Battery cap not venting property?

[SCCLT]

Less than a mile into a ride today I heard and felt a loud pop under the seat. I stopped and carefully lifted the seat to see that one battery cap assy had blown off. One cap covers all four cells on each off my Trojan T-875 Batts. One cell gasket was laying next to the cap. The cells still had water. I do check/fill them twice each month. Do not see bulging or split battery case. I did notice later that the water in that one cell looked dark and cloudy. I noticed under all the caps a black deposit much like what was in the one cell. I lift the seat when charging to help vent the batteries. The battery shows 8.59 volts which is ball park for the others. The specific gravity in the one cell is 1.280 where the other cells are 1.290 without recharging since my approximately 2 mile round trip. I'm thinking the vent cap has been plugged up on that one cell causing the darkish cloudy appearance and the cap to blow off. But why riding and not while charging? Batts are coded A7 for Jan 2017. I bought them new late in Dec 2016. Thoughts would be greatly appreciated. Thanks


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[alchemy]

you sound like you know things but I will confirm that you could have a dangerous situation. I personally don't know a lot about battery explosions and never had it happen in 45 years. You probably realize it could be an actual small explosion too. I know you said the plates were covered but it could probably still happen rarely. Hydrogen ignites extremely easy, even from a hot surface or reaction. That seems quite a lot of pressure to blow a whole 4 caps off perhaps from just one cell.

[alchemy]

never thought much on "cloudiness" of electrolyte in batteries as you mention but I've seen it. Cloudiness in a liquid means more than saturation point. Sulfuric acid is miscible in water so it can't be too saturated to not give a clear solution. Lead sulfate is nearly absolute opposite but a certain ppm will dissolve depending on temperature etc. The only other component unless it got contaminated would be lead dioxide and I don't know how that effects the mixture or even is a factor. I'd have to say the cloudiness would normally be lead sulfate. Cloudiness in a solution, or over saturation, will occur when the solvent is no longer enough or the temperature drops. In this case water is the solvent. Cloudiness also often means the solid is going to begin crystallizing on things or fall to the bottom if it hadn't already. The charge/discharge of the electrolyte mixture/solution is another factor but that's getting beyond me.
Actually you made me realize this myself by thinking about it.

[SCCLT]

Long story short, I replaced the battery with a new one. Thank you for all the comments. I did notice that the cloudiness subsided after the battery had sat for a day. I also recall a previous occasion shortly after charging when I was checking water levels and that cell sort of burped a gas bubble up and the acid looked cloudy. I figured some sediment had gotten stured up with the gas bubble. Otherwise that battery and cell seemed just like all the others relative to voltages-SOC and water usage. Thanks.


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[alchemy]

Originally Posted by SCCLT

Long story short, I replaced the battery with a new one. Thank you for all the comments. I did notice that the cloudiness subsided after the battery had sat for a day. I also recall a previous occasion shortly after charging when I was checking water levels and that cell sort of burped a gas bubble up and the acid looked cloudy. I figured some sediment had gotten stured up with the gas bubble. Otherwise that battery and cell seemed just like all the others relative to voltages-SOC and water usage. Thanks.

That was probably the safest solution. Sounds like it might have had a "hot spot" in that cell for some reason.