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$2.46 Battery Voltage Digital Readout — Parallax Forums

$2.46 Battery Voltage Digital Readout

ercoerco Posts: 20,259
edited 2012-02-16 09:59 in General Discussion
http://cgi.ebay.com/2S-6S-RC-Lipo-battery-portable-Voltage-Indicator-Meter-/140564441139?pt=Radio_Control_Parts_Accessories&hash=item20ba4b2833

$2.46 shipped from China. Designed for 2-6 LiPo batteries, not sure if it can be adapted for other battery chemistries or as a general DVM.

Check this seller's other interesting R/C-related items at http://shop.ebay.com/planemodel-a/m.html?_nkw=&_armrs=1&_from=&_ipg=&_trksid=p3686
batterymonitor.jpg
500 x 500 - 117K
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Comments

  • localrogerlocalroger Posts: 3,452
    edited 2011-07-05 15:46
    For general purpose use, you can get a full blown general purpose DVM form Harbor Freight for around $3 if you wait for a sale.
  • Dr_AculaDr_Acula Posts: 5,484
    edited 2011-07-05 16:59
    I love Erco's "deal of the day", and this one is a great find. Thanks!
  • ercoerco Posts: 20,259
    edited 2011-07-05 18:06
    @localroger: I love those HF Centech meters. Thanks for reminding me, I have their coupon (exp 8/14) for a FREE one with any purchase. Far better than their free LED flashlight!
  • MicrocontrolledMicrocontrolled Posts: 2,461
    edited 2011-07-06 18:07
    @erco: I had one of those multimeters, and I accidentally hooked it up backward to 30VDC (500mA) and it literally exploded. Still, very good for the cost. I now use one of their good ($20) multimeters and I love it!
  • ercoerco Posts: 20,259
    edited 2011-07-07 00:42
    @uC: There is a fuse inside that blows pretty easily. You sure you didn't (in a moment of fuseless weakness) wrap aluminum foil around a blown fuse to "fix" the problem? :)
  • MicrocontrolledMicrocontrolled Posts: 2,461
    edited 2011-07-07 05:57
    No, it fried the ground trace right off the board rather than blowing the fuse. :-)
    I opened it up and reconnected it with a thick copper wire. Then, a few weeks later, I did the same thing and it blew again. After fixing THAT I managed to blow it AGAIN a few weeks later! The knob traces were completely fried off the board, and I had to throw it out.

    So, great for low voltage, not so good for high. :-)
  • ercoerco Posts: 20,259
    edited 2011-07-07 08:34
    Look at the bright side; you three-peated your mistake and results, so you certainly got $5 worth of fireworks alone... ! AND you learned not to repeat a fourth time, n'est-ce pas?
  • GordonMcCombGordonMcComb Posts: 3,366
    edited 2011-07-07 10:01
    But if you are going to be testing batteries with a DMM be sure to do it when the batteries are under load. Most multimeters don't have a Battery Test feature that alternately places and releases a load on the battery, so the reading is a pretty inaccurate scale of the actual capacity left on the battery. Get out those resistors!

    -- Gordon
  • MicrocontrolledMicrocontrolled Posts: 2,461
    edited 2011-07-07 13:24
    @erco: I'll say! Not $5, though, I got it on sale for $3!
    The third time blew the knob off. Good times! :-)
  • iDaveiDave Posts: 252
    edited 2011-07-11 16:23
    Is this voltage readout (erco's deal) breadboardable? ...to get an in circuit voltage reading? I can't tell from the listing. But I guess for the price, what the hay
  • piguy101piguy101 Posts: 248
    edited 2011-07-11 16:59
    erco wrote: »
    ...AND you learned not to repeat a fourth time, n'est-ce pas?

