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Calibrating, Synchronizing Volt Meters
#1
They say a person with one clock knows what time it is. But a person with many clocks does not. Seems the same is true for tools that measure voltage.
When you have 3 volt meters, and they give 3 different readings on the same cell, how do you know which one is right? The one that cost the most money?

I'm in between batches of cells at the moment, and I'm taking a break to improve my methods and equipment. I've got 6 tools now that need to measure voltage accurately, and they don't all agree with each other. So the good news is that the Opus, iMax clone, and my Innova multimeter all agree within 1/100V. So I'm starting with the assumption that they are accurate. Especially because I don't know if the Opus can be calibrated.

Two other tools are also multimeters; cheaper than the Innova, and the voltage can be adjusted by a potentiometer on the circuit board.
[Image: 1214209efe396b3ba79248b17b08ff08.jpg]

Synchronized!
[Image: 915719a55c316bb5aa4a6729667d1111.jpg]

I'm also collecting some voltage displays so I don't have to keep using the multimeters for everything. Very important to get the ones with an adjustment pot on the back, as well as a separate power input if you want to read voltages of less than 3V. I've learned this the hard way...
[Image: 781faf553e6b1d030077fee543d00da3.jpg]

Synched!
[Image: 7e9d370cf22fdb465cb87b17872711d1.jpg]

So my last tool that needs calibrating is one I haven't figured out yet. Maybe you guys can help?
I just bought a genuine SkyRC iMax B6 mini from Amazon. The new model with the USB port. Its about 1/4 Volt low compared to the other meters, and as a consequence is charging the cells about 1/4 Volt too high. I can kind of live with this for now by using the LiIon setting, but it sure would be nice to have all my tools agree with each other. I've tried searching Google and You Tube but those methods work with the clones and not with the genuine iMax's.
-Mike G
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#2
Nice write up on the syc'n of the MM's. I didn't realize they could be adjusted like that (especially the cheapo's from harbor freight or china). I'll definitely take mine and check them against each other to verify they are in sync with each other.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Dollar Shave Club. Best Razor I've ever used
Certified 18650 Cell Reclamation Technician
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#3
I've continued to look into the question of actual calibration rather than just syncing meters. From what I've read, there are 3 ways to go about it.
- Send your meter to a professional for proper calibration (expensive)
- Set up an elaborate system involving heaters, water, thermometers and get a calculated voltage (complicated)
- Get a voltage reference circuit board and read that. (cheap and simple)

I went with option #3. Amazon has this little reference board that runs on a couple 9Vs in series and makes a range of voltages that you can read with multimeter probes.
[Image: 3ba2bb64e42b10c0d9d646c77d742c74.jpg]

It came with a handy little reference sticker which lists what the tester guy found when compared with super accurate measuring equipment. For example, on the 2.5V setting, my little board had 2.49997V. My meter read 2.51V, and I'm calling that close enough for reasons I'll explain later. The reference board also does voltages of 5, 7.5, and 10V. Selected by a little switch on the board.

So, a fun gadget, probably unnecessary, especially if you have access to an expensive meter which was probably very carefully calibrated already.

Speaking of expensive vs. cheap multimeters. I opened up my Innova meter to see if I could set it a little closer to the reference board, but I found that it has 3 pots instead of one:
[Image: 20fc914e42c13d02296b59737cda0a81.jpg]

I don't mean to say that this is an expensive meter, but it is a little higher end than the super cheap ones, and it did cost a little more. But as its slightly higher quality, its also slightly more complicated to adjust. I've not been able to find out yet which pot is the voltage adjuster. So I'm leaving it alone for now.

Moving on from actual multimeters, I decided to see if my Opus BT-C3100 could be calibrated. As far as I know, it has no calibration function in the software, and I don't see any pots on the circuit board. But I had it open, so I took pictures just for fun.
[Image: cd7328f62957007537169c0ca7e9a53c.jpg]
[Image: a5a4fc0f15930dbc832264f5f6e11378.jpg]

I did find a switch on the back labeled 4.2V, 4.35V, and 3.7V. I assume those are to select the top voltage you want the charger to charge the cells? Its got me curious, so I'll have to look into it sometime.
[Image: 8755b2ef4ee7d60dd1ade7a3139c9982.jpg]

For the iMax B6 clone, here's a video that explains it better than I could:




I don't think this works on the genuines though. I did it on my B6AC clone, but the B6 mini I have is a genuine, and I haven't successfully gotten into a calibration mode yet.
not2bme likes this post
-Mike G
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#4
Nice, looks good. In your last picture of the innards of the opus, that's the setting you use when changing from LiCo's to LiFePo cells, since the LiFePo cells only go up to 3.7V to begin with. Not sure about the 4.35V, though.

I did calibrate my 3 MM's against each other (they weren't far off; about .1V). Those pots are sensitive. Barely move them and the gauge moves .10's of volts.

But I think I might get that calibration tool you mentioned. What's the URL of the one you got?

