"Jake" wrote in message
...
I have an electronic GPS datalogging device that is designed to be powered
through a 9v battery. It runs the battery down in about 2 hours, and
because it goes through batteries so quickly, I have been looking for
solutions to make it last longer

I have had success in replacing the 9v battery with a 6 AA battery holder
with attached 9v clip and this powers the device for significantly longer
with 2500 mAh rechargeables giving 7.2v.

I have seen 8 AA battery clips available, that would give me 9.6v but I am
concerned about overvolting and damaging the device. Is the extra 0.6v
likely to cause damage?

Nope.

On 08/07/2012 22:53, Rod Speed wrote:


"Jake" wrote in message
...
I have an electronic GPS datalogging device that is designed to be
powered through a 9v battery. It runs the battery down in about 2
hours, and because it goes through batteries so quickly, I have been
looking for solutions to make it last longer

I have had success in replacing the 9v battery with a 6 AA battery
holder with attached 9v clip and this powers the device for
significantly longer with 2500 mAh rechargeables giving 7.2v.

I have seen 8 AA battery clips available, that would give me 9.6v but
I am concerned about overvolting and damaging the device. Is the extra
0.6v likely to cause damage?

Nope.

But the extra 2.2v when freshly charged batteries are used might do.

It is hard to know how a given device will behave without knowing what
chipsets it is using. Some things are tetchy about overvoltage.

But the OPs confusion between battery *capacity* and voltage is the main
problem here. If it really lasts only a couple of hours on a PP3 it
isn't going to make much difference using 8 AA cells instead of 6!

--
Regards,
Martin Brown

Martin Brown wrote
Rod Speed wrote
Jake wrote

I have an electronic GPS datalogging device that is designed to be
powered through a 9v battery. It runs the battery down in about 2
hours, and because it goes through batteries so quickly, I have been
looking for solutions to make it last longer

I have had success in replacing the 9v battery with a 6 AA battery
holder with attached 9v clip and this powers the device for
significantly longer with 2500 mAh rechargeables giving 7.2v.

I have seen 8 AA battery clips available, that would give me 9.6v but
I am concerned about overvolting and damaging the device. Is the extra
0.6v likely to cause damage?

Nope.

But the extra 2.2v when freshly charged batteries are used might do.

I doubt it. Bet it would survive 12V fine.

It is hard to know how a given device will behave without knowing what
chipsets it is using.

Yes, but there isnt much that has a Vmax of just 9v.

Some things are tetchy about overvoltage.

**** all is by that little.

But the OPs confusion between battery *capacity* and voltage is the main
problem here.

Nope, there is some stuff that isnt happy with too much
of a drop in the voltage from the standard and starting
with just 7.2V can see some stuff give up quite quickly.

If it really lasts only a couple of hours on a PP3 it isn't going to make
much difference using 8 AA cells instead of 6!

You don’t know that either if it gives up at say 7V.

In article ,
Martin Brown wrote:
But the OPs confusion between battery *capacity* and voltage is the main
problem here. If it really lasts only a couple of hours on a PP3 it
isn't going to make much difference using 8 AA cells instead of 6!

What is the capacity of an average PP3? Most decent re-chargeable AAs are
about 2.5 Ah these days. I'd be amazed if a PP3 was close to that.

It also depends on what terminal voltage the device quits at. Many battery
devices these days include a circuit to get the last drop out of them.

--
*Why do the two "sanction"s (noun and verb) mean opposites?*

Dave Plowman London SW
To e-mail, change noise into sound.

On 09/07/2012 10:51, Dave Plowman (News) wrote:
In article ,
Martin Brown wrote:
But the OPs confusion between battery *capacity* and voltage is the main
problem here. If it really lasts only a couple of hours on a PP3 it
isn't going to make much difference using 8 AA cells instead of 6!

What is the capacity of an average PP3? Most decent re-chargeable AAs are
about 2.5 Ah these days. I'd be amazed if a PP3 was close to that.

Rechargable 9v PP3 is about 200mAh or 1/10th of a set of AA's. A full
set of decent quality rechargable D cells would be 11Ah. Primary
alkaline cells might be 20-50% larger effective capacity on a good day -
depends on the device being powered when it cuts off.

The point I intended to make was that you get 10x longer going from PP3
to 6xAA but you will just get a few percent more (if at all) with 8xAA.

It also depends on what terminal voltage the device quits at. Many battery
devices these days include a circuit to get the last drop out of them.

Sadly far too many do quit when the terminal voltage drops below a set
point - which depends critically on battery chemistry. It is usually
high current devices that cause grief in this respect and a GPS logger
should not be drawing much current unless it is to run the chainsaw!

Running cells right into the ground will damage the weakest one.

--
Regards,
Martin Brown

Dave Plowman (News) wrote:
In article ,
Martin Brown wrote:
But the OPs confusion between battery *capacity* and voltage is the main
problem here. If it really lasts only a couple of hours on a PP3 it
isn't going to make much difference using 8 AA cells instead of 6!

What is the capacity of an average PP3? Most decent re-chargeable AAs are
about 2.5 Ah these days. I'd be amazed if a PP3 was close to that.

It also depends on what terminal voltage the device quits at. Many battery
devices these days include a circuit to get the last drop out of them.

IITC a PP3 is about 500maH.

--
To people who know nothing, anything is possible.
To people who know too much, it is a sad fact
that they know how little is really possible -
and how hard it is to achieve it.

