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› charge 2 cell with only 3 cell charger
11-03-2013 05:28 AM  4 years agoPost 1
milocs

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PUERTO RICO

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hi im trying to charge a 2 cell 7.4 battery but my charger is only 3 cell and does not have any form of changing is the a way by putting a dummy cell or how can i still use this charger with out having to buy another for now thanks

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11-03-2013 07:09 PM  4 years agoPost 2
Gregor99

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Western Wa

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What charger is it?

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11-03-2013 10:05 PM  4 years agoPost 3
qraptor

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Illinois

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You definitely do not want to charge 2 cells with the charger at 3 cell setting.

But I'm surprised there is no option to select a 2 cell mode.

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11-05-2013 06:50 AM  4 years agoPost 4
milocs

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ok its one of the eflite efl3105 balance charger 0.80 output
i just was wondering cause i was planning to use it to charge some
radios which i made their nimh batteries to lipos @ 7.4vs and have this charger sitting doing nothing so far i have used it by adding a 3rd cell in to complete the 11.1v but that cell i use as a dummy so is there any way i can bypass that thanks just like to tinker with this stuff thanks

p.s. i do use a lipo safety pouch !!!

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11-05-2013 07:44 AM  4 years agoPost 5
milocs

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ok think i got some where today i opened the charger up and looking around i noticed some trace pads one next to an IC was marked 3 and was jumped to a leg of the ic and saw another make 2 i connected that and unsolder the one that said 3 but no good i soldered the 2 and 3 so that all went back to ic and yesssss using only pins --+ works before was ---+

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11-05-2013 05:10 PM  4 years agoPost 6
Gregor99

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Western Wa

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The LiPo charge program is completely different than the NiXX charge program. You cannot use a LiPo charger to safely and correctly charge NiXX cells. Most modern LiPo chargers include several NiXX modes.

The NiXX modes do not terminate based on voltage and current like the LiPo program. NiXX terminates based on fall back voltage. Using the NiXX program would likely over charge or under charge the NiXX cells.

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11-05-2013 06:54 PM  4 years agoPost 7
qraptor

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Illinois

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Lipos are charged on a CC/CV manner. They are charged at a constant current (CC) until the set voltage is reached, and then the charger holds that voltage (CV), while monitoring the current being supplied to the battery. The current steadily drops, and when the current drops to below 5% of the value, the charging is stopped.

And, as Gregor said, NiMH or NiCads keep getting charged until there is a sudden, small drop in the voltage of the cells.

So, a Lipo setting will not work.

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11-05-2013 06:57 PM  4 years agoPost 8
JKos

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Redondo Beach, CA

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He is trying to charge LiPos with a LiPo charger. Not sure why you guys started talking about NiCd/NiMh.

He figured it out, too. Good job, milocs.

- John

RR rules!

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11-05-2013 08:51 PM  4 years agoPost 9
Gregor99

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Western Wa

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Not sure why you guys started talking about NiCd/NiMh.
Its because despite reading his post several times I barely understood what he actually said. No insults intended. Its just the communications challenges we face as global community and I am trying to cope. Anyway apparently I was incorrect about the NiXX part. Sorry about that. But I still cannot tell if he got it working correctly.

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11-08-2013 01:38 AM  4 years agoPost 10
milocs

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PUERTO RICO

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ok just to update thanks for your help and advice here is what i wanted to do and what i got accomplished for better understanding

1. i have a eflite 3105 only 3 cell 11.1v lipo balance charger (thats the little cheap one that comes with some eflite helis.

2. i built a 2 cell pack 7.4v lipo. which i need to charge and was waiting to make sure the pack would supply the radio good enough before
spending money on a good charger...

3. now since the charger is 3 cell it gave me a battery error both
green and red flashig of course it detects 1 cel is missing
so i added a dummy cell and all worked good charges good

4. but then i went a bit futher and opened the charger and notice that by an ic (intergrated circuit) lol:-) there was a spot where it was marked 2 and another marked 3 which had a blob of solder so i removed that blob and connected it to the one that was marked 2 and nice now i dont need the dummy cell and charges 7.4 the last wire on the balance wire is now dead and no 11.1v on this line

charger is working as specified for lipo 4.20 volts per cell max
all voltage verified and just wating to see how long its taking to charge them thanks to all for your 2 cents ty

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11-08-2013 04:10 AM  4 years agoPost 11
Gregor99

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Western Wa

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Thanks for the additional details. Nice work. What did you use for dummy cell?

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11-08-2013 04:40 AM  4 years agoPost 12
milocs

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PUERTO RICO

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For the dummy cell i used a brand new 3.7v
Cell phone battery of same capacity (mah) as the other lipo since it also had its own little protection board .. i soldered on directly to board connector will post pics and diagram when i get home

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11-08-2013 04:14 PM  4 years agoPost 13
qraptor

rrApprentice

Illinois

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Nice bit of sleuthing.
Would like to see the pics.

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