dwh
Tail-End Charlie
Obviously it doesnt have to fill the entire space, it has to fill 4-74%. Do the calcs, see how long it takes to do that for a standard battery.
You're not listening. It only has to fill a small space at the top of the larger space. The flaw in your "scientific" math is you've screwed up the basic assumption of the volume. You keep assuming the entire volume of the living space. That is irrelevant. The gas will rise to the top, and fill the top of the space. That top layer of stratification is all that has to be at a density sufficient to burn.
So stop telling me to do the math, when you've screwed it up from the get go.
And in case you didn't notice, I linked to a thread from here on ExPo from 4 years ago; a thread where I posted a link to the formula to calculate hydrogen generation from battery charging. But apparently you didn't notice that I obviously knew the math that you keep referring to - at least 4 years ago.
But to refresh (from that page I linked to 4 years ago):
Step 1: Calculating Hydrogen Concentration
A typical lead acid motive power battery will develop approximately .01474 cubic feet of hydrogen per cell at standard temperature and pressure.
H = (C x O x G x A) ÷ R
----------------------
100
(H) = Volume of hydrogen produced during recharge.
(C) = Number of cells in battery.
(O) = Percentage of overcharge assumed during a recharge, use 20%.
(G) = Volume of hydrogen produced by one ampere hour of charge. Use .01474 to get cubic feet.
(A) = 6-hour rated capacity of the battery in ampere hours.
(R) = Assume gas is released during the last (4) hours of an 8-hour charge.
Example: Number cells per battery = 24
Ampere size of battery = 450 A.H.
(H) = (24 x 20 x .01474 x 450) ÷ 4
---------------------------------
100
H = 7.9596 cubic feet per battery per hour
So if he's got 2 x 6v batteries, that's going to produce roughly half of that in the example above.
So 4 cubic feet PER HOUR.
Volume of the truck bed with topper (estimated): 8' x 6' x 5' = 240 cu'.
240 cu' * .4 = 96 cu' to reach 4% saturation
96 cu' / 4 cu' per hour = 24 hours to reach a 4% saturation of the entire space.
Which WON'T HAPPEN because the hydrogen will rise and collect at the top of the space.
Let's just assume for the sake of argument that only the top 10% fills with hydrogen. That's going to take 2.4 hours to reach a saturation density of 4% - which assuming your declaration that hydrogen won't burn at a lower density (which I'm not prepared to accept as a given) is enough to ignite.
As far as the video goes, looks like sensationlism to me, not science.
That's because you either don't actually understand how it works, or you just weren't paying attention. The battery - the top of battery - the small space at the top of the battery - was filled with a mix of hydrogen and oxygen. A bit of that was venting. That was enough to be ignited by a spark, and then the burn traveled down into the battery - which you can plainly see in the slow motion replay. The explosion takes place inside of the battery.
And while you might not believe it, exploding lead-acid batteries is not at all an uncommon occurance.
Do you know what the health of that battery is? How old it is, meaning how close it was to shorting, or what the charger was set to, or how charged it already was before they put it on a charger, what the temperature was, etc, etc., and not many cabs have welder or metal grinder sparks being thrown.
All of that doesn't matter.
Age - irrelevant.
Close to shorting - irrelevant.
What the charger was set to - irrelevant.
State of charge before they put it on the charger - irrelevant.
Temperature - irrelevant.
None of it matters - all that matters is that is was venting hydrogen. All open cell flooded lead-acid batteries vent hydrogen when they are being charged.
Thus to make the experiment valid - ALL you have to do is get the bloody thing to vent hydrogen. By whatever means is irrelevant.
And as for sparks, I make sparks whenever I light the stove in my camper. Or light a candle. I could even make some by plugging in something to be charged. You think some guy camping in the back of a truck is never going to make some sparks? 50 years of camping experience - including in the backs of trucks - tells me otherwise.
PLUS - the fact that hydrogen can also be ignited by catalysis and doesn't require a flame or spark, or even heat, to ignite.
Do something stupid like overcharging an already full battery in high temperature, or an old battery (>5-7 years depending on type) and guess what? Something stupid happens, so don't be stupid, thats all.
You don't have to abuse or destroy a battery to make hydrogen - all you have to do is charge it normally.
Hydrogen doesnt "gather" at a high point unless directed via a tube that way. Hydrogen disperses in all directions when not contained or directed to a specific spot.
Wrong. It rises. Propane does the opposite - it sinks.
Another quote from that page I linked 4 years ago:
'Since hydrogen gas rises are there areas in the ceiling where gas may collect in greater concentrations.'
So have ventilation via several different solutions, understand that almost all cabs are not air tight anyway, don't be on charge when sleeping in the battery area, be smart.
They don't have to be air tight - all they need is a high spot for the gas to collect.