Maha C777 PlusII Caution

I ran into a discussion on this charger here .

It seems someone at Maha seems to think that unprotected Li-Ion cells are not suitable for use with this charger.

"We do not recommend using the
MH-C777 Plus-II
with TP or Kokam Li-Polymer batteries. The reason is because
Li-Polymers are very unstable when charging or discharging, and a protection
circuitry is required to regulate voltage and current; it also allows the battery
to interact with the charger. This circuitry is not built in either TP or
Kokam batteries, which increases the chance of fire or damage.

I'm aware that the MH-C777Plus-II specifies that it will also charge
Li-Polymers. However, it is only safe to charge them with the
circuitry.

This is not only true for our charger, but all chargers out there."

Since Li-Poly cells share the same chemistry as Li-Ion cells, I am assuming that this would also apply to our use as well.

I know several people use this charger and I am wondering if there have been any problems with it observed while charging unprotected Li-Ion cells?

On the other hand, it could be that this customer service person is un-informed...

Tom

Tom:

I read that post and if you read it all, most don't believe that the info was correct.

Hello Bill,

Not according to Fred. He stopped carrying those chargers after having several problems with them.

Tom

SilverFox said:

Hello Bill,

Not according to Fred. He stopped carrying those chargers after having several problems with them.

Tom

Click to expand...

Tom:

I think that there was a problem but it was with the early C777PLUS models which I have also. I never had any problems with the C777PLUS model but the C777PLUS-II has failed to terminate several times. It's at the end of the cycle while in the CV stage, so current is very low and causes no problem at all. The 13 hour safety timmer hasn't worked for me but the temperature probe does work.

i can explain some possibilities that can occur, that i have observed.
if i knew how to

some of the TINY little circuit things are fairly dum. same thing with a protection curcuit.
if the battery is already over the stop voltage, it can blindly continue.
if the things are auto, and they attempt to determine the number of cells, they can fail, and think there is more with a well charged battery.
if the power comes undone at the correct moment, the brains can fail.

if its voltage controlled, it seems to be much safer if the MAX output is the max that the battery could ever get to, via a HEARTY component that has been used for 30+ years now, like the adjustable voltage regulators, then its much safer.

in other words, the tiny chips can only have so much smarts, add in the way mosfet operate, and one shouldnt trust that stuff.

just like you dont charge a charged ni-mhy on most of the ni-mhy chargers, it is probably unwise to top-off li-ions that are fully charged.

changing a battery from one charger to another might be a total misteak.
so say i charge one to 4.35, then toss it into a curcuit that is expecting to eventuallly see a 4.25 for cutoff, and its max is 5v, DEPENDING on the stupid chip they used it could not cut-off.

ok so only silver might understand that, but its there anyways.
Missed the cutoff, because it was already past it.

also the PACK problem, people THINK they can charge unprotected SERIES's of li-ions using a li-ion charger. and that is totally not so. and there are MANY that dont understand the logic of it.

if you have a li-ion charger that will charge a 7.2V camcorder battery, that camcorder battery is protected.
if you think you can put 2 li-ion cells unprotected on that same curcuit, then that is TOTALLY WRONG. because one will be under and the other will have gone over, and the safety vent will open, and you lose the battery.

7.2 charger trying to cut-off at 8.4
one battery at 3.9 other at 4.5 and toasted.

wptski said:

Tom:

I think that there was a problem but it was with the early C777PLUS models which I have also. I never had any problems with the C777PLUS model but the C777PLUS-II has failed to terminate several times. It's at the end of the cycle while in the CV stage, so current is very low and causes no problem at all. The 13 hour safety timmer hasn't worked for me but the temperature probe does work.

Click to expand...

I have a C777-Plus II and have used it to charge appox 24 Li-Ions I pulled from laptop battery packs.

I have had no trouble with it. It has always terminated at 4.15vdc per cell. I have found that it seems happier charging two 18650's in series - 8.3vdc termination. Before starting I usually take a voltage reading and match voltages. Those to far off I charge singlely. The cells are never warm and charging has always terminated.

The only time I have ever had a problem was if a cell was to low and the switch was set to NiMH instead of Li-Ion. The problem was noticed on the lcd display via funny voltages. Disconnected everything, unplugged and then started over, all went well.

Since I recycled my 18650's from laptop packs any cell acting funny (run time, voltage, etc.) gets dropped into the battery recycle bin, I've dumped 6-8 already. I numbered each cell and kepted a log, charging time and mah became very perdictable, example: for two cells in series: 8.3v 2300-2335mah 331-348 minutes, right off the charger cell measures 4.282-4.336vdc on my Fluke DVM.

