Can we charge 3.7 v battery from usb

[karaapak]

Many devices are charging with usb, I know usb can deliver 5 V 0.5 A but we need constant current and voltage at least to charge the battery so we need a circuit that can supply this stability when battery is getting more reinforcement so do anybody knows how they can do this tiny place in a mp3 or something similar.

 

[Nigel Goodwin]

You DON'T need constant current and voltage, and that is in fact impossible (unless you're just charging the exact value resistor that meets the requirements).

Depending on the battery type all you need might just be a simple resistor? (to limit the current), it really depends on battery type and if you want to 'fast charge'.

 

[Ian Rogers]

The Arduino fio does exactly that! here is the schematics it uses the max1555
https://arduino.cc/en/uploads/Main/Arduino-Fio-schematic.pdf

Cheers Ian

 

[dougy83]

A 3.7V battery is most likely referring to a common rechargeable lithium cell. Don't use a resistor to charge unless you have some sort of control circuit limiting the voltage to 4.2V & causing charge termination.

The MAX1555 suggested above is a good bet (charge current limited to 100mA). There are others also, e.g. MCP738xx (charge current adjustable up to 1.2A), and many more.

 

[karaapak]

Thanks for all replies.

Nigel Goodwin
I tried to charge 3.7 v Li-poly battery with a resistor and also I added a diyot to protect the usb from the reverse voltage that may come from battery in case. But in this situation the currect gets down from 100 mA to 10 mA after 1 or two hour later and battery not fully charge. As I understand the original battey chargers are first giving constant current and constant voltage after the battery gets nearly charged the charger gives lower current and a bit more voltage for a while, when chaarger doing this it controls also the temprature of the battery to cut down the charging period at a exatc time. So we may charge batery with only using a resistor but it is not healty.

Ian Rogers and dougy83
I also look at the Max 1555 but I couldn' t found it in my country. I'm also looking for MCP738XX they are not selling either.
I have MIC5265 (n732 as smd) and it only gives 3.3 volt output I found it in a mp3 player so I wondered how they can charge the 3.7 V battery there is any other chip (except flash and memory) I thing 3.3 V for flash and memory but battery charger? I couldn't find how they are doing I am searching reverse engineering circuits of mp3 players but there are not much things I can found.
I am trying to make a regülator/charger with using transistors and zeners when I find exact solution I will write here.

 

[Nigel Goodwin]

Thanks for all replies.

Nigel Goodwin
I tried to charge 3.7 v Li-poly battery with a resistor and also I added a diyot to protect the usb from the reverse voltage that may come from battery in case. But in this situation the currect gets down from 100 mA to 10 mA after 1 or two hour later and battery not fully charge. As I understand the original battey chargers are first giving constant current and constant voltage after the battery gets nearly charged the charger gives lower current and a bit more voltage for a while, when chaarger doing this it controls also the temprature of the battery to cut down the charging period at a exatc time. So we may charge batery with only using a resistor but it is not healty.

Only if you choose 'difficult' battery technology, a simple resistor is perfectly fine for NiCd and NiMh.

As I've already mentioned, BOTH constant current and constant voltage is impossible, you can have either, but not both.

 

[karaapak]

Nigel Goodwin
You probably know better than me I'm searching the charging protocol only a few days. And also you said it is fine for NiCd and NiMh but I'm using Li-poly and the devices that I told uses Li-poly and Li-ion commonly so I think I need a bit complicated thing.

 

[RCinFLA]

Cellphone has a charge controller that limits the current based on mAH of LiIon battery (typically about 65-90% mAH's in mA's) or goes full conduction if the 5v source limits the current at below the maximum acceptable charge current for size of LiIon battery. It then caps the maximum voltage rise on battery to 4.2 vdc (current limited 4.2v voltage regulator) and either terminates charge at this point (leaving battery at about 85% SOC) or holds it at 4.2 vdc until current drops to about 10% of current limited level when it terminates charge.

There are a few other charger safety details on LiIon charger. A cell less then 1.5 vdc is considered defective and no charge is attempted. Between 1.5v and 2.8 vdc cell voltage the initial charge rate is limited to 0.1 C rate until battery voltage rises then goes to higher current rate. If cell is in the 1.5v to 2.8 vdc range and voltage does not rise within an hour then further attempt is terminated and battery is declared defective. Also no charging is allowed if battery is below 0 deg C or above 45 deg C.

There is also a hour to hour and half safety timeout on the length of time for the final 4.2v current taper off. If battery current does not taper off in that much time the charge is terminated but battery is not considered defective. This is common situation if the phone (or other type device) is also on and drawing current which fakes out the current taper termination.

