Reserve Capacity (RC) is a very important rating. This is the number of minutes a fully charged battery at 80 ° F will discharge 25 amps until the battery drops below 10.5 volts.
An amp hour (AH) is a rating usually found on deep cycle batteries. The standard rating is an Amp rating taken for 20 Hours. What this means, say for a 100 AH rated battery is this: Draw from the battery for 20 hours and it will provide a total of 100 amp-hours. That translates to about 5 amps an hour. 5 x 20 = 100. However, it's very important to know that the total time of discharge and load applied is not a linear relationship. As your load increases, your realized capacity decreases. This means if you discharged that same 100 AH battery by a 100 amp load, it will not give you one hour of runtime. On the contrary, the perceived capacity of the battery will be that of 64 Amp Hours.

Understanding that, the RC rating applies to automotive apps, & AH rating apply to apps such as mooring lights on boats (on and low amp draw, when motors are off and alternators are not operating).

Couldn't care less what a 1 amp constant draw does to an automotive battery, I shut everything off, and trickle charge whenever it will be parked over 72 hrs.

I posted the 185RC info in post 12, what applies to automotive applications.

If this was a marine of aircraft forum, the AH would matter.

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'03 X5 4.4 Sport, last of the M62s (8-03 build date)
I believe in deadication to craftmanship in a world of mediocrity!