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Hi, I am currently using 2x 6v 1.3 AH SLA batteries to power a 3w LED globe. will these batteries be ok to power this LED for around about 1 hour or will this be pushing it.

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Is this part of some homework?

The answer is right in the question. The batteries have 2 * 6V * 1.3Ah = 15.6Wh, for the LED you need 3W * 1h = 3Wh.

Hi, thanks for that. I'm trying to build an dive torch and just needed to find out how long those batteries will last. Turns out I'll have enough to last a good length of time underwater. I'm not fantastic in the theory side of electronics so all help is appreciated.
Many thanks.

Well, the calculation is the theoretical side of the problem. In real life, a lot of other factors come into account: How exact is the rating of the battery (how honest is the manufacturer, how old is the battery, how high and when was it loaded...) and the cut-off voltage of the LED resp. the LED's driver circuit, the efficiency of the driver circuit (and voltage converter if there is one). And so forth and son on. All that can be calculated but would need much more information than you gave. In you case, I'd just build the circuit and test it without any casing. That will tell you the best how long it runs and allows for easy modifications.

Hey and if you want to take that thing for something where you have to rely on it (like cave diving) - don't.