Location of Battery Bank

Farmerboyz1721 · October 2016

I am using wet lead acid batteries and was wondering if locating them in the utility room was a bad idea?

With the venting of the batteries and having a flame in the room IE water heater and Boiler.

Thoughts?

Dave Angelini · October 2016

How big is the room?

BB. · October 2016

Lead Acid batteries do output a little bit of Acid Mist (and hydrogen gas)--They should usually be vented or a well ventilated room (for safety and to make sure the mist does not get on nearby things you care about, and some folks are sensitive to the "sulfur" smell).

And when you design/build the system--Use great care, you do not want a source of fire in your home.

-Bill

Farmerboyz1721 · October 2016

7' x 12'
It will have a gas water heater and a gas boiler. There will be a fresh air intake into the room.

Marc Kurth · October 2016

Assuming you have a 20-40 KWH battery bank in that sized room, I would not recommend less than adequate fresh air intakes located low and powered exhaust up high. Check your codes, but if it were mine - I would go with a 15 minute air change rate. So you only need to move a constant 50 CFM to be safe. So, I would not specify less than 50-75 CFM of required flow. Being the conservative guy that I am "one is none, two is one." Some folks will slave the fan operation to charging operation.

Odor is a separate issue, so a conservative design would go a bit higher. Large openings in the right places can give you far more flow than what is required, but cheap and reliable insurance offered by powered ventilation is a good thing!

You could potentially be safe with a convection flow approach with enough openings done the right way, but if you are off on your calculations just a bit- the results are not pretty.

I welcome challenges to my line of thinking. Bring your numbers regarding hydrogen concentration levels and show me what I missed. Seriously, there are a bunch of folks on here who teach me something new - often!

mike95490 · October 2016

Marc Kurth said:..... Large openings in the right places can give you far more flow than what is required, but cheap and reliable insurance offered by powered ventilation is a good thing!.......

Power vent fans are neither cheap or reliable for something like hydrogen gas.
A properly designed ceiling, sloping up to the vent, and allowing gravity to do all the work, is much more reliable than a fan and it's control circuits.

stillchillin · October 2016

Build a tight box around your batteries, drill a 2 1/2" hole low on one side and a hole high on the opposite side. Run a 2" PVC pipe from the high hole through the roof of your room. This will vent the box without a fan, if the venting is not adequate you can add a fan into the vent pipe.

softdown · October 2016

Farmerboyz1721 said:

I am using wet lead acid batteries and was wondering if locating them in the utility room was a bad idea?

With the venting of the batteries and having a flame in the room IE water heater and Boiler.

Thoughts?

Seems like a real bad idea to me. Hydrogen gas + flame + small room = ??????

stillchillin · October 2016

here is a picture off my enclosure prior to the hinged cover. I have found this to be most effective in venting away any undesireable fumes. My batteries are located in my basement close to my oil fired boiler, I have a co2 detector in close proximity and find that it will go off when checking SP during an EQ if I have the cover open for any length of time.

Image: https://us.v-cdn.net/6024911/uploads/editor/sk/8cy1iacp4qat.jpg

Dave Angelini · October 2016

mike95490 said:

Marc Kurth said:..... Large openings in the right places can give you far more flow than what is required, but cheap and reliable insurance offered by powered ventilation is a good thing!.......

Power vent fans are neither cheap or reliable for something like hydrogen gas.
A properly designed ceiling, sloping up to the vent, and allowing gravity to do all the work, is much more reliable than a fan and it's control circuits.

The one I use for my clients for over 15 years is both Mike! The room is way too small so the OP needs to do something!

softdown · October 2016

A potential problem with enclosing batteries is that it may allow a potent build up of hydrogen gas....as others have alluded to. Mine air out in a 500 sq ft room. I never smell anything. To be safe, I keep all flames at least 15' away. Generally...I tend to overdue things.

I think a flame has to be pretty close to ignite....unless the batteries are enclosed in something like a closet without adequate ventilation. One cannot ignore the possibility of the electronics producing a spark.

Bomb ingredients are a lot safer before they get enclosed...

softdown · October 2016

stillchillin said:

Build a tight box around your batteries, drill a 2 1/2" hole low on one side and a hole high on the opposite side. Run a 2" PVC pipe from the high hole through the roof of your room. This will vent the box without a fan, if the venting is not adequate you can add a fan into the vent pipe.

Until a child or pet rolls /stuffs a ball into the 2" pipe. Why not go 4" for the same amount of trouble? Plus....4" fans move ~twice the amount of air of 3" fans as I recall. I have a box of 3" and 4" fans...somewhere. Used to use them to move the heat out of reef aquarium canopies.

Marc Kurth · October 2016

Again, I tend to be conservative in how I lay things out because I like things to work and work safely. So I go by the numbers.

It takes roughly 4%-5% by volume for an air-hydrogen mixture to become particularly dangerous. Assuming the utility room is 7x 12 x 8 = 672 cu ft of air space - minus the space occupied by batteries and other equipment. For this example, I will use 600 cu ft of air in the room. So 4% of that is 24 cu ft of hydrogen required to get dangerous.

