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

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sixty545
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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!

Added: Read about high charge voltage - a safety matter!

 and about Lifespan vs. charge voltage.

Edited by: sixty545 on 01/16/2016 - 10:00
Halo...
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Thanks. Very useful.

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

SIGShooter
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Anywhere I can get some of these resistors cheaply?

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thanks!

sixty545
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SIGShooter wrote:
Anywhere I can get some of these resistors cheaply?

Added a link in the OP.

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Thanks for the info. 

My current and or voltage measurements are only relevent to anything that I measure.

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SIGShooter
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sixty545 wrote:

SIGShooter wrote:
Anywhere I can get some of these resistors cheaply?

Added a link in the OP.


Thanks!
Halo...
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What chips have you identified?
Could you post pictures of the circuit board?

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

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Streamer wrote:

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
sixty545 wrote:
… (I used a 3MOhm plus a 3.3MOhm in V-form between the ends of R5. Resistors can be bought here.

If anything can go wrong, it will.
Matter will be damaged in direct proportion to its value.

hank
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Quote:
in V-form between the ends of R5

explain V-form?

kuoh
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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

hank wrote:
explain V-form?
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OH.  I see.  Then you could also solder   1.5M, + 4.7M,= 6.2M in series, then solder it in paralell to R5.

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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?

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tatasal wrote:
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.

tatasal
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sixty545 wrote:

tatasal wrote:
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)

sixty545
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Halo... wrote:
What chips have you identified? Could you post pictures of the circuit board?

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.

sixty545
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tatasal wrote:
sixty545 wrote:

tatasal wrote:
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)

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.

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4.25V for charging is quite normal, so other than standardizing end voltage and increase battery endurance per OP wish, other members with regular charging use might not need to do this procedure.

Just my viewpoint, this mod slows down charging a bit and leave you with less charge capacity (and of course in doing so increase battery lifespan).

sixty545
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Pulsar13 wrote:
4.25V for charging is quite normal, so other than standardizing end voltage and increase battery endurance per OP wish, other members with regular charging use might not need to do this procedure. Just my viewpoint, this mod slows down charging a bit and leave you with less charge capacity (and of course in doing so increase battery lifespan).

Right! Nice sum up.

You can also use this fix for the 4.35V position if you only have 4.30V cells. Remember that all voltages are changed by the same percentage.

It seems to be a good charger. I just miss lower charge currents. 0.5A is not really good for many batteries. I can only think of 18500, but for 14500 and smaller, I want 0,25A or lower.

sixty545
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New feature in OP. Set your own current.

hank
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Have you checked what those changes do to the NiMN charging behavior?
With an unmodified one, AAA NiMH cells get warm on the 0.5A setting.
I have no clue what method this charger is using charge NiMH cells though.

sixty545
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hank wrote:
Have you checked what those changes do to the NiMN charging behavior? With an unmodified one, AAA NiMH cells get warm on the 0.5A setting. I have no clue what method this charger is using charge NiMH cells though.

I think it is quite normal that AAA NiMH get warm at 0.5A.

I just made myself a mod with 50/100 mA charge current for charging some incoming 10180. I have no intention of using that unit for charging NiMH. Let's see what HKJ finds out about the NiMH charging method and we can act accordingly.

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Excellent find on the current setting! Should be easy enough to remove R10 and swap with slider switch with different resistors, high vs low current.

(I’m too lazy to do it, pass to someone else.)

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Excellent mod, now I can make a decent charger for the 10180.
Thanks!
Keith

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Quote:
Should be easy enough to remove R10 and swap with slider switch with different resistors, high vs low current.

(I’m too lazy to do it, pass to someone else.

paging RMM or anyone else in the business of improving on things …

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Quote:
I have no clue what method this charger is using charge NiMH cells though.

+1

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really thank you

hank
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> quite normal that AAA NiMH get warm at 0.5A.

Agree; some chargers use the change in temp., don’t know about this one.

Yeah, let’s wait on HJK. But if you do discover anything about how your modified chargers handle NiMH, info appreciated.

I’d guess it won’t make any particular difference, but WTFDoIKnow …

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