Replacing 9V batt with 6 AA rechargeables

[Raymond]

Sillly question (maybe ): Let's say, I want to run a DMM from 6xAA cells. I can take a battery holder for 6 cells and put 6 alkalines in there. But would 6 nimh's (LSD if necessary) also work? Total voltage would be 8.4V, which is slightly lower than the 9V from a single 9V battery.

I plan to do some tests later today, but maybe there some people who already have some experience with this?

I want to use such a 6cell battery holder, because AA's have way more capacity than a single 9V battery and I plan to take measurements for many hours (almost days) and don't want to replace the 9V batt often.

Also, would a rechargeable "9V" battery work in a DMM?

ooh: I just discovered this
A 500mAh liPo battery, that's interesting!

Found a LSD 9V battery. Now all I need is a place to buy one.

Thanks

 

[mdocod]

The first 9V battery in my multi-meter lasted for however long I have had the thing, till just a few weeks ago when the little "low battery" indicator came on, so technically, it was still working on that 9 year old battery, but I went ahead and replaced it

In my personal experience, multi-meters don't use much juice, mine had to of had a few hundred hours "on" time over the last 9 years on that 1 battery.

Just saying, maybe you won't need to replace it as much as you think, and maybe a rechargeable solution for that device wouldn't really pay off for a LONG time... Depends on your meter I suppose though.

The lower voltage from NIMH probably won't be a problem if you go that route, alkaline drops below 1.2V per cell at some point through it's discharge and devices are expected to tolerate and continue using that cell until around 0.9V or less if possible. When comparing discharge characteristics, in more normal drain rate applications, like say, half an amp, NIMH spends roughly, off the top of my head, 80-90% of a discharge at a higher voltage than the same size Alkaline cell. The only time the alkaline cells "beats" the NIMH cell is fresh out of the package for the first few minutes of use.

 

[redsfairlane]

I recently put a 9V NIMH into my DMM, it is working fine, I think it should work in just about any small meter.

I'm hoping that it is good for a few months (occasional use) just so I don't have to keep any primaries on hand for it. I think it is the only 9V aplication I have.

 

[Raymond]

Hmm, maybe you're right, and I should just try it out and see how long a normal battery lasts.
Or buy a few of those primary lithium 9V batteries, although those don't make real financial sense ($3 for an alkaline and 2.5x that for a lithium).

 

[bob_ninja]

I use a 8xAA holder from Radio Shack that has a 9V connector for my smoke alarm. When AAs are charged then they register well over 10V, so bit high. Still the alarm doesn't seem to mind.

I could/should simply wire one bay to reduce voltage, just didn't do it yet.

 

[Lynx_Arc]

some 9v devices will run fine off a higher output 6v source, it depends on how sensitive it is to voltage drops.

 

[Fallingwater]

Out of curiosity, I actually hooked my multimeter to my lab power supply.
What I found is that it keeps working more or less correctly until it gets to 5.5 volts or thereabouts, then it starts misbehaving and showing higher values.
It shows the low battery warning at a bit less than 7 volts.
Current consumption is not high enough to register on the power supply's integrated ammeter, which means it's less than one milliamp.
It goes to about 3ma (if I remember correctly) when the backlight is turned on.

I too was thinking of putting six alkaline AAs or AAAs in my multimeter so I didnn't have to worry if I left it on for the whole night or something, but in the end I think it's not worth it. Unless you leave it with the light on it eats so very, very little power that even a supercheap carbon-zinc 9V battery will power it for a long time, even if you occasionally forget it on.

And using rechargeables is just silly.

 

[TorchBoy]

And using rechargeables is just silly.

Nice, Fallingwater. A common-sense conclusion backed up by an actual test.