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Old 12-01-2013, 05:01 PM   #1
kittiwat1
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Default Not getting 4.2 volt per cell count with PL 8

Hi,
I dont know if there is an issue with my PL8. I charge four 6 cells 5000 mAh Lipo packs with a parallel board. When charging is done (alarm sounds), when I measure voltage of each cell of all the batteries some show 4.21, 4.14, 4.19, 4.19, 4.18 etc. I was hoping to get all cells being close to 4.2 v but the gap between each is wider than I would like it to be. Note that all batteries' voltage at the start do not diffier more than 0.2 volts. Is this normal?
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Old 12-01-2013, 05:34 PM   #2
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It's normal for the calles to fall back a little from the 4.2V target, usually 4.18 or 4.17V.. But it's unusual on a quality charger for any cell to be higher than 4.2v and also unusual for any cell to be as low as 4.14v.

A few questions:
  • I take it you are balance charging and not fast charging?
  • What are you measuring the cell voltage with?

If by any chance you are using one of those cheap little cell voltage checkers then that's the cause of the variation. They are useful little gadgets but not especially accurate.
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Old 12-02-2013, 12:12 AM   #3
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Originally Posted by kittiwat1 View Post
Hi,
I dont know if there is an issue with my PL8. I charge four 6 cells 5000 mAh Lipo packs with a parallel board. When charging is done (alarm sounds), when I measure voltage of each cell of all the batteries some show 4.21, 4.14, 4.19, 4.19, 4.18 etc. I was hoping to get all cells being close to 4.2 v but the gap between each is wider than I would like it to be. Note that all batteries' voltage at the start do not diffier more than 0.2 volts. Is this normal?
H'mmm
Have you watched the individual cell voltages on your PL8 charger WHILE it's charging?

I've got two of the PL8 chargers, and the individual cell voltages match to well within 1% near the end of the charge cycle. Usually all the PL8 voltage digits are identical on all of the cells being charged. After the charge cycle ends, your battery might in fact have slightly different voltages, something that also will show up on your PL8's LCD display monitor. That would be a battery issue, not a PL8 issue. This PL8 charger has a very high capability of one ampere difference in charging currents between cells during the balancing while the charging process takes place.

Just checking, your 4.21 and 4.14 voltages are 1.8% variation.

Do you have the Cellpro USB dongle that allows connecting your PL8 charger to your computer while the charge process is taking place? If so, you can watch the charge cycle on your computer, and get a bit more info. That dongle also allows programming your PL8 charger to your exact needs, even to the point to show your name on the LCD display when you power it up.

I've got ten charge routines stored in my PL8, from charging A123's at 30 Amps, to charging a little LiPo at 0.6 Amps. The PL8 LCD display shows on its display the name of the battery type that YOU program in.

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Old 12-02-2013, 12:47 AM   #4
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another thing to watch is if a battery has a bad cell it can effect how the powerlab charger works while charging several packs at once,i had four 4cell 4000mah 40c batteries charging last night and it switched to safety charge.....i used a battery checker after waiting for the packs to get to more than 92% after 2 hr's on the charger when i realized one pack had a bad #2cell. it was in the crash of the 540t and i could feel slight puffing. i'm going to be charging batteries now,but plan on cycling the damaged pack on the powerlab6 tonight. hopefully it can be balanced and put back to use. it's a zippy and cost's around $35. plus i need it to get my extra 300s powered by 7cells running a 3cell with the 4's.

narrow is the place to land...wide is the space to crash....choose the narrow way!
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Old 12-02-2013, 04:58 AM   #5
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Originally Posted by tobydogs View Post
another thing to watch is if a battery has a bad cell it can effect how the powerlab charger works while charging several packs at once,i had four 4cell 4000mah 40c batteries charging last night and it switched to safety charge.....i used a battery checker after waiting for the packs to get to more than 92% after 2 hr's on the charger when i realized one pack had a bad #2cell. it was in the crash of the 540t and i could feel slight puffing. i'm going to be charging batteries now,but plan on cycling the damaged pack on the powerlab6 tonight. hopefully it can be balanced and put back to use. it's a zippy and cost's around $35. plus i need it to get my extra 300s powered by 7cells running a 3cell with the 4's.
Yeah, that PL8, along with most of the rest of the Cellpro line, along with perhaps many other name brand LiPo chargers may go into their "Safety" mode of charging a LiPo battery that is way out of balance.

