Multimeter question

[Danielight]

Aquus 3300 test result for my EagleTac 3100: 4.07 v. I would still like to have Cottonpicker's battery voltage tester just to be able to check the accuracy of the DMM. Do I understand correctly that the voltage checker is available to CPF members for $10 even? Does that include shipping? Is there a code to let the vendor know that you're a CPF member?

 

[Danielight]

I recently bought my first light that uses 18650s (bought the EagleTac D25LC2, and an Eagletac 18650 3100 mAh from illuminationGear). I understand that recharging these batteries requires some caution, and I'd like to be able to do it without risk of fire, etc. I also bought the XTAR MP1S single battery charger. I'm looking for any recommendations on purchasing a digital multimeter (e.g., Amprobe 240?) , and maybe a quick tip as to how to test the 18650 after it comes out of the charger. We may have some posts here in CPF with some instructions. Thanks for any input you can provide. :D

 

[StarHalo]

Quick n' easy: Harbor Freight multimeter for $5 (may be as low as $2 in-store, if one is near you); set it to DCV 20 (direct current, volts, 20 maximum), and red probe positive/black probe negative - if your freshly charged cell reads 4.2 volts or just under that, you're ready to go.

Be sure to check the voltage of your cell from time to time, ideally you should aim to recharge it at not lower than 3.6 volts.

 

[TEEJ]

After you take it off the charger, let it rest a few minutes, then set the meter to DC and volts, and put a + probe on the + end of the cell, and the - probe on the - end of the cell, and read the volts.

If your light only uses one cell, you don't have to worry about matching cells, etc...because with one, you won't have a potential difference between cells, etc. (Heat build-ups/Fire risks, etc...)

You typically want the cell to read 4.2 v +/- 0.05 v (4.15-4.25 v) depending on the cell's specs...but a hair lower is better in the long run, as the cells tend to last longer with "all but" full charge vs FULL charges...so 4.15-4.17 v, etc, is a common desired target.

If its a protected cell, and a decent charger, etc...you will most likely be fine. The main reason you're bothering to check the voltage after charging is to qa/qc the charger...to make sure its not overcharging the cells, etc.

After you're done with the cell, and ready to put it back on the charger...you check the voltage before you put it back on, so you know how low you got it down to (Cells have minimum charge requirements too, and you don't want to drain them down lower than that limit, to help prolong their lives, etc.)

Once you're used to it, its a few seconds here and there...not a big deal.

If only for this purpose, most people seem to be fine with almost any volt meter device, but digital multimeters seem to be preferred. I use a Fluke 115, because I have it for work, but lots here use inexpensive harbor freight versions, etc.

I have lights that take up to 6 cells at a time, so I'd rather have a DMM I feel confident with, but if sticking with single celled lights, while a better DMM is of course better, you would probably be fine with anything that read out what you needed.

Cottonpicker (CPFM) for example has a simple voltmeter for this purpose, etc.

:D

 

[Danielight]

Thanks for the quick responses. I will probably pick up an inexpensive DMM so that I can check to see when the battery needs recharged, and to make sure it's not being overcharged. I figure that the stuff sold by illuminationGear is going to be good, but it's always best to be safe, right? ;) (BTW, would the same precautions hold true for 14500s?)

 

[Danielight]

Cottonpicker (CPFM) for example has a simple voltmeter for this purpose, etc.

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I had a chance to check out Cottonpicker's voltmeter at the Dark Sucks website. This looks like something I could use. Any input from other CPF members who might have this unit? Cost is $12.50; any discount for CPF members? :naughty:

 

[Bigmac_79]

Thanks for the quick responses. I will probably pick up an inexpensive DMM so that I can check to see when the battery needs recharged, and to make sure it's not being overcharged. I figure that the stuff sold by illuminationGear is going to be good, but it's always best to be safe, right? ;) (BTW, would the same precautions hold true for 14500s?)

