Battery charging.

[statik]

I had a bit of spare time today so as usual I ended up in the workshop playing with one of my bikes.  I decided to test the original battery from my old Moto Guzzi to see if it's any good, more out of curiosity than any other reason because I bought two new 6 volt jell batteries and a rubber cover that looks like an old type battery.  It seemed OK so I put it on a trickle charge at 6 volts and it was pulling less than 2 amps.  I put the end of the breather pipe out the window and took out the plugs.  A bit over an hour later the charger amps went down to less than 1 amp.  I continued drilling out broken bolts from the exhaust brackets and tapping out holes.  I was at the other end of the workshop so nowhere near the battery or charger and had the window and door open between me and the battery.  Suddenly there was a massive bang and bits of plastic went everywhere and what was left of the battery flew straight out of the window. 

Heard stories about this happening but never seen it before, shocked the hell out of me.  It was a very loud bang and a powerful explosion.  It pulled the crocodile clips off the end of the charger cables and broke the charger case.  Fortunately it was a small battery so the damage was limited.  I am a gas engineer and understand the dangers of hydrogen gas so took precautions. 

The rest of the day was taken up by cleaning acid off everything in the workshop.  Tools, bike, spare parts were all covered and had to be washed.  Not how I planned to spend the day. 

[rogerwilko]

Were your two six volt batteries connected in series or parallel? If parallel it would be still six volts which would explain your explosion.

[R]

Good job you were there to clean everything off.
And not in the firing line.

Internal fault, and spark.
Or external fault, and spark.
Who knows,
Heard of this happening under someone (car) bonnet, however...

P.S.Battery acid is very good at cleaning off chrome. Very quickly....

[R]

Were your two six volt batteries connected in series or parallel? If parallel it would be still six volts which would explain your explosion.

Says it was the old battery.

And why would 2 x 6v batteries in parallel be a problem with a 6v charger anyway ?

[statik]

I was only charging one battery at the time, the battery that came with the Moto Guzzi Alce.  It was almost flat so I thought I would check it to see if was worth keeping.  After about an hour at 6 volts that happened. I can tell you it was a big bang.  I had all the windows open and a 4'6" door open as well.  There was no warning and it was luck that I was about as far as I could be from it but still got some acid on me.  I found the piece of battery in the garden 2 meters away.  Today I'm making a metal box with a vent to outside and all the charging will be done in that. 

What worries me is I have a small solar panel on the roof and three car batteries charging all the time.  I run some LED spot lights off them in the house.  I think I'll move them into a box in the garden too.  When I'm not using my bikes I put the bike batteries onto the solar system top keep them fresh. 

[statik]

Thought you might like to see a couple of photos.  This it the part that flew out the window. 







I think this is a random occurrence and the only precaution when charging batteries is to keep them outside away from everything.  I don't think this can be prevented, eventually some these old acid type batteries will explode because you have Hydrogen, air and electricity in the same place.  My gut feeling is something failed inside the cells and caused a spark but I can't be sure. 

[wetdog]

i had this with a Uasha 12v bike battery , it also was old , i did notice quite a amount of rubbish in the base of the battery after the bang , is this the case in yours ? is it a case of the plates making contact ? never found out what caused it but taught me a lesson with reguards to hydrogen ,,, "the gass from ASS is hydrogen" ( ASS is something to do with a charging battery but i dont know what it stands for ) i also charge batterys out side now

[statik]

To be honest I didn't look in the bottom, could be debris in there.  Didn't think to take some photos until today, I was too busy washing out the workshop and walking round say "plonker" to myself for letting it happen. 

I do have a nice clean workshop now. 

[R]

I do have a nice clean workshop now.

Freshly acid washed. !

This could catch on.
Or not....

[Revband]

If you look at the specification for the battery you will find it has a MAXIMUM charge rate of one amp not the "less than two amps" it had, this could well be the reason.

[wetdog]

was pulling 2 amp ..... i have not seen a charger rated at 1 amp max , i thought they drop back to the charge amp/hr ....  if they pull over amp/hr does this indicate a fault as i may have to watch this myself thanks

[statik]

I didn't think 2 amps was excessive and it soon dropped as it charged, the battery is a 6 amp 13 AH (I should say was).  I always check the condition before charging and there is a fuse fitted in the positive cable.  There was nothing out of the ordinary until it blew up. 

[Revband]

The details below are copied and pasted from a suppliers web site, note that the 1A is a maximum charge rate, a normal 12v battery should be charged at the "TEN HOUR RATE",  Ie  one 10th of the rated capacity 40 amp hour battery = 4 amp charge rate, for a 6v battery it is advisable to half this. A battery which is charged at a higher rate will give off excessive gas and get very hot, resulting in a possible explosion as here.




B38 - 6A Battery
Specification
Manufacturer: YUASA
Battery type: Dry Charged battery
Electrolyte required: 38% Sulphuric Acid, specific gravity 1.28kg/litre
Electrolyte volume: 0.62 Litres
Dimensions: 119mm x 83mm x 161mm
Capacity rating: 13Ah
Maximum charging rate: 1 Amp

[wetdog]

heres the spec on my small charger trickle so battery is in good order come summer
•Input Voltage:
110 VAC (Model 2.90-6V-110)
220 VAC (Model 2.90-6V-220)
•Battery Voltage: 6 volts
•Maximum Charge Rate: 1.5 Amps per hour
•Number of batteries charged at once: 1
•Supported Battery Technology: Gelled electrolyte, Gell-Cells, or manual filled lead-acid batteries.
have you a charger rated for one amp max ? where did you get it from

[Revband]

Hi Wetdog

Yes I do have a 6v charger rated at 500ma in fact, this one came from Lidl. If you have a look on ebay you can take your pick from dozens of different ones starting from around £5.00, or Paul Goff will be happy to supply you with one, as will many other people.