# [EVDL] Battery box fan



## EVDL List (Jul 27, 2007)

Hell Barry,

I do not use 12 VDC to run my battery box ventilation fan. It's a 120 VAC 
120 cfm fan that is inline with a heavy duty 2 inch inside diameter flexible 
PVC acid proof flex hose that has 1/4 inch thick walls. The fan and fan 
blades are all plastic and the electrical fan wires are seal in totally 
enclose compartments at the fan connections.

I now have been running 33 years with out a fan ventilating the battery 
enclosure while the EV is moving. There is a 2 inch pvc pipe that goes 
below the EV and is elbow forward with a screen and 3M filter material in 
it. The forward movement of the EV brings in air into the battery enclosure 
and exits out the other side.

This fan is used only when I charge the batteries. I install the battery 
box ventilation control system, just like we do in gas fire boiler systems.

First, I must turn on the fan switch which the fan must run first to clear 
any battery venting that may be present. A pressure/vacuum switch detects 
the movement of air present and it will then turn on a 2-pole DC contactor 
that then connects the output leads of the battery charger to the battery.

The pressure/vacuum switches are super sensitive and you can get them from a 
heating and plumbing supplier.

When the fan is up and running and the flow of air is present, a fan 
indicator lite will come on, a flow air lite comes on. I then turn on the 
charger contactor which also gives me a indication, that I am connected.

I then look at the on board charger panel meters which is a AC volt, AC amp, 
DC volt and DC amp. The AC volt meter will indicated that my AC main plug 
is contacted and the DC volt meter indicates that I have main battery power 
present up to the battery charger output contactor.

Before I turn on my charge, I make sure that the charger circuit breaker is 
off and the current knob is at 0 amps. I then turn on the breaker, and 
while watching the AC and DC ampere, I turn the current up while watching 
the indicators meters.

At any time the battery box exhaust fan fails, the fan pressure/vacuum 
switch then turns off the DC contactor which removes the charger circuit 
from the batteries. A larger second fan maintains a positive air pressure 
in a separate totally enclose charger compartment.

The battery box exhaust exits out the bottom of the EV like a exhaust pipe 
does. If I park in the garage with the garage door down, I run out a exhaust 
hose either under the garage door or use a garage door port, like you see in 
gas stations.

My garage maintains a 70 degree temperature a year, so when I am charging 
the batteries, the fans pull this 70 degree garage air through a 3-M filter 
which I cut out of a large 2 inch thick 3M filter material and insert it 
into the air input side of the battery box ventilation system.

You must be care full not to cross feed the battery box exhaust system with 
the air input. At one time, I did not have this fan exhaust system install 
this way. Could always detect a battery vent order. I went into the garage 
where I was charging the batteries and when I turn off the charger, this 
ignited some hydrogen in the charger compartment and blew the charger 
bridge.

Roland


----- Original Message ----- 
From: "Barry Oppenheim" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Friday, June 06, 2008 8:27 AM
Subject: [EVDL] Battery box fan


> When should the fan in the battery box run? I'm trying to determine what
> 12V circuit switch should turn on the fan.
>
> Thanks,
> Barry
>
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## EVDL List (Jul 27, 2007)

I think if you have it come on when charging it should cover the time when
the batteries vent. Maybe have a timer so it runs for some time after the
charger is done. Or hook it to the AC charge cord so anytime it is plugged
in the fan runs. Maybe add a dashboard switch to manually turn it on, like a
bilge pump, just in case they start venting under load.

-- 
-Jon Glauser
http://jonglauser.blogspot.com
http://www.evalbum.com/555
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## EVDL List (Jul 27, 2007)

Use 12V DC fans that blow INTO the battery box, this way you don't have to
worry about arcing, etc. Plus you can use them to vent the box while
driving and not worry about battery acid mist corroding the fans.
I'd have them run whenever you are charging and while driving, unless it's
cold.
Probably wire them to come on whenever the charger is running. Add
secondary wiring to turn them one when the ignition is on, but run it
through a thermostat that opens at, ohh 60 degrees or so.

Having it run all the time can keep any acid mist from collecting in the
box and help cool the box in hot weather.

The output vents from the box should (ideally) slant upwards and be
corrosion resistant (plastic, etc.)
You could probably get away with a small pipe slanting up, to exhaust
hydrogen even if the fan isn't running, and larger pipe(s) that vent out
the back of the vehicle.

That's how I'd do it.

Just keep in mind that (unless you have sealed batteries) there IS going
to be some acid mist occasionally, best to keep it away from anything it
can corrode.

> I think if you have it come on when charging it should cover the time when
> the batteries vent. Maybe have a timer so it runs for some time after the
> charger is done. Or hook it to the AC charge cord so anytime it is plugged
> in the fan runs. Maybe add a dashboard switch to manually turn it on, like
> a
> bilge pump, just in case they start venting under load.
>

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## EVDL List (Jul 27, 2007)

On voltage: Use what's convenient, surplus or whatever works for you
On blowing out or blowing in: If you use a brushless fan, it makes no difference. And a big argument for having the fan pull air OUT instead of forcing it IN the box is that by pulling the air OUT, you have much better control of where the vapors are going when they leave the box.

Use a brushless computer muffin fan with the CFM and voltage you want.

-Myles Twete, Portland, Or.
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## EVDL List (Jul 27, 2007)

> <Myles Twete> wrote:
> 
> > On blowing out or blowing in: If you use a brushless fan, it makes no
> > difference. And a big argument for having the fan pull air OUT instead
> ...


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## EVDL List (Jul 27, 2007)

> Barry Oppenheim wrote:
> > When should the fan in the battery box run? I'm trying to determine what
> > 12V circuit switch should turn on the fan.
> 
> ...


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## EVDL List (Jul 27, 2007)

> Barry Oppenheim wrote:
> > When should the fan in the battery box run? I'm trying to determine what
> > 12V circuit switch should turn on the fan.
> 
> ...


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## EVDL List (Jul 27, 2007)

Hi Barry,

I'm using a 120V AC brushless muffin fan wired in with the AC input 
of the charger. When the charger is on, the fan is on. No need to 
worry about a 12 volt circuit.

I went to the boat store to buy the flanges and the hose. There's 
lots of good stuff at the boat store for hardware to vent bilges 
which works well for venting battery boxes.

Also if you are pulling air out of sealed battery box you should have 
an air intake for cross ventilation. I used plastic boat hose and 
flanges for that hose too.

Chip



> [email protected] wrote:
> 
> > Barry Oppenheim wrote:
> >> When should the fan in the battery box run? I'm trying to
> ...


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