Keeping Batteries Cool

[claychps]

Hi all,

I am just starting out, got the HF 45w deal for a good price and figured I'd knock out the TV, computer and a couple of lights (CFL) off the grid. I bought a couple of Sam's Club Golf Cart batteries and then got to thinking. Here in the So. Ca. desert, it can get pretty warm. I read that above 77F, the batteries can age quicker than I would want. Anyone out there storing batteries outside in the desert and have come up with a way to keep them cool? They will be in a plywood box, in a shed but it still gets warm in there. Thanks for any help !

Robert

[zap]

Why not skip the shed and dig a hole for them?  Just a thought.

And another thought... do you really intend to power a TV, computer, and a couple of CFL lights with only 45 watts?

[Chuck]

A couple things come to mind. To begin with, you'll want to have a charge controller with a temperature sensor (and set it up properly). This adjusts the charging voltage depending on temperature. It will help keep the batteries alive if not exactly happy.

I'd make sure that the shed is well shaded with lots of solar panels, you got a good deal, right ? Insulate the shed well, and make sure it's vented top and bottom. There are greenhouse vents that open at a set temperature, good to use for the top vent. It wouldn't hurt to have the lower vents attached to a pipe buried several feet underground to cool the incoming air. It really depends on how much time/energy/money you have to put into it.

On the other hand, you can just put them on the porch or garage.

[claychps]

Zap,

  Thanks for the responce. I was afraid someone would say that 45 watts wasn't enough to power what I wanted. My problem is I haven't done the math, guess I have to now. I'm building some of my own panels out of CIS cells, 5v 1/4w, that I got on E-bay to add on. I guess I'll start with the computer and satellite receiver first and build a LED reading light. Baby steps.

  The burying idea is good. Maybe I could route the house cold water line around the enclosure before it goes up to the passive hot water heater. I don't know, have to think on it.

Robert

[claychps]

Chuck,

  Thanks. I will definately work on getting a temp. controlled charger and the buried pipe idea is excellent also. I don't have a porch or garage. I was focusing on the enclosure without looking at the big picture and that is what you have inspired me to do, think outside the box...lol (pun intended).

[dnix71]

Those HF panels don't like heat, and they are not tempered glass, either.

I get way more power per panel out of mine in south Florida in the couple of cool months we get (Jan and Feb).

Don't put those panels on a hot tin roof if you can help it and make sure there is plenty on space under them for circulation.

[RandomJoe]

When you do your load calculations, don't just plan on getting the full 45W from those HF panels!  I've read plenty of others questioning their rating, and in my case the most I ever saw from my set was 30W, that was the day I took them out of the box and was very carefully aiming them at the noonday sun in July.  Now that I have them on the roof (about 3" off the roof, decent angle for my area) I only get 20W, but it's consistently that.  On rare occasion I'll see 24-25W.

On the plus side, they start making a trickle of current at dawn, and keep it up until dusk.  So I usually get 9-10AH per day into the batteries.  (I use a "Watts-Up" meter to measure all this.)  They've been up there doing that since last summer.

So far, mine haven't had to face up to any hail.  I'm sure they wouldn't like it much, but I plan to buy some "real" panels soon, and these will come down and get used for whatever random experiment I come up with.  

A friend decided to reinforce his, though.  He mounted his to the top of his "shed" (converted to a ham radio shack) then installed a sheet of (can't remember) plexiglass or lexan over them.  That does stand up to hail (even stood up to the tornado that took down his ham tower and part of the house roof!) and he says it doesn't seem to diminish the panels' ability to charge much.  At least, they still keep the RV battery they are attached to charged.  Don't think he's ever bothered to take measurements beyond that.

[Bruce S]

RandomJoe;

I have a couple sets as well, they've gone through a few hail/ice storms here in St.Louis and held up with no problems. The watts-up meter on them as well. It's nice to just look and see quickly how they're doing.

Cheers

Bruce S

[SteveCH]

I am thinking of a cinder-block-lined hole in the ground. Some sort of insulated cover, of course, maybe even below the floor in a shed. But I'd also want to be sure I designed it-the hole-to make it physically easy to remove the batteries, and large enough to change to a different bank of batteries in the future. Maybe run some cheap conduit [extra plastic pipe you have lying around, etc.] for the wiring and cables. Very little $$ just the blocks [sometimes free for hauling] and some mortar, concrete-pad floor. I am also thinking this would be great in a place it is easy to dig. If your place is rock-hard, maybe above ground will have to do. Great thing about below-ground set-up is, though, that once constructed, it is hassle-free and cost-free to keep cool, no worries. I like no worries.

[claychps]

Thanks all for your help. I ran your ideas by the better half and she said that of course burying them is a good idea.So I am looking around the yard and there is an old freezer that I think I might bury. It has a lid, insulated, can drill through it...Also, ground is sand, easy to dig and no,we never get hail but I have access to all the Lexan I need from old window protectors used in busses. Again, you guys are great, only problem is I am a little discouraged by the output of the HF panels. I'll get over it with more panels or a wind genny backup. A lot of wind here in the desert.

Robert

[zap]

Robert,

The freezer sounds like an excellent way to go.  Probably a few on this board that could give you advise on what type of sacrificial metal to add so the freezer doesn't rust up too fast.

I'm sure water is as precious there as it is here, but when things really start to heat up you can always sprinkle a little water around/on top of the hole in the evening or morning.  Probably wouldn't need much and probably only a day or two a week?

Also, the lower you bury it the more constant the temperature will stay and the less it will swing with the daily temperature.  You'd need to go around 30 feet for a steady temp... way too low for most.

I used to have a few links for soil temperatures from a ground source project a few years ago but have since lost them.

Here's a link to a daily ground temperature map.

http://www.greencastonline.com/SoilTempMaps.aspx

A Google search for "soil temperature" would bring you more links.  Searching "ground temperature maps" gave me this hit.

http://www.greenbuildingtalk.com/Forums/tabid/53/forumid/13/postid/31492/view/topic/Default.aspx

The third post has a few pdf on ground temperatures.

Don't be too discouraged by the HF panel outputs, they're an excellent learning tool.

 

[claychps]

Thanks again for all your great info,Zap. Man this is turning out to be fun, educational, and hopefully, will knock a few bucks off the electric bill. Wish I started this years ago, but anything that I can teach my Grandkids about RE will be worth more than dollars. And as the all to overused saying goes, "if I can do it, anyone can".

Robert