solar power battery maintenence

[twinstick]

I'm in need of something to keep my batteries charged on my 5 th wheel. I have to keep it at a storage yard about 6 miles from my house. Keeping it at the house is not am option right now.

At the storage lot, I do not have access to power. I'm thinking solar power with some type of battery maintainer would be the best solution. I know nothing of solar power. Does anyone have any thoughts or insight on this? Today I had to go pull the battery out, bring it home, charge it, then go take it back and hope it will last 2 nights to run my heat. I put a multimeter on out when I got it home, and the voltage was 0.8, so I'm pretty sure I well be buying a new battery this spring. Thanks for all the help, and is like to keep this project as cheap as possible

[pianotuna]

Hi bpounds,

Try not to put words in my mouth. My statement does not say this is common--just possible. A cheap controller on ebay may be found for under $10.00.

Here is a complete system for under $200 Renogy 100W Mono Starter Kit: 100W Solar Panel+20' Solar Cable+30A PWM Charge Controller+Z Bracket Mounts http://www.amazon.com/Renogy-100W-Mono-Starter-Kit/dp/B00BFCNFRM/ref=sr_1_2?ie=UTF8&qid=1415309399&s...

My personal experience is that, at least where I live, 5 watts would be inadequate to maintain a battery in the winter months. Perhaps nearer the equator that would not be so.

Here is a 90 watt panel for $30

http://sunelec.com/solar-panels/tianwei-90w.html

Shipping may be a killer on that item.

bpounds wrote:
The implication that he can get 100W for anywhere near $67 just isn't true. By the time you get all the stuff you're going to need to do an installation like that you'll be looking at $500 minimum.

[bpounds]

pianotuna wrote:
With panels costing as low as 67 cents per watt, it may be cheaper to get 100 watts and a controller, rather than buying the "package" you suggest which has but 15 watts.

The implication that he can get 100W for anywhere near $67 just isn't true. By the time you get all the stuff you're going to need to do an installation like that you'll be looking at $500 minimum.

You don't need 15 watts to maintain a single coach battery either. Something plug and play like this will do the job:
Solar Battery Tender

You're still going to want the battery disconnect. No sense putting juice in one end with the solar panel, and sucking it out the other with a propane detector that no one will ever hear.

I have a lot of respect for your solar knowledge pianotuna. Not just blowing smoke either, I honestly do. I read everything you post about the subject, because it interests me. The OP just wants an inexpensive solution to keep his battery from dying. So let's offer realistic suggestions.

Incidentally, I didn't see anything on the Harbor Freight site that I would recommend, so I have to correct myself on that.

[D_E_Bishop]

pianotuna wrote:
Hi,

For 9 years I had 30 watts of solar panels with a controller maintaining 210 amp-hours of battery bank.

If you wish to equalize the bare minimum is 60 watts per 100 amp-hours of bank.

With panels costing as low as 67 cents per watt, it may be cheaper to get 100 watts and a controller, rather than buying the "package" you suggest which has but 15 watts.

D.E.Bishop wrote:
Delray now has a solar Battery Tender, 15 watts and three step charging. Basically the same as the 120volt model but no need to plug it. I have one and it works fine if I start with charged batteries, but if not fully charged, it takes a long time to restore the charge.

It seems that the solar police insist on 100watts and a controller. That's okay too but if all you want to do is keep the batteries topped off, not necessary. Look into the 15watt tender at about $98.00 on line. By the way, my storage yard is 45 miles away and I don't have power or water there, just like most National Park Campgrounds.

Okay so I'm not as versed as some of you are in current pricing. Neither do I have any interest in putting anything else on the roof and we don't normally sit in one place very long so my alternator works great between sites for charging. I just know that the SP keep saying it isn't adequate for maintaining.

Your reply has been the first with any real facts and the post by bpounds is the first to be agreeable that 15watts is good for maintenance. There are as he suggest several rigs in our storage yard with the HF or Coleman or other 4"X10" panels and they seem happy with the results. I thought that maybe the extra cost for the Delray panel was worth it with the built in controller instead of just diodes to stop backfeed.

