Getting the most out of Li-Ion charging

MrAl

Flashlight Enthusiast
Joined
Sep 9, 2001
Messages
3,144
Location
New Jersey
Hi NewBie,

Interesting article. I think they did overcomplicate one
design however -- with the pic controller he he, but
that would be cool to make anyway.


I've just finished a switchmode Li-ion charger and have
yet to test it with an actual cell (waiting to run one
down) but it checks out good with simulated loads so far.
I find that the switchmode works really nice for this
kind of charger as the input voltage range is something
like 9v to 30vdc !!!! This means it can also charge from
an automobile with reasonable efficiency too.

Previously i was using a linear charger and of course
it not only wastes more energy it gets sort of hot
in the process of charging. It's a bit simpler of
course though.

I like these kinds of chargers better than the NiMH ones
i guess because they dont require any storage for sensing
minus delta V or anything else like that -- all static
measurements to determine charge termination.

Take care,
Al

PS Having some system problems so i hope i can get back here
again soon.
 

SilverFox

Flashaholic
Joined
Jan 19, 2003
Messages
12,449
Location
Bellingham WA
Hello Newbie,

Excellent article.

2C as a max charging rate is mentioned. Experience has shown that while cell temperatures do not rise at 2C, capacity is reduced as is the number of cycles. I believe the maximum charge rate for "reasonable" performance is 1C and some cell manufacturers (Panasonic, I believe) state 0.7C as the preferred charge rate.

It is interesting to note the end of charge termination comments.

"In the fourth and final stage, the constant voltage charging is terminated. Unlike nickel-based batteries, it is not recommended to continue to trickle charge Li-ion batteries, which can cause plating of metallic lithium, a condition that makes the battery unstable. The result can be sudden, automatic and rapid disassembly."

I do not believe any of the R-CR123 chargers or the universal Li-Ion charger from BatterySpace provide for this. For that matter, using a regulated power supply for charging does not provide for that as well. It looks like leaving cells on these types of chargers for an extended amount of time should not be recommended.

For those not familiar with "sudden, automatic, and rapid disassembly," this is closely related to explosion with flame...

Tom
 

wptski

Flashlight Enthusiast
Joined
Jan 18, 2004
Messages
2,987
Location
Warren, MI
The Duratrax ICE does a trickle charge at the end of the cycle on Li-Ion/Li-Poly cells that "can't" be turned off. It is supposed to be a "special" Li trickle though!
 

SilverFox

Flashaholic
Joined
Jan 19, 2003
Messages
12,449
Location
Bellingham WA
Hello Bill,

The ICE signals the end of the "fast charge" when the current drops to 100 mA and shuts down completely when the current drops to 30 mA.

The Triton shuts down at 100 mA, and the Schulze seems to shut down at a value relative to the capacity of the cell you are charging.

It seems that the more expensive chargers do terminate the end current, while the cheaper chargers do not have that feature.

Tom
 

wptski

Flashlight Enthusiast
Joined
Jan 18, 2004
Messages
2,987
Location
Warren, MI
[ QUOTE ]
SilverFox said:
Hello Bill,

The ICE signals the end of the "fast charge" when the current drops to 100 mA and shuts down completely when the current drops to 30 mA.

The Triton shuts down at 100 mA, and the Schulze seems to shut down at a value relative to the capacity of the cell you are charging.

It seems that the more expensive chargers do terminate the end current, while the cheaper chargers do not have that feature.

Tom

[/ QUOTE ]
Tom:

I know what it does but the point is that "this" article and others I've read state that a "trickle" charge and that what Duratrax calls it, isn't good for a Li-Ion cell. Seems to be a difference of opinion here and there!
 
Top