The same precautions will hold true for all batteries with the lithium-ion battery chemistry, including the 14500 size. You'll need to be even more careful if your cell does not have a protection circuit. Here's a thread that might take some time to read, but it will be worth it for your safety and to prolong the useful life of your batteries:

http://www.candlepowerforums.com/vb/showthread.php?329321-Li-ion-beginner-primer

Quick n' easy: Harbor Freight multimeter for $5 (may be as low as $2 in-store, if one is near you); set it to DCV 20 (direct current, volts, 20 maximum), and red probe positive/black probe negative - if your freshly charged cell reads 4.2 volts or just under that, you're ready to go.

Be sure to check the voltage of your cell from time to time, ideally you should aim to recharge it at not lower than 3.6 volts.

I have one of these cheap Harbor Freight multimeters, it's pretty inaccurate, but I think it would probably be good enough for checking your cell voltage. Mine measures up to .03-.05 V off compared to my nicer multimeter.

 

[Danielight]

After you take it off the charger, let it rest a few minutes, then set the meter to DC and volts, and put a + probe on the + end of the cell, and the - probe on the - end of the cell, and read the volts.

If your light only uses one cell, you don't have to worry about matching cells, etc...because with one, you won't have a potential difference between cells, etc. (Heat build-ups/Fire risks, etc...)

You typically want the cell to read 4.2 v +/- 0.05 v (4.15-4.25 v) depending on the cell's specs...but a hair lower is better in the long run, as the cells tend to last longer with "all but" full charge vs FULL charges...so 4.15-4.17 v, etc, is a common desired target.

If its a protected cell, and a decent charger, etc...you will most likely be fine. The main reason you're bothering to check the voltage after charging is to qa/qc the charger...to make sure its not overcharging the cells, etc.

After you're done with the cell, and ready to put it back on the charger...you check the voltage before you put it back on, so you know how low you got it down to (Cells have minimum charge requirements too, and you don't want to drain them down lower than that limit, to help prolong their lives, etc.)

Once you're used to it, its a few seconds here and there...not a big deal.

If only for this purpose, most people seem to be fine with almost any volt meter device, but digital multimeters seem to be preferred. I use a Fluke 115, because I have it for work, but lots here use inexpensive harbor freight versions, etc.

I have lights that take up to 6 cells at a time, so I'd rather have a DMM I feel confident with, but if sticking with single celled lights, while a better DMM is of course better, you would probably be fine with anything that read out what you needed.

Cottonpicker (CPFM) for example has a simple voltmeter for this purpose, etc.

:D

Thanks for the info, TEEJ. Do you (or any other CPF members) have Cottonpicker's little voltmeter? If so, is $12.50 still the going rate for them? I did see them listed on a different website, and will probably buy one, but would be interested to hear from other "satisfied customers" first.

 

[Bigmac_79]

Here is a thread selling Cottonpicker's charger/voltmeter combo device.

http://www.cpfmarketplace.com/mp/sh...l-Worlds-smallest-Li-ion-charger-with-display

There is probably some info in there about how well the voltmeter works, and some feedback from customers, even though it's not about the voltmeter only.

 

[Danielight]

I did a little more checking online, and found the Equus 3320 auto-ranging digital multimeter. While Cottonpicker's dedicated battery voltage tester looks good, I got to thinking that it might be nice to have a more full-featured digital multimeter for other applications. Any of you familiar with the Equus 3320? Looks like WalMart has it for about $25, and it has gotten pretty favorable reviews. I would want to use it mainly to test Li-Ions (18650 and 14500), so hopefully the battery checking function would be reasonably accurate.

 

[StarHalo]

I did a little more checking online, and found the Equus 3320 auto-ranging digital multimeter.

That's a good one, though it's overkill if you're only going to use it to check batteries; when you test Li-ion cells, you're only using the voltage measuring ability of the device, not the "battery tester", which is just for common commercial batteries.

 

[Danielight]

That's a good one, though it's overkill if you're only going to use it to check batteries; when you test Li-ion cells, you're only using the voltage measuring ability of the device, not the "battery tester", which is just for common commercial batteries.

True, but the price of Cottonpicker's battery voltage checker with shipping would be $18.50, so the price of the Equus 3320 would only be less than $8 more. As far as testing an 18650 (4.2 v), could that not also be tested on the 6 v, 9 v, or 12 v Battery Load Test settings? If not, which function would be used for 18650s? DCV?

