Questions about Amp Hours

Norm,

Thanks - your concise comments cleared quite a bit of mystery for me too - electrical has never been my strong suit. Thats a great benefit of forums like this - have learned quite a bit in the few weeks I've been a member.

Cheers

Phli S

"a 44AH battery at (approx) 26.7degC will put out 44amps for one hour....or 1amp for 44hrs or 22amps for 2 hrs. Do you see?"

Mat not quite. You are forgetting the effect of Peukerts Law It was explained to some extent in the previous answer but you can read more by clicking on the link I have given.

PeterD

Disco did you manage to read the first sentence...."Without getting too COMPLEX" Seriously did you need to muddle an INDUSTRY STANDARD of battery rating of AH....did you think the poster would benefit from the intimate knowledge of Puekerts Law.

Considering the posters reference was to AGMs and with a PK rating of typically of 1.1 not really all that relevant unless you are doing finite calculations of your use and storage. The poster was asking about the AH RATING SYSTEM!!

Seriously Disco....chill out! It was a simple answer to a complex question it was not an opportunity to big note myself.

But thank you for your contribution...and reminding me how good Collyn's book is and that I need to dig it out again for another read.

All the best

Matt.

Matt

The problem with batteries is that they are not simple. You gave a simple answer but did not explain that your answer is approximate because as the charge and discharge of batteries is not quite linear. When you give simple answers to questions without qualifications them punters tend to take these as gospel and lead problems further down the track. Even with a Peukerts constant of 1.1 punters using AGM batteries still run out of power earlier than expected when drawing large currents and can't figure out why (unless you know about batteries non linear characteristics.) I through in a link to Collyn's paper in because it is very easy to read (compared to what I could write) and I thought members should be aware of how batteries work.

This simple explanation rather than exposing punters to the full facts about battery charging, has lead to confusion regarding charging of deep cycle. Lead acid batteries do not sulphate up if you keep the charge level over 60%. To keep costs down, auto alternators employ simple circuitry, and to stop the alternators from overcharging batteries, the alternators are set to only charge batteries to a level of 70-75%. This is commonly referred to in the trade as “fully charged.” I have no problems with this if you remember the application to which you are referring. In the long run this has lead to the belief that auto alternators charge batteries to 100% of their capacity.

PeterD

Ahh Pete this is getting tiresome, seems you are still missing the point of my response to the origonal question.... What is the AH rating.

Technically everything you have said is correct and dont dispute it for an instant...but you seem to have got lost in your facts and still cant see the question.

HOW DO YOU RATE A BATTERY IN AH( remember its an SAE rating).... heres a few responses how dedicated sites also answer a simple question.

ODDESSY FAQs
I do not understand the Ah rating. Please explain.
The ampere-hour (Ah) rating defines the capacity of a battery. A typical battery that is rated as a 100Ah battery at the 10 hour rate of discharge is capable of delivering 10A for 10 hours before the terminal voltage drops to a standard value such as 1.67 volts per cell, or 10.02 volts for a 12V battery. Similarly, a 50Ah battery would supply a 5A load for 10 hours. The BP1000 battery is rated at 42Ah, so it can furnish 4.2A for 10 hours.

Oh and another

www.batteryweb.com FAQ

What is the Amp Hour (Ah) rating?
An amp-hour is one amp for one hour, or 10 amps for 1/10 of an hour and so forth. It is amps X hours. If you have something that pulls 20 amps, and you use it for 20 minutes, then the amp-hours used would be 20 (amps) X .333 (hours), or 6.67 AH. The accepted AH rating time period for batteries used in solar electric and backup power systems (and for nearly all deep cycle batteries) is the "20 hour rate". This means that it is discharged down to 10.5 volts over a 20 hour period while the total actual amp-hours it supplies is measured. Sometimes ratings at the 6 hour rate and 100 hour rate are also given for comparison and for different applications. The 6-hour rate is often used for industrial batteries, as that is a typical daily duty cycle. Sometimes the 100 hour rate is given just to make the battery look better than it really is, but it is also useful for figuring battery capacity for long-term backup amp-hour requirements.


Im sorry I SOOOOO hate to cut and paste but those are the answers to the simple question of how do you RATE IN AH...

Didnt ask about Peukerts, didnt ask about alternators, didnt ask about how to recharge a battery to full 100% didnt ask to know every in and out in battery technology just wanted to know how to RATE A BATTERY IN AH.

As I said before you obviously are well versed in battery technology but the poster wasnt and just asked a simple question and I gave him the simple and correct answer to HOW YOU RATE A BATTERY IN AH.

All the best Peter

Matt.