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Post by Deleted on Aug 15, 2017 20:47:30 GMT
Did a couple of locks with a very pleasant chap today.
He was moving a boat for the owner, and said that last night he'd heard a terrific bang on board, and on investigation, he disovered one of the batteries had exploded. He showed me, and exploded is not an exaggeration. What a mess to the casing.
Now, he said the boat was 24v so the batteries were in pairs. He just disconnected the pair with the damaged battery and worked off the single pair as a temporary measure.
There are no solar panels on the boat, so how can a battery over charge to the extent that one explodes, and how common is it? Is it just a 24v issue?
We're sat in WW2 combat helmets awaiting your knowledgeable replies, thanks.
Rog
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Post by Deleted on Aug 15, 2017 20:49:44 GMT
Did a couple of locks with a very pleasant chap today. He was moving a boat for the owner, and said that last night he'd heard a terrific bang on board, and on investigation, he disovered one of the batteries had exploded. He showed me, and exploded is not an exaggeration. What a mess to the casing. Now, he said the boat was 24v so the batteries were in pairs. He just disconnected the pair with the damaged battery and worked off the single pair as a temporary measure. There are no solar panels on the boat, so how can a battery over charge to the extent that one explodes, and how common is it? Is it just a 24v issue? We're sat in WW2 combat helmets awaiting your knowledgeable replies, thanks. Rog A battery with an internal short will readily explode. It's not 'common' but it does happen. |
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Post by naughtyfox on Aug 15, 2017 20:49:51 GMT
I bet it was Made in China.
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Post by Telemachus on Aug 15, 2017 22:36:22 GMT
Batteries generally explode due to overcharging, which causes the water to dissociate into hydrogen and oxygen, and hydrogen has a habit of going "pop!" Big-time! Why the overcharging? Well a 12v battery has 6 cells with a nominal voltage of 12v and which start to "gas" (dissociate) at perhaps 14.8v (temperature dependant). But if a cell shorts, well now you only have 5 cells, gassing voltage 12.3v or so. Feed that from an alternator at 14.4v and you get ... lots of explosive gas!
Cells short due to plate shedding - lead debris falling off the plates and collecting at the bottom of the cell over time until there is sufficient depth to touch both +ve and -ve plates.
nothing to do with 12v or 24v configuration.
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Post by Deleted on Aug 15, 2017 23:17:52 GMT
I bet it was a sealed one.
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Post by tomsk on Aug 15, 2017 23:45:55 GMT
Batteries generally explode due to overcharging, which causes the water to dissociate into hydrogen and oxygen, and hydrogen has a habit of going "pop!" Big-time! Why the overcharging? Well a 12v battery has 6 cells with a nominal voltage of 12v and which start to "gas" (dissociate) at perhaps 14.8v (temperature dependant). But if a cell shorts, well now you only have 5 cells, gassing voltage 12.3v or so. Feed that from an alternator at 14.4v and you get ... lots of explosive gas! Cells short due to plate shedding - lead debris falling off the plates and collecting at the bottom of the cell over time until there is sufficient depth to touch both +ve and -ve plates. nothing to do with 12v or 24v configuration. Rather disappointingly I can only generally agree with this.  |
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Post by Deleted on Aug 16, 2017 8:15:01 GMT
Thanks for the replies.
On a theme of over charging, I wonder if you have a solar set up AND you're cruising on a very sunny day, do you have to turn solar panels off (disconnect) to prevent over charging the batteries, or does the solar shut down automatically. A general question, I realise solar arrangements can be varied.
Rog
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Post by peterboat on Aug 16, 2017 8:16:59 GMT
My red light from the alternator comes on to say its not charging and the solar finishes it of
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Post by quaysider on Aug 16, 2017 8:50:15 GMT
My red light from the alternator comes on to say its not charging and the solar finishes it of I think it's the other way around on here... when the engine is running (and the batteries can't take both charge loads) the solar charger flashes to indicate the batteries are over voltage and "dumps" the current. Once the engine is shut down, the solar controller kicks back in and continues in float. btw - I did a proper equalisation charge on the remaining 3 batteries at the wekeend (at 15.75v) and it does seem to have brought them back to life... |
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Post by peterboat on Aug 16, 2017 9:04:00 GMT
Mime did an equalisation when I went up the flight last week, it always seems to me that the batteries dont recover until the next day from it. Anyway sun nearly shining washing just finished so its time to get on with work. and stop playing on here
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Post by Telemachus on Aug 16, 2017 9:31:52 GMT
Thanks for the replies. On a theme of over charging, I wonder if you have a solar set up AND you're cruising on a very sunny day, do you have to turn solar panels off (disconnect) to prevent over charging the batteries, or does the solar shut down automatically. A general question, I realise solar arrangements can be varied. Rog No, the whole point of the solar controller is to avoid overcharging the batteries. When they are fully charged the controller will go into float mode and restrict the voltage reaching the batteries to 13.5v or whatever. The problem you mention would only arise if you connect the solar panel directly to the batteries. Hopefully no-one does that, except in the case of a tiny panel just used to keep the batteries topped up when the boat is not in use. |
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Post by Deleted on Aug 16, 2017 9:39:21 GMT
If I remember correctly there is also a need to have something that doesn't discharge the batteries on a cloudy day - is my memory correct?
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Post by Telemachus on Aug 16, 2017 10:21:42 GMT
If I remember correctly there is also a need to have something that doesn't discharge the batteries on a cloudy day - is my memory correct? Do you mean if there is no controller? In which case yes, a diode to prevent reverse current. But most panels have diodes integral. And the problem would only occur at night, not on a dull day. |
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Post by JohnV on Aug 16, 2017 10:22:33 GMT
Batteries generally explode due to overcharging, which causes the water to dissociate into hydrogen and oxygen, and hydrogen has a habit of going "pop!" Big-time! Why the overcharging? Well a 12v battery has 6 cells with a nominal voltage of 12v and which start to "gas" (dissociate) at perhaps 14.8v (temperature dependant). But if a cell shorts, well now you only have 5 cells, gassing voltage 12.3v or so. Feed that from an alternator at 14.4v and you get ... lots of explosive gas! Cells short due to plate shedding - lead debris falling off the plates and collecting at the bottom of the cell over time until there is sufficient depth to touch both +ve and -ve plates. nothing to do with 12v or 24v configuration. Rather disappointingly I can only generally agree with this. so must I |
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Post by Deleted on Aug 16, 2017 10:28:39 GMT
If I remember correctly there is also a need to have something that doesn't discharge the batteries on a cloudy day - is my memory correct? Do you mean if there is no controller? In which case yes, a diode to prevent reverse current. But most panels have diodes integral. And the problem would only occur at night, not on a dull day. I suspect it was a diode, can remember killing a battery in the past using a small solar charger - it was on a sunny (but seemingly the angle of the sun played a part - latitude) hence the use of a 'dull day' |
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