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Thread: Voltmeter mandatory for 18650?

  1. #1

    Default Voltmeter mandatory for 18650?

    I was going to buy one to harvest the 18650s from my laptop battery but when I opened it I found out they were some chinese DLG brand from 2011. Im assuming im better off not bothering trying to salvage any cells so I ordered some sanyo and samsung 18650s. Do I need to measure the voltages they come in new and should I wait to use them until I can verify the voltages?

    Im planning to use all of the batteries in single cell power banks. Are the chinese batteries in my laptop pack completely out of the question?

  2. #2

    Default Re: Voltmeter mandatory for 18650?

    Definitely get a decent DMM to measure voltage. $10-$15 will get you a pretty good one.

    You don't have to check them when they arrive, especially if from a reputable dealer, but it would be smart. I like to just to make sure everything is OK. They should arrive around 3.7v or so. Charge them up and start using them.

    Personally, I wouldn't have a problem using the laptop batteries if they took a charge up to around 4.2v and held that for a couple days without use (say 4.19v after checking them 2 days later). But the safe thing would be to pass on that. Depending on the laptop use, they may be worn to a point where it's just not worth the hassle.
    GOOD TINT!

  3. #3

    Default Re: Voltmeter mandatory for 18650?

    mandatory-no, good idea-yes.

    i threw away 2 cheap dmms, they were in 15-20 bucks range. but if you only need to mesure volts of li ion cells, you can get a small, 2 wire voltmeter. they are less than $5 on ebay.

    http://www.darksucks.com/Images/Sale...tmeter-lit.jpg

  4. #4
    ven's Avatar
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    Default Re: Voltmeter mandatory for 18650?

    [QUOTE=alpg88;4766661]mandatory-no, good idea-yes.

    +1

    Lot of decent chargers these days have V readouts, however its always good to have a reliable meter at hand to check against.

  5. #5
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    Default Re: Voltmeter mandatory for 18650?

    As advised above, a multimeter is a good thing to have, but not required.

    As far as you harvesting batteries from a laptop, go for it if they are to be used in a single cell light or powerbank. I take it you're going to use the PB to charge a cellphone?

    It ain't a big deal if the only last a couple of weeks before self discharging. Once they get to the point that they only last a week with infrequent use, toss um.

  6. #6
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    Default Re: Voltmeter mandatory for 18650?

    [QUOTE=ven;4766665]
    Quote Originally Posted by alpg88 View Post
    mandatory-no, good idea-yes.

    +1

    Lot of decent chargers these days have V readouts, however its always good to have a reliable meter at hand to check against.
    Key word reliable. I almost returned a brand new light to Fenix as defective, when what was really defective was my co-worker's DMM that said the battery was charged.

  7. #7
    Flashaholic Megatrowned's Avatar
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    Default Re: Voltmeter mandatory for 18650?

    If you want something simple, cottonpickers can make you a volt meter (sans charger) for a good price. It's very easy to use. Two wires with two magnets. Stick them on your battery and it reads the voltage
    Welcome to the Dark Side! Which just also happens to be the Light Side.

  8. #8

    Default Re: Voltmeter mandatory for 18650?

    Quote Originally Posted by Megatrowned View Post
    If you want something simple, cottonpickers can make you a volt meter (sans charger) for a good price. It's very easy to use. Two wires with two magnets. Stick them on your battery and it reads the voltage

    Tell me more lol

    Also thanks everyone for the replies. Yeah they will be used to charge smartphones

  9. #9

    Arrow Re: Voltmeter mandatory for 18650?

    Hold on a second ... .... here we are spending $25-$100+ on these lithium ion flashlights and how important is our safety? Explosions, houses burning down and such, I know I'm being extreme, but...why not spend a little money and buy a good quality meter like a Fluke 87 or even an older used model 77? You can find them for $25-$75 depending on the model and they are useful for all kinds of things (measuring resistance, continuity, VAC, VDC, current, diodes). That's the cost of one good flashlight, but it's a great investment really. It's something you can use for years to come and in many applications. Just my 2 cents, thank you and good luck.

  10. #10

    Default Re: Voltmeter mandatory for 18650?

    Hell, you could even use a good charger like the Xtar VP2 (~$32) which gives the voltage. Always accurate in my experience. But really, $15-20 for a good DMM and you're good to go.

    INNOVA 3320 Auto-Ranging Digital Multimeter is a good one.

    GOOD TINT!

  11. #11

    Default Re: Voltmeter mandatory for 18650?

