Charging my $8 Lithium Transmitter Battery

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Re: Charging my $8 Lithium Transmitter Battery

Postby prong » Wed Aug 03, 2011 8:53 am

I don't know what is happening with my battery. I must be doing something wrong with the charger because there is no way I can get the thing to charge at 1.5A. If I try that the charging voltage goes up to 8.4V and I get the battery disconnect error. It does that on any charge I try greater than 0.1A. I've tried the balance charge but after about 5 seconds I get an error that says: "BATTERY VOL ERR CELL CONNECT". I'm wondering if the over voltage protection cuts in and closed down one or both cells. It's very frustrating.

If I can't work it out I'll have to ditch it and buy a LiPO Transmitter pack.
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Re: Charging my $8 Lithium Transmitter Battery

Postby bmsweb » Wed Aug 03, 2011 9:07 am

I was getting the Battery Error once it was almost full. At this point I was getting around 6 hours of battery life. I've just installed (today) a balance plug and it seems to allow me to up the amps to around 1.0 without a problem at all. Having said that one battery got to 4.25 and the other was hanging around 4.03. They stayed pretty even as the voltage went up but one stopped around the 4.03 mark.

Not sure if this helps you at all.

BTW: Make sure you have your balance plug wired the right way. I purchased extension type balance leads an the red was on the opposite pin :roll:
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Re: Charging my $8 Lithium Transmitter Battery

Postby prong » Wed Aug 03, 2011 11:17 am

Thanks bmsweb.

I checked my balance lead and sure enough, the red and black wires were reversed! I was able to swap the wires around by gently lifting the little plastic locking tabs on the balance plug and pulling the connectors out. I just swapped the black and the red wires around and no more battery volume error.

I cranked up the current to 1.2A on the Lipo balance charge setting and away she went. It still says its currently charging at only 0.2A but it's keeping the charge voltage to just below 8.2V. One cell is showing 4.20V and the other is fluctuating at around 3.90V to 3.95V.

Is this how it is supposed to look?

How long should it take to fully charge this 2400mh pack?
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Re: Charging my $8 Lithium Transmitter Battery

Postby bmsweb » Wed Aug 03, 2011 11:50 am

prong wrote:I checked my balance lead and sure enough, the red and black wires were reversed! I was able to swap the wires around by gently lifting the little plastic locking tabs on the balance plug and pulling the connectors out. I just swapped the black and the red wires around and no more battery volume error.


That's great! I nearly wired mine up the same way but thought I had better check just in case :D


prong wrote:I cranked up the current to 1.2A on the Lipo balance charge setting and away she went. It still says its currently charging at only 0.2A but it's keeping the charge voltage to just below 8.2V. One cell is showing 4.20V and the other is fluctuating at around 3.90V to 3.95V.

Is this how it is supposed to look?

How long should it take to fully charge this 2400mh pack?

Well interestingly the first set I charged came to the end of its charge time of 120min but the voltage variation didn't change and its worth noting from about the 60min mark it never really changed.

I charged my son's pack next and one got to 4.20 and the other 4.18 but once again the charger just timed out. Having said that I haven't ran the TX to see how long it takes to go flat . . well for it to alarm. Will let you know how it goes tomorrow when I time how long it runs for.

Cheers
Paul
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Re: Charging my $8 Lithium Transmitter Battery

Postby kaptain_zero » Wed Aug 03, 2011 11:16 pm

Just a couple of notes on "Cheap Chinese 18650 cells".

Cells should normally end up at 4.2v with a quality charger but as the cells age or with variations in quality, some will not want to stay at 4.2v, but will drop to 4.18v or whatever after only a few minutes off the charger.

The charge cycle of LiIon cells with a properly designed charger is CC/CV as in Constant Current/Constant Voltage. This simply means that your charger will charge with the full amperage rating you programmed in.... let's say 1A until the battery reaches 4.2v and then switches to the Constant Voltage portion where the Voltage is held at 4.2v and the battery is allowed as much current (up to that 1A we originally programmed) as the battery will accept until it drops to 10% of the original charge rate... in this case it would stop charging when the current flow drops below 0.1A.

Balancing is done by draining excess current from the cell that reaches 4.2v first but it's the quality of the charger that determines how well this works. Inexpensive chargers such as the Accucell 6 will do a reasonable job of balancing, but I've heard many accounts of it not doing as well as was hoped by the owner of the charger. I suspect it was simply because the cells were so badly out of balance that the minimal balancing drain was insufficient to do a safe balance charge.

