Let's see if I can explain this.
The AH rating of a battery is based on a 20 hour test. How many amps can it draw continuously so that at the end of 20 hours the battery is at 10.2 volts DC.
An example:
If a battery is rated at 200 AH that means it was capable of a 10Amp draw for 20 hours before reaching 10.2 VDC.
The issue here is that just because a 200AH battery can draw 10 Amps for 20 hours doesn't mean it can draw 200 Amps for one hour. So 6AH is not much here. 6/20= .3 Amps. That Batt will handle .3 amps for 20 hrs before it reaches 10.2 VDC. So how many amps will it handle for 4 hrs? Look at the chart for the battery. The other key here if you picked up on it is 10.2 VDC. This is way lower then then usable voltage of most electronics. This is what really skews the AH rating of batteries.
BTW I was the head of the electronics Dept. for the biggest yacht builder in the country. Big Sail boats. Lots of batteries

John
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