Charge Sealed Battery / In Airtight Container

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I'm making a Deer-Alarm to keep the deer out of my yard, thus saving my trees and shrubs / and as a good mental exercise.
It consists of a Motion Detector, 'flashing' LED Lights and a 'loud' Buzzer / all 12 volts.

The Alarm (plastic box) is 4" x 6" x 6" with as large a 12 volt battery as I could find.
I'm sure I will need to occasionally charge the Battery / maybe yearly ?
I included a Voltage Meter to monitor Battery.

I thought of making 'the charging' easier by having a (+) & (-) wire come out the back of Alarm,
to which I would connect the Charger (Battery Tender/slow charge) without having to open the unit up.

Battery Info:
12 Volts / 5Ah
Lead-Acid / AGM Type
Sealed / Non-Spillable

My questions are:
1) Would 'slow' charging this Battery (say from 10 V back to 12 V) create any gasses that would
create corrosive problems (inside the Alarm box) ?
Plastic Box will be as air,water-tight as I can make it.

2) Or should I just settle for removing the Cover any time Battery needs charging ?

3) Will I have to worry about corrosive gases building up between charges ?

Thank you for any advise.

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NOT a good idea. They do create some small amount of gas. If it fails shorted then it will vent much more gas and your enclosure will explode.

If the battery freezes it normally fails and will then vent gas. I would plan to charge at least fall and spring.

There are lots of bug proof rain proof enclosure vents in the $5 to 10 dollar range.

The enclosure companies make a lot of them.

Rod
 
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Put 1 or 2 weep holes in the bottom of the enclosure

Connect a small solar charger and forget about it .
 
Anything mounted outside should have a vent or a weep hole in the bottom, or it will fill up with condensed water. Use a screen fine enough to keep tiny ants out. Tiny ants will go anywhere.
 
Years ago a cousin of mine had a deer corn feeder controls / battery , mounted in a metal USGI ammo box , to keep it dry . Think it had a solar charger on it .

The timer would close a relay . The relay drove a motor to spread the corn . Short version , it evidently collected hydrogen gas and the spark from the relay ignited it . Blew up the ammo can . Can not remember how much of the electrics / electronics he was able to salvage ?
 
I think a couple of vents on sides and bottom would be fine. As someone said above, glue some window screen inside as a pest block. You could probably use a drawer pull as a "louvre" to shield a side/back vent from water intrusion.

Nice work. Looks like a fun box!
 
btw- with the motion detector running full time, I don't think 5AH is going to hold long, and without a daily charge the battery will probably struggle to remain above 80%. A small PV panel with a decent charge controller would probably round this out nicely.
 
Originally Posted by MasterSolenoid
It consists of a Motion Detector, 'flashing' LED Lights and a 'loud' Buzzer


Won't they just get used to that after a while? Don't you have a cat or dog you could put out there?
 
Why such a small battery? Do the math to figure how long it can go between recharges.

If it's AGM and charged properly, it won't vent gasses much.

As several have said, the box should have a little ventilation, despite the thread title.
 
OP here,
From reading the responses, I'd agree that I should add Vent Holes and some Weep Holes in the bottom.
If humidity eventually kills it, that's ok, it's not going to be used 24/7, only when I suspect deer are walking thru the yard.

Originally Posted by atikovi
MasterSolenoid said:
It consists of a Motion Detector, 'flashing' LED Lights and a 'loud' Buzzer

Won't they just get used to that after a while? Don't you have a cat or dog you could put out there?

Answer: 20 LEDs randomly flashing and a Buzzer sooo loud, I had to mount it inside, There is no way the deer would want to be around it.
The toggle switches are so I can turn OFF either light or the buzzer.

How long the battery charge lasts is the big question.
I have the Motion Detector set for a 5 second delay / meaning the Alarm will sound for 5 sec after the deer leave area.
How many times will it come ON during any night ? ? ?
 
Years ago I saw something on TV about a high-school football field that had a problem with deer damage. The grounds keeper went to a barber shop and got human hair from all of the haircuts, and spread that around the field. The deep smelled the hair and stayed away.
 
All AGM batteries say to not charge them in a sealed container.

