It's unlikely that a 1 amp charger could supply enough energy to cause a battery to rupture even if it were in serious failure mode, so the likely cause is the fact that you had 2 batteries in parallel, and a cell in one developed a short circuit. This would cause the good battery (13.2+v) to discharge into the now faulty 5 cell battery. That impresses  2.65+v per cell on each of those cells and also forces a very high current flow through the faulty cell which then suffers overheating, a boiling of the electrolyre, a mass eviction of H & O, all of which greatly increase the pressure and temperature in the cell, with a resultant violent rupture of the case.

brian wrote:

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oldtrack123 wrote:

  I tend to think the same way

THAT is one of the draw backs of paralleling batterries.

 

PeterQ

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 Unfortunately it is mostly impossible to obtain a large enough Ah capacity without resorting to paralled batteries whilst still being able to lift them.

Yet another reason why I prefer vented batteries.

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 HI Brian

Again I agree

At least vented batterries do not build up pressure

But then the gas mixture can become a problem if there is spark or heat source

BUT like it or not parallel batterries are a fact of live  in most cases as you say simply near impossible to gt the Ahr capacity in a handable single battery

Now watch the LiPoFe boys come out of the woodwork

Vanderee wrote:

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Thanks for the tech explanation Brian, 

Are the DC HD wet batteries a better proposition perhaps? 

I don't have enough space for parallel  6 volt batteries, but I can modify the battery

holders for 2 x 6 volt wet cells. Is a parallel 4 x 6 volts possible ? I suppose we should all wear eye protectors when

working on batteries? The calcium ones are getting very scary.

I appreciate your advice. Thanks. 

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 Wet cell (flooded) batteries are not necessarily a better proposition. It is unusual for a sealed battery to suffer a shorted cell, but when they do, you've seen the result. Calcium was added to the sealed batteries to keep the gassing to a minimum so that recombination was better achieved, so they are safer in that regard than the Lead Antimony type.

All Lead Acid batteries, apart from extremely small ones, consist of series and parallel configurations. A single cell of your 100Ah battery will have a number of +ve and -ve lead plates connected in parallel assemblies, these are then connected in series with the other 5 cells to form the battery.

So it is impossible to fully escape a parallel setup, but if only one +- pair of plates in a cell goes faulty, there is only the voltage of that cell across it, and only a fraction of the total current passing through it, so little problem will occur.

Assuming your original setup was around 220Ah, your options for a similar capacity are:-

1. A single 220Ah 12v AGM, but they are expensive ($600+), and heavy to handle as a single piece (65+kg).

2. A series pair of 6v 225Ah AGMs, also expensive ($650+/pr), but lighter to handle at 30kg each.

3. A series pair of 6v 225Ah floodeds, cheaper at around $400+/pr) and about 30kg each. More attention to venting of the battery compartment is required with flooded batteries

4. A  LifePo4 battery setup. These are becoming the new favourite, they do offer superior performance for about 60% of the weight, and although you can get away with less capacity due to their performance, they will still cost you more than the LA types.

For most RVers who don't wish to be troubled with battery maintenance or to try the LifePo4s, the AGMs are the best alternative.

If you are happy to add water occasionally, then floodeds are a cheaper alternative. They are also more forgiving of mistreatment as it is virtually impossible to rupture them. Occasional overcharging normally just requires the replacement of the water, although constant overcharging will erode the plates. They don't recharge as rapidly as AGMs but also don't suffer fatally from overcharge  

A parallel 4 x 6v as you have suggested would still be just 6v, you need 2 x 6v batteries in series to get 12v but at the same Ah of one battery. You can then parallel them with another 12v set to increase the Ah capacity.

For example:- 2 x 100 Ah 6v batteries in series gives you 100Ah at 12v, parallel these with an identical pair and you now have 200Ah at 12v.

I have 6 x 6v 225Ah flooded batteries in a series parallel configuration for 675Ah at 12v. I water them on average once every 3 months.

Hope this helps.