Battery Vent Fan - Only "On" When Charging: how?

[trekerboy]

Almost finished with the electrical portion of our '79 Airstream Excella 500 renovation and I'm at the point where I'm considering a few different options for venting the battery box.

I have 4 Duracell EGC2 6V wired in Series-Parallel that I need to vent. The position of the battery box is just behind the driver-side axel (don't worry, I'm keeping track of balance and tongue weight) and there's no built in vent nearby (closest is fridge vent 6 feet away). Due to the construction of the cabinets around the battery box I don't have the ability to have a continuous up-sloped vent hose leading to the outside (up-slope needed to vent lighter-than-air fumes resulting from charging flooded batteries). Instead of using a passive venting system I've decided to go the "active" route by placing a small fan inline with the vent hose to force the air outward.

The accomplish this "active" venting setup I need someway to tell the fan to turn on when the batteries are charging. Because I'm using an all-in-one inverter/charger I can't just connect the fan to the power charge line (since it's powered all the time whether the charger is one or not). Also, the combo unit I have doesn't have any sort of connection that's only powered when the charger is running. The only way to know that the combo unit is charging is an LED that lights up on the unit itself.

As far as I can see, I have 4 options to turn on the fan when the batteries are being charged.

1. Connect the fan to the Shore Power breaker, so whenever I'm connected to shore power (and therefore, charging since the combo unit charges the batteries whenever shore power is connected) the fan would turn on. I'm adding solar in the future, so I'm not sure how I'd ensure the fan is one when solar is charging the batteries.
2. Use a manual switch to turn on/off the fan that I'd have to flip every time the batteries are charging. This options sucks.
   
3. Use a "Photoelectric Switch Sensor Relay" which would detect when the "charging" LED is lit on the combo unit and subsequently turn on/off the fan.
   
4. Use a "Voltage Sensitive/Sensing Relay" (VSR) that turns on at 13.4v (this voltages indicates charging is active) and turns off at 12.9v (this voltage indicates batteries are full and no charging is happening).
   

So here's my question... If you do "Active" venting in your AS (passive isn't an option for me), which method do you use? One of these, or something else?

By the way, I'm using very low power, very silent fan (less than 20db, which is less than a whisper).

[TG Twinkie]

Fans create static electricity. Are you sure about using this method? Batteries emit gasses when discharging as well.


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[Glenritas]

One thing , Be sure the fan is mounted before (inlet side) the battery compartment blowing in.

If you mount it on the exit side it will be in the Hydrogen gas and could ignite it. To be located there it has to be rated explosion proof.

[trekerboy]

Originally Posted by Glenritas

If you mount it on the exit side it will be in the Hydrogen gas and could ignite it. To be located there it has to be rated explosion proof.

Thank you Glenritas! I didn't think about that but you're absolutely right. I think I'll have to switch the type of fan I had planned on using to ensure none of the fan electronics could ignite the H2 gases. Thinking of using this one now from Atwood:



It's normal application is for for venting gases out of a boat engine bay. I'm assuming it's "rated explosion proof" if it's intended to be used for that purpose.

See any problem with this type of fan?

[Glenritas]

Never "assume" BUT do check the spec's. IF it checks out, go for it. Looks like a clean install.

[trekerboy]

Originally Posted by Glenritas

Never "assume" BUT do check the spec's. IF it checks out, go for it. Looks like a clean install.

Here are the specs:

http://www.attwoodmarine.com/store/p.../turbo-4000-ii

What should I look for to confirm it's "explosion rated"?

[Glenritas]

I looked at your link and couldn't find an answer other then it was CE certified.

But what does that mean ?

Best to call Attwood (8-5 eastern) or contact them Contact Attwood: Marine LED lighting, Boat accessories, Marine hardware : Attwood Marine Products® and ask if its suitable for your situation.

[Phoenix]

This is a bilge/engine compartment fan, which must be explosion-proof with heavy gasoline and battery fumes present. However, there is one big drawback -- these fans are extremely noisy!

In boats, they are only run for several minutes, before starting the engine, while refueling, and while the boat is idling or running at slow speeds (and the passive vents are ineffective). Since the engine makes considerable noise when it's running and the run time is brief, most people don't notice how loud the engine compartment fan is.

However, if you intend to vent your battery compartment using this fan, you will be very disappointed; because this fan will sound several times louder than an automobile heater, blower motor and fan running on high, with the defroster vents open. In fact, I can think of no fan noise as loud as this, that most people are commonly exposed to, that could referenced for comparison.

