weirdness with accucel 8...

[jmpaul320]

been trying to do some charges/discharges with li-ion today… the voltage seems to be reading .3-.5v lower than my DMM when put under a 1-3a load… i have no idea why. i tried different leads with magnets and it did not help.

the charging cycle seems to terminate around 4.15v too… not 4.2…

i do not see this behavior when charging nimh (i usually charge at a lower current)… i dont quite understand what could be causing the voltage drop? maybe my banana plugs have crappy wires that cause voltage drop with higher currents?

i have a li-ion i am discharging now… its reading 3.26v (discharging at 3.5 amp - done to exaggerate the effect i am having)… if i put my DMM leads on the battery it reads 3.77v

here is a photo for reference…

i can provide more info if needed

ive had the charger for a few months… ive mostly used it for my mag 458 pack of 16 aa nimh batteries… and some times i would quick charge some imrs at 3amps to 4.1v then switch them to an ultrafire charger to top off to 4.2

[scaru]

When you say the charger is reading lower than your DMM, did you take the measurements at the same time?

[jmpaul320]

@scaru

When you say the charger is reading lower than your DMM, did you take the measurements at the same time?

yes sir - put the leads on the battery while it was discharging

[scaru]

Then that rules out my first guess, have you tried measuring through the leads used on the charger? My DMM uses the same banana plugs as my accucel 6.

[jmpaul320]

@scaru

Then that rules out my first guess, have you tried measuring through the leads used on the charger? My DMM uses the same banana plugs as my accucel 6.

cell read 3.8v with both sets just now

[scaru]

Ok, so that means the leads aren't the problem. The voltage measuring chip in the charger is messed up.

[jmpaul320]

@scaru

Ok, so that means the leads aren’t the problem. The voltage measuring chip in the charger is messed up.

great…. i should have checked this out when i first bought it… ive had it for long enough where hobby king probably doesnt want to know anything about it

[AlexGT]

Calibrate the charger by pressing the Enter and -Dec button while being powered up, then adjust the voltage to match your multimeter, try it and report back

You might also want to clean all the contacts in your charger with the de-oxit

[Electroman187]

Sounds like you’re getting an IR drop on your connection leads. Does it do the opposite when charging? How about during no current flow?

[jmpaul320]

@Electroman187

Sounds like you’re getting an IR drop on your connection leads. Does it do the opposite when charging? How about during no current flow?

yes, when charging it stops at 4.11-4.15 and says its at 4.20 (Early termintation while charging and discharging)

[jmpaul320]

@AlexGT

Calibrate the charger by pressing the Enter and -Dec button while being powered up, then adjust the voltage to match your multimeter, try it and report back

You might also want to clean all the contacts in your charger with the de-oxit

went to adjust voltage… DMM read 4.22v charger read 4.21v

i left it alone

i put the fresh cell on the charger to discharge… within 10 seconds the voltage dropped from 4.2 to 3.7 and then it dropped to 3.39 at 1 minute dmm reading 3.77v at 1 min

contacts look brand new as the charger is only a few months old… hmmm

edit: it definitely sounds like an IR drop

[tatasal]

During charging or discharging in a hobby charger, there is always a discrepancy between the voltage of the cell being being charged/discharged compared to the voltage reading coming from the hobby charger since it takes a while for the electrical energy being put into the cell to be converted into chemical energy inside the cell.

As for the the terminal voltage on the cell involved, one of the factors is the health of that cell. The charger might terminate at 4.19 to 4.2v, but the cell will quickly drop to 4.15v or even lower, depending on the health of the cell.

On an ‘unhealthy’ (meaning significantly low mAh capacity) of the cell, a discharge rate of 3A is too high, making the charger display ‘done’ much earlier. In my case, I have an SC600. Its Turbo mode lasts exactly 5min, 3 secs on a ‘healthy cell’. Putting in an ‘unhealthy’ cell, that cell cannot finish the entire 5min without dropping to HIGH, although that cell had come out at 4.2v off the charger.
It simply shows its ‘unhealthyness’ when put under load.

In short, the weirdness of your charger might be caused by a bad cell…

[jmpaul320]

@tatasal

During charging or discharging in a hobby charger, there is always a discrepancy between the voltage of the cell being being charged/discharged compared to the voltage reading coming from the hobby charger since it takes a while for the electrical energy being put into the cell to be converted into chemical energy inside the cell.

As for the the terminal voltage on the cell involved, one of the factors is the health of that cell. The charger might terminate at 4.19 to 4.2v, but the cell will quickly drop to 4.15v or even lower, depending on the health of the cell.

On an ‘unhealthy’ (meaning significantly low mAh capacity) of the cell, a discharge rate of 3A is too high, making the charger display ‘done’ much earlier. In my case, I have an SC600. Its Turbo mode lasts exactly 5min, 3 secs on a ‘healthy cell’. Putting in an ‘unhealthy’ cell, that cell cannot finish the entire 5min without dropping to HIGH, although that cell had come out at 4.2v off the charger.
It simply shows its ‘unhealthyness’ when put under load.

