exploding battery

[terrencecolp]

The other night I was awoken at 3am by an extremely loud bang. I had no idea what it was. After looking out my windows and throughout trailer I went back to sleep completely oblivious to what had happened.
Well the next morning I found out. I noticed my battery box door was open. OK I thought, the wind was pretty strong last night. Funny that it was still locked but oh well. My battery had exploded, blowing its top off, the caps off, the cables off, and the door open. This is a regular car battery that would no longer hold a charge that I installed to check my Univolt's operation mainly. It would run a single light for about 3 hours before going completely dead. Mainly like I said I was testing my system before investing in a new battery. Now I don't know if I should install a new battery.

[overlander63]

Remove the old battery, and wipe a solution of water and baking soda everywhere in the battery compartment, including the door. Then install a new deep cycle battery.
A more modern converter may help keep this from happening in the future.

[Protagonist]

Originally Posted by terrencecolp

It would run a single light for about 3 hours before going completely dead. Mainly like I said I was testing my system before investing in a new battery. Now I don't know if I should install a new battery.

Actually, there should be no problem at all with a new battery. In my opinion, the problem was that you were trying to charge a bettery that wouldn't hold a charge, and instead it cooked the battery because there was nothing to tell the converter to stop charging. Doesn't mean it would cook a good battery.

[Colin H]

Originally Posted by Protagonist

Actually, there should be no problem at all with a new battery. In my opinion, the problem was that you were trying to charge a bettery that wouldn't hold a charge, and instead it cooked the battery because there was nothing to tell the converter to stop charging. Doesn't mean it would cook a good battery.

Univolts are notorious for cooking batteries, "good" included.
Colin

[Protagonist]

Originally Posted by Colin H

Univolts are notorious for cooking batteries, "good" included.

Won't dispute that. But trying to charge an unchargeable battery is not the proper way to test one.

[Colin H]

Originally Posted by Protagonist

Won't dispute that. But trying to charge an unchargeable battery is not the proper way to test one.

Correct, but a great sign to change both
Colin

[perryg114]

I have never had a problem with my old Univolt. It stays on 100% of the time and the battery is fine. I have a backup unit that I have not installed yet. I am going to run that Univolt till it dies. I need to add a volt meter to my control panel just to see what the voltage is. I think the problem is that old battery. The plates are crumbling and you may even have had a shorted cell. The resistance is high on a spent battery so all you were doing is turning water to H2 and O2 and that is the perfect mixture to go boom. Take the advice of others and soak everything with baking soda and water. Make sure you pay attention to areas under the frame where acid might hide. We have seen several trailers with the A frame rotting off from acid exposure from poor maintenance by owners and previous owners.

Perry

[RickDavis]

There have been several different "univolts" over the years.
The one run in the early 70's was notorious for losing regulation and frying things. Almost any power surge or nearby lightning strike would do them in.
They have a circuit board with a regulator circuit with several transistors.
I am not sure what the situation was in 1976 but suspect it was still that design.
If the voltage output is over 13.8 max. the thing is bad.
The MagnaHytek units used later were much better better but am not sure what year the change was made
Back in the 70's one of the Ham radio operators in the WBCCI radio club provided a diagram and repair info on these older units. I still have that info filed at home and have successfully repaired them but the repeat failure rate is still high.
I can't remember who the manufacturer of that unit was, but some versions had a drop down front panel with fuses inside, other versions fed an external panel

[idroba]

The real problem was the old, already dead and damaged battery. The charger saw it as a heavy load and just kept pumping current into the battery causing overheating and warping of the plates. Lots of gasses produced in the process. Finally an internal spark from the warped plates touching ignited the gas and the explosion happened.

Never try to charge a known bad and dead battery. Although they do not always explode, they overheat at least, and may leak acid all over.

[Jammer]

Originally Posted by terrencecolp

. My battery had exploded, blowing its top off, the caps off, the cables off, and the door open. This is a regular car battery that would no longer hold a charge that I installed to check my Univolt's operation mainly. It would run a single light for about 3 hours before going completely dead. Mainly like I said I was testing my system before investing in a new battery. Now I don't know if I should install a new battery.

You're lucky you still have a trailer.

Batteries converters and univolts are not magick. Their inner workings are not difficult to understand.

One of the most common ways for batteries to fail is with a shorted cell. Then you end up with a 5 cell battery that has a 10.6 volt float voltage and needs a 12.0 volt charge voltage, in series with a shorted cell that looks an awful lot like an 0.1 ohm resistor.

Charge the battery with any charger -- a Univolt from olden time or the latest fancy newfangled 7 stage charger, and two readily predictable things will happen:

1) The 5 "good" cells will be overcharged because the charger is applying a charge voltage suitable for 6 cells. These cells will then a) run hot and b) gas, that is, emit a mixture of hydrogen and oxygen gas through the vent.

2) The shorted cell, meanwhile, will overheat, because of the resistive heating effects. The electrolyte will eventually boil off (actually boil, not gas) from the heat.

Once that's happened, the temperature of the shorted cell will climb until the ignition temperature of the plastic case is reached. The case then ignites the mixture of hydrogen and oxygen gas. Kaboom.

When a battery has a shorted cell it is also possible for it to catch fire while discharging for the same reason. An explosion is less likely since hydrogen gas is not ordinarily present in any quantity in this scenario.

It is vitally important to check the electrolyte level in flooded cell batteries before charging them and periodically during use. An unusually low electrolyte level in one cell is a sign of trouble and indicates that the battery should be tested. A battery that can't deliver 12 volts under a C/4 to C/2 load (amp hour capacity divided by 4 hours) should be scrapped. A battery that boils electrolyte in one cell during the load test has a shorted cell and should be scrapped.

As for the old Univolt, they're not great but it's unlikely that it contributed to the problem. Even if it has poor output control, a battery in good condition with proper electrolyte levels will not gas enough with overnight charging to reach the point where it could explode.

If you're using an automotive type battery then pry the lids off to see what the electrolyte level actually is. There is less difference between automotive and deep cycle batteries than is generally believed but you still have to watch electrolyte levels.

Frozen batteries -- ones that have been discharged to the point where the freezing point of the electrolyte rises above the ambient temperature -- also explode fairly frequently through a similar mechanism.