Reserve Capacity Question (Battery)

MEXICOWANDERER wrote:
Reserve capacity is figuring out how long a battery can last powering a car with fuel pump and ignition load (no lights A/C or other loads) until the engine utterly stops dead in the road.

Sucking down a battery to ten volts is hard on it especially if it's a thin plate engine starting battery. There are legitimate reasons to want a high R/C like extending runtime in very rural areas. But if that is your concern use multiple batteries.

This value can assist a buyer who wants to judge if CCA is impinging on ampere hour rating. But by itself it is almost worthless if extremely cold cranking amperage is vital or low amperage discharge capacity is concerned.

For cycling, ampere hours / weight is a lot more valid. As is the name of the manufacturer. Cold cranking amperage is the vital value when a battery attempts to crank over something tough like a diesel.

An intriguing reference is to compare a battery's 20 hour rate to it's 100 hour rate. Smaller batteries end up in fractions of an ampere. You'll never see a smaller battery's 100 hour rate. It's like sneaking up behind it and yanking down it's drawers. Or, maybe inquiring about plate thickness.

Interesting initial analogy. I once drove a class B Chevy van 30 miles on the interstate to a repair facility in Billings MT on just a GR34 Duracell Deep Cycle AGM. The alternator gave out 30 miles shy of Billings, but the battery got us there, and there was enough left in the morning to start it to get it into the service bay area. I was impressed.