 |
 |
| View previous topic :: View next topic |
| Author |
Message |
rnielsen
Joined: 23 Sep 2003
Posts: 852
Location: Utah
|
| Battery amp hour definition |
 Posted: Wed Jun 14, 2006 3:44 pm |
 |
|
I've searched for information on battery amp hours and can't find what I'm looking for.
If you have a 12V battery that is rated at 5AH and discharge 5A for one hour(the full capacity of the battery), what should the voltage, of the battery, be at the end of one hour? Should it be completely dead or would the voltage, at that time, start to dive downwards?
Ronald |
|
 |
PCM programmer
Joined: 06 Sep 2003
Posts: 21708
|
|
| Posted: Wed Jun 14, 2006 4:02 pm |
|
|
The best way is to look at the data sheet for the battery.
Here is the Energizer website:
http://data.energizer.com/DataSheets.aspx
Who is the manufacturer and what is the model number of the
battery that you're using ? For a 12 volt lantern battery, here
is the data sheet:
http://data.energizer.com/PDFs/732.pdf
You may have to extrapolate the curves to get the information you need.
(Or, do an actual physical test). |
|
|
SherpaDoug
Joined: 07 Sep 2003
Posts: 1640
Location: Cape Cod Mass USA
|
|
| Posted: Wed Jun 14, 2006 8:25 pm |
|
|
You may have to apply a "Salemanship" filter to those specs. Worst case is that the end voltage will be zero. But of course the current usually drops as the voltage does so laboratory conditions and real life differ appreciably. Look carefully at the battery manufacturer's specs.
_________________
The search for better is endless. Instead simply find very good and get the job done. |
|
|
kender
Joined: 09 Aug 2004
Posts: 768
Location: Silicon Valley
|
| Re: Battery amp hour definition |
| Posted: Wed Jun 14, 2006 9:28 pm |
|
|
| rnielsen wrote: |
If you have a 12V battery that is rated at 5AH and discharge 5A for one hour(the full capacity of the battery), what should the voltage, of the battery, be at the end of one hour? Should it be completely dead or would the voltage, at that time, start to dive downwards?
|
You maight also find this web site useful:
http://www.batteryuniversity.com/
Unfortunately, the battery voltage "is a nonlinear function of everything": temperature, discharge rate, history of use. |
|
|
Ttelmah
Guest
|
| Re: Battery amp hour definition |
| Posted: Thu Jun 15, 2006 4:06 am |
|
|
| rnielsen wrote: | I've searched for information on battery amp hours and can't find what I'm looking for.
If you have a 12V battery that is rated at 5AH and discharge 5A for one hour(the full capacity of the battery), what should the voltage, of the battery, be at the end of one hour? Should it be completely dead or would the voltage, at that time, start to dive downwards?
Ronald |
It would be long dead!.....
The 'Ah' figure, is based on discharge at 1/10th the rated current. So a '5Ah' battery, should deliver 0.5A for 10 hours, and after this time, the battery will be down to just over 1.8v/cell (11v). At 'C/1' (the discharge rate represented by 5A), the battery will reach this point after only about 15 to 20 minutes (depends to some extent on the cell design of the battery).
You should also remember though, that the 'life' of a battery, is reduced far more than linearly, when you operate into the lower half of the discharge curve. Basically, the longer the battery spends in a semi discharged condition, the less time it'll actually work for. Batteries called 'deep discharge' designs, have slight alterations to the cell structure and chemistry to _reduce_ this effect (but not get rid of it). For good durability, it is better to design so that the battery is not routinely taken below 25 to 30% charge. Finally, the available power, declines at lower temperatures. The quoted figure is normally for 20-25C, and if the battery is outdoors, the expected performance should again be degraded by a few percent.
So for a battery that is reliably going to deliver 5A, for one hour, and keep doing it again and again, you need to be looking at something in the order of a 25Ah battery!...
Best Wishes |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
FAQ 
Search
Register
Profile 
Log in to check your private messages 
Log in
