battery box blower

Sojourner · February 05, 2009, 09:58:23 PM

About venting battery box with fan or blower...always apply fresh air into top-side or top of box with exhaust vent thorough the open bottom. Hydrogen gas is explosive when ignited via spark from electro static of the open brush type electric motor.

About a power tap source to automatically turn on fan whenever generator is charging...is to tap on the Relay terminal at the generator. You only want the fan running whenever it making hydrogen gas.

About a charger to energize the fan...I would call the charger's manufacture support and ask for information where to tap in to control fan's relay

Sojourn for Christ, Gerald

HB of CJ · February 06, 2009, 02:08:52 AM

Blowing and not sucking is the key. Hydrogen goes up, which means it most likely will not hang around the bottom of the battery compartment. Perhaps a dedicated small muffin fan located in the forward bottom of the battery box will work.

The forward section because it will get help from the Bus Conversion going down the road. Bottom because the gas will go up. An outlet in the aft upper portion of the box will work for same reasons. Wire it thru your inverter/charger. HB of CJ

gus · February 06, 2009, 01:23:03 PM

As HB says, vent Hydrogen from bottom to top. Trying to vent it out the bottom is like pushing on a rope.

It is much lighter than air, the very reason it was used in dirigibles.

Unfortunately, it is also very explosive - the reason it was stopped being used in dirigibles!!

Hartley · February 06, 2009, 02:55:29 PM

Lot of over thinking here...

Temp sensor in battery box to start fan and shut off when done.

Charging makes heat. Shorts make heat.. DUH...

buswarrior · February 06, 2009, 03:03:38 PM

Depending on construction of the battery enclosure, some consideration as to whether the unwanted gases will be pushed out cracks, or otherwise accidentally directed to unintended areas by pressurizing the cavity...

Maybe best to run the fan as an exhaust, not as a supply?

happy coaching!
buswarrior

Tim Strommen · February 06, 2009, 03:08:25 PM

Quote from: DrDave-Reloaded on February 06, 2009, 02:55:29 PM
Temp sensor in battery box to start fan and shut off when done.

Charging makes heat. Shorts make heat.. DUH...

This was mentioned at the end of my first reply yesterday:

Quote from: Tim Strommen on February 05, 2009, 12:42:57 PM
Of course, the most acurate way to control fans is when they are needed (battery temp gets too high). You would also want to start dumping loads and/or sound an alarm if you batteries are getting hot enough to out-gas (and probably turn off the charger if that is causing it). For that, a small temperature sensor, melted into the lead battery terminals will give you a good reading (one for each battery). This of course gets a bit more complicated. -T

If you have a little bit of a draft in the box (of course then reducing the likelyhood of an explosive gas build-up) - a box temp sensor might miss one hot battery, but having a sensor in direct contact with the plates (via the lead terminals attached to said plates), will give you a damn good reading

. With the right circuitry attached, you could even single out the battery without opening the box up.

But then again, he said "simple"...

Quote from: buswarrior on February 06, 2009, 03:03:38 PM
...some consideration as to whether the unwanted gases will be pushed out cracks, or otherwise accidentally directed to unintended areas by pressurizing the cavity...

...Maybe best to run the fan as an exhaust, not as a supply...

I second this - and even with bottom outlets/vents, a duct that goes to the high-point in the battery box and has a fan on the other end that sucks out the fumes is a good way to go. Assuming that the fan is ignition-source free (since you will then be handling a dangerous gas mix...). Cheap brushless computer fans are good enough for this (no brush = no spark, and did I mention "Cheap"?).

-Tim

WEC4104 · February 06, 2009, 03:14:00 PM

Quote from: DrDave-Reloaded on February 06, 2009, 02:55:29 PM
Lot of over thinking here...

Temp sensor in battery box to start fan and shut off when done.

Charging makes heat. Shorts make heat.. DUH...

I understand what you are saying, but my understanding is that his battery box is the entire compartment that houses eight batteries (big volume). If the bus is parked in the July sun, the box ambient temp could easily hit 95-100F, with nothing running and no need for the blower.

In February, with an outside temp of 20F, he could be charging or having a failure with outgassing like crazy, and the box temp may not hit 70F. (At least not until the explosion)

So at what temp do you set the thermal sensor to activate?

gus · February 07, 2009, 02:54:04 PM

It is a simple high school physics that a fluid (air) will rise when heated (or pressurized) and will escape through the path of least resistance. So, it will not seek cracks if there is a large vent at the top. This is not to say that it won't find its way into cracks once it is outside the compartment.

This is all about relative temps and gas weights, not ambient or generated temps.

Blowing into a compartment with explosive gases is always safer than sucking it out. Sucking it through an electric motor (even if exp proof) because there can always be a spark from any electric or metal hitting metal source.

The over thinking here is trying to make it power instead of natural circulation. No matter what the temp there will always be natural circulation when there is air being heated, Hydrogen being generated or the bus moving.

Large battery volume means using large intake and exhaust vents.