Battery Temps - life expectancy

[madlabs]

Hi All,

Got my lawnmower charger cranking out 50 amps. Wheee! I need a bigger alternator and a bigger pulley and I think I can get way more.

Anyway, now I need to make a decision about locating my battery bank and inverters. I have two options:

Option #1: Outside a 40' storage container, on the north side, under a shed roof but essentially outside. I live in Northern CA on the coast, so my lowest temps are about 25 degrees F, highest around 100, although temps at those extremes are fairly rare.

Option #2: Inside the storage container. The container is set to solar south on it's long side, so I can mount both PV and thermal panels on it. This means that interior temps are going to be pretty high on a hot day, I'm guessing up to 120 degrees F on a hot day.

An extra factor is security. Some local dirtbags like to break through my gate onto my property to steal redwood trees and firewood. I will be living at the site part time as I transition to full time living there. So, I worry about theft. In an ideal world, I think I'd like to have the batteries outside and the inverters inside. While the temps are high for the inverters inside, I can run a vent to underneath the container for cool air for the fans on the inverters, and the humidity would be lower. We have plenty of fog here. However, if the higher temps won't be really bad for the batteries, inside would be great.

Thanks!

[bob g]

well your going to need security for sure, or they will steal them from you.

as for temps, 120 is out of the question in my opinion, even 100F is too hot for my likeing.

i don't remember the formulae off the top of my head, but ever 10 degrees over 77F

takes a toll on battery life, capacity increases but lifespan decreases.

as for the cooler side of the equation, cooler increases lifespan be decrease capacity, similar relationship with the 10 degree thing.

maybe an underground bunker?

bob g

[madlabs]

I was afraid of that. What do you think about the inverters? Is it worse to have the higher temps, or humidity in the cooling air? We do get a lot of fog etc.

Thanks for the help!

[TomW]

mad;

I don't know what inverter you plan or have, but:

We have an Outback FX and it is rated pretty much anywhere on earth except immersed. If I recall correctly Something like -45F to +135F. You would need to check their specs online but I recall it had a huge operating range. My concern is cold because that is the extreme we have -40F is not uncommon for several days over 100F for long is seen but uncommon.

If I was worried about heat I would just bury some tube in the ground and draw outside cooling air into the area through it to near the inverter. Maybe go so far as to give it its own little climate controlled box with a common household thermostat to kick on boost fans if it needs more air flow. Cooling is all about getting the heat away. moving air does that. Same for batteries which need venting anyway. With some thought you could condense a lot of the moisture out of fog in the underground tube. Properly place holes and drain pits full of pea gravel or something. Be sure to set the batteries on a thermal break from concrete, steel, etc a rubber mat is nice and acid proof in case of spills.

Cooler is better [for both]

If it is stolen its of no use to you so security may trump environmental concerns

Good luck with it.

Tom

[bobfandango]

You didn't say, but assuming vented lead acid batteries, make sure you properly vent the charging gases away from the inverter.  Hydrogen can explode and even small amounts of hydrogen sulfide will corrode the heck out of just about anything.  Keep this in mind when designing ventilation and especially if you are planning on keeping them in the same enclosure.

[PaulJ]

   I keep my off grid house size (1000Ah 48V) battery bank in a shipping container in southern Australia.

   Summer temps here have recently been as high as 47C (115F?) in the shade, I hate to think what the temperature would have been inside the container.

   No doubt this isn't doing the batteries any favours, but it's better than having them stolen or tampered with.

   They've lasted 4 years so far, and were second hand to start with. I painted the container white which reduced the internal temperature quite a bit.

   Paul.

   

[thirteen]

Will you need to use the batteries for power while you are not there? Until needed full time you might get a small trailer and make it into a power supply trailer. A couple of longer leads to your power panel might work. These batteries and inverters have alot of $$$ in them so this might be an usable idea. Maybe take a small section and insulate and paint part of one of the containers to help reflect the sun. Constant high heat will shorten your batteries life. Just a couple of ideas.  

[madlabs]

Great info, as always. Perhaps an insulated box inside the container, with vents through the floor. I have the container raised 6" or so off the ground. Hydrogen rises of course, so perhaps a flexible duct from the top vented through the side of the container, although I'd like to avoid punching any holes in the container to prevent water damage wheb it rains. I suppose being such a large container, I could just have a top vent that I open when chgarging, I can always have the door of the container open when charging, as I'll be there.

Whipped up a PIC micro to control the field coil on the alternator last night, I'm going to go and see how that works out right now. I'm getting really excited about all this moving off grid stuff. It fits well with my geek side!

I have to say again what a great forum this is. Such practical info by folks who are really doing it. Thaks to all for your replies.

[Airstream]

Why not partially bury the shipping container, reduces the variations in temperatures all four seasons...

If you want the container to stay cooler just buy more PV panels to make sure it stays in the shade during peak solar hours!

If none of the above two options fit your plans how about adding a wood shed on the south side and perhaps a quicky roof just to protect the storage from repeated days of heating while you are not in residence to open doors, etc. to allow evening cool off? If done sneakily you could have the PV panels obscured from direct view, the PV panels would sure worry me more being unattended than half a ton of batteries.

[scottsAI]

Madlabs,

If someone wants to steel from you they will.

Locking it up, keeps the more/less honest folks out.

If crooks can tell your not there to stop them, they have time to use tools to get in, using blot cutter etc.

The best you should do is NOT to let people know what you have and make it inconvenient to steal it.

Hiding things from plain sight is a big deterrent.

Bolting things down helps slow down stealing.

I know a guy who put in an alarm system before going away on 2 weeks vacation.

Came back to find a Door way cut into an outside room (library) without windows. Chain saw was used.

Room was cleaned out, including the carpeting.

Someone told someone about it.

Most of the time the thief is someone you know, neighbor, friend, family.

Common story is someone knows your away. Quickly they Put a For sale sign in front yard. Next week moving van shows up. Cleans out house. Often the moving van co is not even aware they are stealing...

Have fun,

Scott.