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Old Mar 06, 2012, 12:15 PM
RVA
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odd cell reading while charging...

I have a quick question on a curious matter. I have a brand new, never used Turnigy Nano-Tech 1800mah 4s, 25-50c. Link here. When connected to my charger (lead + balance tap), two of the four cells are giving off VERY erratic numbers, mostly very low and constantly changing. The other two are normal and relatively constant as you would expect. Here's the kicker: when I connect the battery to my handy cell-checker, all the cells register normal. Any idea what could be happening? I am not sure if it is a bad cell or two or perhaps a loose lead or something else.

I will add that I have plenty of other batteries and all seem to be charging just fine. Its only this one battery that is giving the funny readings. I am afraid to leave it on the charger too long out of fear of fire or damaging the charger. Thoughts?

Thanks,
-RVA
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Old Mar 06, 2012, 12:37 PM
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The cell checker is telling you that the pack is OK. Bad cells can't give good readings.

Sounds like a problem is in the contacts between the battery balance connector and the charger balance connector. What happens if you wiggle that connector a bit while charging?
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Old Mar 06, 2012, 01:34 PM
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I've done the "jiggle" a couple of times and there are no changes in reading of note. Balance tap on the charger seems to work fine with others so I am left to believe that, if it is a connection problem with the tap, it is under the heat shrink covering of the battery. Does anyone have any advice or experience in cutting that open and poking around? If so, what should I be looking for?
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Old Mar 06, 2012, 07:10 PM
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Quote:
Originally Posted by RVA View Post
I've done the "jiggle" a couple of times and there are no changes in reading of note. Balance tap on the charger seems to work fine with others so I am left to believe that, if it is a connection problem with the tap, it is under the heat shrink covering of the battery.
If that were the case, wouldn't your cell checker be acting just like the charger?
Your cell checker is telling you the pack is OK. If there were problems under the shrinkwrap wouldn't the cell checker show that just like your charger does?
Something else is going on.........

What are the cell voltages the Lipo Checker is reporting?
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Old Mar 06, 2012, 10:23 PM
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Yes, I see your point. I stand corrected.

The lipo checker reads: 4 cell, 14.9, 3.75 x 4 (all cells reading the same)

The charger readings per cell: 1: 1.2 - 2.35 (fluctuating frequently but closest to 2.35) 2: 3.75 - 5 (also fluctuating frequently but not as frequently as cell 1) 3: 3.75, 4: 3.75 (cells 3 and 4 both stable)

I tried charging at 1c and the charger cut out with a "low voltage reading". Then tried to balance at approx .25c and it stayed on. Again, I have not let it run until I feel more comfortable with knowing what the problem is. While it was hooked up to the charger, I did some more playing around with the balance tap, wiggling and such. There was no change in the reading.

Still stumped...
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Old Mar 06, 2012, 10:50 PM
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What cell checker are you using?
What charger are you using?
What settings on the charger?
Are you connecting both the main charge leads and the balance connector?
Is the battery connected directly to the charger or are you using a balance board?
If you are using a balance board are the batteries that test OK using the same ports?

Probably none of that is pertinent but it never hurts to know these things.

Even though the cell checker reads good I would clean all of the battery and charger contacts with some electronic contact cleaner.

I suggest this as the cell checker does not draw any current (well practically none) from the battery under test. However when charging there is significantly more current through the contacts and a slightly dirty contact might result in the readings you are seeing. Shot in the dark? Maybe. Try it anyway.

Glen
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Old Mar 06, 2012, 11:45 PM
RVA
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HK 200w charger. Thumb-drive style cell checker. Lipo charging settings include charge, balance, discharge and storage - all of which work as designed on other batteries. I always use the charging and balance taps together. For all other batteries, charger cell readings during charging and cell-checker readings match. But, Glen, your pointed questions raise one difference - this is only 4cell battery I have. All others are 1-3 cells. Perhaps there is a problem with the 4-cell balance port on the charger? I don't have any electronic contact cleaner. Is there a household substitute for that?

