How much do people have their flooded battery compartments vented? My boat was originally designed with the battery compartment vented with some holes into the engine compartment. I have added three bigger batteries into a space next to the existing battery compartment and there are holes in the board between theses compartments thus ultimately venting the new compartment into the engine space via the previous compartmet. I'm trying to figure out how much effort I need to put into venting this compartment. The boat is 15 years old and never blew up with the existing arrangement. With the extra batteries though I'm wondering if I need more "aggressive" venting? I was thinkig of installing a blower or a small computer fan to actively vent the batteries into the engine compartment. Then I was wondering if that would not be enough and if maybe I should connect a specific vent hose to the compartment with or without a fan to vent directly outside? Am I overthinking all this? And while I'm on the subject...it seems like motoring would be the main time that hydrogen could be produced. Attached to shore power the charger will drop off as the batteries reach capacit, but motoring the alternator keeps charging at the max amps. This seems like maybe the most important time to have the compartment vented. Does this make sense? Like I said, maybe I'm overthinking this, but I don't want to blow myself up!!
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Battery Vents
I've got a battery isolator on my two batteries aboard my MacGregor 26S. The isolator prevents the alternator from overcharging the "house" battery and from either battery draining out of the other... Just wanted to mention that as seems relevant for some reason to me at the moment!! Take care, Greg
I've got a battery isolator on my two batteries aboard my MacGregor 26S. The isolator prevents the alternator from overcharging the "house" battery and from either battery draining out of the other... Just wanted to mention that as seems relevant for some reason to me at the moment!! Take care, Greg
Battery Vent'ing
There’s a fairly complete discussion titled “Battery Ventilation when ‘Fast’ Charging” at: cruisersforum.com/forums/showthread.php?t=3344 http://www.cruisersforum.com/forums/showthread.php?t=3344
There’s a fairly complete discussion titled “Battery Ventilation when ‘Fast’ Charging” at: cruisersforum.com/forums/showthread.php?t=3344 http://www.cruisersforum.com/forums/showthread.php?t=3344
You don't need much of a vent
you are trying to vent hydrogen gas. It is lighter than air and the (going techy) molecules move at such a high speed they can find ANY hole in very short order. Since you are venting into an engine space just make sure the engine space is ventlated so the stuff has a path off the boat. The only case I can think of where you would need active venting is if the top of a container was airtight and there was NO air movement inside it. Just the heat of a charging battery would be enough to move the air around. one 0.5" hole in the top and one in the bottom would work. If you put something that smells strongly into the compartment and can smell it after closing it up you have enough ventlation.
you are trying to vent hydrogen gas. It is lighter than air and the (going techy) molecules move at such a high speed they can find ANY hole in very short order. Since you are venting into an engine space just make sure the engine space is ventlated so the stuff has a path off the boat. The only case I can think of where you would need active venting is if the top of a container was airtight and there was NO air movement inside it. Just the heat of a charging battery would be enough to move the air around. one 0.5" hole in the top and one in the bottom would work. If you put something that smells strongly into the compartment and can smell it after closing it up you have enough ventlation.