    Quote Originally Posted by Dr. Tweedbucket View Post
    Hold on a second ... .... here we are spending $25-$100+ on these lithium ion flashlights and how important is our safety? Explosions, houses burning down and such, I know I'm being extreme, but...why not spend a little money and buy a good quality meter like a Fluke 87 or even an older used model 77? You can find them for $25-$75 depending on the model and they are useful for all kinds of things (measuring resistance, continuity, VAC, VDC, current, diodes). That's the cost of one good flashlight, but it's a great investment really. It's something you can use for years to come and in many applications. Just my 2 cents, thank you and good luck.

    That's exactly what I'll be doing soon - buying an older, used Fluke cheap from Ebay. Why not? They're inexpensive and will probably last a long time.

  12. #12

    Default Re: Voltmeter mandatory for 18650?

    Aren't most battery testers cheaper and more accurate than most multimeters? In an older thread most people recommended battery load testers. You can't get that accuracy with a multimeter unless you use a separate resistor together with the multimeter. Unfortunately, I don't know what battery tester to recommend. Mine has no screws and may be glued together and I can't confirm there's a resistor inside for checking batteries under load. I'm assuming there is. They cost about $8.

  13. #13
    Flashaholic* kosPap's Avatar
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    Default Re: Voltmeter mandatory for 18650?

    I would suggest looking ahead.
    Soon enough the OP will find himself measuring current draw, etc...
    so if money is no issue get a decent one. not cheap but not expensive either
    Else buya cheap one.

  14. #14

    Default Voltmeter mandatory for 18650?

    I would also recommend one further and further into this hobby as it comes in handy, especially if you are into electronics. It's also good for safety, better safe than sorry sometimes, A $15 DMM could save you a disastrous multi-thousand dollar house burning down (on the extreme side).

    A cheap $10-$20 AUTO-RANGING (good idea to get auto-ranging, it saves a heap of time) should do the job for now. I'd say get it off your local electronics store or an trusted online dealer .

  15. #15

    Default Re: Voltmeter mandatory for 18650?

    Something like this is extremely accurate and less than $50

    http://www.ebay.com/itm/Fluke-77-DMM...4AAOSwhcJWM81o

    The only problem is these should be periodically calibrated, but really all I would do is check it against a new alkaline energizer which should come in right at 1.6VDC. If that's what you're reading, you know you are +/- about a tenth of a volt. When we're talking about 18650s not exceeding 4.2 VDC, you need that kind of accuracy.

    The idea of the Xtar chargers with the volt meter is also an excellent idea. Still, I'd rather have a VOM in addition just to use for other things, they are so handy. I have a couple of Flukes and they are of very good quality!

  16. #16
    ven's Avatar
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    Default Re: Voltmeter mandatory for 18650?

    Good chargers are usually + or - (1%) so to be exact 0.042v, for ease 0.05v so 4.15-4.25v is in spec Of course closer to 4.2v is better,ideally even a bit under. Most cells will settle to under 4.2v after being stood.

  17. #17

    Default Re: Voltmeter mandatory for 18650?

    I was looking at Greenlee multimeters and even for the autoranging PDMM-20 there's the warning "Electric shock hazard: Do not change the measurement function while the test leads are connected to a component or circuit." I'm afraid I'll forget about that.

  18. #18

    Default Re: Voltmeter mandatory for 18650?

    I just put mine on auto ranging and let it do it's thing. Don't forget the meter leads, there are a lot of crappy leads out there that will skew your results, so buy good quality leads/probes too!

  19. #19
    *Flashaholic* ChrisGarrett's Avatar
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    Default Re: Voltmeter mandatory for 18650?

    Mandatory if you're going to play with lithium-ion anything. Heck, even primaries benefit from having a DMM.

    If you're going to cheap out, cheap out on toilet paper and napkins.

    Chris
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  20. #20
    Flashaholic* MidnightDistortions's Avatar
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    Default Re: Voltmeter mandatory for 18650?

    Quote Originally Posted by ChrisGarrett View Post
    Mandatory if you're going to play with lithium-ion anything. Heck, even primaries benefit from having a DMM.

    If you're going to cheap out, cheap out on toilet paper and napkins.

    Chris
    Totally agree, i make it mandatory to have a DMM regardless of the battery type. You never know when you need it and it's great to test your car battery with, though a DMM won't tell you the whole story of how your car battery is doing.
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  21. #21

    Default Re: Voltmeter mandatory for 18650?

    Quote Originally Posted by ven View Post
    Good chargers are usually + or - (1%) so to be exact 0.042v, for ease 0.05v so 4.15-4.25v is in spec Of course closer to 4.2v is better,ideally even a bit under. Most cells will settle to under 4.2v after being stood.

