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Possibly faulty balance charger?

ComikzInk

Soft and Foofy
#1
Hi All,

Was charging up some batteries for a quick test of some new RC kit. I've noticed that when charging my batteries with my balance charger the last cell is always lower then the rest. I'll leave it charging till it reports the charge is complete but both on the charger and a multimeter I can see that the last cell is significantly lower than the rest.

These are being balance charged at 1C (tried 0.5C too) but regardless of if I do them individually or use a parallel charger the last cell will sometimes not charge at all. The charger does see all cells too, I have yet to switch it to show voltage readout and watch the charging process yet but it may come to that lol.

I first noticed this with a few of my Gremlin batteries. I assumed as they were batteries I bought were cheap and from China that it may just be a bad batch but I've noticed it doing it across the board on all batteries be it 2, 3 or 4 cell.

My charger is the Keenstone K6AC+80W (which if I look to Amazon for the item they've upgraded it to https://www.amazon.co.uk/gp/product/B015DKGZK0 )

I've recovered some of the batteries by manually charging the last cell through the balance lead with a DIY adapter. Some were too far gone to recover and it appears some had even vented as I was getting 0v across the cell when dissecting the dead ones.

I'm wondering if anyone else has had a similar issue and it's just something I'm not doing correctly or if I should get a new charger. Would love to hear if anyone else has had a similar issue or suggestions in case I'm being a complete plonker.

Kind regards
Lia <3
 

ElectriSean

Eternal Student
Mentor
#2
I would replace the charger ASAP. My guess is that one of the discharge circuits or sensing circuits is damaged and over discharging that one cell. LiPo batteries can go to 0 volts without venting if discharged slowly, which is probably what is happening to you. Trust me, if one had vented you would notice it ;)
 

ComikzInk

Soft and Foofy
#3
Figured as much, as the fault moves to the last cell it's bound to be something not latching but couldn't be sure it wasn't me being daft.

Didn't realise they could go down that far without venting, I assumed it was a certainty (not to say I'm not going to be any less careful with these things).

Cheers for the heads up, I'll have to ignore the balance charge option and leave a voltage alarm on the balance leads when charging till a new one comes. Any recommendations on a good one? :)
 

ComikzInk

Soft and Foofy
#5
Aaaaand Ordered :)

Up to 6s is enough for me I think for now, it looks so small and clean.
Thanks for the suggestion :)

When it's here I might teardown the old one and see what's up.
 

ComikzInk

Soft and Foofy
#8
Just a quick note, the SC-608 requires a DC power supply, it can't take AC in. Your existing charger may be able to do this, if not you'll need something like https://www.banggood.com/Universal-...-p-1065073.html?rmmds=search&cur_warehouse=CN
I've got a few DC power supplies laying around from one of the old 3d Printers that isn't used anymore. Looks like it takes quite the range of voltage so I'll use a 12V one just so there is minimal voltage conversion to be done.

Thanks for pointing that out, it looks like the unit alone will keep me going for a bit.

Alternatively, if you need a decent, but cheap, 150W AC to DC power supply you can check this out -
http://forum.flitetest.com/showthread.php?36595-5-150W-Charger-Power-Supply&highlight=Xbox
I've actually got an old xBox brick laying around funnily enough, might be worth using it for something like that. I'd never checked the voltage supplied from those but just from the diagrams I'm seeing a few useful rails.
 
#9
If its all your batteries, then the charger is duff... shame as its not a cheap charger well the price isnt cheap anyway. My htrc b6 mini clone (80 watt upgraded version) was 20 gbp, same price i paided for the clone b6 AC and is way better
 

ComikzInk

Soft and Foofy
#10
If its all your batteries, then the charger is duff... shame as its not a cheap charger well the price isnt cheap anyway. My htrc b6 mini clone (80 watt upgraded version) was 20 gbp, same price i paided for the clone b6 AC and is way better
It does it sometimes, the only battery that hasn't suffered is my Fatshark 2s battery, however my other 2s batteries have suffered as with a few 3s ones too. Is a shame, I'll keep it for non balance charges and my NiMh batteries but for Lipo I think I'll avoid :D

Sounds like you got quite the deal, I remember just selecting this as it was the first one in my search and didn't have bad reviews. Bit careless of me now I think of it.



On another note the replacement charger arrived :)

It's so tiny, I was expecting something bigger but am pleasantly surprised at how small it is. Compared to my old one with the parallel charger glued on top it's absolutely tiny~!
Img (4).jpg

Decided to give it a challenge so I juiced up the first cell and then plugged it in. Cells showed a little more out of sync than I set them mind you.
Img (3).jpg

However, all is not great, after leaving it for a bit I found the battery was getting exceptionally toasty even on a low charge rate. Turns out the voltages aren't calibrated D: My second cell is measuring 0.06v too low so my battery had a second cell voltage of 4.26v, eep!

