Lead acid battery exploded

[Mtneer]

Went to check our backup generator before the incoming storm. No cranking love. Look things over and find that the starter battery has literally exploded. Blew the top cap off and cracked the case on one side. I can fill 5 out of the 6 cells. It did this once before a year ago, blowing the cap off but didn't crack the case. I refilled and recharged, everything seemed back to normal.

I checked it this spring when I did an oil change. Battery is dated 11/2013. This is the first battery I've had in decades that requires checking fluid levels. Seems odd for an emergency appliance. Part #51 72J, 625 cranking amps, if that means anything.

Would welcome advice on either a much better battery or what I need to do better. Don't think this storm will be an issue but I want to be ready for the next one.

[BushMasterBoy]

Water evaporated and the electrolyte became too acidic. That caused flowering of the plates and battery case cracked. Batteries are usually only good for 5 years. Batteries Plus or a similar store should be able to find you a replacement. A sealed gel cell should fit and be of more cold cranking amps (CCA) than a typical lead acid battery.

[colorider]

Agm battery would be my choice.

[Erni]

Where is the bat located? Does it see extreme heat and cold?

[OtterbatHellcat]

Hensley is a good place to get batteries.

[Mtneer]

Thanks guys, I'll probably get an AGM for replacement.

Erni, the generator is outside so battery sees same temps as a vehicle with far less vibration. Rarely gets below 0°F anymore and seldom above 93°F.

[SideShow Bob]

I had an old 1963 Chevy pick up converted to an alternator, I didn’t do the conversion correctly. It would over charge the battery causing the fluid to boil, in turn causing excessive out gassing (hydrogen & oxygen) and a sparking which caused the battery to actually explode violently.
This happened twice before I figured out the problem.

If you get an acidic sulfury smell when the generator isrunning, or see misty gases venting from the battery, shut down the generator and check the charging system.

[sportbikeco]

What maintains voltage on this battery?

I would recommend quality Deka brand no maintenance type, bet you it lasts a very long time (5+ yr easy) if you have it on a quality maintainer ("battery tender jr" would do it)

[sportbikeco]

I had an old 1963 Chevy pick up converted to an alternator, I didn’t do the conversion correctly. It would over charge the battery causing the fluid to boil, in turn causing excessive out gassing (hydrogen & oxygen) and a sparking which caused the battery to actually explode violently.
This happened twice before I figured out the problem.

If you get an acidic sulfury smell when the generator isrunning, or see misty gases venting from the battery, shut down the generator and check the charging system.

Very good point here as there is likely a separate charging system for maintenance and one that runs with the gens motor.

[TheSparkens]

This is why all building emergency generators have a quality battery maintainer and a battery heater. Cold will kill a battery.