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Magna1
Feb16-04, 12:31 PM
A battery has a rating of 250AH What is the total amount of charge this battery can supply to a cct? And What is the max current this battery can provicde for 5 min?
I don't know what formula's to use?
I have C=QV I=q/t
but I don't which ones to use or even worse where to apply for these
Doc Al
Feb16-04, 12:44 PM
I assume that "AH" is Amp-Hour, which means that the battery can provide: 250 Amp-Hours of charging. By definition, 1 Ampere is 1 Coulomb of charge per second. So how much charge does a 1 Amp current provide in 1 Hour? In 250 hours?

That 250 AH can be delivered over 250 hours (at a current of 1 Amp) or it can be delivered in 1 hours (at 250 Amps). (The greater the current, the quicker you use up the battery.) So what's the maximum current it can deliver for 5 minutes?
Magna1
Feb16-04, 01:20 PM
250 AH/60min = A/min x 5min= Amp@5min=20.83333 But 1c x 300secs= ???? This again is a sticky point. What is the charge in Coulombs? Do I multiply 20.833 by something?
Am I at least on the right train of thought?[*(]
Doc Al
Feb16-04, 03:43 PM
Originally posted by Magna1
250 AH/60min = A/min x 5min= Amp@5min=20.83333 But 1c x 300secs= ???? This again is a sticky point. What is the charge in Coulombs? Do I multiply 20.833 by something?
Am I at least on the right train of thought?[*(]
Separate the two problems. First find the total charge delivered by the battery:
Q = 250AH = 250 Amp-Hours = 250 (Coulombs/sec)Hours(3600 sec/hour) = ??

You take it from here.

For the second problem, realize that 5 minutes is 1/12 of an hour.
Magna1
Feb17-04, 05:20 PM
In that case 250AH x 3600=900 000 Then 900 000/300= 3000 A is the answer to the max current?

I think that this is what you were talking about ..... yes????
Doc Al
Feb17-04, 06:00 PM
Originally posted by Magna1
In that case 250AH x 3600=900 000 Then 900 000/300= 3000 A is the answer to the max current?

Excellent. You found the total charge that the battery could supply (Q = 900 000 C), then used I = Q/t to find the max current. Perfect.
NateTG
Feb17-04, 06:01 PM
Originally posted by Doc Al
Excellent. You found the total charge that the battery could supply (Q = 900 000 C), then used I = Q/t to find the max current. Perfect.

Now it's time to bring in the Ragone (spelling may be incorrect) plot. [;)]
Doc Al
Feb17-04, 06:05 PM
Originally posted by NateTG
Now it's time to bring in the Ragone (spelling may be incorrect) plot. [;)]
I think it best if we just skip over that one, NateTG. [o)]