Jump to content

Battery cooler box


superdiy

Recommended Posts

4 minutes ago, Don said:

I just think that the airflow produced by the mattress pump is insufficient to properly ventilate the box, maybe I am wrong. 

I don't know how knowledgeable you are with the chemistry, but maybe you can assist. If you look at it volume wise, the total volume of air in the box is not that much; 1100mm x 500mm x 100mm above the batteries and maybe about 10 litres all around, say 20 litres worst case, which equates to a total of about 75 litres. 4% of that is 3 litres - so it would be dangerous if 3 or more litres of hydrogen is present inside the box. The timer is currently set to turn the pump on for 1 minute daily. I'll try to measure how much air is pumped in that 1 minute, but I guess it might be in the region of 20+ litres.

What I won't know is:

  • how much hydrogen is generated during a charge cycle
  • how much hydrogen will be removed during a pump-action of say 1 minute

I'll measure the amount of air "moved" in 1 minute in the mean time.

Link to comment
Share on other sites

Isn't this sort of thing generally measured in air changes per hour? A random googled doc found on the APC website says you need two air-changes per hour. I believe that should be enough to work out how often it should run and for how long. Seems to me at the very least you have to flush it out twice an hour.

Link to comment
Share on other sites

33 minutes ago, plonkster said:

Isn't this sort of thing generally measured in air changes per hour? A random googled doc found on the APC website says you need two air-changes per hour. I believe that should be enough to work out how often it should run and for how long. Seems to me at the very least you have to flush it out twice an hour.

OK, so what does 1 flush mean? Does it mean that if I have 100 litres of air in a container I have to pump 100 litres of air into the container? Obviously the whole 100 litres will not be replaced, because the old and the new will mix inside, but some of it will be replaced. Is that technically a flush?

Link to comment
Share on other sites

I believe as long as you have twice the volume of air flowing through it every hour you're within the letter of the requirement. I suspect the mixing doesn't matter so much since it's really the concentration you're worried about.

See, all those American home-improvement shows is good for SOMETHING. I learned this stuff from the airflow requirements in the typical American garage (where airflow is often restricted because of wooden construction, vapour barriers, cold and hot side, pipes freezing, etc), but you also have to get rid of the carbon monoxide created by the cars in there.

:-)

Link to comment
Share on other sites

To maintain a safe concentration of hydrogen, the fan must supply 25 times the volume of hydrogen generated under the worst possible conditions. A bank of batteries using a 1 KW charger that fails to shut off can generate 3.4 liters per minute of hydrogen, requiring 85 liters per minute of fresh air to prevent an explosion. This amount of continuous ventilation virtually eliminates the effectiveness of any insulation that may exist in the walls and roof of the enclosure.

http://www.zomeworks.com/battery-electronic-enclosures/hydrogen-venting-system/hydrogen-vent-example-1/

http://www.zomeworks.com/battery-electronic-enclosures/hydrogen-venting-system/hydrogen-vent-example-2/

http://www.zomeworks.com/battery-electronic-enclosures/hydrogen-venting-system/hydrogen-vent-example-3/ 

http://www.zomeworks.com/battery-electronic-enclosures/hydrogen-venting-system/example-4/

http://www.zomeworks.com/battery-electronic-enclosures/hydrogen-venting-system/example-5/

Link to comment
Share on other sites

14 minutes ago, The Terrible Triplett said:

To maintain a safe concentration of hydrogen, the fan must supply 25 times the volume of hydrogen generated under the worst possible conditions. A bank of batteries using a 1 KW charger that fails to shut off can generate 3.4 liters per minute of hydrogen, requiring 85 liters per minute of fresh air to prevent an explosion. This amount of continuous ventilation virtually eliminates the effectiveness of any insulation that may exist in the walls and roof of the enclosure.

http://www.zomeworks.com/battery-electronic-enclosures/hydrogen-venting-system/hydrogen-vent-example-1/
http://www.zomeworks.com/battery-electronic-enclosures/hydrogen-venting-system/hydrogen-vent-example-2/
http://www.zomeworks.com/battery-electronic-enclosures/hydrogen-venting-system/hydrogen-vent-example-3/

http://www.zomeworks.com/battery-electronic-enclosures/hydrogen-venting-system/example-4/
http://www.zomeworks.com/battery-electronic-enclosures/hydrogen-venting-system/example-5/

Thanks for this, should not be very difficult to implement. 

Link to comment
Share on other sites

The general air changes required for any factory or workplace is 6 air changes per hour. For a battery room or "Box", the required air changes per hour is 12 air changes per hour. I used to be the Group Ventilation and Refrigeration Engineer for Anglo Platinum with 35 years service. I can design a ventilation and refrigeration system for a mine till end off life in 50 years time. The problem with these small boxes is you cannot accurately measure the flow rate of these pumps delivering small volumes and therefore go on what is written on the specification sheet. If you connect a little pump to a box that seals perfectly and you have a very small air outlet. You will probably pressurise the box and as a result of the pressure, drop the volume in half. 

7 hours ago, The Terrible Triplett said:

Without doing any calculations, my gut feel says, you need one of these. 

 

7 hours ago, superdiy said:

Those are stock standard computer fans. Cut off the corners / mounting tabs and glue it into a piece of PVC pipe...  You don't need a vent cap to block the reverse flow of cold air in Cape Town.

That is what I initially proposed. Install one of those computer fans (the one blowing air onto the evaporator) on the opposite side of the box, to drag the air across the batteries. Ideally the intake should be on the bottom of the box on the opposite side. The problem is not ventilating the box during normal charge and discharge cycles. Very little Hydrogen is given off. The problem comes in when something goes wrong in one of the battery cells and stuff starts to boil. Then the cooler box changes into into a bomb within minutes. I think 90% of us have the same problem. Box or no box.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...