If I noticed that the cells were quite far apart to start, I would do a charge on each cell individually first, to bring them all up to the same level and then use the balance charge for the pack to keep them in balance.

Again, it bears repeating.... Xxxxxfire 18650 cells are *cheap* cells..... You WILL run into substandard ones if you buy enough of them. The ratings on the label.... as in 2400mAh for example is a number that should be taken with a large pinch of salt..... Cheap LiIon cells rarely meet the specs printed on the shrink wrap. Good quality Korean or Japanese 18650 cells will meet their published specs and cost 100% - 200% more than the typical Xxxxfire brand.

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 bmsweb » Thu Aug 04, 2011 4:14 am

kaptain_zero wrote:If I noticed that the cells were quite far apart to start, I would do a charge on each cell individually first, to bring them all up to the same level and then use the balance charge for the pack to keep them in balance.


Thanks for the info Christian, a lot of food for thought. However I don't understand why you would need charge them individually. Isn't a Balance Charger like the Accucell 6 supposed to do this automatically when connected via a balance plug? Sorry if this is a silly question but I come from the old Nitro Powered models days and electrics are all still very new to me.

Cheers
Paul
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Re: Charging my $8 Lithium Transmitter Battery

Postby RCModelReviews » Thu Aug 04, 2011 8:04 am

Yes, there are some really awful cells on the market, which is why I provided a link to those particular cells because they've turned out to be nice and reliable -- unlike some of the others being sold at DealExtreme.
RCModelReviews.com, just the facts.
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Re: Charging my $8 Lithium Transmitter Battery

Postby bmsweb » Thu Aug 04, 2011 8:54 am

I'm getting around 8.5hrs out of mine so all is good :)

http://www.youtube.com/watch?v=Zdaf4TP4aik
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Re: Charging my $8 Lithium Transmitter Battery

Postby kaptain_zero » Thu Aug 04, 2011 9:27 pm

bmsweb wrote:
kaptain_zero wrote:If I noticed that the cells were quite far apart to start, I would do a charge on each cell individually first, to bring them all up to the same level and then use the balance charge for the pack to keep them in balance.


Thanks for the info Christian, a lot of food for thought. However I don't understand why you would need charge them individually. Isn't a Balance Charger like the Accucell 6 supposed to do this automatically when connected via a balance plug? Sorry if this is a silly question but I come from the old Nitro Powered models days and electrics are all still very new to me.

Cheers
Paul



Paul, I did write I would, and not have to. <smile> My reason is simple, even inexpensive chargers such as the accucell can charge an individual lithium cell in about 2 hours if you select anything close to 1C of charge rate. If you attempt to charge a pack with cells that are far apart, such a charger simply charges at the set rate but has to apply a discharge on the higher charged cell, once it reaches it's maximum voltage, to keep it from going too high in voltage. This resistor drain is quite small, which is fine if the cells are nearly balanced but when they are far apart it can take what seems like forever to get the pack fully charged. Many times the charger will run up against the safety timer and shut down, leaving you with an unbalanced and not fully charged pack.

So, if the cells are out of balance by a significant amount.... just charge the one cell first and when it's full, charge the second cell and the total should be less than 4 hours. Now that they are both fully charged, they should remain close to each other and only require normal balance charging which should not take much more than charging a single cell.

Another point I should mention in case I forgot is that all Lithium rechargeable batteries prefer shallow discharge/charge cycles instead of deep discharge and full recharge cycles. It's the nature of the chemistry. Charge your pack up, use it for the day and then remember to charge it shortly before your next outing and you will get the maximum lifespan from your pack.

For a lot more information about all manners of rechargeable batteries, I'd suggest a visit to http://batteryuniversity.com/ which has a wealth of information and I have read the original "Batteries in a portable world" and it was well worth the read, but I have yet to read the updated one. Still, there is much to read on the website itself...

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 bmsweb » Thu Aug 04, 2011 9:35 pm

kaptain_zero wrote:Another point I should mention in case I forgot is that all Lithium rechargeable batteries prefer shallow discharge/charge cycles instead of deep discharge and full recharge cycles. It's the nature of the chemistry. Charge your pack up, use it for the day and then remember to charge it shortly before your next outing and you will get the maximum lifespan from your pack.


Thanks for the additional information Christian, I've actually charged them individually and they seem to have all come up fine. Thanks for the tips & link.
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