Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

Tomi Koskela — Wed, 05 Nov 2025 10:47:15 GMT

Hello,

Note you should check the battery datasheet for the charging current spec. It can be 0.5C for instance and not 1C. The jumper wires+connectors can easily add extra resistance of 20-30mohm which will cause ~20mV difference between charger and the cell voltage. So this will add to the difference seen between charging voltage and the battery rested voltage. Shorter wires directly soldered to the board is recommended in this case.

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

mhni — Tue, 04 Nov 2025 10:19:56 GMT

Hello,

Thank you for your response. I didn’t get the datasheet for the battery.

Since I don’t have the official datasheet, I am assuming the maximum charging voltage is 4.20 V, as this is typical for 3.7 V Li-ion cells.

I The test setup photo is attached above.

I don’t have the matching battery connector, so I have connected the battery positive to the VBAT pin, battery negative to GND, and used a 10 kΩ resistor at the R9 position for the NTC input.

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

Tomi Koskela — Mon, 03 Nov 2025 11:25:15 GMT

Hello,

Does the voltage after charging period increase on each subsequent charging cycles? What is the maximum specified charging voltage for the battery? Increasing the termination voltage above the maximum charge voltage might cause also the battery PCM to prevent overcharging of the battery.

Do you have picture of the test setup? Long wires for the battery can cause considerable voltage drop.

Could you also share the datasheet for the battery?

After charging is completed at 4.2 V as per datasheet, the battery voltage naturally relaxes to a slightly lower value (e.g., 4.13 V) due to electrochemical relaxation. This is a normal behavior and does not indicate a loss of capacity or partial charge. Only if charging is terminated at very tiny currents would it stay very close to 4.2 V.

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

mhni — Mon, 03 Nov 2025 10:46:44 GMT

Hello,

I have tried increasing the termination voltage to 4.30 V to reach the expected battery voltage of 4.20 V.
However, every time on the first power-on, the charging stops at around 4.13 V.
After re-enabling charging, the battery then charges up to 4.20 V as expected.

This behavior is observed using the nPM1300 EV Kit with the nPM PowerUP application.
Could you please share your suggestions or possible reasons for this behavior, and how it can be adjusted so the charging reaches 4.20 V on the first cycle?

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

Tomi Koskela — Fri, 31 Oct 2025 12:40:12 GMT

Hello,

We don't have that kind of automatic behavior in the PMIC if that is the question. But it could be done with SOC/software control if needed.

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

mhni — Fri, 31 Oct 2025 11:51:11 GMT

Hello,

Thank you for the detailed information.
As the termination current is fixed at 10% of the charging current, would it be possible to automatically reduce the charging current after the battery reaches about 80% SoC to achieve a lower termination current and a termination voltage closer to 4.2 V?

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

Tomi Koskela — Fri, 31 Oct 2025 10:57:49 GMT

Hello,

Note the termination current is typically specified in the battery datasheet. This is for safety reasons and avoiding overcharging the battery. So if you will follow the battery manufacturer guidance for charging the battery you will see this voltage step between the termination voltage and the cell voltage when charging has ended. If you want to get smaller termination current (and get closer to the termination voltage when charging stops) you can adjust the charging current lower through TWI. Unfortunately the lowest termination current is 10% of the charging current, so to get lower you would have to change the charging current itself.

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

mhni — Fri, 31 Oct 2025 10:22:16 GMT

Thank you for the clarification.
Could you please provide your final suggestions or best practices to achieve accurate charging termination at 4.2 V?
I’d like to ensure consistent performance similar to the intended termination voltage behavior.

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

Tomi Koskela — Fri, 31 Oct 2025 07:43:25 GMT

Hello,

Not knowing the full details on the IP2312 charger I would assume the difference is in the termination current. It seems it does not have specific termination current, but it relies on timer function to stop the constant voltage charging. So yes it is different in that sense.

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

mhni — Fri, 31 Oct 2025 04:15:32 GMT

Hello,

When using the IP2312 Battery Charger IC, the charging process stops at around 4.32 V in accordance with the termination voltage setting.

In contrast, with the Nordic charger IC, the charging does not terminate at the same voltage, indicating a difference in termination voltage behavior.

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

Tomi Koskela — Thu, 30 Oct 2025 12:18:13 GMT

Hello,

This is due to battery behavior and internal ESR and it is completely normal to have higher cell voltage with 111mA charging current vs when there is no current sourced to the battery. The battery voltage will also drop slightly when rested due to the battery chemistry. This is considered already on the fuel gauging during the battery modelling that the rested voltage is not the same as the termination voltage.

The higher the charging current the higher the termination current and that makes the step bigger when charging stops.

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

mhni — Thu, 30 Oct 2025 12:00:36 GMT

Hello,

I also tried with another battery to verify the behavior:

Battery: 3.85 V, 1200 mAh Li-ion
Charging current: 800 mA
Termination voltage: 4.35 V
Trickle/Fast charging threshold: 2.9 V
Charging termination: 10% (default)
The first attached screenshot shows the charger operating in Constant Voltage mode, with a battery voltage of 4.37 V and charging current of 111 mA.
The second screenshot was captured after charging completed — the application reports 100% full, but the actual measured battery voltage is 4.26 V, while the expected set termination voltage is 4.35 V.
Could this early termination be related to the 10% termination current threshold, or possibly a voltage drop between the charger IC and the battery terminals?
I would appreciate any suggestions or guidance on how to ensure the charger reaches the configured termination voltage, or if there are recommended settings or additional tests to verify this behavior.

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

Tomi Koskela — Wed, 29 Oct 2025 11:54:38 GMT

Hello,

Ok this sounds normal to me. Battery voltage will be lower when charging has ended compared to when you charge it with 73mA (which is roughly the set 10% termination current). The higher the charging current the bigger difference you would see.