    My meter (which I've always called a VOM Volt Ohm Meter, not sure what DMM stands for) consistently reads a little higher than what my Nitecore D2 charger says. For instance my latest battery acqusition, 2 EVVA 18650s at 3500mAh both read exactly 3.75 volts on my meter but when I put them in the D2 to top them off the D2 read their voltage as 3.66 volts. Is this within normal margin of error? Should I get a new VOM or is my D2 wrong?


    edit: Ok, I guess "DMM" is digital multimeter. Funny how a new designation can fool one. Guess I'm a little old school and VOM was before we had digital.
    Last edited by Short_Circuit; 11-01-2015 at 10:52 PM.
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  22. #22
    *Flashaholic* ChrisGarrett's Avatar
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    Default Re: Voltmeter mandatory for 18650?

    Quote Originally Posted by Short_Circuit View Post
    My meter (which I've always called a VOM Volt Ohm Meter, not sure what DMM stands for) consistently reads a little higher than what my Nitecore D2 charger says. For instance my latest battery acqusition, 2 EVVA 18650s at 3500mAh both read exactly 3.75 volts on my meter but when I put them in the D2 to top them off the D2 read their voltage as 3.66 volts. Is this within normal margin of error? Should I get a new VOM or is my D2 wrong?
    Digital Multi-Meter.

    DMM.

    You need one.

    They're mandatory for anything 'battery,' IMO.

    Chris
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  23. #23

    Default Re: Voltmeter mandatory for 18650?

    Double post sorry.
    Last edited by Short_Circuit; 11-01-2015 at 10:52 PM.
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  24. #24

    Default Re: Voltmeter mandatory for 18650?

    Quote Originally Posted by ChrisGarrett View Post
    Digital Multi-Meter.

    DMM.

    You need one.

    They're mandatory for anything 'battery,' IMO.

    Chris

    Thanks Chris, I do have one I was just wondering about the different readings on my meter vs the one on the D2 charger.
    Half of being smart is knowing what you're dumb at.

  25. #25
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    Default Re: Voltmeter mandatory for 18650?

    Quote Originally Posted by Short_Circuit View Post
    Thanks Chris, I do have one I was just wondering about the different readings on my meter vs the one on the D2 charger.
    How old are the batteries in the meter?

    Some meters can become remarkably inaccurate when the batteries are starting to fall off a bit, even before the low battery indicator (if any) comes on.
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  26. #26
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    Default Re: Voltmeter mandatory for 18650?

    Quote Originally Posted by Short_Circuit View Post
    Thanks Chris, I do have one I was just wondering about the different readings on my meter vs the one on the D2 charger.

    The manufacturers tolerance on most consumer DMM or VOM units is fairly large, especially when measuring low voltages and ohms.

    As Ven posted above, a tolerance of +/_ 1% of the scale is enough to make a final determination on voltage to two or three decimal places meaningless.

    Add in the variation of the meter and the variation of the D2 charger and you fall in around +/_ 3.5%.

    You asked if your meter was any good? It falls within the industry standard, so measure away.

  27. #27

    Default Re: Voltmeter mandatory for 18650?

    Quote Originally Posted by Phlogiston View Post
    How old are the batteries in the meter?

    Some meters can become remarkably inaccurate when the batteries are starting to fall off a bit, even before the low battery indicator (if any) comes on.

    That's a good question and I'm not real sure. I suspect it's been awhile as till recently I have not used it all that much. I think it takes either one or two AA Alkaline batteries which tend to last several years in storage and I generally use either Duracell , Energizer or Ray-O-Vac alkalines. Just for the heck of it I'll put new batteries in it and see if my readings change any though in the past it's usually worked fine right up till it quits. But thanks for reminding me.

    Quote Originally Posted by NoNotAgain View Post
    The manufacturers tolerance on most consumer DMM or VOM units is fairly large, especially when measuring low voltages and ohms.

    As Ven posted above, a tolerance of +/_ 1% of the scale is enough to make a final determination on voltage to two or three decimal places meaningless.

    Add in the variation of the meter and the variation of the D2 charger and you fall in around +/_ 3.5%.

    You asked if your meter was any good? It falls within the industry standard, so measure away.
    Thanks for the info NNA!
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  28. #28
    Flashaholic* kosPap's Avatar
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    Default Re: Voltmeter mandatory for 18650?

    guys we forgot a strong reason for getting a DMM when using li-ions
    That of finding the charge state of the battery by measuring its voltage.

    that is SO convenient for new users especially.

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