Overcharge protection?

[jasonck08]

Why do so many so called "protected cells" have there overcharge protection set so high? Most "protected cells" overcharge protection kicks in at 4.3v or more.

Wouldn't people like it to kick in a little earlier? Such as 4.20 or 4.25v? Then you wouldn't have to worry so much about accidently overcharging with a crappy charger?

It seems like if your going to put an IC on the PCB for a protection circuit, you might as well make use of it.

What do you guys think?

 

[richardcpf]

Been using the WF139 without knowing it charged some cells up to 4.5v if I let them there after charging complete... but got no problems so far

 

[jasonck08]

Been using the WF139 without knowing it charged some cells up to 4.5v if I let them there after charging complete... but got no problems so far

Wow thats scary high voltage. Enough to almost pop the cell!

 

[JCD]

Why do so many so called "protected cells" have there overcharge protection set so high? Most "protected cells" overcharge protection kicks in at 4.3v or more.

Wouldn't people like it to kick in a little earlier? Such as 4.20 or 4.25v? Then you wouldn't have to worry so much about accidently overcharging with a crappy charger?

It seems like if your going to put an IC on the PCB for a protection circuit, you might as well make use of it.

What do you guys think?

It depends on the cell.

There seems to be some debate about the actual danger posed by "overcharging," aside from simply shortening cell life, so I wouldn't want it set too low. I would consider anything below 4.25 V to definitely be too low, since that's still within most charging recommendations (4.20 V ± 0.05 V).

 

[BIGLOU]

My crappy WF-139 only charges to 4.15 after checking it with my DMM.

 

[TranceAddict]

1. Do not use crappy *fire brands like WF-139.
2. PCB overvoltage protection is meant for secondary protection, and should only kick in when charger failed to cut-off, it is really meant for last resort.
3. A lot of charger uses high voltage PWM pulse to increase charging efficiency, settle cut-off voltage too low will trigger false termination.
4. back to the point, throw off your wf-139/*fire/*shine/*ergy craps and get a quality one.

 

[Ray_of_Light]

A proper charger (but not the WF-139) is supposed to provide the constant voltage phase of the charge cycle at 4.20 V for several hours, then cut off.
If you set the overvoltage protection at 4.2 V, the cell will skip the CV phase, and never charge completely.
The cell internal protection is really meant, as others said, as additional measure of protection; this is why is normally set at 4.3 V. There is little choice here.

Regards

Anthony