Assuming 8 batteries: If each battery produces only 3 cu ft of hydrogen in a closed room......... uh oh......
So next, time has to be considered - how fast are the batteries producing hydrogen and what is the dilution rate via makeup/exhaust/convection/leakage, etc. There are tables to lookup hydrogen production for different batteries, and easy ways to prove out dilution rate.

If there is ever a problem, I would want to be the guy who "went by the numbers", added a safety factor - and documented it all!

Marc

mcgivor · October 2016

Met a guy who was a welder, he was hired to do some welding in a steel fishing vessel, unknown to him the ships battery bank was located below where the job was to take place. Splatter somehow ignited the hydrogen and caused an explosion directly below where he was standing, buckling the 1/4" deck plate which liquified the bones in his feet resulting in permanent disability as the bones fused together. That was his story, but it shows how dangerous batteries in a confined space could potentially be

notes · October 2016

You have a boiler and a water heater in same room as batteries. I hope you size combustion air for both. If not enough, that room will go into a negative and pull air down that pvc pipe in your battery box.

Dave Angelini · October 2016

Generally a building inspector (who is reasonable wants an L16 1,100 AH 48V bank in a space like a garage.The gas burners should be fed with outside combustion air, that is my requirement.

WaterWheel · October 2016

As I understand NEC code a large battery bank must be kept where there is no chance a person can inevitably short the batteries. example, you need to make sure nobody drops a wrench on the terminals ect. Common sense dictates that you want some protection in case something like a ladder falls over shorting the batteries so just build a ventilated box and install a Aux controlled vent fan piped outdoors.

My battery box is in a 3 car garage so I put in a Aux controlled vent fan for safety, the charge controller controls the fan. Once, with a garage door open and the battery box top open I gave the batteries a really strong EQ and the gases were strong enough to slightly burn the eyes and make breathing a bit difficult with the gas smell. In my uneducated opinion you need to build a battery box and vent it with a fan. The large brown plastic deck box from Home Depot easily hold eight L-16 batteries and you can put intake and exhaust holes for a vent fan in it. http://www.homedepot.com/p/Suncast-134-Gal-Resin-Wicker-Deck-Box-BMDB134004/203014102

The sponsor for this site sells vent fans, I use the 48v version.

stillchillin · October 2016

Of course it should be safety first, that being said if it were me I would lean towards a heating device that is designed to have combustion air ducted directly to the burner. Rinnia makes a combination hot water boiler/ on demand hot water heater that ducts combustion air directly to the burner through a concentric vent pipe. They are > 95% efficient come in both LP and natural gas. I have installed several of these units and have never had a problem with them. I know there are other manufactures out there but I am familiar with these. They are a bit pricey but if its a safety issue money should not be an object. good luck

Farmerboyz1721 · October 2016

Thanks for the feedback from everyone.

Here are the numbers that i have using an online calculator

Hydrogen Gas Produced Per Hour12.03 cubic feet
Total Volume of Room688.03 cubic feet

Percentage of Hydrogen Gas1.75 %

Volume of Room 688.03 cubic feet
Hydrogen Gas Produced per Hour12.03 cubic feet
Max. percentage of hydrogen gas allowed1% (Industry Standard)

Complete Air Exchange Every34.32 minutes

Volume of Room688.03 cubic feet
Complete Air Exchange Every34.32

Fan Requirement20.05 cubic feet per minute

The fan requirements do not seem to be that 'big' and definitely manageable.

Can the room be vented into the family room on the same floor? Or should it be vented to the outside?

Farmerboyz1721 · October 2016

@stillchillin I have been looking into the tankless water heaters that have the direct combustion. I am definitely going with those..not just safety factor but they really are cool units.

BB. · October 2016

20 cfm is not a large fan. Math can be your friend.

Tankless water heaters--Research the brands and talk to people that have installed them to see if you will be happy.

Tankless water heaters save money because they do not hold water hot 24x7.

They are "different animals". You have to warm up the heater and adjust the hot water flow (on many units) to get the "right temperature". Too low of flow, will not turn on. Too much water flow (and very cold input water), and you don't get very hot water.

Also, if you have hard water--They can have significant scale/calcium buildup internally (install a "flush kit" valves and connections and flush tankless heater once a year with ~3-5 gallons of white vinegar/weak acid?).

https://www.youtube.com/watch?v=T4FaqGod3VU

And finally, tankless water heaters can be pretty noisy (large gas flame, possibly forced air flow depending on model).

-Bill

mike95490 · October 2016

Tankless owner here.
Pros: Little standby loss. Endless supply (not just 20 gallons on the top of a 40 gallon tank). Extra closet space when the big tank goes away.
Cons: Huge burner, may need gas line upgrade to fuel it properly. No 40 gallon emergency reserve tank of potable water. The cold slug problem. The limited temperature rise/flow rate problem.

Dave Angelini · October 2016

Add on to the cons the no brainer that to do solar hot water, you do need a tank......

BB. · October 2016

Also, check on spare parts/service tech availability--Tankless units are much more complex and much more to go wrong vs a simple tanked water heater.

-Bill

Dave Angelini · October 2016

Definately Bill,
you should hear the stories from some of my clients about tankless. I try not to gloat over telling them about taking the time (in their busy schedules) to just do solar hot water, even an open loop that is drained during winter is cheaper and there are so many do it yourself ways to do this very economically.

I never say I told you so.....

Location of Battery Bank

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