Is my Imax overcharging my 3S Lipo??

bournevexed

bournevexed

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Jan 21, 2019
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Hey all!

Not sure if this is the right place! I have the malectrics spot welder which works fine & runs off of a 3S 5000mah 65-130C Lipo.
Now when i bought this Lipo it wasn't fully charged. If i remember two cells were around 3.4v & one was at 3.8v.
So I balance charged the Lipo to 12.60v(4.2 per cell) with my Imax b6 ac v2

Yet when the Imax was done I tested the voltage of the full pack & each cell with the Imax, a multimeter(UNI-T 203), & a digital battery capacity checker.

Each cell was over 4.2v.
two were around 4.219 & 4.215.v
The highest one was 4.261v

The full pack was 12.695v
Surely this isn't right? Maybe I need a new charger?

I'm charging the Lipo up again. Though it seems to be balancing the cells at the moment.
I have a feeling it won't be properly balancedwhen its done!

It finished & overall battery voltage was 12.717v.
cell01 4.227v cell02 4.223v cell03 4.267v

Either the Imax isn't balancing properly? or its the battery? I'm puzzled!!

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The balance can take hours and several tries if it was that off that you had.

But.. Is the iMax genuine or not? Its a known charger to have fakes that doesnt work properly
 
Thanks daromer I didn't know it can take several tries to get it balance!
Yes it is a genuine Imax with the sticker on the back.
I have checked the number on the website that states it is genuine!

Here is a picture of a fake.


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I dont own an imax, but I do own some pretty decent to high end chargers it should not take several tries to get it balanced It should do it on the first try, every time, but it might just take time to complete.

At the end of a balance charge, everything is perfectly balanced.

Perhaps you have some settings turned on forcing the termination based on time explore your menu options to see if such an option exists.

Another thing to consider is calibration I can and do calibrate my chargers against my Fluke DMM. Perhaps you can explore that as well.
 
Interesting, this certainly isn't right and it should work on first try. Also, it especially shouldn't go over the target voltage while trying to balance. This should never happen. Because the IMAX shows 4.20V I'd also say that it might be time to do some calibration. And make sure you're running the latest firmware.
 
Thanks Crimp DaddyYeah!! I originally thought it should balance on its 1st charge as other cells (Li-Ion & Lipo) have!

Thanks DarkRaven! I do have the latest firmware & have checked my settings after updating latest firmware!
Thecollaboration allegedly can only be done with 6 cells in series. There is a video on ytube about that.
I'll have to rig up a 6s1p pack with some 18650s to see if i can get it done.

Thing is the voltage test i did with all imax then multimeter then capacity checker were all showing over charged
voltage on each Lipo cell & overall pack voltage.

I'm just running another balance charge as I used the Lipo again earlier on the spot welder to create a 6P4S from 24 IFR26550 cells.
Here is a a few latest pics on balance charge voltage of the same Lipo.
You can see it balancing but as in previous balance charges it somehow stops balancing & over charges the cells.


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Crimp Daddy and others: the reason it takes time to rebalance some packs is when they are way out of balance. Due to a time constraint built in and the limited balancing current the time it leaves for balancing will run out. I have seen this MANY times happen. This though does not answer why voltage is way way off.
 
Oh, this is what you meant. Yeah ok, that's right, if you don't disable the time limit then you might indeed need several runs to balance the battery. I usually disable it and never thought about it. For me it's just a matter of time but it will always work first try.
 
Yes thanks daromer DarkRaven & Crimp Daddy. I am aware of thetime constraint that is built in
though i do have "safety Timer" & "Capacity Cut-Off" switched off
as i have always had it that way even after updating firmware everytime.

I think I've had this imax for around two years maybe more.

& as I was originally thinking it should've balanced this Lipo on 1st balance charge.

Talking of calibrating the charger.

Do i do this while the Lipo is in it's overcharged state?

Or do I do a small discharge to get the cells between 4.0 to 4.2v?

There is a serious amount of disinformation on ytube about calibration on these
Imax chargers. One being "you can only calibrate once".

This Lipo "brand new" cost me 60 & I do not want to kill it in any way!

I do have "safety Timer" & "Capacity Cut-Off" switched off
as i have always had it this way even after updating firmware!
 
It doesn't really matter how well charged (or overcharged) the battery is. Maybe SkyRC gives some clues about best practices for calibration. But basically it's just about adjusting the voltage measured by the charger against known good values, for example a trusted multimeter. An argument could be made that you should calibrate it at exactly 4.2V (or as close as possible) to prevent these overcharging situations in case the offset isn't exactly linear.

In any case I would discharge the battery slightly so that it isn't stored in its overcharged state.
 
Now, you seem to have a genuine B6AC, but it may be a bit off with the said cell of 60 mV.

As a vivid user of the B6AC i can say, that another possibility to solve your problem can be seen in the very first picture you sent, and in the first post in this thread, where you write:

So I balance charged the Lipo to 12.60v(4.2 per cell) with my Imax b6 ac v2
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Use the Li Ion program, it will charge nominally to 4.10, possibly to about 4.15 in your case.

Such a unit basically is no measurement Instrument, but a charger. When you check the currents, they are far more off than the voltages anyway, so dont worry.

I like the ongoing discussions about accuracy (in Voltage, Current, IR, ....), since people start to worry about what they do, and what they get from their equipment. But still - a charger is a charger, and not a measurement instrument.
 
A charger needs to be both because it can't charge reliably if its measurements are way off. And the B6 v2 is able to do much better than it does in this case so something must be wrong here.
 
DarkRaven said:
A charger needs to be both because it can't charge reliably if its measurements are way off. And the B6 v2 is able to do much better than it does in this case so something must be wrong here.
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I cannot contradict because i by myself have given the first B6AC genuine back, its currents where so way off there was nothing to use it.
 
Problem sorted!! I rigged up a 6s1p pack. Charged them up on the liitokala 1st then let them sit for a day in parallel then measured the voltage
& wrote the voltage of each cell down on paper Then created the 6 in series(spot welded). Addedmain pos & neg & then the balance wires(Soldered).
Hooked it up to the Imax b6 & then successfully calibrated the charger!
You can tell its its firing proper now!! :D :D

Thanks for your input anyway guys! :cool:
 
Awesome, I figured calibration was the culprit Nice work.

There are instances where things can leave the factory with a less than ideal calibration so its always good to check.
 
bournevexed said:
Problem sorted!! I rigged up a 6s1p pack. Charged them up on the liitokala 1st then let them sit for a day in parallel then measured the voltage
& wrote the voltage of each cell down on paper Then created the 6 in series(spot welded). Addedmain pos & neg & then the balance wires(Soldered).
Hooked it up to the Imax b6 & then successfully calibrated the charger!
You can tell its its firing proper now!! :D :D

Thanks for your input anyway guys! :cool:
Click to expand...
Can you tell me how to get the imax (genuine) into calib mode ? Thanks.
 
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