multitester confusion


I bought a radio shack multitester to check my batteries, primarily my laptop batteries. First on my old dead battery of Toshiba laptop, they had a positive and negative mark shown..so it was easy to check it out with the tester. But I bought it to check my Dell battery that lasted 1 year to the day of the end of my warranty. Fortunately, i did get a refurbished one in time. Disappointed that it only lasted a year and I had only used it a total of maybe 10 hours with the battery on my last vacation...10 hours in 1 year and poof it went. The battery does not have a pos and neg shown like the toshiba one..so I cannot test it that way. In the meantime, I was trying to check some AA and AAA batteries that I had and was able to understand on how to test them..but I do not know how to interpret the readings I used the ACV side with it set at 15. I really don't know what does numbers mean. The manual is a joke, at least for those of us that have no experience. The line moved a little to the right where it seem to end a couple of notches on that ac 15v scale. It read the same for the new battery as well, so what is it telling me that its a 1.5v battery? How does one know if the battery is weak or whatever? Does anyone know of a web site that can tell me what those readings represent? I did a search in google but nothing came to what I was hoping for.
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Boothbay wrote:

You have the meter set on AC. Batteries are DC, so you want it set on one of the DC ranges. Sounds like you have an analog meter, in which case you need the polarity correct for the meter to move to the right. With the digital meters I have seen, polarity doesn't matter. If you have it reversed, the voltage will just read with a minus sign in front.
If the battery is new it should read 1.5V.
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Boothbay wrote:

All batteries are DC so you need a DCV range. With a digital meter it doesn't matter which is positive and negative as it will simply show the correct voltage with a - sign if you have it backwards. With an analog meter the needle will go backwards to the stop and you just have to reverse the leads. The meter will be of limited use for rechargeable batteries like a laptop one since it only tells you the voltage, not the state of charge.
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Pete C. a ιcrit :

batteries may be DC but some chargers give out AC, it allow the use to connect the batterie pack to the charger wihout any care for polarity the battery pack contain diode that correct the AC to DC, that could explain why there arent any polarity sign.. but beware laptop aren't my speciality....
system21 u568567
Check out his game <br><a href=http://gc.gamestotal.com/ Galactic Conquest</a>
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snipped-for-privacy@gmail.com wrote:

???
Can you give an example of such a charger?
I expect the reason for no polarity sign is that the battery can be inserted into the unit in only one way.
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Boothbay wrote:

Tool manuals are not intended to provide lessons, in your case, on electricity. You need a simple book that includes basic discussions and standard abbreviations. That is where you start, not with the multimeter. For example, ACV means alternating current voltage. Batteries don't use AC they use DC (direct current) so your meter should be set on DCV. Further you need to read some about batteries and there are excellent sources online so just look at google results for "batteries." Standard (alkaline) nonchargeable AA and AAA cells read about 1.6 volts when new and about 1.3 when discharged to a level they won't work in most equipment.
Alkaline, NiMH, and Li-Ion (your laptop) batteries have different characteristics that you need to read about before you can analyze the voltage readings.
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I know you said multitester, but since you mentioned that you are using the AC scale, can I safely assume you mean a multimeter?
Multimeters are not always the best device for testing batteries. Yes they will indeed tell you when a battery is just about dead, but they can be misleading when a battery is weak.
Most multi-meters don't put enough of a load on battery when they are being tested, so they may read the full voltage when bench tested, but once the batery is put back in the device, they may not be strong enough to power said device.
When testing a battery with a multimeter, it should be tested under load.
http://support.radioshack.com/support_tutorials/batteries/batgd-B08.htm or http://www.nifty-stuff.com/battery-tester.php
Boothbay wrote:

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Chances are the battery died because you didn't use it. Batteries self- discharge. If left discharged for significant periods of time, the battery will die early.
Bob
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Bob F wrote:

Possibly, but I always had my ac adapter connected to it, so I assumed that it was constantly being recharged. If lack of battery usage...what is considered normal usage, so I won't lose my refurbished one the same way?
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Boothbay wrote:

You need to do some reading about how battery voltages change with state of charge. Lots of those type sites on the web. Something like this one that I found with a quick look:
http://www.uoguelph.ca/~antoon/hobby/techbat.htm
Your Dell battery is a set of several hooked in series. The voltage will be approximately 1.2 times the number of batteries. For example a 15 cell NICAD battery will measure about 18 volts (1.2 x 15). If it suddenly drops by about 1.2 volts it means that one of the cells has shorted.
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What the others have said.

That's why I don't like things that run on batteries. I'm 59 and when I grew up, anything other than a flashlight that required batteries was a luxury. I still feel that way, although I have a few more things than I used to that use batteries.

One of the purposes of the meter is to identify + and -. Hold it on one and tap it on the other to see whih way the needle moves. If it moves to the left, reverse the leads.

We went over this in high school chemistry (which was almost as high level as my college chem oourse) and I'm sad to say that I can't reproduce the numbers, but I saw them and they made sense. That is, g the arithmetic shows that it's the nature of chemical reactions that the voltage stays rather high until the battery is almost fully discharged. So even moderate decreases in voltage represent major loss of charge in most cases. They are right that different kinds of batteries are different in details, but all share this. For a flashlight battery it has to be 80% discharged before the voltage drops to 80% of original. Or maybe 90% and 90%. But like someone said, the voltage might be 90%, but it doesn't have the capacity to put out the amount of current you still need.
When you have doubts if it is the battery or the device, try a good battery and see if it works better.
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I am surprised nobody else mentioned this but you should also choose a scale on the meter that will get your reading about center of the scale. i.e. if you where testing a battery where you expected about 1.2 volts you should be using a scale that is about 0-2.5 volts. Analog meters are most accurate in the center of the scale.
mm wrote:

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Buy a $3 digital tester from Harbor Freight and you won't need to worry about being in the middle of the scale and you won't need to worry about polarity (it will tell you). The lowest scale on many testers is in the 20-25V range anyway.
JGolan wrote:

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On the guys main problem, notebook batteries, I went through a couple batteries on my Gateway, which is now about 6 years old. The original battery lasted about 2 years. That one I had always left in the PC, so it was mostly constantly charged, with occasional use disconnected. The next battery was an aftermarket one I bought on Ebay. That one lasted about a year.
Then I started to realize that for 99% of how I used the notebook, I didn't need the battery. I pretty much used it at home or when away at a hotel or similar place that had AC. It was rare that I really needed or wanted to use it on a plane, car, etc.
So, I concluded for my usage model, the simplest thing was to remove the battery. It not only solved the problem, but made the notebook considerably lighter as well. Not suggesting that's what everyone should do, but if it fits your usage model, it is an option.
As for Gateway, I'd never buy a system from them again. My system came with Windows ME. Less than a year later MSFT was shipping XP, which the system was clearly capable or running, but because of driver issues, I can't install it on mine and Gateway refused to provide updated drivers for a year old system. The final insult was while I was logged into their website looking for drivers, a scum bag calls up trying to sell me memory, which I didn't need and explaining how XP is a whole new system, and it's all MSFT fault that I can't put it on my PC. Funny thing that I upgraded and put it on another PC that was a no-name I had put together about the same time off a website by checking MB from X, Disk from Y, Display Adaptor from Z, etc.
Seemed pretty obvious to me Gateway tracks users by identifying their PC's from service info and when they log in looking for support, instead of providing a driver, they hit them up for more sales.
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On 24 Dec 2006 04:26:44 -0800, snipped-for-privacy@optonline.net wrote:

Good idea. It probably fits 80% plus.
Tell Ann. (Addressed to a friend.)

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