Discharged the cell down and did a little research, turns out the SC-608 had a few that are not calibrated accurately and require a firmware update so I've ordered the usb to 4pole adapter and will get it updated and calibrated. Never heard of firmware for a charger but I guess it's nice to have that level of tuning that doesn't rely on replacing resistors :)
 
Last edited:

ElectriSean

Eternal Student
Mentor
#11
I didn't know about that firmware issue - or that it could be updated - that's pretty sweet :) Mine has been flawless. I love how little space it takes up in the backpack, I can't even fit my 'main' 4 channel one in there ;)
 

ComikzInk

Soft and Foofy
#12
Firmware lead hasn't arrived yet but decided to put the batteries down to a safe storage voltage as I don't think I'll be flying while the weather is a bit wet and windy :(
Whilst doing it I decided to compare the voltages measured across all my chargers and measuring tools for the same battery. Results varied as expected.

First up a test with a multimetre
IMG (11).jpg
Cell 1 : 3.88
Cell 2 : 3.88
Cell 3 : 3.93

Let's now compare it with the battery alarm
IMG (12).jpg
Cell 1 : 3.90
Cell 2 : 3.89
Cell 3 : 3.95

Lets test the old charger that I believe to be faulty
IMG (4).jpg
Cell 1 : 3.90
Cell 2 : 3.90
Cell 3 : 3.94

And here is the new charger that I suspect is uncalibrated
IMG (3).jpg
Cell 1 : 3.93
Cell 2 : 3.85
Cell 3 : 3.95

 

Multimetre

Battery Alarm

Old Charger

New Charger

Cell 1

3.88

3.90

3.90

3.93

Cell 2

3.88

3.89

3.90

3.85

Cell 3

3.93

3.95

3.94

3.95



So Although my old charger doesn't charge correctly sometimes it's not that far off, maybe 0.01v - 0.02v too high on all cells. Battery alarm is a bit out in all of them variably but it's a cheap estimation tool so I'll let it pass. The new charger is waaaaaaay out on cell 1 and 2 with a little off on cell 3 so that will certainly need tweaking. My multimetre isn't perfect but it's a good reference and adds more data to estimate where the voltage should be.

Hope this encourages anyone reading to test their chargers to see just how accurate they are :)
 

ComikzInk

Soft and Foofy
#14
Huzzah so the updater cable arrived!

It's not a simple process believe me but it's well worth it. I'll consolidate my experience below for anyone else looking to do this.

Things you'll need
  • ISDT SC-608 charger
  • Power supply for the charger
  • ISDT usb firmware adapter
  • A functioning battery, More cells (up to 6) the better.
  • An accurate (or close enough) voltmeter with at least 2 decimal places worth of precision (eg 3.85v). I used my cheapo multimeter.

Updating the charger
1. First of all you'll want a firmware updater cable, this will be a 4pole 3.5mm jack to usb adapter which ISDT supply such as this
https://www.amazon.co.uk/dp/B0758BGRVQ
2. You'll also want the latest firmware, the one I've upgraded to is V2.10.0.15
http://www.isdt.co/download
3. Extract and run the application inside the main folder
4. Power on your charger
5. Plug in the usb adapter to your PC and the 4 pole jack into the charger
6. On the application install the driver first and wait for that to complete.
7. When complete click "Update". Do not close the app or unplug the charger as it updates, you risk leaving a partially flashed charger that will no longer work.
8. When complete the charger will reboot and check itself. On my firmware version that was it, no calibration required.

Calibrating your charger
9. Measure your battery voltages per cell then the total and make note of each, if you have a 6s battery you can calibrate all 6 points on the charger, otherwise use your highest cell count battery.
10. Long-press the button on your charger to get into the main settings and scroll down to "System Information". Go inside and you should see your firmware version, hardware number and so on.
11. To get into the calibration menu long press the button 3 times, each with a beep to say you have held long enough. When done another menu shall appear.
12. Plug in your battery via both the XT-60 and your balance lead
13. Select "Voltage Calibration"
14. This is where some people have an issue, on older versions you used to contact ISDT, give them your hardware and serial number and they'd send you a key to unlock this next section, on my firmware V2.10.0.15 it actually gives you the long hexadecimal code above where you enter it (search me why?) so just enter that as is and it'll take you to the next menu, you shouldn't have to do that again now unless you update the firmware again.
15. With the voltages you measured earlier match the cells to what you have as correct. When done exit out and you should be done :)


There you have it, a calibrated tiny 150w balance charger! I've just tested mine now and fully charged a 3s which is bang on 4.20v per cell. Hope this helps, many thanks to ElectriSean for suggesting the cute little charger.

Lia <3