CBA voltage accuracy

[jasonck08]

So I just RMA'ed my CBA III because the voltage reading at idle was .04v off (4.16v reading for a 4.20v charged Li-ion). They said they would calibrate it and sent it back.

Since they just moved, the sent a brand new replacement unit which is also off by .04v.

I'm comparing it to my brand new Fluke 179 DMM which I know is spot on because a friends unit reads the same exact voltage.

Looking at the spec page for the CBA, they claim: "0-5 volt accuracy: typically better than + - .005 volts." .04v off for a single cell Li-ion is about 3-4% off.

My question for other CBA owners, is how off is your CBA when measuring a Li-ion cell with no load? Please be sure and list what type of DMM you verified this with.

 

[SilverFox]

Hello Jacksonck08,

Sorry to hear of your issues with the CBA.

Mine is right on and has been verified with various voltmeters (Fluke, Techtronics, Extech, HP, etc...) as well as precision voltage sources.

Tom

 

[jasonck08]

Hello Jacksonck08,

Sorry to hear of your issues with the CBA.

Mine is right on and has been verified with various voltmeters (Fluke, Techtronics, Extech, HP, etc...) as well as precision voltage sources.

Tom

Wow, I'm surprised to hear that its spot on. Do you have the pro version or regular version?

Also CBA II or III ?

 

[SilverFox]

Hello Jasonck08,

It's actually a CBA... The original version.

Tom

 

[HKJ]

You have to be careful how you measure the voltage, when discharging a battery it is very easy to have a 0.04 volt drop in the wires!
I.e. you have to check voltage when current is 0 to get full accuracy.

 

[jasonck08]

HKJ if you refer to my first post I stated that the voltage reading at idle was .04v off (ie. no load).

I'm fully aware that there is voltage drop across the wires, especially at higher currents.

Also, you have a CBA don't you? How accurate is yours?

 

[LuxLuthor]

My CBA-II software (Ver 2.1.0.18 Pro) reports 0.03V to 0.04V higher than Fluke 189 or 179 actual readings of cell clamped in holder when not under discharge load--just the opposite of what you are seeing. That variation at rest is true with all Li-Ion cells when compared sitting idle.

However the Pro version has a calibrate voltage function normally designed to add a resistance adjustment to address voltage drop for your setup. It would normally assume you need to add a positive resistance Ohm number based upon the CBA reported vs. DMM measured readings, but in my case, I have the resistance set to a small negative Ohm reading (i.e. -0.006 to -0.015 Ω depending on discharge current variable). It always asks me if I am sure I want a negative Ohm calculated value when I save a new one depending on the intended current discharge run.

This adjustment does not change the incorrect idle CBA reported reading without load, but once I start the discharge load test, the DMM and CBA reported voltage values are then perfectly matched throughout the run from that stored Ohm adjustment which is the important thing.

I saw no point to go through a return just to get matching Voltage readings at rest, which is nearly irrelevant. I resolved this question by phone when they pointed out the use of the Pro version calibration tool.

 

[jasonck08]

I'm fully aware that there is a Pro version that allows you to calibrate the voltage.

But to pay $100 for the Pro software, because my unit is out of spec is ridiculous! I already sent it back only to receive a unit with the same issue! Money wasted + 2 weeks without my CBA = Unacceptable.

End of rant.

 

[LuxLuthor]

I'm fully aware that there is a Pro version that allows you to calibrate the voltage.

But to pay $100 for the Pro software, because my unit is out of spec is ridiculous! I already sent it back only to receive a unit with the same issue! Money wasted + 2 weeks without my CBA = Unacceptable.

End of rant.

You asked for feedback on our readings which I provided, and now you rip on me trying to be helpful by mentioning the Pro version's calibration adjustment when you didn't mention only having the non-Pro software? :thumbsdow

You may wish to consider the wisdom of ranting about not being willing to spend the money to do accurate, calibrated discharge graphs when starting a battery selling business. Doesn't sound too professional.