In short, the weirdness of your charger might caused by a bad cell…

very interesting… thanks for the input… ive cycled two sanyo 2600 mah cells a few times today and noticed that they seemed to slowly get better… probably due to being stored at 3.7-3.8v for 2 months… i dont think the cells are “bad” per se they charged to 4.18-4.2v on a different charger and held that voltage over night… i bought them new in may of this year and prob cycled both a dozen or so times…

but still - this is very useful information… i will try some newer panasonics soon to see if i get any different results

[tatasal]

@jmpaul320

@tatasal

During charging or discharging in a hobby charger, there is always a discrepancy between the voltage of the cell being being charged/discharged compared to the voltage reading coming from the hobby charger since it takes a while for the electrical energy being put into the cell to be converted into chemical energy inside the cell.

As for the the terminal voltage on the cell involved, one of the factors is the health of that cell. The charger might terminate at 4.19 to 4.2v, but the cell will quickly drop to 4.15v or even lower, depending on the health of the cell.

On an ‘unhealthy’ (meaning significantly low mAh capacity) of the cell, a discharge rate of 3A is too high, making the charger display ‘done’ much earlier. In my case, I have an SC600. Its Turbo mode lasts exactly 5min, 3 secs on a ‘healthy cell’. Putting in an ‘unhealthy’ cell, that cell cannot finish the entire 5min without dropping to HIGH, although that cell had come out at 4.2v off the charger.
It simply shows its ‘unhealthyness’ when put under load.

In short, the weirdness of your charger might caused by a bad cell…

very interesting… thanks for the input… ive cycled two sanyo 2600 mah cells a few times today and noticed that they seemed to slowly get better… probably due to being stored at 3.7-3.8v for 2 months… i dont think the cells are “bad” per se they charged to 4.18-4.2v on a different charger and held that voltage over night… i bought them new in may of this year and prob cycled both a dozen or so times…

but still - this is very useful information… i will try some newer panasonics soon to see if i get any different results

Li-Ion cells does not benefit from repeated charge/discharge cycles like niMh, it only hastens its demise. If the concerned cells are charging up to to 4.2V on the other charger, I would suggest trying on the newer Panasonics first to further isolate the problem through more process of elimination. Have you tried getting the discharge capacity of the concerned cell on the hobby charger, but charged to 4.2V on the other charger? Or in the end, your Accucell is malfunctioning.

[BILL_G]

I have a accucel8. I see about .01V per Amp between charger + DVM. You have about 10 times that. If your outside leads + conn. are OK look for a bad conn. inside the charger.

[antonkochubey]

@kreisler

what do other accucel8 users report?

when the hobby charger says “4.20V COMPLETED” and one (not you lol) takes out the 18650, does the DMM read 4.200V?

i am going to bet that the method of adjusting the calibration (Enter -Dec) will not help your situation (discrepancy of voltage readings hobby charger vs. dmm). and for sure it doesnt help the real origin of the problem.

i dont know what the real origin of the problem is. but it might be the tolerances of the IC parts on the electronics circuit board. yes you could have tested the accuracy of the hobby charger right after the purchase!

the point is, i had my share of experience and frustration with hobby chargers, voltage reading discrepancies, and recalibration (Enter -Dec), and testing, testing, testing, testing, retests, etc, and i got sick of it all. i said to myself no more. my i4 does such a beautiful job at terminating at 4.200V, i take the cells out and my dmm reads 4.200V. because of the ease of use i appreciate the i4 so much. so how do i know how much capacity is in my cells? — very simple. from HKJ’s battery reviews. and if capacity has decreased after years of use and abuse (e.g. NCR18650B, 2900mAh instead of 3400mAh), then i wouldnt notice and i wouldnt care.

hobby chargers are perfect, very satisfying stuff and a must for out-of-round shaped liion cells, either single singular cells or battery packs, and their main purpose or essential feature is to do balance charging. yes i can measure the capacity of single round cells with it … but once i did that (repeated times to ensure measurement integrity) the hobby charger lost its practical purpose in my household and i would henceforth only use my i4 (or Ultrafire) to recharge round cells. hobby chargers in my household? good riddance

You’re a bit wrong there.
Cell should not under any circumstances read 4.200V after being taken out of 4.2V CC/CV charger. That’s what a tiny bit, but still overcharged, cell would read.

[Woody]

@Shadowww

Cell should not under any circumstances read 4.200V after being taken out of 4.2V CC/CV charger. That’s what a tiny bit, but still overcharged, cell would read.

I’m confused. What should they read out of the charger?

[antonkochubey]

@Woody

I’m confused. What should they read out of the charger?

4.2V minus [cell’s internal resistance*charger’s termination current].
Usually 4.18V - 4.19V on new cells with low internal resistance.

[atbglenn]

None of my cells ever measure 4.2 volts out of any of my chargers including 2 hobby chargers. Usually between 4.15 to 4.18 depending on the cell, and I'm perfectly fine with that. I have brand new Panasonic 3100 mAh protected cells I got a couple of weeks ago, same end result..

[AlexGT]

I have the exact same charger and I had to calibrate it, It charges good cells to 4.20v and my multimeter shows 4.20v, BTW I charge using the LiPo function because the LiIo function only charges to 4.1v, but the charger clearly says so, maybe try charging in LiPo mode, I noticed that using DeOxit after cleaning the banana plugs and opening up the plug just a little bit so that it gets in tight and not u pluging it anymore helps to the accuracy of the voltage reading, so far it hhas been a good charger for me.