you're depleting your group 31s in one night. But like you said you have the generator to fall back on in worst case situations.

Solarblvd sent me email w/ black Friday sale of $1 watt 12 volt panels. 100 watt for $100. etc. If I was in your shoes and on a budget I'd start with 300W and build the system with expansion capability (maximize empty roof area, wiring, etc...

Do you typically park in full sun when camped?

Also in conjunction with this, I'd be certain my converter/charger is capable of 14.4 plus volts in first stage of battery charging.

Also as you probably know, keep eye on demand end. LEDs, reduced furnace time by using more blankets at night, lower idle loads such as inverter, possibly more efficient CPAP, low draw electronics, laptop, etc...

Here is a simple flow chart.

Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT. What ever type of controller is chosen, make sure it has adjustable set points and a temperature probe that is on the battery.

If you use solar as a battery charger, one rule of thumb is between 60 and 150 watts of panels per 100 amp-hours of storage. The smaller the battery bank the higher the wattage needed (per 100 amp-hours). Here is a link to the rather special spreadsheet which includes an energy audit, that N8GS has created to help size solar battery charging systems!

http://w8usa.org/club-library/documents-presentations/

If you full time or use an inverter lots, then populate the entire unshaded area of the roof with panels. I'm considering replacing my awning with solar panels.

For a nice explanation of solar, try this link:

http://www.jackdanmayer.com/rv_electrical_and_solar.htm#The%20Golden%20Rules

Thanks for all the responses, I know it takes time to type all that stuff, and I really appreciate it. With the info you have presented, I am developing the following opinions: Get cheap batteries, and don't worry about making them last 4 years+. Look for a cheap, basic system that someone else has already engineered. If it does 80% of the job 80% of the time, and furnace is still running when I wake up, I'll be happy. There rest of the time, I'll go for a drive or start the generator. The thing is, I work 50 - 60 hours a week, and I have interests and hobbies outside of solar power. Thus I don't have time or interest in reading about it, or learning about it. Sorry, but I intend to be a pathetic mooch, and suck off of the smart people out there who have done all the leg work and research. Kind of like my wife stepping the gas pedal: she doesn't want to know how an internal combustion engine operates. She just wants to go to the store.

So can anyone recommend a kit, or a few components? Hopefully a link to something I can buy online? Maybe that black Friday sale item?

On the front slope, I should have bene more clear: (see red arrow) The front of the roof is clear of obstructions.



Thanks, Joel