They are unlikey to offgass, unless overcharged, but in a sealed container they are more likely to be overcharged, due to higher battery temperatures from being inside an enclosure.

When they do offgass , the gasses are hydrogen and oxygen. We know hydrogen rises in our atmosphere, will oxygen too? Weep holes on the bottom only might simply allow any potential escaped hydrogen collect up top. Add spark and go boom!

You should measure how much loads your devices actually consume, and draining the battery to dead over a year, would likely yield a battery that would then discharge to Completely dead in half a year if it even took a charge.

A solar panel would be great, if the box sees a few hours of direct sun each day, and the panel is appropriately sized for the maximum load/ discharge of the battery with a solar controller to prevent overcharge.

Do make some sort of mushroom vent on top, to allow lighter than air gasses to escape and also prevent water entry. weep holes to allow escaped air to be replaced from below.

Keep some space around the battery, including under it too, to allow convection to remove heat from it.

If it does see direct sun, paint the enclosure white on the south side to help keep the battery cooler and it will then degrade slower than it would if hotter.

No lead acid battery likes being slowly drawn to dead. A 100% discharged lead acid 12v battery is dead at 10.5v, and draining it lower than this is very bad for it. very little useful energy below 10.5v. The lower the state of charge, the easier they will freeze, and then become useless.

All lead acid batteries, for maximum longevity, want to be 100% charged always.
How much lower than this they go and how long they remain there, along with their average temperature, dictates the rate of capacity loss until uslessness sets in.

The average state of charge and average temperature of lead acid batteries, play a much bigger role in battery longevity than who made the battery or who stuck their sticker on it and who sold it, or what bubbajoeinternetpro claims to be the best battery ever..
 
That is an SLA Gell Cell battery. SLA stands for sealed lead acid. SLA batteries are TOTALLY sealed so they can be used in ANY position and NO gases are released during normal charging. Yes, you can (and should) seal the box. Forget about weep holes. If water can't get in they are not needed.
As others have said, this would be a perfect application for a small solar panel charging system. If you keep it under 3 watts you won't even need a charge controller. A 1.5 to 2 watt will be big enough to keep the battery fully charged and small enough in size to mount above the IR on a fabricated bracket.
 
Operative words being normal charging. Even moderate overcharging (e.g. solar with no charge controller) will release hydrogen gas.

The early terminology was "sealed lead acid." Technically they are valve regulated, with relief valves which can open to vent gas.
 
the big question for me is the steady-state draw from the motion detector. I can see that alone being 100MA which will deplete the battery quickly. At 100MA, that would equate to 5AH in roughly 48 hours. You could extrapolate some, right? at 100MA the battery reaches 80% SOC in 10 hours. Even with a large PV panel, every night it would dip to 70% SOC just for the motion sensor, resulting in a battery that will have a short lifespan. Sensor drain needs to come way down, or battery capacity needs to come way up, unless the sensor is at something like 15MA draw, which even then would need weekly charging.
 
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Originally Posted by mk378
Operative words being normal charging. Even moderate overcharging (e.g. solar with no charge controller) will release hydrogen gas.

The early terminology was "sealed lead acid." Technically they are valve regulated, with relief valves which can open to vent gas.
It takes fairly significant overcharging to open the vent valves on an SLA battery. Under full sunlight a small 1.5 to 2 watt solar panel is only going to output about 100 ma to 125 ma, not nearly enough to overcharge a 5ah SLA battery in cyclical use.
 
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Originally Posted by meep
the big question for me is the steady-state draw from the motion detector. I can see that alone being 100MA which will deplete the battery quickly. At 100MA, that would equate to 5AH in roughly 48 hours. You could extrapolate some, right? at 100MA the battery reaches 80% SOC in 10 hours. Even with a large PV panel, every night it would dip to 70% SOC just for the motion sensor, resulting in a battery that will have a short lifespan. Sensor drain needs to come way down, or battery capacity needs to come way up, unless the sensor is at something like 15MA draw, which even then would need weekly charging.
Most PIR detectors don't draw anywhere near 100 ma. I have a battery powered remote PIR detector next to my front door that I use as a door bell (so it also has a transmitter in it), it's 2 AAA batteries usually last 18 months or so.
 
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