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Old 29-03-2014, 09:16   #1
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Wiring in a Fan for Battery Charging

Simple enough project you'd think but......

What I'd like to do is wire in a small fan that I can attach to the gas vent line in my battery box so that it runs during charging to help extract any excess H2 gas that might be produced.

My old battery had a small fitting that the vent line attached to but the new one does not have this so i was thinking a small computer type fan funnelled into the line would do the trick.

My thinking is to wire the system "backwards" between the negative and positive connectors and use a blocking diode (or 2) to prevent the fan running during discharge. Would this work in practice?

Cheers

Keiron
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Old 29-03-2014, 09:23   #2
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Re: Wiring in a fan for battery charging

There are various electronic devices that can activate a circuit at a set voltage. So can switch on the fan when voltage at the battery terminal reaches 13.6 or whatever your min charging voltage would be.

But do you really need this fan? Unless the battery box is sealed or at least sealed at the top, any gas generated should dissipate pretty easily.
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Old 29-03-2014, 09:26   #3
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Re: Wiring in a fan for battery charging

The answer is why not??? Sounds plausible to me....

You'll need to have one of the battery leads directly connected with a diode to the fan/hot lead from the charger... Not to a regular switched load connector....
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Old 29-03-2014, 09:33   #4
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Re: Wiring in a fan for battery charging

You can get an automatic controller from Backwoods Solar - Automatic Control for 12 or 24 Volt Battery Fan Backwoods Solar that is used by the off-the-grid people.

It starts automatically when the battery reaches gassing voltage, it can power fans or blowers up to 50 amps and then it runs for an additional 15 to 20 minutes after the charging stops to evaporate any splashes and cool the compartment.
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Old 29-03-2014, 09:45   #5
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Re: Wiring in a fan for battery charging

Whilst the battery compartment is not sealed in the strictest sense of the word there is not a lot of circulation through or around it. Hence the reason for the original gas vent line attached to the port on the original battery and why I was thinking to add a mini extractor fan. Basically a case of if it can be done simply then better safe than sorry.

I like the automatic control but at $84 plus postage from US to Croatia, and import duty on top, it's a bit steep. However it does give me something to look for on this side of the pond.

Not wanting to sound completely daft but a simple sketch wiring diagram would really help visualise how it would all hook up.

Cheers

Keiron
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Old 29-03-2014, 09:55   #6
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Re: Wiring in a fan for battery charging

Wow! That's $5 cheaper than Yandina's own site. I have one on my own house bank. Yandina makes clever little products.
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Old 29-03-2014, 10:35   #7
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Re: Wiring in a fan for battery charging

Keiron

Crap quick diagram, but you get the idea... keep the wire sizes the same, fan leads can be tiny...
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Old 29-03-2014, 10:36   #8
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Re: Wiring in a fan for battery charging

Not to throw a wrench at anything but just out of curiosity. Since H2 is considered a combustable gas wouldn't you want a fan that is explosion proof rated? Could a simple computer muffin fan cause concern as a possible ignition source?
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Old 29-03-2014, 10:56   #9
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Re: Wiring in a fan for battery charging

Quote:
Originally Posted by Tellie View Post
Not to throw a wrench at anything but just out of curiosity. Since H2 is considered a combustable gas wouldn't you want a fan that is explosion proof rated? Could a simple computer muffin fan cause concern as a possible ignition source?
I would use blower duct, and put it 2' upstream pressure side... Wouldn't worry that way at all... Besides... the computer fans are all brushless mag inductive... (I think) *Tellie advised disclaimer* "do this at your own risk!"
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Old 29-03-2014, 16:08   #10
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Re: Wiring in a fan for battery charging

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Keiron

Crap quick diagram, but you get the idea... keep the wire sizes the same, fan leads can be tiny...

you'd need massive diodes and you'd lose 1.5v of your charging which is really dumb.

actually you only need the lower diode, the upper one just loses voltage but doesn't help you. so you'd lose .7v. but still dumb idea.


is this only for the charger or for the alt too? if just for the charger run an AC relay off the charger ac line. dc to relay switch for fan power.

