How do you use a multimeter??

[JimmerG]

Can someone help out here - I've just bought the multimeter shown below.. a Skytronic 600.005 - and I cannot get a proper battery reading out of it...

It's got a couple of battery testing clicks on the dial one for 1.5V (40mA) and 9V (24mA) If I link up a protected 18650 to the 9V setting, I get a reading of 10.4..

Can anyone explain to me exactly how to test an 18650 with a multimeter?

 

[bguy]

Those battery testing settings are for regular 1.5V and 9V batteries, not lithium. For testing 18650s, just put it on DC voltage. On that meter you have to select the 20V range. The icon for DC is a line with dots under it.

Bradley

 

[JimmerG]

Of course - it all makes sense... I'll give it a go.

 

[JimmerG]

I've discovered where I went wrong - have the positive wire in the amps socket and not the volts socket - idiot.

So now I'm up and running with this multimeter - its as if a blindfold has been removed, finally I can see what's going on inside the cells.

It seems to measure 18650 fine - mine are coming off the charger at 4.18. It also seems to measure 1.2v Nimh cells fine aswell.

I found this very usefull table in another CPF post for 18650 cells..

4.2 volts 100%
4.1 about 90%
4.0 about 80%
3.9 about 60%
3.8 about 40%
3.7 about 20%
3.6 empty for practical purposes
<3.5 = over-discharged

Does anyone know is there's an AA 1.2 Nimh version?

 

[SilverFox]

Hello Jimmer,

There isn't a similar table for NiMh...

The voltage with this chemistry remains flatter making it difficult to interpret. For example a cell that is completely discharged will have an open circuit voltage of 1.2 volts or over. The best way to measure NiMh cells is to apply a load to them and measure the voltage under load. This also has difficulties, but gives a better indication of the state of charge of the cell.

Tom

 

[45/70]

You can't really check the condition of a nickel based rechargeable battery by measuring open circuit voltage, however it is generally accepted that if you obtain a reading of 1.2 Volts or less, the cell is dead.

Dave

 

[hopkins]

putting a load of a 10 ohm resistor (or in that range) on a Nimh cell
while measuring the voltage gives you a good idea of its 'state of charge'

approximatly ---- 1.37volts is full ----- 1.16volts is empty and time to recharge.

Sort of like your car gas tank -empty means you better get to a gas station before it is really empty., NimH empty means better recharge before the cell chemicals are damaged by over discharge and loses capacity and life (number of charge cycles)

 

[SkipH]

How many watts does the 10 ohm resistor need to be so it won't go while doing this test?

putting a load of a 10 ohm resistor (or in that range) on a Nimh cell
while measuring the voltage gives you a good idea of its 'state of charge'

approximatly ---- 1.37volts is full ----- 1.16volts is empty and time to recharge.

Sort of like your car gas tank -empty means you better get to a gas station before it is really empty., NimH empty means better recharge before the cell chemicals are damaged by over discharge and loses capacity and life (number of charge cycles)

 

[VidPro]

How many watts does the 10 ohm resistor need to be so it won't go while doing this test?

just get one of these
http://www.radioshack.com/product/index.jsp?productId=2062291
and you can do about anything without flames

picture shows the 2W one, but the idea is the same.
if you get a nice fat 10W resister, you have the space, and you can toss it across about anything from a AA to a car battery without it charring up.
and then it wont CHANGE ever, because a carbon one overloaded will change resistance, which wont help keeping things contant for comparison.

also note that whenever the battery is connected TO it, it will be drawing off power from the battery (as if you didnt know)

 

[SkipH]

Thanks for the info....I think I've got one like that somewhere....used it for loading up computer power supplies to get hard disks to come on...time for a trip to the junk box.

just get one of these
http://www.radioshack.com/product/index.jsp?productId=2062291
and you can do about anything without flames

picture shows the 2W one, but the idea is the same.
if you get a nice fat 10W resister, you have the space, and you can toss it across about anything from a AA to a car battery without it charring up.
and then it wont CHANGE ever, because a carbon one overloaded will change resistance, which wont help keeping things contant for comparison.

also note that whenever the battery is connected TO it, it will be drawing off power from the battery (as if you didnt know)

 

[Mr Happy]

a car battery

Yeah, I'd be a bit careful there. At 12 V, the power in a 10 ohm resistor is going to be:

W = V²/R = 144/10 = 14.4 W

If you are holding onto that resistor with your bare hands at the time you are in danger of burning your fingers

 

[labrat]

I've discovered where I went wrong - have the positive wire in the amps socket and not the volts socket - idiot.

