amp hour help
TC
Posts: 1,019
I know this is not a parallax question, but I do not know where to go for help. I am thinking of getting two batteries for my car. But I am having trouble understanding “Amp Hour” The batteries I am looking at are rated at 72Ah, if I understand amp hour right the battery can provide 72 amps for one hour, then I times that by two that would be 144Ah. Also is there a way to estimate discharge. My system can pull up to 190A (one hundred ninety amps). How fast would the batteries discharge if they had a 190A load on them?
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Any help in the right direction would help
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Thanks TC
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Any help in the right direction would help
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Thanks TC
Comments
batteries are funny first the temp of the environment 75 degrees F ok
less then not so good
really check the batteries in real world conditions. it will surprise you!
most circuit need at least 11.5 volt to work properly
and of course remember to calculate the proper supply voltage when
spec-ing out amps to watt conversions
standard answer
"x" amp discharge at 80 degrees F in 1 hour
yea right !
japer
Two 72Ah batteries in parallel·= 144Ah.· So, 144Ah / 190A = 0.76 h
All Ideally-theoretically (Your Results Will Likely Vary)
And the above is best case MAX.....
I would say the .4-.5 hour would be a more accurate estimate..
bob N9LVU
You are correct in concept, but not in practicality.
Two new 72 AH rated car batteries will definitely give you about 144 AH....... perhaps only once while brand new, and under lab conditions, discharging at a 20 hour rate. So that's 7.2 Amps for 20 hours.
If you need to draw 190 Amps, I would expect the "apparent" capacity of the batteries to be in the order of perhaps 20 percent of their rating. So at that current level, I would suggest 10 or so minutes, perhaps less. Here in Canada we get to crank our cars' starter motors (hundreds of Amps) plenty when its minus 30 or minus 40 degrees C (equals minus 40 F), and under those conditions, which are probably a lot harsher than what you are expecting, we don't get a lot of minutes before the battery is "dead". Do realize that "dead" means different things. As a battery discharges under such large draws, the voltage on it's terminals drops drastically, perhaps to such a low level as to be not useful for you. You would get much more of your battery's capacity, perhaps double my previous estimate, if you could put them in series and operate whatever at 24 volts.
There are better, albeit much costlier battery technologies available than car batteries, and depending on your application those may be a better choice.
In summing up; car batteries are great for starting a car....... not much else.
Cheers,
Peter (pjv)
190A will heat up a wire pretty quick.
The AH rating gives an idea of what the battery can handle. If it's rated for 70 AH....don't try and draw 200A's for too long, the plates and such could get damaged and you'll never get the same capacity out of it.
Take care of your battery and it'll take care of you! haha
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Steve
"Inside each and every one of us is our one, true authentic swing. Something we was born with. Something that's ours and ours alone. Something that can't be learned... something that's got to be remembered."
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Thanks TC