On 09/07/2012 08:34, Martin Brown wrote:
On 08/07/2012 22:53, Rod Speed wrote:


"Jake" wrote in message
...
I have an electronic GPS datalogging device that is designed to be
powered through a 9v battery. It runs the battery down in about 2
hours, and because it goes through batteries so quickly, I have been
looking for solutions to make it last longer

I have had success in replacing the 9v battery with a 6 AA battery
holder with attached 9v clip and this powers the device for
significantly longer with 2500 mAh rechargeables giving 7.2v.

I have seen 8 AA battery clips available, that would give me 9.6v but
I am concerned about overvolting and damaging the device. Is the extra
0.6v likely to cause damage?

Nope.

But the extra 2.2v when freshly charged batteries are used might do.

It is hard to know how a given device will behave without knowing what
chipsets it is using. Some things are tetchy about overvoltage.

But the OPs confusion between battery *capacity* and voltage is the main
problem here. If it really lasts only a couple of hours on a PP3 it
isn't going to make much difference using 8 AA cells instead of 6!



I would expect any decent piece of kit will have a DCDC convertor as the
first stage of voltage regulation and be capable of handling an input
voltage range about of the order +/-25% around nominal voltage. Having
said that I've seen some really crap modern designs for battery powered
equipment.

On Mon, 09 Jul 2012 16:42:38 +0100, The Natural Philosopher
wrote:

Dave Plowman (News) wrote:
In article ,
Martin Brown wrote:
But the OPs confusion between battery *capacity* and voltage is the main
problem here. If it really lasts only a couple of hours on a PP3 it
isn't going to make much difference using 8 AA cells instead of 6!

What is the capacity of an average PP3? Most decent re-chargeable AAs are
about 2.5 Ah these days. I'd be amazed if a PP3 was close to that.

It also depends on what terminal voltage the device quits at. Many battery
devices these days include a circuit to get the last drop out of them.

IITC a PP3 is about 500maH.

A dry cell yes, rechangeable usually much less.

http://data.energizer.com/PDFs/522.pdf


--

The Other Mike wrote:
On Mon, 09 Jul 2012 16:42:38 +0100, The Natural Philosopher
wrote:

Dave Plowman (News) wrote:
In article ,
Martin Brown wrote:
But the OPs confusion between battery *capacity* and voltage is the main
problem here. If it really lasts only a couple of hours on a PP3 it
isn't going to make much difference using 8 AA cells instead of 6!
What is the capacity of an average PP3? Most decent re-chargeable AAs are
about 2.5 Ah these days. I'd be amazed if a PP3 was close to that.

It also depends on what terminal voltage the device quits at. Many battery
devices these days include a circuit to get the last drop out of them.

IITC a PP3 is about 500maH.

A dry cell yes,

That was what he asked...

rechangeable usually much less.
ITYM rechargeable. Sigh.


http://data.energizer.com/PDFs/522.pdf




--
To people who know nothing, anything is possible.
To people who know too much, it is a sad fact
that they know how little is really possible -
and how hard it is to achieve it.

On 09/07/2012 16:42, The Natural Philosopher wrote:
Dave Plowman (News) wrote:
In article ,
Martin Brown wrote:
But the OPs confusion between battery *capacity* and voltage is the
main problem here. If it really lasts only a couple of hours on a PP3
it isn't going to make much difference using 8 AA cells instead of 6!

What is the capacity of an average PP3? Most decent re-chargeable AAs are
about 2.5 Ah these days. I'd be amazed if a PP3 was close to that.

It also depends on what terminal voltage the device quits at. Many
battery
devices these days include a circuit to get the last drop out of them.

IITC a PP3 is about 500maH.

Primary alkaline cell for single use yes but the NiMH rechargeables are
only 200mAh, 250mAh tops.

--
Regards,
Martin Brown

On 10/07/2012 09:24, Martin Brown wrote:
On 09/07/2012 16:42, The Natural Philosopher wrote:
Dave Plowman (News) wrote:
In article ,
Martin Brown wrote:
But the OPs confusion between battery *capacity* and voltage is the
main problem here. If it really lasts only a couple of hours on a PP3
it isn't going to make much difference using 8 AA cells instead of 6!

What is the capacity of an average PP3? Most decent re-chargeable AAs
are
about 2.5 Ah these days. I'd be amazed if a PP3 was close to that.

It also depends on what terminal voltage the device quits at. Many
battery
devices these days include a circuit to get the last drop out of them.

IITC a PP3 is about 500maH.

Primary alkaline cell for single use yes but the NiMH rechargeables are
only 200mAh, 250mAh tops.

I checked Rapids best - typical PP3 primary alkaline 550mAh (~2.50p) ,
best possible capacity Lithium Ultralife 1.2Ah (£7.20).

And rechargables mostly around 200-250mAh.

Several well known brands are very coy about declaring Ah ratings.

--
Regards,
Martin Brown

On Tue, 10 Jul 2012 01:52:30 +0100, The Natural Philosopher
wrote:

The Other Mike wrote:

rechangeable usually much less.
ITYM rechargeable. Sigh.

don't blame me blame my spel chukcer and bad eyesight


--

On 10/07/2012 23:28, The Other Mike wrote:
On Tue, 10 Jul 2012 01:52:30 +0100, The Natural Philosopher
wrote:

The Other Mike wrote:
rechangeable usually much less.
ITYM rechargeable. Sigh.
don't blame me blame my spel chukcer and bad eyesight


found this site.
http://www.reuk.co.uk/High-Capacity-...lt-Battery.htm