Designing a battery room

System · August 2008

My wife and I are going to have a Solar Passive House buit in Argentina. We are currently designing the house. After construction is finished, we will take it off the grid. We would like as much details incorporated in the design, so we have a queston about the battery room.

We have planned to put the battery room inside the brick walled garage/shed, measuring some 9 by 6 meters (some 27 x 18 ft). Along the short side we could square of 1 mtr or so to create a 5x1 m2 battery room. This would allow passive ventilation from both ends (we will prob. have to use non-sealed batteries, those are available there).

We could use some help with the folowing:

1: 5 x 1 mtr (15 x 3 ft) seems rather big for storing batteries. We will not consume more than 2 kWh per day, so we don't have to accomodate huge amounts of batteries. Is this setup realy necessary or can we make it shorter with only one side having direct access to outside air. Would we then need active ventilation (fans)?

2:we plan to put generator, inverter and charger in a fysically separated area inside same shed/garage, but close to the battery bank (to prevent sparks igniting H2). Is this a good idea or shouldn't we bother?

3: we plan on putting insulation around the battery room to protect it from heat and cold (winter nights down to -13 celcius). But with passive ventilation (2 screened openings facing each other) cold comes in anyway. Should we bother with the (expensive) insulation in floor, walls and roof?

4: do we want our normal electricity panel (with all the fuses and switches for groups) close to this installation or can we keep it inside the house where it would nornally be?

We apreciate any help, suggestions etc., because the subject is very uncommon in Argentina and our architect knows nothing of the subject whatsoever.

From Spain,

Giri

mike95490 · August 2008

Re: Designing a battery room

Cool - what neat project. !

> 5 x 1 mtr (15 x 3 ft)

Does not seem wide enough. Get a wheeled cart of the type you will install and move the batteries with, put bricks or cement blocks on it, and roll it around and set it down, pick it up. Can you do that in 3' wide ? I would guess at 5' wide at least:
2' storage shelf, 3' isle
Batteries are heavier than cement blocks, and much more fragile

Although you only require 2KW daily usage, you should have a bank large enough to have 3 days storage, before you have to run the generator - 6KW of usage. Additionally, at the 3 days, your bank should only be 50% discharged, as deeper discharges age batteries faster. 12KW of batteries now !

The floor and first foot of the walls, could be of a material resistant to acid spills, in case a battery splits.

I would insulate the roof, to keep heat out. -13C won't harm the batteries, but it will reduce their capacity somewhat.

I think I would have the battery room be a separate room, from the generator shed, as batteries and generators do have a habit of burning up if mistreated, and you don't want them to burn your main house or garage down.

I would also plan on having a "small" 1 or 2 KW generator you can hand start, because if all your batteries have gone flat for some reason, you cant start the big generator, you can always hand start a little one.

You need electrical switch area too - to manage the Grid, Generator, Inverters and Battery wires and protection devices.

niel · August 2008

Re: Designing a battery room

i'm glad mike addressed the size of the battery bank, but if you have a backup generator you don't need the extra 3 days worth of storage and if all else fails you can just do without until the batteries do charge up. i think 2kwh x2 for not exceeding 50% dod is a must and this translates for a 12v battery system (you could have 24v or even 48v if you wish to, but 12v is a common small system voltage) as 4000wh/12v=333ah battery capacity with half of that for a 24v battery bank. consider this 333ah as the minimum capacity you'd need. keep in mind you may need to stay within 5-13% for the charge rate and this will be a factor in sizing your pv system.
anyway, for small systems like this i don't think ventilation will be that much of a problem unless you are overcharging the batteries or charging at the higher percentage rates over 13%. i ran about this much battery ah capacity in the past without ventillation and through my error i even had overcharged them boiling them to the plates and no explosions had occured with the room being 25% larger than the room you propose. i also see no problem with you lining the batteries along the side of one wall, but for parallel connections it may get a little bit more cramped and i still see it as doable. slightly wider may prove better for you though and you won't need it 5 meters deep imho as that could be cut in half with no problem leaving some room for future expansion too. if you want to still have ventillation then go with a small screened area that you may have the option of closing off, like as in a window. place it higher up as the hydrogen will rise being very light weight, but still within arms reach. now i wouldn't go with ventillation myself, but know that even a round 50mm opening near the ceiling of the room going to the outside would vent the hydrogen with no problem should it appear for a small battery system. it seems small to you, but during the warm months everything is opened more to the outside and in the colder months the temperature differential will move lots of air to the point that you may wish to have no vent at all at times.
you can still go with some insulation, but the room doesn't need it as only the batteries need. give them some room to breath if just going around the batteries and no generators in the same room of course. fusing and disconnects should be near the batteries as well as any inverters, but they don't need to be in the same room. keep leads as short as you can going from the battery room to the other room with all of this associated stuff.
i'm going on too much here so i'll stop at this time.

nigtomdaw · August 2008

Re: Designing a battery room

On a lighter note build in a rodent free enclosure, I made my 2100 ah 24v battery bank well insulated with 2 inch styrofoam (aka as rodent bedding) Didnt seal the top off when I should as I have done now with plexiglass, Created a nice not too hot not 2 cold battery enviorment, placed an add in Rodent Gazette got s$$t loads of applications , made a finca paradise for Roddy the Rat.Killed him got Rudolph and Ralph to replace him, Fed them to death with rat nosh, hoovered uploads of Styrofoam bedding, still waiting to see if the little buggers can survive on PVC tubing (aka auto watering system ) and Rat grub. They really are persistent squatters. Problem is I cant squeeze Felix inside the compartment to fix the problem.

Just a minor prob in my off grid Nirvanna................rats. mices I hateem to pieces:grr

Finished Rant Sos:p

nigtomdaw · August 2008

Re: Designing a battery room

PS the battery enclosure was made with concrete blocks, what Im saying is get it rodent free asap I left mine 12 months b4 sealing it up properly in the Spanish countryside and by then my warm apartment was all the rage with Critters Ville. Getting Ratty and his family out is becoming tiresome.

I can see why OB developed a tight system enclosure for there gear even the VFX stuff is virtuallly mosquito proof.

My solar cheese wedge shed has plenty of ventillation needs bug proofing, time to buy steel mesh and bug it up. You live u learn, Plenty of PV power plenty of bugs, rodents and head aches.

Guess Rome wasnt built in a day eh?

niel · August 2008

Re: Designing a battery room

good point about the rats nigel as nobody wants them for live-in guests.

you are entitled to your RAnT.:roll:

Designing a battery room

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