perhaps, but
I cannot recommend that the Hydrogen Gas, produced by Battery Charging, be vented anywhere except outside. DO NOT vent to your living quarters, nor to any space with an ignition source. Under most common conditions, Hydrogen has a lighter density than air and tends to rise upward when in contact with air. Warmer air is less dense than cooler air, and so warm air tends to push upwards when in contact with cooler air. However, high and low vents are unreliable and therefore hazardous. One expects them to expel lighter hydrogen rich air through the high vent while fresh air flows in through the low vent. This will only take place when the hydrogen rich air is as warm or warmer than the outside air. When the hydrogen rich air is colder than the outside air, the flow is stifled and the hydrogen can easily reach explosive concentrations. High and low vents also admit hot air during hot weather and cold air during cold weather, eliminating the advantage of an insulated battery enclosure, exposing the batteries to damaging temperature extremes. The goal of any hydrogen ventilation system is to keep the concentration below the LEL of 4%. When no Hydrogen is present, no air should be moving through the ventilation system in order to conserve heating/cooling energy and to reduce temperature extremes. During normal battery charging, up to 20 cubic centimeters per hour per battery may be released. To achieve a 1% hydrogen concentration, this must be mixed with 99 times its volume of air, or 1,980 cc/hour/battery. To maintain a concentration below 4%, over 480 cc/hour/battery of air must be mixed with the hydrogen. During thermal runaway*, the need for ventilation depends on how many Watts the battery charger can pass into the batteries. Each Watt can produce up to 3.4 cc/min or 204 cc/hour, requiring about 20,200 cc/hour per watt of air to maintain a 1% mixture, or 5,000 cc/hour per watt of air to stay below a 4% concentration. * Batteries in enclosures can go into thermal runaway, which very rapidly produces hydrogen, whenever several conditions are simultaneously present. 1. The batteries are exposed to high temperatures inside the enclosure (above 100 deg. F) for a sustained period, either because the enclosure is unprotected, or because the cooling system is inadequate or has failed. 2. The batteries continue to be charged at high voltage and current because there is no temperature compensation in the battery charging circuit, or because said circuit has failed. 3. Batteries have aged and become dehydrated. Or, perhaps we ARE overthinking this ...
I cannot recommend that the Hydrogen Gas, produced by Battery Charging, be vented anywhere except outside. DO NOT vent to your living quarters, nor to any space with an ignition source. Under most common conditions, Hydrogen has a lighter density than air and tends to rise upward when in contact with air. Warmer air is less dense than cooler air, and so warm air tends to push upwards when in contact with cooler air. However, high and low vents are unreliable and therefore hazardous. One expects them to expel lighter hydrogen rich air through the high vent while fresh air flows in through the low vent. This will only take place when the hydrogen rich air is as warm or warmer than the outside air. When the hydrogen rich air is colder than the outside air, the flow is stifled and the hydrogen can easily reach explosive concentrations. High and low vents also admit hot air during hot weather and cold air during cold weather, eliminating the advantage of an insulated battery enclosure, exposing the batteries to damaging temperature extremes. The goal of any hydrogen ventilation system is to keep the concentration below the LEL of 4%. When no Hydrogen is present, no air should be moving through the ventilation system in order to conserve heating/cooling energy and to reduce temperature extremes. During normal battery charging, up to 20 cubic centimeters per hour per battery may be released. To achieve a 1% hydrogen concentration, this must be mixed with 99 times its volume of air, or 1,980 cc/hour/battery. To maintain a concentration below 4%, over 480 cc/hour/battery of air must be mixed with the hydrogen. During thermal runaway*, the need for ventilation depends on how many Watts the battery charger can pass into the batteries. Each Watt can produce up to 3.4 cc/min or 204 cc/hour, requiring about 20,200 cc/hour per watt of air to maintain a 1% mixture, or 5,000 cc/hour per watt of air to stay below a 4% concentration. * Batteries in enclosures can go into thermal runaway, which very rapidly produces hydrogen, whenever several conditions are simultaneously present. 1. The batteries are exposed to high temperatures inside the enclosure (above 100 deg. F) for a sustained period, either because the enclosure is unprotected, or because the cooling system is inadequate or has failed. 2. The batteries continue to be charged at high voltage and current because there is no temperature compensation in the battery charging circuit, or because said circuit has failed. 3. Batteries have aged and become dehydrated. Or, perhaps we ARE overthinking this ...
From a practical standpoint....
