January 18, 20179 yr Author 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.
January 18, 20179 yr 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.
January 18, 20179 yr Author 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?
January 18, 20179 yr 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. :-)
January 18, 20179 yr 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/
January 18, 20179 yr Doing some research again, for I also need to find a solution for my batt box. Found this: https://www.altestore.com/store/deep-cycle-batteries/ventilatorsbattery-fans/zephyr-industries-powervent-12v-battery-box-ventilation-p2287/
January 18, 20179 yr Author 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.
January 18, 20179 yr Author 9 minutes ago, The Terrible Triplett said: I want one of these ... http://zephyrvent.com/installation-diagrams/ DIY, without the smoke please.
January 18, 20179 yr Author 9 minutes ago, The Terrible Triplett said: I want one of these ... http://zephyrvent.com/installation-diagrams/ 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.
January 18, 20179 yr 31 minutes ago, superdiy said: DIY, without the smoke please. No. Will wait for you to make yours, for you wanted to make 2, one for me.
January 18, 20179 yr 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: I want one of these ... http://zephyrvent.com/installation-diagrams/ 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.
January 18, 20179 yr Here is an online Battery Room Calculator I just found on the internet. https://pocketengineer2.sharepoint.com/Pages/battMV.aspx
January 19, 20179 yr Author 11 hours ago, Don said: Here is an online Battery Room Calculator I just found on the internet. https://pocketengineer2.sharepoint.com/Pages/battMV.aspx Thanks Don
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