I had read this:Originally Posted by Joe_Black
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Optima D31M Blue Top, D31A Yellow Top and D31T Yellow Top Batteries: The D31 series is Optima's most powerful single-unit deep cycle battery. Like all Optima batteries, the D31 series deep cycle batteries offer exceptionally high CCA for their size and boast 75 amp hours of current storage for long deep-cycling run times. The D31 deep cycle batteries will not off-gas in normal operation, but for complete safety in enclosed spaces their overpressure vent will accept a remote venting tube. If you have room for a D31 series battery, they represents the best performance/cost value on the market. They're stellar performers in virtually any deep cycle battery application, and their Spiralcell AGM construction make them tough as nails. The D31A has automotive-style (SAE) posts, the D31T has top mounted stainless steel threaded studs for flat-loop connectors, and the versatile D31M has both SAE posts and threaded studs. The difference in color between yellow and blue top batteries does not denote a performance difference. See specs & delivered price in table below.
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So they just have cool additional spots to hook up accessories... lol
I need to find this "leak".. i had just heard other vx owners having the issue of a dead battery if they leave the car sitting