Compression Ignition Addict
Join Date: Jul 2010
Location: Falls Chruch
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Now i disagree. The issue has to do with over charging and under charging the battery bank. This battery bank is now composed of 3 different types of batteries when the ignition is turned on, and only one current sensing alternator. The alternator has no idea that one of the three batteries is fully charged, it sees the whole circuit as one. This is the same reasoning behind running two of the same batteries under our hoods. We use the same batteries, and replace both at the same time. Now in the case of my set up, the smaller battery will fully charge prior to the huge batteries up front, yet the alternator will still supply amperage as the TOTAL battery bank voltage is yet at max. The large batteries run the risk of not fully charging, leaving you stranded in the cold... but of most interest is what happens when you OVER charge a lead acid battery.
Here is a snippet from Wikipedia:
Any lead-acid battery system when overcharged will produce hydrogen gas. If the rate of overcharge is small, the vents of each cell allow the dissipation of the gas. However, on severe overcharge or if ventilation is inadequate or the battery is faulty, a flammable concentration of hydrogen may remain in the cell or in the battery enclosure. Any spark can cause a hydrogen and oxygen explosion, which will damage the battery and its surroundings and which will disperse acid into the surroundings. Anyone close to the battery may be injured.
Sometimes the ends of a battery will be severely swollen, and when accompanied by the case being too hot to touch, this usually indicates a malfunction in the charging system of the car. Reversing the positive and negative leads will damage the battery and may lead to gassing and explosion. When severely overcharged, a lead-acid battery gases at a high level and the venting system built into the battery cannot handle the high level of gas, so the pressure builds inside the battery, resulting in the swollen ends. An unregulated alternator can put out a high level of charge, and can quickly ruin a battery. A swollen, hot battery is very dangerous, and should not be handled until it has been given sufficient time to cool and any hydrogen gas present to dissipate.
A person handling a car battery should always wear proper protective equipment (goggles, overalls, gloves) and make certain there are no sparks or smoking close by.
I'm more comfortable with 13volts charging my trailer battery and break away than I am with the above.