 

[StarHalo]

As far as testing an 18650 (4.2 v), could that not also be tested on the 6 v, 9 v, or 12 v Battery Load Test settings? If not, which function would be used for 18650s? DCV?

You use the DCV setting and whatever number is closest above 4.2. Any multimeter can do this, hence the aforementioned $5 model (though this model also has a standard battery tester.)

 

[entercpf]

True, but the price of Cottonpicker's battery voltage checker with shipping would be $18.50, so the price of the Equus 3320 would only be less than $8 more. As far as testing an 18650 (4.2 v), could that not also be tested on the 6 v, 9 v, or 12 v Battery Load Test settings? If not, which function would be used for 18650s? DCV?

Why waste $25 while you can waste $5 for the same garbage? Get a cheapo $5 from Harbor Freight.

 

[Bigmac_79]

Why waste $25 while you can waste $5 for the same garbage? Get a cheapo $5 from Harbor Freight.

Because the $5 model from Harbor Freight can be very inaccurate. It might suffice for testing battery voltages, but Danielight said he wants to get a multimeter that he can use for other applications as well. I don't know about the Equus 3320 model, but in general, you get what you pay for.

 

[mattheww50]

Because the $5 model from Harbor Freight can be very inaccurate. It might suffice for testing battery voltages, but Danielight said he wants to get a multimeter that he can use for other applications as well. I don't know about the Equus 3320 model, but in general, you get what you pay for.

Sorry, but I have to chuckle. When I got my EE Degree, the only thing we had were jeweled meter movements and Vacuum Tube Volt Meters (VTVM) for very high impedance measurments, and if you had a really good one, it was +/-5% at full scale. That was considered accurate. By the time I was building Computer Peripheral Subsystems in the late 1980's, we needed 1% accuracy on the Emitter Coupled Logic Power supplies. If you really want it, you can probably buy a Keithley that is good to a few parts per million. It is hard to find a DMM these days that is worse than 1%. what you tend to get in more expensive meters is more 'bullet proof' designs. I.E. if you accidentally connect on the wrong scale the worst thing that happens is you blow a fuse.

 

[Danielight]

Because the $5 model from Harbor Freight can be very inaccurate. It might suffice for testing battery voltages, but Danielight said he wants to get a multimeter that he can use for other applications as well. I don't know about the Equus 3320 model, but in general, you get what you pay for.

Right, and I'm looking for a happy medium here. If I thought for sure that the Cottonpicker battery voltage tester was consistently more accurate than either the $5 or the $25 multimeter, I might just spring for the Cottonpicker now, and get a DMM later if I really needed it for other applications. I'm just thinking that I don't mind spending a little more now (I doubt that I'll ever be in the market for a $100 Fluke!), as long as the $25 Equus will be as accurate as the Cottonpicker for testing Li-Ion voltages before & after the battery charger.

 

[Lite_me]

If it means anything, I have both the Harbor Freight and the Equus 3320 model, plus an older Micronta (Radio Shack). In the 1.5 to 4.2v range, my Equus and Micronta are identical. The Harbor Freight reads .02-.03v higher. Close enough? Up to you. Other samples of the same tester(s) may be a bit different though, of course. This is just what mine read.

 

[Danielight]

If it means anything, I have both the Harbor Freight and the Equus 3320 model, plus an older Micronta (Radio Shack). In the 1.5 to 4.2v range, my Equus and Micronta are identical. The Harbor Freight reads .02-.03v higher. Close enough? Up to you. Other samples of the same tester(s) may be a bit different though, of course. This is just what mine read.

Thanks, Lite_me. Wife & I are heading to WalMart today anyway, so I may pick up a DMM while we're there (especially if they have the Equus 3320). WalMart is very user-friendly about returns if something doesn't work. [BTW, I do like your avitar. Is that your pug?] :wave:

 

[Lite_me]

[BTW, I do like your avitar. Is that your pug?] :wave:

ha ha... I just noticed yours. I wasn't paying attention. No, she's not mine, I'm just a tech-dog. :laughing: