Maha C777PlusII Charger

[Windscale]

Having used the Maha (Powerex) C9000 charger for AA batteries, I was quite satisfied with its ability to rescue old batteries. So I have also bought a Maha C777PlusII charger for charging Li-ion 123as and 18650s etc. Many Ultrafire protected batts of 880mah turned out to be over 1000mah after charging. The charging process took about 4 hours. The charger indicated "FULL". This is contrary to some CFPers who wrote that most R123As turned out about 600mah after charging. Also, most Ultrafire 18650s (2400mah) turned out to be well over 2800mah after charging. But the process took some 8 hours before reaching "FULL".

The charging process would take well less than 2 hours with the ordinary Ultrafire charger.

Battery capacities appeared to have increased by some 30% using the Maha charger. I have also verified this by timing the actual discharge duration using a lamp for this purpose.

Please can anyone enlighted me as to whether what I have done with the new Maha charger is safe. And whether it is time to throw the Ultrafire charger away. Is it all right to charge the batts so fully that this will affect their life.

 

[max52]

I have used the C777Plus on all variety of Lion cells. I Have even used it on D Lion cells. It has always terminated at a safe voltage of 4.1X volts. the only problem is that it is slow. The Triton Is faster, and when set on 3.6 volts charges to 4.1X volts. In fact, I use the C777Plus on many packs because it charges NiMh and NiCad packs to a higher capacity than my Triton.

My feeling is that it is safe, reliable, but slow.

 

[Closet_Flashaholic]

Please can anyone enlighted me as to whether what I have done with the new Maha charger is safe. And whether it is time to throw the Ultrafire charger away. Is it all right to charge the batts so fully that this will affect their life.

I have also have the C777PlusII and find that it tends to fry (Xtreme overcharging) NiMH batteries. I haven't used it much with Lithium-ion types. I like the features of it a lot, I just have to keep an eye on it when charging lower capacity types. I ended up buying another charger to compliment the Maha and use in situations where I can't monitor the charging as closely.

 

[Windscale]

Closet Flashaholic,

Which charger did you buy? Is it good for charging R123as and 18650s?

 

[hburner]

I have been using the MAHA for about 2 years now, charging NIMH, LION, and NICAD, without issues from any of the before mentioned. But I will agree that it could charge a little faster.

 

[matrixshaman]

Windscale - what voltage do your Li-Ions read when they come off the Maha? I assume you have seen Silverfox's info on end voltage numbers versus cell life. I don't have a chart in front of me but if they are done at around 4.10 to 4.15 they will tend to have a long life. If they are up to about 4.20 they are still pretty good but 4.25 or above and life starts getting real short.

 

[Windscale]

I have not measured the voltage straignt off the charger. I shall do this measurement next time I charged up a batt and then come back to this space.

 

[mdocod]

definetely test that voltage fresh off the charger.. It's very possible to cram a LOT more capacity into a li-ion by overcharging it, just doesn't last long.

 

[racer7]

Had a strange episode with a pair of unprotected 2000 mAH 18650s last night on a 777.

They were in a FiveMega modded 3C ROP hotwire and when charged through the plug on the body, the front batt overheated (got about as hot as a hot NiMH). One batt came out at 4.5+ V (!!) and the other at 2.7V and wouldn't charge on anything. Both batts should have been in good shape prior to that charge cycle at at high enough voltage to not create any issues; the light had only a few minutes of use and had been charged this way with the same batts a number of times.

Not sure whether the ROP current overtaxed a cell leading to failure, the batts are poor (they're not LG or AW), or the charger contributed to it. It hasn't caused me any issues charging AW's C Lions in a FiveMega 1185 setup.

I don't want or need faster but wished NiMHs didn't get so hot on it. Just about any time you put energy through anything, cooler is better for long life.

 

[SilverFox]

Hello Racer,

The cell at 4.5 volts is at too high a voltage. You need to discharge it to a safe level (4.2 volts or lower).

It appears that your battery pack is not balanced. You can try to charge the 2.7 volt cell, but keep an eye on it.

Cell imbalance can be caused by higher resistance connections, over discharge, high current rates, and aged cells. Check your setup carefully and be thankful that your overcharged cell did not go ballistic on you.

Tom

 

[Windscale]

Thank you for all the contributions to this thread. I have learnt so much. My next question is about 'balancing'. At the moment I only feel safe charging 18650s one at a time using the C777 for fear that if I charged a pack (with cells lined up in series), the cells may be imbalanced and hence not safe. I have heard about 'balancers' used by flight hobbyists to charge battery packs. These will balance out the batts even they are in series.

Please enlighten me as to what these balancers are and whether if I get one I can charge 18650s packed in series safely and have the cells balanced after a charge. If this be the case, please recommend a brand to me. Thanks again.

 

[SilverFox]

Hello Windscale,

Balancers require that the cells in the pack have a wire running from each end of each cell. They monitor the voltage differences between the cells and adjust the charge, or bleed off excess charge to keep the cells in the pack at the same voltage. This eliminates the problem of one cell in a pack being overcharged, and makes for a safer way to charge.

If your pack has taps installed, you can pick up a balancer, like the Astro Blinkey, and use it. If your pack does not have taps, you would need to install them.

Packs used within "normal" rates, usually don't show an imbalance between cells for several hundred charge cycles. Some people check the balance every 5 charge cycles to keep track of how things are going. Others put safety first and balance with every charge.

The alternative to charging Li-Ion cells in series with a balancer is to parallel them and charge them that way. When parallel charging, no balancing is needed.

Tom

 

[racer7]

Tom,
I was "nearby" when the one cell went hot. Because the 777 end of charge alarm hadn't sounded about when I expected it to, I examined the light, immediately noticed the front cell heating up and disconnected it. I don't leave unprotected cells unattended but this is the first time I've had an issue like this - makes one wonder what might have happened had it ben left overnight in the sealed light body. The 777 has a thermal sensor but depending on sensors isn't my thing- I see way too many fail at work and I won't own a car without a dipstick, either.
Putting another pair of batts in the light showed it to function normally and it has no wiring problems.
I don't think there's any obvious way to tell if the cell developed a problem prior to charging,whether it failed during the charge cycle or the 777 exacerbated a problem but if you have any ideas I'd like to know how. One thing for sure, I was probably about to find out if the overheat error/stop on the 777 actually works had I not interrupted it first.
It makes a good case for better batts than unprotected 18650s for ROPs or similar hotwires even if one's charger has a thermal cutoff.

 

[SilverFox]

Hello Racer,

I am glad you were there to intervene.

Sometimes cells do weird things. That's why it is always a good idea to keep an eye on things. It sounds like your issue is with the cell and not the charger.

Tom