See where this is going? That’s where there is an issue. Where this becomes a proper issue is, say, in two-, five- or eight-years’ time, your AGM is dead and you’re done with the box and want to change it up, and you put it on Marketplace or Gumtree, and some young bloke comes along with no idea, works out the battery has died and needs to put a new one in, goes and gets himself a lead-acid battery and puts it in the sealed box without a second thought because he can’t afford a you-beaut AGM jobby. See, the AGM batteries absorb most of the hydrogen and oxygen again and turn it back into water, so they’re reasonably well-sealed, yet they still have vents that will vent some gas. But I only run AGM batteries, so they’re fine… right? We worked out that one 12v battery with six cells in a ‘room’ 1.5ft x 1.5ft x 3ft (the size of the average sealed space case) needs to have the air completely replaced every 7.63 minutes for it to not become explosive. Yep, 4.1 per cent hydrogen mixed with air will go boom.įrom another perspective, we looked up the OHS/legal safety requirement for a battery storage/charging room. Where this gets really interesting is that to become explosive, hydrogen needs to be in a concentration with air of between just 4.1% and 75%. Each cell of a lead-acid battery will produce 0.42-litres of hydrogen gas for each and every Ah beyond the battery’s capacity.Ģ0Ah x 0.42-litres of hydrogen (per Ah per Cell) x 6 cells = 50.4 litres of H2 or hydrogen gas. So 100Ah needs 120Ah put into it to be ‘fully charged’. It’s generally granted that to fully charge a lead-acid battery, you need to put in about 20 per cent over the recommended Amp Hour (Ah) rating. There will need to be a bit of maths, but stick with me. You’d probably be surprised hell, I was when I did the research for you good folks. It doesn’t take a genius to realise that one tiny spark… and the whole thing will go BOOM!ĭoes anyone still remember the Hindenburg? Hydrogen gas at work… Photo: Universal History Archive Surely it can’t make that much hydrogen gas? All of a sudden you’re putting a bunch of 12-volt gear (charger, solar controller, Anderson plugs, ciggy sockets, etc.) in a sealed container that will fill up with hydrogen gas. Where this becomes a problem is when you go and buy a ‘sealed’ box or space-case. That’s why on the side of a lead-acid battery it says to store, use and charge in a ‘well-ventilated area’. So as soon as your charger goes over 14.1-volts (2.35-volts times six cells), it’s generating a hell of a lot of hydrogen gas. In our specific case, your 12-volt lead-acid battery has six cells. This occurs when your battery voltage goes above about 2.35-volts per cell. It’s actually hydrogen and oxygen (two parts hydrogen, one part oxygen – from water H20). Most folks probably realise that when you’re charging a lead-acid battery, it gives off hydrogen gas. Until of course, you open the lid! How exactly am I turning the battery box project into a bomb?! For the more scientifically minded, it’s essentially Schrodinger’s Box both a battery box and a bomb, at the same time. There’s only one problem: by using sealed boxes, you’re basically turning your neat DIY project into a bomb. I absolutely understand the concept behind them they’re portable, easy to plug-in, can be moved to the different accessories using them, and are a nice and easy DIY jobbie you can do at home. In a rather concerning trend I’ve noticed as of late, there are a lot of people building ‘battery boxes’. We really need to stop turning battery boxes into hydrogen bombs!
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