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Re: [EVDL] EV Digest, Vol 3, Issue 85

Hi Chris,

For ventilating the battery boxes I'd think about it in terms number
of air exchanges per minute. My enclosed battery box (from the
Voltsrabbit kit) is about 3'x2' with about a 4" gap between the
batteries and lid. This is about 2 ft^3.

I think the fan I'm using is in the neighborhood of 10-15 cfm. That
makes for 5-7 air exchanges per minute, which seems entirely fine to

As for pushing or pulling air, I also chose to push air into the box
for the same reason, but also because clearing out the H2 is one of
the main reasons to ventilate, and explosion proof fans are harder to
find. Honestly I was more worried about the acid mist eating the fan

I have my fan hooked up to AC, from what I understand, if the
batteries are gassing when you're discharging, there are bigger
problems brewing since you've probably reversed a battery. I haven't
done it yet, but I bought a couple reed switches and intend to have
them control the AC to the fan. The reeds will be pulled in by the
current in the DC charging wire. This way, the fan only runs while the
battery is actually charging. I haven't put it in yet because I
haven't made sure that the switch will still be closed at 2-3 amps
during finish charging.


> Message: 17
> Date: Wed, 31 Oct 2007 10:46:04 -0500 (CDT)
> From: "Christopher Robison" <[email protected]>
> Subject: Re: [EVDL] Blowers
> To: "Electric Vehicle Discussion List" <[email protected]>
> Message-ID: <[email protected]>
> Content-Type: text/plain;charset=iso-8859-1
> Thanks for your input Roland; I have a few questions/comments for you or
> anyone else:
Roland Wiench wrote:
> > Hello Christopher,
> >
> > I am using total all plastic box fan from Rotron that is use for my
> > battery
> > box. It is duel voltage rating of 230 vac at 340 cfm at 3300 rpm, or you
> > can run it at half speed on 115 vac.
> >
> > source of supply is
> I'm looking for a continuing source of fans, instead of buying surplus.
> Apparently "Rotron" applies to two different companies; Comair-Rotron
> ( who make one model of biscuit AC blower at
> only 22CFM, and Ametek-Rotron who make larger blowers, but only sell to
> military and aerospace (
> Is 340cfm really necessary? This has me concerned, as the crossflow fans
> I've chosen supply a maximum of 50cfm. Having to choose another fan at
> this point will complicate the design (should have asked earlier).
> >
> > I do not ventilate my battery box with the fan running.
> Do you mean, you don't ventilate the battery box with the "car" running?
> > outlet pipe pointing straight down with the 45 degree cut pointed to the
> > back. The inlet also has a 45 degree cut pointed to the front, so now we
> > have a ram air system when the vehicle is moving.
> This seems like a good idea. At any rate, it seems like you're
> recommending airflow through the battery box during discharge. Is the
> problem of outgassing just as high as when charging? Since the ducting
> will be difficult to fit in the current design, I may have to use a DC
> blower to provide airflow while driving.
> > I do use a larger Dayton Blower in my equipment enclosure to pressurize
> > it,
> > that contains a PFC-50 charger, contactors, fuses, and circuit breakers.
> > The blower is rated at 165 cfm at 115 volts. Uses a 6 inch carb type air
> > cleaner on it for the inlet air. I use that 3-M bulk air filters that
> > look
> > like scotch pads but is about 1 inch thick. I cut a piece of this in
> > stuff
> > it into the inlet air for the battery boxes.
> Early PFC chargers certainly needed very effective cooling; I'm hoping
> more recent ones deal with heat a bit better, here in Austin.
> --
> Christopher Robison
> [email protected]
> <-- 1999 Isuzu Hombre + Z2K + Warp13!

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