    Pourquoi en fran
  • ercoerco Posts: 20,259
    edited 2011-07-16 22:08
    Got one, pretty nice. It scrolls through each cell voltage and then shows the total voltage. Haven't tried other battery types yet. I don't wanna release the magic smoke just yet...

    video at http://www.youtube.com/watch?v=TpTFLZngoNA

    Somewhat similar to this $13 "Cell Spy" unit: http://www.youtube.com/watch?v=1zleStIMkbY but cheap enough to be built in to a project.
  • ercoerco Posts: 20,259
    edited 2012-02-04 09:58
    Just tested this unit as a 5V/9V voltage monitor and it worked. No smoke! These babies aren't just for LiPos anymore. Might be handy in your Stamp/Prop projects. Pin0 to ground, Pin1 to Vdd (5V), Pin2 to Vin (9V):


    These are widely available for ~$2.31 on Ebay: http://www.ebay.com/itm/RC-Voltage-Lipo-Battery-Meter-Indicator-2-6-cells-LED-/290495353747?pt=Radio_Control_Parts_Accessories&hash=item43a2df5393

    TTYTT, I recognized the readout from ExDxV's latest video at http://www.youtube.com/watch?v=F3u0rTNBCuA He used it this way and realized I never followed up on my original post. So thanks for the unintentional kick in the pants, ExDxV! :)
  • Ron CzapalaRon Czapala Posts: 2,418
    edited 2012-02-04 13:20
    @erco,

    Have you ever found any documentation/specs on these gizmos? I wonder if they would work with 12 volts...
  • ercoerco Posts: 20,259
    edited 2012-02-04 14:03
    At the MOST, it would cost you $2.31 to find out... :)

    JK, I'll smoke test it right now...
  • ercoerco Posts: 20,259
    edited 2012-02-04 14:09
    Works fine on 12V. I just put 12V into the same Stamp2 HW board as that video, so cell No. 1 showed 5.01V, cell No.2 showed 7.25V, All showed 12.2V.

    Phew...!
  • Ron CzapalaRon Czapala Posts: 2,418
    edited 2012-02-04 14:12
    erco wrote: »
    Works fine on 12V. I just put 12V into the same Stamp2 HW board as that video, so cell No. 1 showed 5.01V, cell No.2 showed 7.25V, All showed 12.2V.

    Phew...!

    Great! How long does shipping take from China??
  • ercoerco Posts: 20,259
    edited 2012-02-04 14:14
    10-14 days to Los Angeles.
  • Ron CzapalaRon Czapala Posts: 2,418
    edited 2012-02-04 14:20
    erco wrote: »
    10-14 days to Los Angeles.

    Not too bad - I just ordered two.

    Thanks for testing it with 12V!!

    - Ron
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-02-04 14:46
    erco wrote: »
    Works fine on 12V. I just put 12V into the same Stamp2 HW board as that video, so cell No. 1 showed 5.01V, cell No.2 showed 7.25V, All showed 12.2V.

    Phew...!

    So have you tried 12V as a single cell?

    BTW, I agree, these things are great.

    I told you I used the one you gave me with a Nerf Vulcan I modified to use a 3-cell LiPo? I attached the read out to the side of the gun so I could monitor the voltage of the cells. It looked like some futuristic energy weapon.

    We had a fun Cub Scout Pack Meeting with one cub defending a flag with the gun as the other tried to capture it (the flag). It was a blast! (pun intended)

    I'm going to get a bunch more of these things. They'll probably pay for themselves by the LiPos they will save from being drained too low.
  • ercoerco Posts: 20,259
    edited 2012-02-04 17:39
    Duane Degn wrote: »
    So have you tried 12V as a single cell?

    No, I'll leave that to a braver, richer man who likes the smell of 'lektrik smoke in the morning. The Ebay description says 2-6 cells, and the intent is 3.7V lithium cells, so it should be capable of reading up to at least 6x3.7=22V, though not necessarily in one step. From what I gather, the device itself is powered from the first 3.7V cell, so the limiter is whatever its regulator can handle. Besides, it's far cooler to have it scroll thru multiple voltages!
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-02-04 18:36
    erco wrote: »
    Besides, it's far cooler to have it scroll thru multiple voltages!

