Blown up battery

[kenneal - lagger]

Anyone any idea why this leisure battery connected to a little used 12V lighting circuit and charged by a 110W solar panel through a charge controller should blow up as it appears to have done. Don't know when it did but luckily there was no one around when it went.

Sorry but I've tried to get the image to show direct but can't seem to get it to do so with any of the codes supplied by this website. Anyone got one that will publish pictures on here?
https://imgshare.io/image/201102-blown-battery.NqiUvQ

[adam2]

The most likely reason is gross overcharging this results in the production of a great deal of oxygen and hydrogen and reduces the electrolyte level.
The gas pressure might be enough to burst the battery case (not very likely as low pressure relief valves are usually fitted)
Or a stray spark might have ignited the gas(not very likely unless there was a source of sparks nearby)
Or the electrolyte level might have dropped so low that a spark occured internally(most likely)

There are two likely charges of gross overcharging.

Firstly the charge controller might be defective and have charged continually. Not that likely, but if you re-use the charge controller, keep a close eye on it.

Secondly, and more likely is that the battery developed an internal short circuit in one cell, so that you had in effect a 5 cell battery of 10 volts nominal. A charge controller for a 12 volt battery would grossly overcharge what is now a 10 volt battery.

This is a drawback of modern multi voltage LED lamps ! They work just fine on what is now a 10 volt battery. As a result the defect may go unnoticed for a long time.
A 12 volt incandescent bulb will be very dim at10 volts which should prompt investigation.
A 12 volt flourescent light will be dimmer and reluctant to start at 10 volts, again drawing attention to the problem.

A much less likely cause of the accident is an external short circuit or gross over current. This can either boil the electroylyte or melt an internal connection and result in explosion. VERY UNLIKELY in this case as the wires look small and show no sign of heat damage.

A BATTERY SUSPECTED TO BE DEFECTIVE SHOULD NOT BE CLOSELY APPROACHED. DISSCONECT THE CHARGING SOURCE AND THE LOAD REMOTELY, CUTTING THE WIRES AT ARMS LENGTH IF NEED BE.
LEAVE ALONE FOR AT LEAST 24 HOURS.
THEN GENTLY TAKE IT OUTSIDE AND IGNORE IT FOR A MONTH.
WEAR SAFETY GLASSES AND NEVER LEAN OVER THE BATTERY.

[clv101]

Secondly, and more likely is that the battery developed an internal short circuit in one cell, so that you had in effect a 5 cell battery of 10 volts nominal. A charge controller for a 12 volt battery would grossly overcharge what is now a 10 volt battery.

That would be my bet. On our array I measure a mid-point voltage and if the the two halves of the array differ by more than a tiny percentage it alarms. It should identify the presence of a single failing cell at the earliest opportunity. This approach isn't available with a single 6 cell unit like this though.

[adam2]

for a 12 volt system used domestically, fit a small incandescent bulb to a light that is used regularly, but only briefly. A toilet light perhaps.

The extra amp hours used wont be bad due to the short hours of use, but the loss of 2 volts will make the lamp significantly dimmer.

[kenneal - lagger]

Thanks guys. I'll have to check the charge controller before I fit another battery.

[adam2]

Another simple way of drawing attention to a failed cell in a 12 volt battery occurs to me.
For a regularly used light connected to the system, obtain a multi voltage LED lamp that gives a constant light on any reasonable supply voltage down to typically 10 volts.

Connect in series with the lamp three small silicon power diodes that will in total drop about 2 volts.

Under normal conditions with the battery working correctly this lamp will light as normal.
Battery on charge at about 14.1 volts=lamp receives about 12 volts and lights normally.
Battery on discharge at about 12.5 volts=lamp receives about 10.4 volts and lights normally.

Now consider a defective battery that is in effect a 10 volt battery.
Battery on charge at about 13 volts=lamp receives about 11 volts and lights normally.
Battery on discharge at about 10 volts=lamp receives about 8 volts and either fails to light or is very much dimmer.

