Charging my $8 Lithium Transmitter Battery

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Re: Charging my $8 Lithium Transmitter Battery

Postby Sid Sideslip » Thu Sep 08, 2011 10:28 pm

kaptain_zero wrote:Just a quick thought, Sid. Do you have a multimeter kicking around? I'd be curious to see the actual charge voltage coming out of that charger, particularly just before the disconnect error message. To me it sounds like the protection circuit on the cell is kicking in due to excessive voltage. Then again, these cheap batteries/protection circuits don't have the best reputation for quality control, though I have not run across too many bad ones. I've had 2 bad circuits and one bad cell (this was a premium one no less) so it can happen and this is over about 30 - 40 odd lithium cells of varying sizes. I use 10440, 14500, 17670, 18650 and RCR123a... to name a few.

A separate Digital Multi Meter aka DMM should show what's going on. I know the charger measures voltage, but we need a "second opinion" from another meter as things are behaving strangely. If the DMM reads markedly different, something is up and a third, known to be accurate, DMM, should be called in to settle the issue of "Is it the Charger or the Cells or.....?"

Looking at your picture, the balance plug is wired correctly, but I cannot vouch for your soldering as I can't really see it that well.

Regards

Christian


The voltages I gave after each cell triggered the Connection Break error (4.1v and 4.09v) was taken by my new DMM and are after a few minutes off the charger. Admittedly, it is only a cheap DMM.

The charger was showing 4.13v a minute or two before it cut out, as I was keeping a written log. It was the same voltage for both cells. Unfortunately, when I do get the connection error, I can no longer access the info screen to see what the charger's voltage readings were precisely at cut-out.

This morning after resting overnight and and without using the Tx, the voltages are 4.08 on each cell according to my DMM.
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Re: Charging my $8 Lithium Transmitter Battery

Postby kaptain_zero » Thu Sep 08, 2011 11:18 pm

Sid Sideslip wrote:The voltages I gave after each cell triggered the Connection Break error (4.1v and 4.09v) was taken by my new DMM and are after a few minutes off the charger. Admittedly, it is only a cheap DMM.

The charger was showing 4.13v a minute or two before it cut out, as I was keeping a written log. It was the same voltage for both cells. Unfortunately, when I do get the connection error, I can no longer access the info screen to see what the charger's voltage readings were precisely at cut-out.

This morning after resting overnight and and without using the Tx, the voltages are 4.08 on each cell according to my DMM.


Sid, measure the voltage DURING charging..... my suspicion is that your charger is putting out more than 4.2V per cell during charging, something it should NOT do and which is what I'm thinking might trip the protection circuits. In a 2 hr full charge, voltage should be allowed to rise to 4.2V per cell by the charger during the first hour. Once the voltage output of the charger reaches 4.2V per cell, it should clamp the voltage and allow the max current to continue until the pack accepts only 10% of the original current while all along clamping the Voltage to the max allowed, aka 4.2V per cell. Lithium cells will generally drop slightly in voltage after being removed from the charger.... the older the cell is, the more it will drop after charging stops, but it will settle after a short while.

Regarding the voltage your *charger* is reading.... it may simply be poorly calibrated by the factory or it may have drifted after manufacturing.... We won't know until you measure the same pack during charging that the charger is measuring while it's charging it.

My iChargers come with instructions on how to recalibrate if necessary, my other chargers don't.

This could be much like you driving down the road at 50KMh on your speedometer but your GPS unit says you are traveling at 60KMh. Confirmation comes when the friendly policeman pulls you over and gives you a ticket for going 60KMh in a 50KMh zone... His radar confirmed that your GPS was correct and you speedometer was wrong! :mrgreen:

Regards

Christian
"I'd like to live as a poor man with lots of money."
-- Pablo Picasso
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Re: Charging my $8 Lithium Transmitter Battery

Postby Sid Sideslip » Fri Sep 09, 2011 12:02 am

Yeah you're right Christian and thanks. I may take it over to my brother in law's lab, as he's an electronic engineer at the Dpt of Physics at the University of Tasmania. I imagine his test gear will be as accurate as it gets...after all, he's the guy who calibrates all the speed cameras for Tasmania Police (a nice coincidence, given your speeding analogy ;) ).

If my charger is putting out too much voltage on the lipo setting (there is no separate li-ion setting) for these batteries he should be able to re-calibrate it.

Edited: Before I posted this I tested it myself. The pictures tell the tale (at least if my DMM is accurate). The charger reads the voltage a bit low when I connect up one cell.

When I charge however, the charger says it's doing so at 4.11 volts @ 90% charge, but the DMM shows 4.23 volts, so the charger is exceeding the 4.2 cut-off voltage.


No charging, just reading power supply and battery voltages.
Image

DMM disagrees.
Image

Charging. Charger says voltage within overcharge limit.
Image

DMM says voltage is too high.
Image
Last edited by Sid Sideslip on Fri Sep 09, 2011 1:02 am, edited 1 time in total.
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Re: Charging my $8 Lithium Transmitter Battery

Postby Sid Sideslip » Fri Sep 09, 2011 12:57 am

Added: I just noticed that HobbyKing have some Turnigy accucel 6 chargers in at the Oz warehouse for $AU23, which is cheap as chips.

So I said to hell with it and bought one as a spare (I have a pc power supply I can use for it too). Plus with the accucel you can calibrate them yourself easily.

Image
Last edited by Sid Sideslip on Fri Sep 09, 2011 3:40 am, edited 1 time in total.
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Re: Charging my $8 Lithium Transmitter Battery

Postby rogueqd » Fri Sep 09, 2011 1:39 am

Sid Sideslip wrote:Plus with the accucel you can calibrate them yourself easily.
You can? Care to make a tutorial? (or at least write up a few hints here?)
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Re: Charging my $8 Lithium Transmitter Battery

Postby Sid Sideslip » Fri Sep 09, 2011 1:56 am

rogueqd wrote:
Sid Sideslip wrote:Plus with the accucel you can calibrate them yourself easily.
You can? Care to make a tutorial? (or at least write up a few hints here?)


I stumbled upon it in the first review on the HobbyKing website. Quoted here:

"You can even calibrate the charger if you feel the readings are a little incorrect.

For calibrating this charger follow these steps:

1.) Power off the charger.
2.) Press and hold the (dec" and "start" buttons.
3.) Power on the charger. (you will hear 3 beeps in a row). Keep the buttons pressed.
4.) You will enter into the calibration screen where the voltage detected by the charger is displayed on the screen (voltage on output leads).
5.) Attach any battery to the output leads of the charger.
6.) Using a digital multimeter, correct the reading of the voltage by pressing "inc" or "dec" buttons till the reading matches with that of the multimeter.
7.) Press "Stop" when you are done.
8.) Your charger is calibrated now.

You can repeat these steps as many number of times"

http://www.hobbyking.com/hobbyking/store/__7028__Turnigy_Accucel_6_50W_6A_Balancer_Charger_w_accessories.html
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Re: Charging my $8 Lithium Transmitter Battery

Postby rogueqd » Fri Sep 09, 2011 3:31 am

Great! Thanks! :)
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Re: Charging my $8 Lithium Transmitter Battery

Postby prong » Mon Jan 02, 2012 7:59 am

Hi there, I had to pack my RC gear away for a couple of months while while we sold our house and moved. I just tried to charge up my $8 Tx battery and got a low voltage error. I checked each cell and one is showing 3.8V and the other, 0V. I guess that cell has died. That could account for some of the erratic problems I had with charging the battery initially. I'll have to order some more tonight.

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