Battery Containment - Necessary?

[Crofter]

Plausible scenario: Batteries under heavy charge 90% full and gassing. Engine shutdown due to false trip on engine safety controls. Batteries still gassing. Engine restart and a BACKFIRE into explosive mixture (I've seen my diesel fire and run backwards!). 911 call for unrecognizable body covered with acid and burned in a house fire. I'm a software engineer and design has to take into account what can go wrong, because eventually it does. A failing battery can also out gas prodigiously. 

Tom those scenario and the fact that valves can leak back from clearance or seating issues or sticking open. Restricted exhaust will also cause flashback into the intake.  Sure the odds do not lead to it being a common occurrance but when you are dealing with highly explosive gas mixtures you should have double redundancy at least for any easily forseeable events. I think it is irresponsible to promote and attemtp to justify such hare brained ideas. All the more irresponsible if you have qualifications that suggest you should know better. Even using the most strenuous application of all safety codes bad things happen. Once you start down the road of shortcutting safety factor and removing layers of reduncancy trouble is a certainty.  Enough of beating a dead horse though!

[Lloyd]

Starting, Marine, and Deep-Cycle Batteries


    * Starting (sometimes called SLI, for starting, lighting, ignition) batteries are commonly used to start and run engines. Engine starters need a very large starting current for a very short time. Starting batteries have a large number of thin plates for maximum surface area. The plates are composed of a Lead "sponge", similar in appearance to a very fine foam sponge. This gives a very large surface area, but if deep cycled, this sponge will quickly be consumed and fall to the bottom of the cells. Automotive batteries will generally fail after 30-150 deep cycles if deep cycled, while they may last for thousands of cycles in normal starting use (2-5% discharge).
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    * Deep cycle batteries are designed to be discharged down as much as 80% time after time, and have much thicker plates. The major difference between a true deep cycle battery and others is that the plates are SOLID Lead plates - not sponge. This gives less surface area, thus less "instant" power like starting batteries need. Although these an be cycled down to 20% charge, the best lifespan vs cost method is to keep the average cycle at about 50% discharge.
    *
    * Unfortunately, it is often impossible to tell what you are really buying in some of the discount stores or places that specialize in automotive batteries. The golf car battery is quite popular for small systems and RV's. The problem is that "golf car" refers to a size of battery (commonly called GC-2, or T-105), not the type or construction - so the quality and construction of a golf car battery can vary considerably - ranging from the cheap off brand with thin plates up the true deep cycle brands, such as Crown, Deka, Trojan, etc. In general, you get what you pay for.
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    * Marine batteries are usually a "hybrid", and fall between the starting and deep-cycle batteries, though a few (Rolls-Surrette and Concorde, for example) are true deep cycle. In the hybrid, the plates may be composed of Lead sponge, but it is coarser and heavier than that used in starting batteries. It is often hard to tell what you are getting in a "marine" battery, but most are a hybrid. Starting batteries are usually rated at "CCA", or cold cranking amps, or "MCA", Marine cranking amps - the same as "CA". Any battery with the capacity shown in CA or MCA may or may not be a true deep-cycle battery. It is sometimes hard to tell, as the term deep cycle is often overused. CA and MCA ratings are at 32 degrees F, while CCA is at zero degree F. Unfortunately, the only positive way to tell with some batteries is to buy one and cut it open - not much of an option.

any battery that lists CCA is not a deep cycle battery

beware, of those hybrid types known as marine batteries, they are a cross between starting and deep cycle,  sort of a jack
of both trades but master of neither.

expect a marine battery to maybe make 100-300 cycles, a starting battery to make maybe 30-50 cycles, and a true deep cycle 1000 to as many as
3300 or more depending on depth of discharge.

with batteries you generally get what you pay for.

are those sam's club golf cart batteries listed with CCA too?

having said all that, i strongly suspect that a good automotive battery might well make many hundreds of cycles "if" the depth of discharge is very shallow. something like the top 5-10% and then a complete recharge, much like a car battery normally see's in daily use, might well work out to be effective, however not many applications can adapt to the parameter or provide rapid recharge as needed with that kind of frequency.


bob g