The fuel gauge accuracy and value depend on the selected battery model and how well it matches with the used battery.

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

mhni — Wed, 29 Oct 2025 11:41:50 GMT

Hello,

Here are the screenshots from nPM PowerUP showing the battery status during and after charging with the nPM1300-EK.

During charging, the battery voltage gradually rises until it reaches 4.2 V, and the charger enters constant voltage (CV) mode.
In CV mode, the charging current slowly decreases from the set 800 mA (in this case, it dropped to around 73 mA) as the battery approaches full charge.

Battery charging completed (V = 4.10 V, I = 0 mA, Fuel Gauge = 93.2%)

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

Tomi Koskela — Mon, 20 Oct 2025 07:29:26 GMT

Hello,

In nPM PowerUP what does the battery status show? Does it go to constant voltage mode and what is the indicated battery voltage?

This is with nPM1300-EK and nPM PowerUP with the same settings you mentioned. Once the 4.2V is reached, the charger enters constant voltage mode and the charging current slowly drops from the set 800mA (in this case it has dropped to 550mA).

Thanks.

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

mhni — Fri, 17 Oct 2025 11:25:37 GMT

I have tested using the nPM1300 EK and configured the charger using the nRF Connect for Desktop – nPM PowerUP application with the following parameters:

Charging current: 800 mA
Termination voltage: 4.2 V
Trickle/Fast charging threshold: 2.9 V
Charging termination: 10% (default)

I also tested both configurations — with and without a 10 kΩ NTC thermistor .

The setup was powered using a 5 V adapter. During charging, the VBUS voltage is around 4.9 V, and after charging completes, it stabilizes at 5.0 V. The battery used is a Li-ion (3.7 V nominal, 950 mAh).

In both cases, the charging still completes around 4.13 V, instead of reaching the expected 4.2 V termination voltage.

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

Tomi Koskela — Thu, 16 Oct 2025 06:19:39 GMT

Hello,

Ok thanks for the information.

It would be good if you can try to replicate the setup on EK using the same 5V power adapter. Just to make sure there is nothing wrong with the connection or the adapter. Have you measured the 5V adapter output voltage with oscilloscope to see how stable it is?

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

mhni — Wed, 15 Oct 2025 11:10:50 GMT

Hi,

During charging, the VBUS voltage is around 4.9 V, and after charging completes it rises back to 5.0 V.

I also read the BCHGERRREASON register but did not see any errors reported.

I tried reducing the charging current to 500 mA, but it didn’t affect the termination voltage.

When I set the VBUS current limit to the default 10%, the charging stops around 4.13 V.

So far, charging seems to stop normally without any error indication, but the termination happens earlier than the expected 4.2 V.

Yes, I do have the nPM1300-EK .

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

Tomi Koskela — Wed, 15 Oct 2025 06:56:32 GMT

Ok, VBUS level sounds good then. So the VBUS voltage itself is not limiting the achieved termination voltage. Just to confirm, the VBUS is at 5V during charging?

Checking the event registers would reveal if the charger has generated some error what causes the charging to stop.

Reducing charging current could be also something to try, just to see will it effect the termination voltage.

Do you have nPM1300-EK to try to replicate the setup?

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

mhni — Tue, 14 Oct 2025 12:38:01 GMT

Hi,

I checked the VBUS voltage in this condition, and it is 5.0 V.

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

Tomi Koskela — Tue, 14 Oct 2025 11:35:35 GMT

Hello,

Ok, thanks for the clarification. Yes you are correct 3.9V is not a valid value, but something lower than the 4V you already got previously with 4.2V setting could be checked to confirm the control works as expected.

Did you check the VBUS voltage level in this condition?

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

mhni — Tue, 14 Oct 2025 11:22:58 GMT

Hello,
Thanks for the troubleshooting hints.

Charging current when it stops
→Charging Current Stops when It goes to 0 mA immediately (i.e., the charger reports 0 mA once charging finishes).
How VBAT is measured
→ VBAT is measured using the ADC.
Termination voltage testing / BCHGVTERM
→ I wanted to try setting termination to 3.9 V to test whether the charger would stop at 3.9 V, but the BCHGVTERM register options in the datasheet don’t allow 3.9 V. I set BCHGVTERM to 4.00 V instead, and charging stops at 4.00 V — so the regulator is following the BCHGVTERM setting as expected.

RE: Battery Stops Charging at 4.0 V (Expected 4.2 V Termination, 20% Termination Current)

Tomi Koskela — Fri, 10 Oct 2025 11:35:00 GMT

Hello,

When the charging stops, does it go to 0mA immediately or just slowly go down? Charging will slow down anyway when the VTERM is reached and charger goes to constant voltage mode. How is the VBAT measured in your case? With the ADC or with some measurement equipment? How about the charging current? If you have current meter in series with the battery there is also some voltage drop across the meter itself that has to be considered as well.

1. I cannot think limit that could affect this

2. No, it will just effect the thermal regulation and JEITA temperature ranges for charging current.

3. You can check errors for the charger in the CHARGERERRREASON register. You can check EVENTSBCHARGER1SET register for the charger status events. There are also other event registers you could check, but these are the first ones to check. Note the event registers are latched and you need to clear them if you want to see does it trigger again.

4. Yes it can be that VBUS is too low, good to check that in this condition. VBUS must be at least 150mV higher than VBAT to be able to charge.

5. Termination voltage has 1% tolerance, so this is not caused by 1% difference. And for the recharge to activate the battery would first be charged to full anyway.

You could try to set the termination voltage to 3.9V for example to see does it then stop at 3.9V. This is to see is the control for the BCHGVTERM correct and is there something else in the system limiting the voltage (for example VBUS voltage).