Thanks for your suggestion. I will see about cleaning the connections and ports to see if that helps.
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Old Mar 07, 2012, 09:22 AM
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RVA, your cell #1 is bad. Very low voltage in one cell will cause erratic readings on a cell checker and will not charge on a balancing charger.
Want proof?
Use a hand held volt meter and test each cell, one at a time. My guess is cell 1 is in the 1 to 2 volt range.
Solution? Discharge pack 100% and toss it.
If your charger did not monitor cells when charging you likely would have had a lipo fire with that pack.

Rick
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Old Mar 07, 2012, 10:45 AM
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RVA, your cell #1 is bad. Very low voltage in one cell will cause erratic readings on a cell checker and will not charge on a balancing charger.
Want proof?
Use a hand held volt meter and test each cell, one at a time. My guess is cell 1 is in the 1 to 2 volt range.
Solution? Discharge pack 100% and toss it.
If your charger did not monitor cells when charging you likely would have had a lipo fire with that pack.

Rick
Rick,

In his first post he says "Here's the kicker: when I connect the battery to my handy cell-checker, all the cells register normal."

And in a later post he states that the defective reading comes from his only 4 cell battery.

I don't think he has a bad battery.

Glen
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Old Mar 07, 2012, 11:10 AM
RVA
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I will check the per-cell voltage with my multimeter. If Rick is correct, I think its safe to say my checker is crap because it clearly gives me standard voltages for all 4 cells.
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Old Mar 07, 2012, 11:34 AM
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multimeter = cell checker

Ok, so took Rick's suggestion and checked all cells with my multimeter. All cells are reading within .02 of the cell checker, all of which are falling right around 3.75 to 3.77. Safe to say the battery is ok? Assuming it is, this would then mean the problem would be with the 4-cell balance port on the charger. A clear confirmation would be to hook up another 4-cell battery to the port but I don't have one. What ever is wrong with the charger, its giving enough of a false positive to shut down the charging process. Not sure there is a way to get around it.
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Old Mar 07, 2012, 11:44 AM
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RVA,

So try my suggestion to clean the contacts on the charger/adapter. You can get the contact cleaner at Radio Shack or even Home Depot.

BTW how is it in Long Beach these days? It's my home town.

Glen
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Old Mar 07, 2012, 11:51 AM
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My cell checker draws the voltage for operation from cells #1&2 and needs >3V(total) to operate.
If his is similar he has enough V to power on the checker.

Interesting problem.....

You guys post toooooooo fast. I'm behind the post curve.

-------------------------------------------------------------------------------------------------
Catching up-
Do you have another 4s balance connector to the charger?

Try the Discharge Function and see what the voltages read. (See if it is related to the Charge function only).

Is the battery connected to a separate 4s balance connector or to a balance connector board?

Try giving a gentle tug to each wire going into both the charger and battery balance connectors to see if there is a loose connection in there.
The wires are crimped into the metal socket connectors.
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Old Mar 07, 2012, 01:48 PM
RVA
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My checker is the key-type and, for all I can tell, is drawing enough to make a reading.

I am plugging the balance tap directly into the charger's 4-cell port. The ports are flush and can not inspect the internal connections without taking the charger apart. No, I don't have another balance board or 4-cell battery - too bad. Have inspected and tugged the wires on the battery. Absolutely nothing out of the ordinary about them.

Will next try to clean my connectors and then try a discharge to see if I can get a consistent reading. At this point, it is less about saving the battery or charger but solving this mystery!

Lastly Glen, the LBC treats me and my family well. I'm not native SoCal but have been in LB for about 9 years. I find the city a bit of a bastard child of LA - no one really pays attention to us, which is fine by me. We're a little out of the LA rat race but close enough to have all the fun. I fly at El Dorado park (great guys!), which is less than a mile from my house. That alone has fueled my rc obsession. When did you leave? GA is quite a bit different than LB, no?
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Old Mar 07, 2012, 02:44 PM
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Quote:
Originally Posted by RVA View Post

Will next try to clean my connectors and then try a discharge to see if I can get a consistent reading. At this point, it is less about saving the battery or charger but solving this mystery!
Just a short discharge should tell the tale.

One sure fire test
Put it in your plane and see how it spins the prop. It would really be neat to have a power meter in line when you do that to measure the voltage and current. You can get a partial answer by plugging the cell checker into the battery when you do that to watch what happens to cell voltages.
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