So now I'm up and running with this multimeter - its as if a blindfold has been removed, finally I can see what's going on inside the cells.

It seems to measure 18650 fine - mine are coming off the charger at 4.18. It also seems to measure 1.2v Nimh cells fine aswell.

I found this very usefull table in another CPF post for 18650 cells..

4.2 volts 100%
4.1 about 90%
4.0 about 80%
3.9 about 60%
3.8 about 40%
3.7 about 20%
3.6 empty for practical purposes
<3.5 = over-discharged

Does anyone know is there's an AA 1.2 Nimh version?

You cannot trust these measurements for LiIon cells.
16350 or 18650 cells, I have had a couple of cells that read 4.20 Volts after charging, but the ZTS meter shows no charge, and trying to read any power output from them gives hardly 250 mA output just shorted through the meter!
They are gone! Empty.Ready for recycling.
Same goes for NiMh.
The above mentioned trick with a load resistor is better and more accurate, just don't hook up too long!

 

[divine]

Let's see here. This is how you check the "open" voltage of the cell.

I drew a black line to show where you put the setting on the meter. The horizontal solid line next to the horizontal dotted line means DC, the 2 means you're setting your range to be 1-10 volts, com is your negative, and the V is your positive voltage.

Yes, I know this is a rough example! :laughing:

 

[45/70]

Generally, I find testing 3.7 Volt cells works better on the 20 Volt scale than the 2 Volt scale, when those are the choices. Sorry divine, just couldn't resist!

Dave

 

[labrat]

You can't really check the condition of a nickel based rechargeable battery by measuring open circuit voltage, however it is generally accepted that if you obtain a reading of 1.2 Volts or less, the cell is dead.

Dave

NiMh cells have a nominal Voltage of 1.2 Volts.
To regard them as "dead" if you read an open voltage of 1.2 Volts, is not correct.

 

[Illum]

if your buying a multimeter purely for measuring batteries, I would suggest buying one of these instead
http://www.lighthound.com/ZTS-MBT-1...-37-volt-rechargeable-batteries_p_6-2389.html

yes, its a tad expensive, but like its ZTS brothers uses a low curent load to test the capacity of cells rather than interpretation by voltage:twothumbs
I have the ZTS mini, this ones fully loaded with button cells AND lithium ions [note: although it only states RCR123A, 18500, 17650, 18650 on the cover al lithium-ions behave the same in terms of voltage, 4.2 = full, 3.7 = dead]

 

[45/70]

NiMh cells have a nominal Voltage of 1.2 Volts.
To regard them as "dead" if you read an open voltage of 1.2 Volts, is not correct.

nominal=under load

Wattnot ...... eh, nevermind.

Dave

 

[divine]

Generally, I find testing 3.7 Volt cells works better on the 20 Volt scale than the 2 Volt scale, when those are the choices. Sorry divine, just couldn't resist!

Dave

:laughing:

 

[labrat]

nominal=under load

Wattnot ...... eh, nevermind.

Dave

http://en.wikipedia.org/wiki/Nickel-metal_hydride_battery

 

[Mr Happy]

NiMh cells have a nominal Voltage of 1.2 Volts.
To regard them as "dead" if you read an open voltage of 1.2 Volts, is not correct.

No, it's true. If an NiMH cell reads 1.2 volts open circuit, it indicates that it is fully discharged. A fully charged cell should read 1.35 volts or more.

If an NiMH cell ever shows a resting voltage much lower than 1.2, it is a sign that it is either defective or damaged.