If you have any ventilation and air moving, you're not gonna go boom. Having said that, I am not in any way, shape or form disagreeing with Gord
My experience comes from installing over 100 sets of LARGE (up to 360 GALLONS of electrolyte per set) battery systems in telephone stations in Egypt. Almost all of the battery rooms had fans, most of them worked, and at some sites they actually kept the fan on. Smoking? Of course they smoked in the battery room ;D My favorite story: While working in the battery room (we were equalizing the batteries and they were gassing merrily) in the bowels of a huge bunker complex, I heard a rustling from the loft (yes, they had a loft in the battery room - it was about 15 feet above the floor, and 3 feet ABOVE the level of the (non-functional) exhaust fan). The straw started to move and I got ready to evacuate the room, thinking there was a LARGE rat up there. Imagine my surprise when an Egyptian soldier crawled over the side and down the ladder.... his nap was over! Moral of the story: keep some air moving and you'll be fine. Cheers, Bob s/v X SAIL R 8
If you have any ventilation and air moving, you're not gonna go boom. Having said that, I am not in any way, shape or form disagreeing with Gord
My experience comes from installing over 100 sets of LARGE (up to 360 GALLONS of electrolyte per set) battery systems in telephone stations in Egypt. Almost all of the battery rooms had fans, most of them worked, and at some sites they actually kept the fan on. Smoking? Of course they smoked in the battery room ;D My favorite story: While working in the battery room (we were equalizing the batteries and they were gassing merrily) in the bowels of a huge bunker complex, I heard a rustling from the loft (yes, they had a loft in the battery room - it was about 15 feet above the floor, and 3 feet ABOVE the level of the (non-functional) exhaust fan). The straw started to move and I got ready to evacuate the room, thinking there was a LARGE rat up there. Imagine my surprise when an Egyptian soldier crawled over the side and down the ladder.... his nap was over! Moral of the story: keep some air moving and you'll be fine. Cheers, Bob s/v X SAIL R 8Call me paranoid
This is why I put ignition protected fuses in the battery compartment, on the battery cables and the charging wires. Just in case. Cost a lot but it only takes once. Dan
This is why I put ignition protected fuses in the battery compartment, on the battery cables and the charging wires. Just in case. Cost a lot but it only takes once. Dan
Batteries do blow up but
not for the reason most people think. As an auto mechanic I had the opportunity to work around auto batteries every day for about 6 years. I only saw 1 blow up. The new guy was jump starting a dead battery and instead of connecting the jumper cables and then turning on the charger he turned on the charger and as he was making the ground connection on the battery instead of on the engine, it sparked. The H2 inside the battery cells lit up like a bomb and it threw hydrocloric acid all over him and the engine. He had perscription glasses so his eyes where saved but was not what I'd call a fun day for him. The moral of this story is IMHO it is far more likely that a spark will cause the H2 gas inside the battery to ignite when you are reconecting the battery than any H2 in the air around the battery during normal operations. So no sparks around the battery when you are doing maintance, turn your head when making the last connection to complete the circut, or better yet complete the circut by connecting the ground on the engine (common ground point, 3-way) away from the battery, And never ever work on a recently charged or discharged battery that has accumulated H2 in and around its' cells. And yea I think we are over thinking it.
not for the reason most people think. As an auto mechanic I had the opportunity to work around auto batteries every day for about 6 years. I only saw 1 blow up. The new guy was jump starting a dead battery and instead of connecting the jumper cables and then turning on the charger he turned on the charger and as he was making the ground connection on the battery instead of on the engine, it sparked. The H2 inside the battery cells lit up like a bomb and it threw hydrocloric acid all over him and the engine. He had perscription glasses so his eyes where saved but was not what I'd call a fun day for him. The moral of this story is IMHO it is far more likely that a spark will cause the H2 gas inside the battery to ignite when you are reconecting the battery than any H2 in the air around the battery during normal operations. So no sparks around the battery when you are doing maintance, turn your head when making the last connection to complete the circut, or better yet complete the circut by connecting the ground on the engine (common ground point, 3-way) away from the battery, And never ever work on a recently charged or discharged battery that has accumulated H2 in and around its' cells. And yea I think we are over thinking it.
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