# Any Idea/Solutions of Battery charging (Two 3.6V Li-Ion in series) based on temperature variation

#### mishra87

Joined Jan 17, 2016
947
Hi Guys,

Could anybody suggest me any idea of Battery charging (Two 3.6V Li-Ion in series) based on temperature variation.
Lets say below temperature 15degC charging current will higher
Beyond 15degC charging current will be lesser .

Which method i should opt for this ?
Temperature measurement of battery cell will be done by NTC.

Regards,

#### mishra87

Joined Jan 17, 2016
947
To add here microcontroller i have if some one wants to suggest any discrete circuit.

#### Audioguru again

Joined Oct 21, 2019
4,106
Why do you increase or decrease charging current when temperature changes? Battery University.com article BU-410 says that normal charging temperatures for a Li-Ion battery are from 0 degrees C to 45 degrees C.

#### mishra87

Joined Jan 17, 2016
947
Why do you increase or decrease charging current when temperature changes? Battery University.com article BU-410 says that normal charging temperatures for a Li-Ion battery are from 0 degrees C to 45 degrees C.

The ideal was to reduce the charging at temperature more than 15decC and increase the charging current at below 15dec to 0degC.

I am not much aware about battery specification but at the end this is requirement and i have to find the solutions.
May be this is because of battery constraint.

Thanks again !!!

#### mishra87

Joined Jan 17, 2016
947
I want to correct my above statement after reading battery university articles i came to know that lower charge current required at lower temperature.

One thought in my mind came that We can control the charging current using PWM of microcontroller.
A mosfet based switching circuit needed and the charging current can be control by PWM siganl.

Can anyone have any idea or thought on same ?
What could be the best charging method two 3.6V Li ion battery ?

Thanks !!!

#### Audioguru again

Joined Oct 21, 2019
4,106
The best charging method for Li-ion battery is to use a Li-ion battery charger IC made by most semiconductor manufacturers.
Assembled chargers are made for radio controlled electric model airplanes, drones and cars sold at local hobby stores.

#### mishra87

Joined Jan 17, 2016
947
The best charging method for Li-ion battery is to use a Li-ion battery charger IC made by most semiconductor manufacturers.
Assembled chargers are made for radio controlled electric model airplanes, drones and cars sold at local hobby stores.

My charger is CC/CV for battery charging and we have used BMS System for overcharge protection.
Now i am working on charging current based on temperature as per above.

So could you suggest some discrete circuit to switch the charging current based on temperature.
Lets say i have CC/CV Charger rated 1A charger to charge two 3.6V/2100mAh serial battery. Now i want charge the battery with 400mA when temperature is less than 15degC and when temperature is more than 15degC charging is 1A.

So how do switch this current.

My thought is -

1> Switch the charger supply with MOSFET based circuit and drive mosfet using PWM from MCU. By changing the duty cycle we can switch the current based on temperature .
2> Make two current source and switch the current based on temperature.

Could anybody help me out here ?

#### Audioguru again

Joined Oct 21, 2019
4,106
Why doesn't your charger have a current setting that you can set at a low current for a tiny battery or set to a high current for a large battery? All battery charger ICs have this.

#### mishra87

Joined Jan 17, 2016
947
Why doesn't your charger have a current setting that you can set at a low current for a tiny battery or set to a high current for a large battery? All battery charger ICs have this.
Is this based on temperature variation?

Hope you understood my objective or some more information do you need ?
the objective is to control charging based on temperature for at least two threshold based on above .
Could you sugeest some part number for my reference study ?