Battery Venting Quandary

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Bigwooo
Bigwooo Solar Expert Posts: 62 ✭✭
I have a condo in a beach resort in Nicaragua. Due to frequent short duration power losses, I’m planning to install a battery backup system to keep the ceiling fans, fridge and a light or two available when the power’s out.

My concern is that they don’t vent the batteries to the outside. There’s really no effective way to run venting from where the batteries need to be located to the outside.

The developer has installed several of these backup systems. They’re installed in a closet that has louvered doors venting into the main living area. They say that that works just fine and that they’ve never had a problem. (Yea, no problem so far).

I’m trying to locate AGM batteries so I don’t have to worry about venting, but I’m not sure they’re available there. If I have them install this system, what are your thoughts about not having any outdoor venting for the batteries? Am I more worried about it than I need to be?

This will be a very small system with only about 250 watts of battery backup, unless I can find AGM, the batteries will most likely just be normal sealed lead acid RV type batteries.

Thanks

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,497 admin
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    Re: Battery Venting Quandary

    Do you mean "sealed" as in Gel or some other sort of VRLA battery?

    Batteries should always be vented, but if this is a small system, perhaps it will not be as dangerous...

    Also, look at the various water saver type caps for wet cell batteries (which are probably better for you than Gel Cell).

    Some include a catalyst (platinum/palladium?) which recombines the hydrogen and oxygen back into water... Work well for normal charging, but can over heat during equalization (recommended to remove them from battery when equalizing). May need to replace them every 3-8 years (not cheap).

    Another type just catches the acid vapor from the bubbles popping... Does not recombined the hydrogen and oxygen, but keeps the acid fumes down and also saves water.

    If you can open a window during equalization--you may be a bit safer. Also, make sure that the batteries cannot be shorted and that the cabling in firmly mounted so that it cannot flex or come loose and short.

    Running motors with batteries is typically a big power draw... How long of outage do you plan for and how much power do you need... The larger the bank, the more ventilation it will need.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Battery Venting Quandary

    as bb said a small system shouldn't be bothered, but being in the closet could cause a buildup there. you are in a warm climate so the batteries will be warm to hot making a remote battery temperature sensor a must to help eliminate any excesses in charging. agms are a fine way to go, but they can outgas if they exceed their voltage maximum. outgassing on an agm will ruin them as the water can't be replaced. with a quality controller and bts there should not be much of a worry of a failure. the agms will also add more efficiency to the system as their charge efficiencies are higher. costs are too unfortunately.
    as to availability there i can't say, but i'm sure battery manufacturers and dealers in those batteries are able to ship them to you. be advised that some smaller agms are ups-able as my pvx 1040 was ups shipped to me. the larger 200ah+ batteries are too heavy for the guys on the ups trucks to lift.
  • Bigwooo
    Bigwooo Solar Expert Posts: 62 ✭✭
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    Re: Battery Venting Quandary

    Thank you for the input.

    Power outages are generally from 2 to 8 hours.

    As far as battery type, the only deep cycle batteries I've been able to find so far are (a brand I've never heard of) 6v "sealed" lead acid battery, I think they're the same ones they use in golf carts there. I'm hoping to find gell or AGM somewhere, but so far my hopes are not high. Shipping from the U.S. or Costa Rica (where there is greater availability) is out of the question mostly because of the hassles going through customs (never seeing them again) and very expensive shipping fees.

    The caps sound like a good idea if I can find deep cycle wet cell batteries. Pretty slim pickings so far though. Nicaragua's is not big on solar. I will definitely get a battery temp sensor. The batteries will be between 70 and 85degrees most of the time.

    The closet is vented pretty well. The closet door is louvered and has good airflow.

    The system will be very small and will only power a 150 watt ceiling fan, 125 watt fridge and a couple of 50 watt lights when power is out. I figure over 8 hours my max draw will be about 175 amps. Power outages over 8 hours are pretty rare.

    I'm going to have them install 250 amps of battery with (most likely) a Xantrex dr2412 inverter/charger.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Battery Venting Quandary

    for an 8hr outage you may need to double your battery capacity to 500ah because adding up all of your draws and multiplying them for 8hrs yields 3000wh. 3000wh/12v=250ah. you don't want to kill your batteries by going all the way with it.
    as to shipping your ip address is california and there wouldn't be a problem there unless i'm missing something else here.
  • Bigwooo
    Bigwooo Solar Expert Posts: 62 ✭✭
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    Re: Battery Venting Quandary

    Thanks Niel,

    IP is California, but getting batteries to Nicaragua where I plan to install the backup system is nearly impossible due to customs restrictions and prohibitive shipping costs.

    I did find some AGM batteries in the capital,Managua though. Universal battery has a distributer their and they sell AGM batteries. Althought they're definitely not Concord quality, I think they'll do the job and I won't have to worry about gasses.

    You're right about the battery bank size. I decided to increase it so I don't drain the batteries below 50% over 8 hours.
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
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    Re: Battery Venting Quandary

    you're welcome and no problem. if you manage to hold your draws to 175ah you may get away with about 350ah in battery capacity, but more won't hurt unless your charging source is to low for a proper charge. batteries won't always be exactly what one figures anyway as you may wish to get say, 4 rated at 100ah for 400ah or even 2 at 210ah (if available) for 420ah and so on. the minimum charge rate should not be less than 5% or the maximum charge rate greater than 13% without the manufacturer saying it is otherwise capable.
  • System2
    System2 Posts: 6,290 admin
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    Re: Battery Venting Quandary

    Load will be: "a 150 watt ceiling fan, 125 watt fridge and a couple of 50 watt lights".
    Hummm, pretty heavy loads for a small battery system.
    First thoughts are conservation.

    Ditch the 50 watt light bulbs and go with CFL - - same light, 1/4 the power draw.

    Forget the 150 watt ceiling fan and go with a smaller, high efficiency table fan, for localized breeze during power outages. Perhaps 1/5, or 1/10 the power draw.

    As is oft repeated on this form, the fact is, it's far cheaper to conserve than to generate, and / or store power.

    All the best
    Wayne