I have a 7 amphour battery which runs 7amps each hour for 20 hours, but what if?

Question

I was to run my electric outboard at 45 amps every hour. How long will it last and why?

THE RATING ON THE SIDE OF THE BATTERY SAYS 7AH/20HOUR,IM SURE ITS A 7AH NOT 140AH AS SOME MAY SUGGEST BY MULTIPLYING 7X20.

Answer 1

I think the labeling means that If you choose a load that will exhaust the battery in 20 hours (approx. 1/3 amp) then it will provide 7 amp hours.

If it is actually a 7 amp hour battery then drawing 45 amps, it would go from full charge to dead in approximately 9 minutes.

If this batterry is large like an automotive battery then it would be 140 amp hours. In that case it could produce 45 amps for approximately 3 hours.

Answer 2

If you look at the battery 7amp for 20 hrs
7x20=140 amps total battery life
45 amps per hr divided into 140
equals 3.11 hours
So would trust it to about 3 hrs

Thats what I came up with let me know if I am right.

That is assuming that the pull is constant 45amps and not taking into account the added resistance of the wire or the heat level of the battery

Answer 3

A 7Ah battery will run 7A for 1 hour, so if you're running a battery for 7A at 20h, then you have a 140Ah battery, not 7. If you really do have a 7Ah battery it would run 45A for about .15h, or 10 minutes. This of course assumes that the battery is even capable of delivering that level of current and that the battery life rating doesn't change as a result of higher (significantly higher) discharge rate.