Thanks for the info! Smile
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Dollar Shave Club. Best Razor I've ever used
Certified 18650 Cell Reclamation Technician
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#5
4.35V is for LiHV cells, simply cells that must charge until that voltage to get the rated capacity.

http://www.diypowerwalls.com/showthread.php?tid=1751
Korishan likes this post
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#6
A breakthrough! But more on that later.

Here is the link to the voltage reference board I found: DROK AD548 Precision Voltage Reference.
One guy in the reviews said the on/off switch is labeled backwards. This was the case for me.
Another said his came with the capacitor wired in backwards. I don't know enough to check that, but mine seems to work fine.

So the breakthrough...
I bought a genuine SkyRC iMax B6 mini a couple weeks ago, and I've been trying to calibrate it ever since. So it finally happened today!
Its not like calibrating the clone iMax's. Way more picky. I'm so excited that I went and made a video:





Here's the gist of it.
- Make sure the firmware is updated to at least v1.13.
- You'll need a 6s battery to plug into the balance port.
  - Gotta be 6s or it won't work.
- You'll need to make sure the 6s battery is at or near fully charged
  - Cells have to be at least 4V or it won't work. I'm not sure what the cutoff is.
- Set the menu to Battery Meter
- When you're in Battery Meter and you see all 6 cells showing voltage, press and hold Enter/Start for around 6 seconds.
  - This was the part I couldn't get to for what seemed like ages!
- From there, the Dec. and Inc. buttons will let you adjust each cell voltage till it matches what you find on a trusted volt meter.
- Enter/Start moves you from one cell to another.
- When you're done, press and hold Enter/Start for another 6 seconds or so till you get a calibration save message.

That should be it! I'm super excited to share this because I couldn't find this procedure anywhere on the internet. There are bits of it out there, but I had to piece it together myself from multiple sources. I put the 6s battery through the LiPo charge setting again and this time it came out right where it should have. Within about 1/100V of my meter, which is close enough for me.
mormor1971 likes this post
-Mike G
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#7
(07-20-2017, 08:24 PM)rebelrider.mike Wrote: A breakthrough! But more on that later.

Here is the link to the voltage reference board I found: DROK AD548 Precision Voltage Reference.
One guy in the reviews said the on/off switch is labeled backwards. This was the case for me.
Another said his came with the capacitor wired in backwards. I don't know enough to check that, but mine seems to work fine.

So the breakthrough...
I bought a genuine SkyRC iMax B6 mini a couple weeks ago, and I've been trying to calibrate it ever since. So it finally happened today!
Its not like calibrating the clone iMax's. Way more picky. I'm so excited that I went and made a video:





Here's the gist of it.
- Make sure the firmware is updated to at least v1.13.
- You'll need a 6s battery to plug into the balance port.
  - Gotta be 6s or it won't work.
- You'll need to make sure the 6s battery is at or near fully charged
  - Cells have to be at least 4V or it won't work. I'm not sure what the cutoff is.
- Set the menu to Battery Meter
- When you're in Battery Meter and you see all 6 cells showing voltage, press and hold Enter/Start for around 6 seconds.
  - This was the part I couldn't get to for what seemed like ages!
- From there, the Dec. and Inc. buttons will let you adjust each cell voltage till it matches what you find on a trusted volt meter.
- Enter/Start moves you from one cell to another.
- When you're done, press and hold Enter/Start for another 6 seconds or so till you get a calibration save message.

That should be it! I'm super excited to share this because I couldn't find this procedure anywhere on the internet. There are bits of it out there, but I had to piece it together myself from multiple sources. I put the 6s battery through the LiPo charge setting again and this time it came out right where it should have. Within about 1/100V of my meter, which is close enough for me.
Just happened to come across this while browsing through. Great job on getting access to the calibration menu on the b6 mini. I have 4 of them. I looked for weeks on how to fix them after realizing that they weren't giving the correct voltages.

This was also throwing off the capacity testing as well, which turn me over to using the Liitos that I was hesitant to use because of heating issues. I haven't used the mini's since then, ~8 months ago. Lol

I'm definitely going to get these guys calibrated and back into action. Thanks for the great work! [emoji367][emoji7]
Cell progress: 2016/10/17:
180cells@2.0
600cells@2.1-2.6a
70cells@2.7a+

Projects:
Mobile PowerBox
8Kw Powerwall
Insight Parallel PowerPak
1Kw PowerBlade
PowerRack (concept)
12v LED Sconce
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#8
Thanks!
My genuine iMax still doesn't show correct overall voltage. Plenty close enough for ordinary charging, but for testing I'm favoring the clone. I think some clones are better than others though. Whoever made mine seems to have put some effort into making it a decent charger.
BlueSwordM likes this post
-Mike G
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#9
Wait, a clone is actually better than the original? First time I've heard that for an electronic product.
It's better to over engineer something than to cheap out.
As I say: You pay once, you cry once.
                                 You pay multiple times, you are a doofus
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#10
awesome my charger was overcharging my cells to 4.22. now it's fixed!
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