My PL8 chargers go to a 500 milliampere charge rate under this condition, even when it's programmed for a 30 Amp charge rate for my A123's. (That is a 12S2P pack being charged as a 6S4P pack.)

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Old 12-02-2013, 03:26 PM   #6
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Thanks all for your help. I use a battery checker to take measure of cell voltage after a complete charge by PL8. Although it’s not an expensive one (USD 20), I get an almost consistent readings between this checker and the reading from another charger so I know it’s not the the battery checker issue giving me an inaccurate reading. I also try to use another checker (I have two) and the results are the same. Note that while charging with the PL 8, its screen shows equal voltage for each cell right until the end of the charge when the alarm sounded which shows all cells reaching 4.2 volts from below 4 volts at the starting point. That’s well and good, however, only when I recheck the voltage using the battery checker did I find the discrepancy. Next I recharge the battery that has one cell at 4.14 volt while another cell at 4.21 volt. The PL 8 now recognized the cell with 4.14 volt and the other cell with 4.21 volt at the beginning of the charge (as read by the external voltmeter) whereas during parallel charging by PL 8 all cells were shown 4.2 at the end of the charge. Had I not have a separate volt meter, I would have believed that all cells were exactly at 4.2 volts as read by PL8. The PL8 tried to reduce the cell that was overcharged from 4.21 to 4.2 and add voltage to the cell that was undercharge i.e. from 4.14 to 4.20. This indicates that the PL8 is not totally broken as it is trying to charge the battery to the specified 4.2 volt for all cells and done so successfully for that single pack battery. This problem only happens when I do parallel charging i.e. more than one battery. Now I wonder if the parallel board is the culprit as the volt reading is correct for that single battery charging by PL8. By the way, I have been using Faster Charge mode and will use Accurate charge mode to see if the issue persists. Note that I also use the batteries’ balancers for all above charging and I have not used a dongle to connect to a PC (don't have one yet).
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Old 12-02-2013, 06:14 PM   #7
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Unfortunately, this is common with parallel charging and is not the fault of the charger. It can caused by an issue with the balance board. If you are not using a fused balance board some of the traces could have burned.

Even with a working balance board, cells can end up not perfectly balanced when charged in parallel. This is more commonly seen in lower grade or aged packs. When you encounter this, check all packs in parallel separately. For any cells which are far off, check the same cell number on the other packs. What you will likely see is one or more cells are high while one or more cells are low. If there is only one cell that is very high or very low, there could be an issue with that pack. If you leave the packs connected to the parallel board or cable for about 20 minutes after the charge cycle has completed, then cells in parallel will equalize and all packs will be closer to being perfectly balanced.

Also note that the Powerlabs always balance charge the packs even when the fast preset is used. This is different than the other chargers where you must select balance charge or the balancer will not be active.
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Old 12-06-2013, 03:22 PM   #8
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Originally Posted by Gregor View Post
Unfortunately, this is common with parallel charging and is not the fault of the charger. It can caused by an issue with the balance board. If you are not using a fused balance board some of the traces could have burned.

Even with a working balance board, cells can end up not perfectly balanced when charged in parallel. This is more commonly seen in lower grade or aged packs. When you encounter this, check all packs in parallel separately. For any cells which are far off, check the same cell number on the other packs. What you will likely see is one or more cells are high while one or more cells are low. If there is only one cell that is very high or very low, there could be an issue with that pack. If you leave the packs connected to the parallel board or cable for about 20 minutes after the charge cycle has completed, then cells in parallel will equalize and all packs will be closer to being perfectly balanced.

Also note that the Powerlabs always balance charge the packs even when the fast preset is used. This is different than the other chargers where you must select balance charge or the balancer will not be active.
Thanks for this. I balance charged four aging LipO 5000 mAH 6S of same brand last night and the results were satisfactory to me. They were all about 4.16-4.19 v and none exceeded 4.2 v - and these are almost 2 yrs old packs. I will try to charge only same brand and exactly same type of Lipos going forward. That should make easier for PL 8 to obtain its best performance.
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