    Preaching to the choir here. I have a bunch of 6-cell LiPos I use with my helicopter. I plan to get at least one of these readouts for each device I have that use LiPos or LiIons.

    There are a great find erco.
  • ercoerco Posts: 20,259
    edited 2012-02-04 19:16
    Duane Degn wrote: »
    They'll probably pay for themselves by the LiPos they will save from being drained too low.


    The meters do consume some power themselves. The chip on the back got barely warm in my tests. If it uses a linear regulator (which would be dumb by today's standards, but who knows), then it could get warmer the higher first cell voltage is. So don't let your meter drain your fancy LiPos!
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-02-04 19:23
    erco wrote: »
    The meters do consume some power themselves. The chip on the back got barely warm in my tests. If it uses a linear regulator (which would be dumb by today's standards, but who knows), then it could get warmer the higher first cell voltage is. So don't let your meter drain your fancy LiPos!

    Yes, I wouldn't leave the readout attached all the time. I might leave one on while I'm actively using the device in question. I'll unplug them when the device isn't being used.

    At the price they sell them, I doubt they're using a switching regulator.
  • ajwardajward Posts: 1,130
    edited 2012-02-14 14:15
    Just got one of these gadgets and had a "DOH!" moment. I plugged the module into my Gadget Gangster Prop USB board. The digits came on and started flashing gibberish??? After a few seconds, I thought "That looks strangely familiar." Then I realized I was holding it upside down... a genuine "Blonde Moment" if I've ever had one! :innocent:

    Amanda
  • ercoerco Posts: 20,259
    edited 2012-02-14 16:02
    Hint: Shell Oil=71077345 :)
  • Ron CzapalaRon Czapala Posts: 2,418
    edited 2012-02-16 06:35
    I wonder about the accuracy of these things. I used three 1.5v alkaline batteries to test it.
    The ground was hooked to pin0, 4.5v to pin2 and 1.5v to pin1.

    The display shows No1=2.15 No2=4.27 ALL=6.35

    A second one shows No1=2.15 No2=4.35 ALL=6.43

    Am I missing something here? Where is it getting over 6 volts with 4.5 volt supply?
    EDIT: If I switch pin1 to 3v, No1=4.27 No2=2.15 ALL=6.35

    It appears that the "ALL" value might just be a sum of the individual readings, not a reading of all the cells in series...
    But the values are high in any case.
  • ercoerco Posts: 20,259
    edited 2012-02-16 09:22
    Sounds odd, Ron. I have not tried it hooked up using lower voltages as you have. Not lots of info available on these. I know they are designed for LiPo batteries and that they get power from the first 3.7V cell on pin 1. Perhaps 3.5-3.7V is a minimum value into pin 1 to supply power. If you're using alkalines, maybe try 4.5V into pin 1, and a fourth series cell into pin 2 and report your results.
  • Ron CzapalaRon Czapala Posts: 2,418
    edited 2012-02-16 09:36
    erco wrote: »
    Sounds odd, Ron. I have not tried it hooked up using lower voltages as you have. Not lots of info available on these. I know they are designed for LiPo batteries and that they get power from the first 3.7V cell on pin 1. Perhaps 3.5-3.7V is a minimum value into pin 1 to supply power. If you're using alkalines, maybe try 4.5V into pin 1, and a fourth series cell into pin 2 and report your results.

    Actually I think they get power from pin 2 but it seems 4.5v is not sufficient.

    I tried 6V across pin 2 and I get more realistic values:
    with 1.5v on pin 1, I get No1=1.49 No2=4.66 ALL=6.08
    with 3v on pin 1, I get No1=2.98 No2=3.17 ALL=6.08
  • ercoerco Posts: 20,259
    edited 2012-02-16 09:59
    XLNT, thanks for the update.
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