if you want it to run off alt too then I'd look at voltage measuring circuits that will activate at voltage.
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Old 29-03-2014, 16:58   #11
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Re: Wiring in a fan for battery charging

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you'd need massive diodes and you'd lose 1.5v of your charging which is really dumb.

actually you only need the lower diode, the upper one just loses voltage but doesn't help you. so you'd lose .7v. but still dumb idea.


is this only for the charger or for the alt too? if just for the charger run an AC relay off the charger ac line. dc to relay switch for fan power.

if you want it to run off alt too then I'd look at voltage measuring circuits that will activate at voltage.
I definitely think you're route is TWO better ways to do it... Voltage sensing relay being my choice, set for say 13.5....
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Old 29-03-2014, 17:27   #12
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Re: Wiring in a fan for battery charging

My fan is wired into the ignition. When ever the motor is running then the fan is running. If I charge with a 120V charger then the cover is off of the compartment. KISS
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Old 08-04-2014, 03:52   #13
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Re: Wiring in a fan for battery charging

Now this is the reason why I raised the question in the first place - to find out all these niggles and problems, so thanks to all for the input.

Yes H2 is an explosive gas but like all explosive gases there is a Lower Explosion Limit (or concentration) below which it simply will not ignite. Not sure for H2 but as there's no explosion proof or EX electronics anywhere on the average boat I can't see adding a small PC fan (brushless) would present a problem. The idea is to keep the concentration as low as practicably possible anyway.

Given I am not an electrical (or electronics) engineer I'll take it as gospel that there would be a loss of charging voltage, not that I fully understand how or that it could be that large given the small amount of amps the fan would need but I'd rather not compromise the charging efficiency.

So I think I will just rig up a "oven hood" type of arrangement to funnel any H2 naturally into the pre existing vent line and maybe look into increasing the natural ventilation under the cabin seat where the battery lives.

Many thanks again to all who have replied

Keiron
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Old 08-04-2014, 04:33   #14
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Re: Wiring in a Fan for Battery Charging

I think the fan is a good idea, and one I want to keep the battery box cool by ventilation. But spending $84 to make a $5 fan work is not feasible...

But what about ripping one of those garden lights apart (87 cents at Walmart) and using it for the photo electric switch?

Run the photo electric cell outside somewhere inconspicious and then when the sun pops up and your solar charges the batteries the fan comes on.

And making it could be quite fun and at 87 cents, a gift!
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Old 08-04-2014, 04:51   #15
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Re: Wiring in a Fan for Battery Charging

Quote:
Originally Posted by kas_1611 View Post
Now this is the reason why I raised the question in the first place - to find out all these niggles and problems, so thanks to all for the input.

Yes H2 is an explosive gas but like all explosive gases there is a Lower Explosion Limit (or concentration) below which it simply will not ignite. Not sure for H2 but as there's no explosion proof or EX electronics anywhere on the average boat I can't see adding a small PC fan (brushless) would present a problem. The idea is to keep the concentration as low as practicably possible anyway.

Given I am not an electrical (or electronics) engineer I'll take it as gospel that there would be a loss of charging voltage, not that I fully understand how or that it could be that large given the small amount of amps the fan would need but I'd rather not compromise the charging efficiency.

So I think I will just rig up a "oven hood" type of arrangement to funnel any H2 naturally into the pre existing vent line and maybe look into increasing the natural ventilation under the cabin seat where the battery lives.

Many thanks again to all who have replied

Keiron
You bet man! What it's all about... bouncing ideas until the best solution for you appears...

Quote:
Originally Posted by MarkJ View Post
I think the fan is a good idea, and one I want to keep the battery box cool by ventilation. But spending $84 to make a $5 fan work is not feasible...

But what about ripping one of those garden lights apart (87 cents at Walmart) and using it for the photo electric switch?

Run the photo electric cell outside somewhere inconspicious and then when the sun pops up and your solar charges the batteries the fan comes on.

And making it could be quite fun and at 87 cents, a gift!
Like it Mark!
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