A cell phone charge regulator may get hot due to the charge current and the voltage drop across the regulating transistor in the phone. When it gets too warm the phone may back down or temporary terminate charging until things cool down. This is a common problem with large battery smart phones that can be 1200 to 1800 mAH batteries. (5.5v - 3.2v)/ 1000 mA charge rate produces over 2 watts in series pass device in phone that will heat up the phone's internal series pass regulator. Some phones use a current limited charger wall pack to allow phone's internal device to go into full saturation connection reducing the internal phone heat dissipation.

LiIon battery takes 2-2.5 hours to fully recharge from total depletion. There are devices that claim 1 hour or 1 1/2 recharge time but they are just terminating charge when battery hits 4.2 vdc. This actually makes battery have greater longevity, but only yield about 85% C of battery potential capacity.

 

[karaapak]

I am sharing this because may someone needs it like me.

THIS IS MAX8934G

Key Features Applications/Uses
Li+ Charger with Smart Power Selector, No External MOSFETs Needed
Monitors Battery Temperature and Adjusts Charge Current and Termination Voltage Automatically per JEITA Recommendations
Active-Low OT Flags System of a Hot Battery During Discharge
Ultra-Low IQ, Always-On 3.3V LDO
Common or Separate USB and Adapter Inputs
Automatic Adapter/USB/Battery Switchover
Load Peaks in Excess of Adapter Rating are Supported by Battery
Input OVP to 16V (DC) and 9V (USB)
40mΩ SYS-to-BATT Switch
Thermal Regulation Prevents Overheating
4.35V SYS Regulation Voltage

THIS SITE HAVE A CİRCUIT BUILD ON MAX 1811 AND IT IS FOR SPECIALLY LI-POLY BATTERY CHARGING

USB Single Cell LiPoly Charger


AND IF YOU WRITE ''USB powered AA charger schematic'' THERE ARE A SCHEMATIC FOR TWO AA SİZE BATTERY CHARGER TAKING POWER FROM USB BUT NOT ADEQUATE FOR 3.7 V IT NEEDS SOME MODIFICATION

 

[karaapak]

Cellphone has a charge controller that limits the current based on mAH of LiIon battery (typically about 65-90% mAH's in mA's) or goes full conduction if the 5v source limits the current at below the maximum acceptable charge current for size of LiIon battery. It then caps the maximum voltage rise on battery to 4.2 vdc and either terminates charge at this point (leaving battery at about 85% SOC) or holds it at 4.2 vdc until current drops to about 10% of current limited level when it terminates charge.

There are a few other charger safety details on LiIon charger. A cell less then 1.5 vdc is considered defectived and no charge is attempted. Between 1.5v and 2.8 vdc cell voltage the initial charge rate is limited to 0.1 C rate until battery voltage rises then goes to higher current rate. If cell is in the 1.5v to 2.8 vdc range and voltage does not rise within an hour then further attempt is terminated and battery is declared defective. Also no charging is allowed if battery is below 0 deg C or above 45 deg C.

There is also a hour to hour and half safety timeout on the length of time for the final 4.2v current taper off. If battery current does not taper off in that much time the charge is terminated but battery is not considered defective. This is common situation if the phone (or other type device) is also on and drawing current which fakes out the current taper termination.

A cell phone charge regulator may get hot due to the charge current and the voltage drop across the regulating transistor in the phone. When I get too warm the phone may back down or temporary terminate charging until things cool down. This is a common problem with large battery smart phones that can be 1200 to 1800 mAH batteries. (5.5v - 3.2v)/ 1000 mA charge rate produces over 2 watts in series pass device in phone that will heat up the phone's internal series pass regulator. Some phones use a current limited charger wall pack to allow phone's internal device to go into full saturation connection reducing the internal phone heat dissipation.

LiIon battery takes 2-2.5 hours to fully recharge from total depletion. There are devices that claim 1 hour or 1 1/2 recharge time but they are just terminating charge when battery hits 4.2 vdc. This actually makes battery have greater longevity, but only yield about 85% C of battery potential capacity.

Thanks RCinFLA this is the summary that I searched

 

[Nigel Goodwin]

Nigel Goodwin
You probably know better than me I'm searching the charging protocol only a few days. And also you said it is fine for NiCd and NiMh but I'm using Li-poly and the devices that I told uses Li-poly and Li-ion commonly so I think I need a bit complicated thing.

You do, you should choose an IC specifically designed for the battery technology you're using.