=D~~ Kilted

Kilted said:

I have a C777-Plus II and have used it to charge appox 24 Li-Ions I pulled from laptop battery packs.

I have had no trouble with it. It has always terminated at 4.15vdc per cell. I have found that it seems happier charging two 18650's in series - 8.3vdc termination. Before starting I usually take a voltage reading and match voltages. Those to far off I charge singlely. The cells are never warm and charging has always terminated.

The only time I have ever had a problem was if a cell was to low and the switch was set to NiMH instead of Li-Ion. The problem was noticed on the lcd display via funny voltages. Disconnected everything, unplugged and then started over, all went well.

Since I recycled my 18650's from laptop packs any cell acting funny (run time, voltage, etc.) gets dropped into the battery recycle bin, I've dumped 6-8 already. I numbered each cell and kepted a log, charging time and mah became very perdictable, example: for two cells in series: 8.3v 2300-2335mah 331-348 minutes, right off the charger cell measures 4.282-4.336vdc on my Fluke DVM.

=D~~ Kilted

Click to expand...

I think my unit is a lot older than yours as I used it to charge my cellphone batteries from my last phone which was a around two years old.

Last night I charged the "same" Li-Ion cellphone battery that failed to terminate at least once. This is odd too! You know how after it finishes it's cycle, it beeps(should have heard the C777PLUSs ) and retains charge info on the screen? It beeped during the night but when I get up to go to work, screen is like there's no battery there. I forgot to check the voltage earlier but it's 4.09V and the charger won't even start with that cell connect but will with another cell that reads 4.13V! Maybe this cell did get damaged or is funky to begin with?

VidPro said:

i can explain some possibilities that can occur, that i have observed.
if i knew how to

also the PACK problem, people THINK they can charge unprotected SERIES's of li-ions using a li-ion charger. and that is totally not so. and there are MANY that dont understand the logic of it.

if you have a li-ion charger that will charge a 7.2V camcorder battery, that camcorder battery is protected.
if you think you can put 2 li-ion cells unprotected on that same curcuit, then that is TOTALLY WRONG. because one will be under and the other will have gone over, and the safety vent will open, and you lose the battery.

7.2 charger trying to cut-off at 8.4
one battery at 3.9 other at 4.5 and toasted.

Click to expand...

Why don't you try posting this in a RC Forum that you can't charge unprotected Li-Ion cells wired in series as a pack? What do you think a 2P3S pack is? That's done all the time! They may get unbalanced, true but some add taps or some come with balancing taps.

I'm still trying to figure out what your trying to say about charging protected cells in series!

wptski said:

Why don't you try posting this in a RC Forum that you can't charge unprotected Li-Ion cells wired in series as a pack? What do you think a 2P3S pack is? That's done all the time! They may get unbalanced, true but some add taps or some come with balancing taps.

I'm still trying to figure out what your trying to say about charging protected cells in series!

Click to expand...

i was saying what your all saying. if you KNOW what is going on then your OK, and obviously we know what is going on.

YET there are out there, people purposfully setting fires (for sensationalism), and people who do not knowing what is going on. and neither the products nor the cell should be condemned for how people end up using them , and TALK of sombody failing with particular units, because they dont comprehend the logic of the operations, means little to nothing, to the people who know how to operate it correctally.
there is now a rediculous ammount of disclaimers put on li-ion sales sites now, and bs talk of being sued and all :-( they are hard enough to get as it is.
if humans dont understand them, or dont read the manuels for them, then they should ONLY use packs that will balance themselves, and are protected, so the rest of us can continue. (like they can stick to consumer products, that charge their own batteries, with thier own chargers, no wires to connect, or thought required)

i was basically discussing unprotected in that sence.

in the sence of protected, there is both the pack that CAN balance, and there are packs that are not capable of rebalancing themselves. but at any rate without the protection, and/or an aware human, the technology is wasted.
and
single cell protection, in series packs will not self balance, because one cuts off the seires. so if you toss a bunch of pila type cells IN SERIES in a light, and stick an appropritate charger on that light, eventually an imbalance will occur and continue till the pack is weak, or untill sombody seperates and tops each seperate cell off.
its not like the other rechargables which could easily handle a light overcharge to balance it, the protections cuts off the sieries, even if some of the cells are not charged (balanced to the rest)

if were going to have access to loose cells, different cells, and chargers that work great as long as the human comprehends the actions, then those people that we hear about that cant operate thier computer , thier microwave, or could blow the engine on thier car, with some stupid misteak of awareness, shouldnt be ALLOWED to touch the things