So thank you for your frank and outstanding response to the OP's question. Now he has a lot more information available on which to make a decision.

[pianotuna]

Hi,

For 9 years I had 30 watts of solar panels with a controller maintaining 210 amp-hours of battery bank.

If you wish to equalize the bare minimum is 60 watts per 100 amp-hours of bank.

With panels costing as low as 67 cents per watt, it may be cheaper to get 100 watts and a controller, rather than buying the "package" you suggest which has but 15 watts.

D.E.Bishop wrote:
Delray now has a solar Battery Tender, 15 watts and three step charging. Basically the same as the 120volt model but no need to plug it. I have one and it works fine if I start with charged batteries, but if not fully charged, it takes a long time to restore the charge.

It seems that the solar police insist on 100watts and a controller. That's okay too but if all you want to do is keep the batteries topped off, not necessary. Look into the 15watt tender at about $98.00 on line. By the way, my storage yard is 45 miles away and I don't have power or water there, just like most National Park Campgrounds.

[bpounds]

If you just want to maintain the batteries during storage, you don't need a full blown solar system. Of course, you might want solar for other reasons. But it gets expensive.

Just to maintain your batteries during storage, the most important thing you want to do is install a battery disconnect. The reason your battery is dead is because the little things like the propane detector and radio draw a parasitic level of current 24/7. But you're not there, so those things aren't needed. You want zero current draw during storage and the disconnect does that.

Secondly, you could pull the battery when you put the trailer into storage and take it home to your garage. Run one of the various maintainers on it in the garage. You will also avoid freezing temps on the battery that way.

If you don't want to remove the battery, install the disconnect and just get one of the small solar maintenance systems from Harbor Freight. They are inexpensive and if it gets stolen or damaged by weather you haven't lost much.

Either way, the disconnect is the most important piece of gear for storage. Oddly, I don't even have one, but then I am plugged in 24/7 at home.

[D_E_Bishop]

Years ago in a far different galaxy, folks who took their batteries home used Delray's battery tender. The idea was if your battery was fully charged the battery tender would keep it charged without having to worry about boilover are overcharging.

Delray now has a solar Battery Tender, 15 watts and three step charging. Basically the same as the 120volt model but no need to plug it. I have one and it works fine if I start with charged batteries, but if not fully charged, it takes a long time to restore the charge.

It seems that the solar police insist on 100watts and a controller. That's okay too but if all you want to do is keep the batteries topped off, not necessary. Look into the 15watt tender at about $98.00 on line. By the way, my storage yard is 45 miles away and I don't have power or water there, just like most National Park Campgrounds.

[Timay]

twinstick wrote:
I put a multimeter on out when I got it home, and the voltage was 0.8, so I'm pretty sure I well be buying a new battery this spring

If your battery was at .8volts, it is shot an won't keep a charge from your house back to the RV! New battery now, not this spring...

Tim

[austinjenna]

Mine is kept in the storage lot too. I have 2 batteries that I keep topped off with a 120w panel I bought from solar blvd and a morningstar controller. I also added a battery cutoff switch. It works very well for me

[pianotuna]

Hi,

The bare minimum is about 15 watts per 100 amp-hours of storage. However, it may cost more for a 30 watt panel than for a 100 watt one. A true case of "more is less".

[christopherglen]

For storage a smallish 10-50 watt will go a long way with ALL loads disconnected. Leave the propane detector powered, and you are closer to 100 watts.

[time2roll]

I recommend 100 watts and a good controller.
s/b $200 to $300 self install, complete.

Here are some to compare:
http://www.solarblvd.com/Solar-Panels-&-Systems/c1/index.html

Here are some installs with pictures. Many are larger than you need for storage.
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/25705772.cfm

[N-Trouble]

LOTS of solar threads in the TECH forum...

[pianotuna]

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.

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!

Solar Spread Sheet N8GS

For a nice explanation of solar, try this link:

Golden rules of solar

[2oldman]

Solar storage search.. Tech