Mickel
Guest
Sun Feb 28, 2010 7:04 am
I have a torch which used 4 AA batteries in series. It draws approx 1.1
amps so should got for over 2 hours with 2650mAh batteries. However when
I tested it was getting down at 1.25hrs and was pretty much completely
flat at 1.5Hrs. Is the rating rubbish or am I missing something? These
are Duracell batteries purchased from a large chain retail store so I
presume they are genuine.
Cheers,
Michael
Bruce Varley
Guest
Sun Feb 28, 2010 7:30 am
"Mickel" <mickel_at_nospam.com> wrote in message
news:4b8a078c$0$24251$afc38c87_at_news.optusnet.com.au...
Quote:
I have a torch which used 4 AA batteries in series. It draws approx 1.1
amps so should got for over 2 hours with 2650mAh batteries. However when I
tested it was getting down at 1.25hrs and was pretty much completely flat
at 1.5Hrs. Is the rating rubbish or am I missing something? These are
Duracell batteries purchased from a large chain retail store so I presume
they are genuine.
Check out the duracell website, IIRC there are curves there that will show
you the rated capacity at various current ratings. You'll see that as the
load current increases, the capacity of the cell decreases.
Phil Allison
Guest
Sun Feb 28, 2010 7:31 am
"Mickel"
Quote:
I have a torch which used 4 AA batteries in series. It draws approx 1.1
amps so should got for over 2 hours with 2650mAh batteries.
** No way is it that simple.
The mAh capacity of cells is a function of the discharge rate.
Duracell's 2650 mAh figure for AAs relates to discharge at 25mA where it
will take just over 100 hours to get down to 0.8 volts.
Quote:
However when I tested it was getting down at 1.25hrs and was pretty much
completely flat at 1.5Hrs.
** Normal.
The way to get better results is to use NiMH AA cells which can cope with
continuous discharge rates up to 5 amps with little loss of capacity.
..... Phil
Phil Allison
Guest
Sun Feb 28, 2010 7:32 am
"Bruce Varley"
Quote:
Check out the duracell website, IIRC there are curves there that will show
you the rated capacity at various current ratings.
** Seem to have all disappeared.
The Energiser site still has them.
..... Phil
Mickel
Guest
Sun Feb 28, 2010 1:57 pm
On 28/02/10 5:31 PM, Phil Allison wrote:
Quote:
"Mickel"
I have a torch which used 4 AA batteries in series. It draws approx 1.1
amps so should got for over 2 hours with 2650mAh batteries.
** No way is it that simple.
The mAh capacity of cells is a function of the discharge rate.
Duracell's 2650 mAh figure for AAs relates to discharge at 25mA where it
will take just over 100 hours to get down to 0.8 volts.
However when I tested it was getting down at 1.25hrs and was pretty much
completely flat at 1.5Hrs.
** Normal.
The way to get better results is to use NiMH AA cells which can cope with
continuous discharge rates up to 5 amps with little loss of capacity.
Thanks Phil and Bruce for the reply. As long as it's expected then
that's good. I thought maybe I had a poor charger. The torch will
actually take 8 batteries to produce 4.8 volts, so with only 0.5 amps
maybe I'll get more than twice the time.
Charlie+
Guest
Mon Mar 01, 2010 3:39 pm
On Sun, 28 Feb 2010 23:57:03 +1100, Mickel <mickel_at_nospam.com> wrote as:
snip
Quote:
Thanks Phil and Bruce for the reply. As long as it's expected then
that's good. I thought maybe I had a poor charger. The torch will
actually take 8 batteries to produce 4.8 volts, so with only 0.5 amps
maybe I'll get more than twice the time.
You might consider the new hybrio type NiMH which dont self discharge so
quickly - this is a major fault especially with the high capacity cells I
found. Hybrio type are more expensive tho.
The normal high capacity ones (eg.AA - 2500+mAh) seem to self discharge a
large chunk of their capacity in about two+ weeks! Energiser seem the
worst of the ones I have, -had actually, I sent them to the recycler as
useless in real life!
Charlie+