You should definitely go to hear one of these in operation before purchasing it. I'm sure a marine parts store (e.g., Westmarine) will demo it for you by connecting the loose wires to a battery.

Note: "CE Certified" is the International Marine Certification Institute's certification, which is a UL (Underwriters Laboratories)-type testing agency for marine products.

[trekerboy]

Originally Posted by Phoenix

This is a bilge/engine compartment fan, which must be explosion-proof with heavy gasoline and battery fumes present. However, there is one big drawback -- these fans are extremely noisy!

You're spot on with this one; I don't want something that sounds like a jet engine warming up every time I'm charging the batteries! It was specifically for this reason that I opted for the "Attwood Turbo 4000" unit; the reviews say it's extremely quiet and Attwood's marketing material for the product depict this feature as what makes it stand out among competitors. We'l see how loud it really is when I hook it up!

[Sealrocker]

Originally Posted by Phoenix

Note: "CE Certified" is the International Marine Certification Institute's certification, which is a UL (Underwriters Laboratories)-type testing agency for marine products.

From Wikipedia:
The CE mark, or formerly EC mark, is a mandatory conformity marking for certain products sold within the European Economic Area since 1985. The CE marking is also found on products sold outside the EEA that are manufactured in, or designed to be sold in, the EEA. This makes the CE marking recognizable worldwide even to people who are not familiar with the European Economic Area. It is in that sense similar to the FCC Declaration of Conformity used on certain electronic devices sold in the United States

[trekerboy]

I actually found another solution that's made specifically for my situation. It's called "FumeOut" and it's essentially a programmable VSR, brushless12v DC fan and casing all in one package. Price is a little steep, but my comparable DIY active ventilation solution was already about $100.00.



http://www.bestconverter.com/FumeOut_c_213.html

[idroba]

Don't assume that batteries only produce gas when charging. Heavy discharge also produces gassing as I recall. It is one reason batteries have exploded when wrenched, that is a wrench is dropped on them causing a massive short. The gases are produced as the discharge occurs and the wrench provides the spark.

BTW, most all little computer fans are brushless and produce no sparks when in operation. One of them would be what I would use for your application. However, I think you would be better off thinking of a gravity venting solution.

[TG Twinkie]

I said it in an earlier post. But I will say it again. Batteries emit gases virtually all of the time. Some times more than others.
Even though the motor is brushless and doesn't spark at the commutator. Just the fan blade spinning in the air will create static electricity.
The winds blowing in the higher altitude are what cause charges to build up in the atmosphere. That is what causes lightning.


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[trekerboy]

Originally Posted by TG Twinkie

I said it in an earlier post. But I will say it again. Batteries emit gases virtually all of the time. Some times more than others.

Thanks TG Twinkie. I think the only way to use an active ventilation system that's intelligent to know when to turn the fan on and off would be connect the fan to a hydrogen gas detector. Many of these detectors have relays built into them for use in activating an external alarm, but they could just as likely be used to turn on a fan. Here are a couple examples I've come across:


SBS-H2: http://www.sbsbattery.com/products-s...nt/sbs-h2.html


H2Scan has a number of products that detect hydrogen: http://www.h2scan.com/products/hy-alerta/600


This one is from a company called "Arrgh!": http://www.arrgh.com/hydrogen_gas_detectors.php


A company called BHS makes one too: http://na.bhs1.com/products/accessor...gas-detectors/

The problem with all of these is that they are expensive and the sensors themselves don't last more than a couple years. I suppose you could remember to change the sensor when you're doing your regular maintenance on the batteries, but that seems like overkill.

[TG Twinkie]

My question would be. Will you use the detector to prevent the fan from running when it detects hydrogen gas? Would that not defeat the purpose of the fan. After all. Preventing the build up of gases is the purpose of ventilation.


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[trekerboy]

Originally Posted by TG Twinkie

My question would be. Will you use the detector to prevent the fan from running when it detects hydrogen gas? Would that not defeat the purpose of the fan. After all. Preventing the build up of gases is the purpose of ventilation.

I won't be using a hydrogen gas detector, but if I was I would wire it such that it turned on a fan to vent the compartment when hydrogen sulfide was detected (instead of just using a VSR to detect when the batteries are charging since gassing can occur during discharge as well).