For others who are not "fully aware," the Pro software calibration adjustments allow you to compensate for a variety of battery holder/test lead resistances, current, temperature, etc. Almost all electronic devices lose factory calibration over time, so it is great to have the capability of doing your own calibrations. There are a number of other functions added with the CBA Pro software, and I'm glad I paid the $40 introductory rate to upgrade when first offered.

 

[HKJ]

HKJ if you refer to my first post I stated that the voltage reading at idle was .04v off (ie. no load).

I overlooked that small word.

I'm fully aware that there is voltage drop across the wires, especially at higher currents.

Many people forget that.

Also, you have a CBA don't you? How accurate is yours?

I have just checked at 4 volt it is 0.04 volt below my Fluke meters.

 

[jasonck08]

You asked for feedback on our readings which I provided, and now you rip on me trying to be helpful by mentioning the Pro version's calibration adjustment when you didn't mention only having the non-Pro software? :thumbsdow

You may wish to consider the wisdom of ranting about not being willing to spend the money to do accurate, calibrated discharge graphs when starting a battery selling business. Doesn't sound too professional.

For others who are not "fully aware," the Pro software calibration adjustments allow you to compensate for a variety of battery holder/test lead resistances, current, temperature, etc. Almost all electronic devices lose factory calibration over time, so it is great to have the capability of doing your own calibrations. There are a number of other functions added with the CBA Pro software, and I'm glad I paid the $40 introductory rate to upgrade when first offered.

I did not mean to sound like I was directing my post at you directly. I appreciate what you posted. My post was more of a rant directed towards WMR. I'm just stating the fact that paying extra money to correct a problem that shouldn't have been an issue (if I was sold a product that was within manufacturer specs), is not a true solution.

If I was offered a $40 upgrade initially, I may have accepted it. But the $100+ that they want currently doesn't float my boat (especially since I probably won't use the other features it offers. Just voltage calibration). I'll wait for their email response to my issue and update this thread with what happens.

My sincere apologies Lux, I did not mean to offend or attack you.

----------------

@ HKJ - sounds like our meters are exactly the same... .04v off when measured by a fluke.

 

[LuxLuthor]

Thanks. That resolves it completely for me. :thumbsup:

 

[march.brown]

I find that the easiest way to check the accuracy of any digital voltmeter is to check it against a 'Precision Voltage Reference Source' rather than check it against another meter ... Mine is a 5.000V 0.02% device ... It actually measures 5.0002V at 72 Farenheit ... It cost $14-55 plus postage from America.

I realise that my two DMM's are not in the same price range as the Flukes etc , but I can at least see how far out they are and allow for it in the readings.
.

 

[bcwang]

When I first got my CBA-II it also showed like .04v off when there was no battery. I had to send it in to be calibrated and ever since it's been exactly at 0v with no battery.

Maybe they don't test and calibrate each one after manufacturing until the customer complains, then they'll calibrate yours.

 

[jasonck08]

When I first got my CBA-II it also showed like .04v off when there was no battery. I had to send it in to be calibrated and ever since it's been exactly at 0v with no battery.

Maybe they don't test and calibrate each one after manufacturing until the customer complains, then they'll calibrate yours.

Interesting... Thanks for your post. I guess I'll wait for their response and propose that maybe they do a cross shipment for one that they actually calibrate. The one they just sent me was NIB and probably was not calibrated since it left the factory.

WMR apparently moved to another State recently, and may have been acquired by another company.

 

[VegasF6]

If I was offered a $40 upgrade initially, I may have accepted it. But the $100+ that they want currently doesn't float my boat (especially since I probably won't use the other features it offers. Just voltage calibration). I'll wait for their email response to my issue and update this thread with what happens.
.

I do see your point Jason, I would expect greater accuracy as well. But, just to point out one more thing, You state "I probably won't use the other features it offers." I can tell you one feature you are already attempting to use:
CBA III Pro

Same as CBA III plus:

• Calibration data
• 1 yr limited commercial use warranty

In a commercial use situation, the non-pro version warranty isn't valid.