A little experiment may be needed, if the lamp is noticeably dimmer under normal discharge conditions, then try 2 series diodes rather than three.
There is of course an ongoing waste of energy whenever the lamp is lit, but it is relatively small, especially with say a toilet light.

[adam2]

To add to the points already made, some types of sealed deep cycle battery have a "magic eye" charge indicator.
This is an internal hydrometer whereby small dayglow balls float in the acid and are viewed through a small window.
Usually green for charged and red for discharged.

If any such indicator turns black or any very dark colour this MAY indicates that the electroylyte level has dropped, perhaps to a dangerous degree. Read the instructions (some older batteries used green for full charge, black for half charge and red for discharged)
If black indicates faulty then be very cautious.

ANY SUCH BATTERY SHOULD NOT BE CHARGED, DISCHARGED OR TESTED. OR CLOSELY APPROACHED. DISSCONNECT IT AT ARMS LENGTH
AND LEAVE UNDISTRUBED FOR AT LEAST 24 HOURS.
THEN GENTLY TAKE IT OUTDOORS AND LEAVE ALONE FOR A MONTH BEFORE DISPOSAL
WEAR SAFETY GLASSES. NEVER LEAN OVER A SUSPECT BATTERY.

[BritDownUnder]

When we were commissioning a 'station' battery for power stations they consisted of separate cells and voltages could be monitored individually very easily and it was easy to identify failing cells. I have never seen a battery fail like this so obviously.

A good thing to have is a FLIR infra red camera. They do cost a bit but I got mine for the equivalent of 400 pounds a few years ago. I think checking the battery with the FLIR both during charging and discharging from time to time would be very useful. We could see failing cells glowing red on the camera quite easily.

With words such as 'lagger' in your name and your previous comments on insulation I think you can also find a use for such a camera with your 'day job' and make money from it. Mine is also tax deductible. I can see absences of insulation quite easily in walls.

[RevdTess]

With words such as 'lagger' in your name and your previous comments on insulation

Oh! All these years I thought he was declaring himself to be slow on the uptake!

[kenneal - lagger]

..................With words such as 'lagger' in your name .........

A now banned climate change denier used to refer to me as "lagger" for my promotion of insulation and as he thought it a derogatory term. I took the name as I was quite happy to own it, seeing nothing derogatory in it at all.

I am trying to get our local environmental group to purchase an infra red camera to use to help promote insulation and draught proofing locally. I'm not bothered about taking on another string to my bow at 71. Having to pay for a purchase like that is too much hassle while doing the odd survey free of charge, which lots of environmental groups do, is not too troublesome. We can get one for about £800 to £900 which will do the job nicely thank you.

[Potemkin Villager]

Ken, I presume your first step was to check the insulation of the battery
to see if that was the problem.

[kenneal - lagger]

Thermal or electrical, PV?

[BritDownUnder]

..................With words such as 'lagger' in your name .........

A now banned climate change denier used to refer to me as "lagger" for my promotion of insulation and as he thought it a derogatory term. I took the name as I was quite happy to own it, seeing nothing derogatory in it at all.

I am trying to get our local environmental group to purchase an infra red camera to use to help promote insulation and draught proofing locally. I'm not bothered about taking on another string to my bow at 71. Having to pay for a purchase like that is too much hassle while doing the odd survey free of charge, which lots of environmental groups do, is not too troublesome. We can get one for about £800 to £900 which will do the job nicely thank you.

I am not 71 but still old enough to remember being exhorted to 'lag' your hot water tanks in adverts in the UK. There are so many uses for a FLIR and I think your group should invest in the money. In Australia they can easily rent out for $100 per day.

I would like a better photo of the battery as well.

I am interested to know which denier it was. The obvious RGR or Mean Mr Mustard or An Inspector Calls? I often wonder what happened to them, and indeed all of the former posters to this forum.

[kenneal - lagger]

AIC. Don't encourage them back, pleeease!!