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What is meant by the words written on the car battery 40Ah
What is meant by the words written on the car battery 40Ah
That is the rating of the battery, based on the current and time it takes to go from a full charge to fully discharged.
For instance, 40Ah would mean (roughly) you could draw one amp for 40 hours.
Here is a decent article on the subject.
http://overlandresource.com/what-is-an-amp-hour-and-how-to-calculate-battery-capacity
Depends on the make and model of the car but very unlikely to be that.I wonder if that's actually the sustainable discharge rate? A 40 Ah battery is pretty puny for a car; I have fire alarm panels backed up by twin 12vdc 100Ah batteries, and they look like they'd be about the right size for a motorcycle. Unless the OP left off a zero and meant 400 Ah.
In the US at least, a battery which is sold for motor vehicle cranking use will rarely have an AH capacity specified, let alone marked on the battery itself.Depends on the make and model of the car but very unlikely to be that.
On a Renault 5 or a basic Ford Fiesta it's a 40Ah battery.
On a fully loaded model with all the boys toys (electric everything) like a Range Rover, it might be 100Ah
I wonder if that's actually the sustainable discharge rate? A 40 Ah battery is pretty puny for a car; I have fire alarm panels backed up by twin 12vdc 100Ah batteries, and they look like they'd be about the right size for a motorcycle. Unless the OP left off a zero and meant 400 Ah.
It may be case here too. It isn't marked on mine and the battery is made to a Johnson Controls Battery division (USA) specification.In the US at least, a battery which is sold for motor vehicle cranking use will rarely have an AH capacity specified, let alone marked on the battery itself.
In the US at least, a battery which is sold for motor vehicle cranking use will rarely have an AH capacity specified, let alone marked on the battery itself.
To me that indicates that either it is a deep-discharge battery designed for RE use or it was intended for somewhere other than the North American market.The car battery I just got, from Baterries Plus, did not have a CCA value, it was rated in AH. This was a first for me
We supply UPS systems from time to time.To me that indicates that either it is a deep-discharge battery designed for RE use or it was intended for somewhere other than the North American market.
That is why in the US the primary rating is the ColdCrankingAmps or CCA, which measures Amps delivered at a defined voltage (>7.2V) for a set minimum period of time (30 seconds) when the battery is cold (0F), simulating a cold weather start. With sufficient engineering to lower the internal resistance you could in theory deliver that kind of starting power in a 5AH battery.I can't think of any circumstances where the rated capacity would be stretched.
We supply UPS systems from time to time.
Mostly we use Yuasa batteries. They usually have Ah rating on the individual batteries. It's the 20 hour rate as a rule.
The data sheets we get and have to provide our customers have Ah ratings typically for 20, 10, 5, and one hour.
The curves go from 0.05C (20 hours) to 3.0C at 25degC.
Maybe such information is available for batteries used in automotive applications.
Mine is called 60Ah. The main function is to crank the engine to start it. It's a 2.2l Diesel. With the higher compression ratios of that compared to gasoline, the initial torque is greater. But starting is not more than a one or two second event. After that, the alternator takes over.
I can't think of any circumstances where the rated capacity would be stretched.
No Problem. My reply sat in the edit window for awhile too, so it was a toss up who would post first.Whoops! Left my post in the edit bin a little too long. Didn't mean to step on yours, GoldDigger.
No Problem. My reply sat in the edit window for awhile too, so it was a toss up who would post first.Whoops! Left my post in the edit bin a little too long. Didn't mean to step on yours, GoldDigger.
For yourself and the Gadfly, a couple or three points in no particular order or relevance.That is why in the US the primary rating is the ColdCrankingAmps or CCA, which measures Amps delivered at a defined voltage (>7.2V) for a set minimum period of time (30 seconds) when the battery is cold (0F), simulating a cold weather start. With sufficient engineering to lower the internal resistance you could in theory deliver that kind of starting power in a 5AH battery.
The AH capacity would determine how many start attempts the battery could make without the engine firing, so with no help from the alternator.
The reason that Reserve Capacity (RC) (which BTW is the number of minutes at 25A, not the number of amps for 20 minutes as I originally stated) is important is that we Yanks tend to live in our cars and have tailgate parties without the engine running. The drain of radio, parking lights, vent fan, etc. is approximated at 25A, and we need to know how long we can keep that up before we have to start the engine.
It is also useful for keeping the ignition going to drive home after you jump start a car that has a dead alternator.
That is why in the US the primary rating is the ColdCrankingAmps or CCA, which measures Amps delivered at a defined voltage (>7.2V) for a set minimum period of time (30 seconds) when the battery is cold (0F), simulating a cold weather start. With sufficient engineering to lower the internal resistance you could in theory deliver that kind of starting power in a 5AH battery.
The AH capacity would determine how many start attempts the battery could make without the engine firing, so with no help from the alternator.
The reason that Reserve Capacity (RC) (which BTW is the number of minutes at 25A, not the number of amps for 20 minutes as I originally stated) is important is that we Yanks tend to live in our cars and have tailgate parties without the engine running. The drain of radio, parking lights, vent fan, etc. is approximated at 25A, and we need to know how long we can keep that up before we have to start the engine.
It is also useful for keeping the ignition going to drive home after you jump start a car that has a dead alternator.
Did he connect it in parallel with the dead battery?Funny you should mention starting power from a small battery and engineering. A guy I know who is challenged in the IQ department tried to jump start a work van with a brand new Ultra tech brand 33 AH SLA battery.
Did he connect it in parallel with the dead battery?
That was on an episode of "Car Talk".Who was is that described a guy turning the second battery upside down and connecting it terminal to terminal since he did not have jumper cables?