I now have 2 chargers that terminate below 4.2V, instead of buying another one to see if it can fully charge a battery i thought i’d ask if its possible to fix the ones i have
Usually not without rewriting firmware on the chips that regulate the charge.
What are the chargers ?.
Yup, unless it’s a hobby charger, it’s very hard to adjust the termination voltage.
ml-102 from fasttech and an unnamed intl outdoor charger
why would they write wrong firmware in the first place?
Does it deviate too far from 4.20V?
They probably did correctly program it and/or used the correct chip, it’s just that the tolerances of the components are not good.
For example, my Accucel-6 hobby charger had bad resistors that would vary in resistance by a lot whenever there was a lot of current flowing through them.
the intl outdoor charger is 4.15V and the ml-102 is 4.11V
I guess I've been lucky. Most of my chargers over charge. At least I can get a perfect charge by monitoring charging with a multimeter. You can't do much if it's under charging. All this uncertainty about chargers is what will probably force me to get a hobby charger. At least then I can tweak the settings to get a full charge.
Hmm, might be worth taking it apart and swapping in higher quality components. Not worth it financially, but it'd provide peace of mind and be educational. I'll do this with my Nitecore i4 if I can't get it exchanged. Mine terminates way too early...like it basically doesn't work with li-ion's 85% of the time.
You know that DMMs have tolerances, too? Unless yours is calibrated, it could easily be off by 0.05V..
lalalalala…I don’t hear you!
good point, so i checked with another meter and got 4.16V, so that suggests that at least one is not quite calibrated correctly, but the chargers are still undercharging (unless both are off quite a bit)
That depends on the charger, sometimes it is build into a chip and cannot be changed, other times it is controlled with external resistors and can easily be changed (If you can locate the correct resistor).
If you have an error margin of 1% in any part of the charger, its amazing that they still charge close to 4.2V. ;)
1% of 4.2V is 0.042V, now multiply that with all the parts involved in charging. LiIons may be charge up to 4.25V per spec, but its better to stay below. My Xtar WP2 charges to 4.17V, and I dont mind. Its not as if there would be much energy in those 0.03V..
Yeah, charging 0.10V under the max voltage supposedly doubles the life cycle of the cells. 
Yes, undercharge is a good thing. I have one cheap charger which terminates at 4.35V. There are no resistors, just some chip.
for the ML-102 you reviewed is there a way to adjust it (i have the v5 but i assume the same method might work)
@ryansoh3 i agree that most of the time i don’t need 4.2V, and tbh i am happy to have a charger that terminates at less then 4.2V, but i want one charger that fully charges for the odd time i am going to use the light a lot and have no extra batteries on me
As far as I know it uses a single chip with everything inside for charging, i.e. it is not possible to adjust voltage.
darn, thanks for replying though, next time i can afford to play the charger lottery i’ll give it a whirl
ML-102 use TP4057 charging control IC. (as fasttech say)
So it impossible to adjust termination voltage.
However you can reduce charging current by changing charge current program resistor.
TP4057 designed to stop charging when charging current dropped below 1/10 of programmed current.
if charger programmed to 1A, it terminate current drop to 100mA
that way, some batteries actually terminated below 4.2V due to increased internal cell resistance.
so if you reduce current to 500mA, terminatation current is 50mA and battery will charge more. Just try it!