9Volt vs. AA Recheargeable Batteries

[missmoo]

Hello,

I'm not quite an electrical engineer (YET! but I do some of this as a hobby as I get my degree. I have a question I need assistance with, hope you can help me.

At my job we are working with magnetometers that are powered by a pack of 7 AA batteries (Rechargeable) encapsulated in a pack that has a 9v type connection to the circuit board. One of those devices is connected to a simple 9V rechargeable battery instead of the pack.

The batteries are at terrible shape (due to neglect and bad maintainance of the devices, mostly) and we are about to change them all. As the only person that knows half a thing about electrical currents and circuits, the job of choosing the replacements fell on me.

My question is this: Which type of rechargeable battery is better? The 9v or a pack of 7 AA ? which would hold out longer, or which would survive longer? Is there really a difference?

I apologize if I don't supply information that is relevant, I don't know much about batteries. If you need more information, please ask. I also apologize if this is in the wrong forum. Again, I'm doing this as a Hobby, and try to learn in the process.

Thank you very much,

Moriel

 

[Noway2]

I mentioned the part about code requirements as that is what I was told. The comment was made by the local fire chief. I don't recall his exact words, but it was something to the effect of using 9V batteries only in fire protection and other 'monitoring' equipment. To me this explains why they still exist in clocks, DVMs, etc.

The idea behind his statements was that the use of 9V batteries was discouraged (if not prohibited) in devices that would encourage the average Joe or his offspring from removing the batteries by making them useless in most consumer electronics. Granted, technical issues involving reduction in normal operating voltage may have helped.

 

[IRstuff]

SOMEONE has their history confused. 9V batteries were used exclusively in transistor radios up until fairly recently. When the Japanese were touting the "3 transistor" radios, I didn't even have smoke alarm.

Walkie talkies, DVMs, RC transmitters all used 9V batteries. The only reason that quad AAs are used is the poor current capacity of a 9V battery.

TTFN

FAQ731-376