Is this bad for my scanner?

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sjcscanner

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So im sitting there, listening to a fire... and then my scanner starts the "low battary beep". I take out the battary cartrige, rotate the battarys, and put it back. It lasts about 15 min. I do it again, it lasts about 5 and then just turns off, and starts hissing. Is streching the battarys to their limit bad for your scanner?
 

Shortwavewave

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No, not really just a low voltage would, but Ive always wondered that why is it the batts will last a little longer if you switch them around???
 

LEH

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I don't know the physics behind it (or even if there is any), but the battery closest to the positive terminal always seems to run down soonest. Swapping them around will extend the life a bit.
 

n2mdk

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There really is nothing bad that will happen to the scanner, the only thing you might do cause one of the batteries to discharge past it's voltage threshold so it balks at taking a recharge.
 

zz0468

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LEH - Have you put a volt meter across the cells and actually observed the voltage to see that the one closest to the positive terminal is REALLY lower, or are you just swapping them around?

I think that what's happening is that shutting down long enough to rotate the batteries is allowing them to build up enough surface charge to make it appear that the one nearest the positive terminal is running down fastest. They're in series, so the theory says that the current through each cell will be identical. But as they get low, you will see the slight differences in the cells become more apparent.

Is it bad for your scanner? No, but it IS bad for your batteries. Rechargable batteries aren't meant to be discharged past a certan point. In the case of ni-cads, that's about 1 volt per cell. Going past that point will drastically reduce their life span. If you go too far, they will actually reverse polarity (negative voltage on the positive terminal!) on you which can cause all manner of problems when you try to recharge them later.

If you're using disposable batteries, you're fine squeezing every drop of power out of them.
 

DaveH

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n2mdk said:
There really is nothing bad that will happen to the scanner, the only thing you might do cause one of the batteries to discharge past it's voltage threshold so it balks at taking a recharge.
That's a good reason not to try to operate past the low-voltage warning.
If one of the cells drops too low, it will be essentially "dead" but current
still running throught it is essentially trying to charge it with the wrong
polarity...bad for that cell. I am not sure of the exact equivalence with NiMH
but with NiCD, the cell could short, rendering it useless. Now you're down
a cell and you might be able to "zap" the short, but that cell will be the
weakest and die first from that point on. Replacing the cell, you'll no longer
have all matched. In that case, it'd be best to redeploy the remaining cells
elsewhere and replace all scanner ones at one time; or replace the pack
if it isn't discreet cells, could be pricey.

Dave
 

DaveH

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LEH said:
I don't know the physics behind it (or even if there is any), but the battery closest to the positive terminal always seems to run down soonest. Swapping them around will extend the life a bit.
Strangest thing I've ever heard, but in certain scanners, I'm guessing that
if the batteries are charged in the radio, and there is any heat buildup from
the charge regulator circuit, it could affect particular cell(s) over time, or even
on a short-term basis. Just a theory.

Dave
 

gmclam

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zz0468 said:
I think that what's happening is that shutting down long enough to rotate the batteries is allowing them to build up enough surface charge to make it appear that the one nearest the positive terminal is running down fastest. They're in series, so the theory says that the current through each cell will be identical. But as they get low, you will see the slight differences in the cells become more apparent.

Is it bad for your scanner? No, but it IS bad for your batteries. Rechargable batteries aren't meant to be discharged past a certan point. In the case of ni-cads, that's about 1 volt per cell. Going past that point will drastically reduce their life span. If you go too far, they will actually reverse polarity (negative voltage on the positive terminal!) on you which can cause all manner of problems when you try to recharge them later.

If you're using disposable batteries, you're fine squeezing every drop of power out of them.
I agree with this post. Try turning off your scanner for the same amount of time it takes to swap the batteries, but do NOT swap them. I think you'll get the same extended time.

This is good for NiCds as they should be fully discharged before being recharged. It is OK for alkalines, as you're getting the most out of them. It is bad for other rechargables (ie NiMHs).
 

N1BHH

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Even though a scanner has a low voltage indicator, most of these are actually low current indicators. The PRO-97 is an example where, the low battery indicator beeps and flashes on the screen. This is actually a low current indicator. The voltage drops, but not as low as some people seem to think. NiCd's and NiMH's will operate at near 1 volt but not power the device which it is inserted in if the current drops below the design current rating. What you are draining more from a battery is current as opposed to voltage. I have actually had a single cell that had .75 volts and 700 milliamps along with the rest at their full voltage and current and the radio still operates.

When the low battery indicator comes on it's giving you time to plug in some power so that you can continue using your device. I don't plug mine in until the backlight flashes and the radio squelch motorboats. I usually just pull them out and put a fresh set in, I have 5 sets in total. This indicates the batteries have reached the end of supplying proper current to the device.

You may notice when running alkaline cells that your device "dies" quicker than with re-chargeables. That is due to the combination of both voltage and current dropping off, mostly voltage. NiCd's and NiMH's are a different breed altogether, and a better investment, along with a good charger and you'll have many years of life out of re-chargeables because you don't want to shell out a few bucks every time your batteries "die" on you.
 

Zaratsu

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voltage differences in rechargeables can result in one battery charging the weaker one. I have heard of lithiums going explody in situations like this. Not really a battery expert, but I was doing some research because I had an itch to blow a few notes on a surefire flashlight and noticed the minimal risk of using crap batteries and the reasons behind failure.
 
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