# How to fix high charge voltage in Liitokala Lii-100 and how to make lower charge currents

Based on measurements on six Liitokala Lii-100 bought in december 2015 I found that the charge voltage for 3.7V LiIon was a little high, all close to 4.25V. I like the uniform result (a quality sign). The voltages are nothing to be alarmed over, but personally I prefer to trade maximum power from a battery for a longer lifespan of the battery so I would like to lower the voltages a little.
I did some reverse engineering on a unit and found that it was easy to change the charge voltage. Two resistors (R5,R6 =150 kOhm, 1%) form a voltage divider for feedback of the output voltage. The fix is so simple that a picture is not necessary. All selectable voltages will be changed by the same percentage (in this example 1.2%).
FIX:
1. Unscrew the six screws and flip out the circuit board (secure the slider rail with a piece of tape).
2. R5 is found on the topside of the board just besides the +battery terminal (look at post #10).
3. Solder a 6.2 MOhm resistor across R5. Preferably SMD as there are not much space in the height. Can be mounted flat besides R5 and soldered at the ends (I used a 3MOhm plus a 3.3MOhm in V-form between the ends of R5. Resistors can be bought here.
4. Now, the charge voltage is dropped 0.05V.

I will not go into the formula for calculating the parallel resistor, just mention that another 6.2 MOhm (total 3.1 MOhm) across will lower the voltage a further 0.05V and so on. The 6.2 MOhm does not have to be exact. 20% off means 0.01V on output. If you just want to lower the voltage 0.025V then a 12 MOhm resistor will do it.
The charge voltage can be made higher if the operation is done on R6 instead.

Edit: SETTING LOWER CHARGE CURRENTS:

Modding the charger for use with smaller cells is equally easy. High and low current will always be 2 to 1 though.

R10 is sitting just behind the micro USB plug (look at post #10). It is a power resistor of value 0.050 Ohm. This gives 0,5 and 1 A charge current. The charge current is inverse proportional to that resistor (the other big resistor, R19 is for the power bank output). Fortunately there is good space to mount a leaded resistor.

Change R10 into:

0.100 Ohm and get 0.25A and 0.50A (for 14500, 16340, 18350 and larger)

0.200 Ohm and get 0.125A and 0.25A (for 10440 and larger)

0.500 Ohm and get 0.05A and 0.1A (for 10180 and larger)

I just bought two more chargers to make into dedicated ones.

Happy modding!

and about Lifespan vs. charge voltage.

Thanks. Very useful.

Thanks.
Maybe I’ll need it when my 2 Lii-100 arrive.

Anywhere I can get some of these resistors cheaply?

thanks!

Thanks for the info.

Thanks!

What chips have you identified?
Could you post pictures of the circuit board?

I don't see any 6.2M listed in the link provided.

• 10 units each of 1M, 1.5M, 2M, 2.2M, 4.7M, 10M, 1.2M, 3.3M, 5.1M, 3M

In case anyone needs it, Lii-100 is on the left. Teardown.

explain V-form?

It means he wired the two smaller resistors in series, then the set in parallel with the existing r5 resistor. The 3 resistors would physically form a triangle. If you stack the single larger resistor as recommended, you won’t need to bother with this.

KuoH

OH. I see. Then you could also solder 1.5M, + 4.7M,= 6.2M in series, then solder it in paralell to R5.

Is the 4.25V figure in the OP the voltage of a cell after it has been charged or is it the voltage of the charger taken while the charger is empty while plugged and measured the the + and - ends?

The measured values around 4.25V is the end voltages during charging. I have a piece of alu foil in each end of the battery and a Fluke 179 voltmeter with MINMAX function enabled connected to the foils. It stores the max voltage on the display.

May I know the voltages taken from the cell/s that was charged AFTER it was taken from the charger? (not DURING charging)

The main IC is a 14 pin unknown circuit (there are no markings on it). There is a separate 6 pin booster to make 5V marked AL579 but I have not yet found it by Googling. There are 3 MosFets marked 2300, a 3 pin Voltage reference TL431, marked 431, and a lot of other components. Interresting is that the charging current comes from an extra switcher, not directly from the 5V input.

I don't have that information, that is up to the type and age of battery, especially the inner resistance. I use different batteries, old and newer. It is not the battery, but the charger I am evaluating.