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BQ24170EVM-610-5V: Current recharge to battery uncontrolled, up to 4.7 A; V_ISET: 0.19 V, V_ACSET: 0.58 V

Nahum Loredo
Prodigy 30 points
Part Number: BQ24170EVM-610-5V
Other Parts Discussed in Thread: BQ24171

First, a development kit was purchased [BQ24170EVM-610-5V] which is used to charge a 3.7 V cell up to 2 A (maximum up to 4 A) of current. This kit has been modified to adapt it to a 12 V supply [from a car battery], thus limiting the charging current to the battery.

This same kit is intended to be used to be powered with a voltage range of 10 V to 14 V to charge 2-cell batteries [3.7V each, 2S1P] with a maximum recharger current of 1 A.

http://www.ti.com/tool/BQ24170EVM-610-5V

In the tests that were done, a laboratory voltage source with current limitation was used. In this way, it does not exceed the recharge current in the battery.

Identifiers/labels from components correspond at next link, page 18, schematic diagram.

http://www.ti.com/lit/ug/sluu463/sluu463.pdf

 

Voltage operating range: OPVSET

Supply voltage: + 12V

R_AC => R2 = 10 mOhms

Total current operating range: I_DPM

I_DPM = V_ACSET / (20 R2)

V_ACSET = 3.3 * (R18 / (R18 + R31))

R18 = 22k

R31 = 100k

V_ACSET = 0.59 V

R2 = 10 mOhms

I_DPM = 2.97 A

 

Current range of charge to the battery: I_charge

I_chrage = V_ISET / (20 R15)

V_ISET = 3.3 * (R30 / (R30 + R32))

R30 = 232k

R32 = 15k

V_ISET = 0.2 V

R15 = 10 mOhms

I_charge = 1.0020 A

R_SR => R15 = 20 mOhms

I_charge = 0.5010 A

 

Despite the changes made, the recharge current to the battery goes up to 4.7 A, The LED that indicates ~STAT is blinking when current is high but do not cut off supply to system neither to battery.

http://www.ti.com/lit/ds/symlink/bq24170.pdf

 

Changes of components made

R2:     0.01 Ohms

R6:     1 MOhm

R15:    0.02 Ohms

R18:    22 kOhms

R32:    15 kOhms

 

No changes in

R8, R9, R10, R19, R22

 

Should I use the BQ24171 integrated circuit?

Wish Parameters

Power Supply: +12 V

Current to system: 2 A

Current to recharge battery: 1 A [max]

Battery voltage: 7.4V [2S1P]

Kind regards.

  • 0
    TI__Mastermind 24075 points
    Hi Nahum,
    STAT LED flashing indicates a fault condition. Possible reasons could be 'Charge suspend, Input over-voltage, Battery over-voltage, timer fault, battery absent'. What voltage do you measure at OVPSET? Can you show the values of input current, actual system load (how much current it draws), and charge/discharge current (is 4.7A into battery or is battery discharging to system). Also what value are you limiting current of power supply to?
  • 0 in reply to Kedar Manishankar
    Prodigy 30 points
    OVPSET Voltage [TP9] is: 1.09 Volt. Input current: 1500 mA, Current in load [I_SYS] 500 mA and battery Charging current 998 mA, the maximum charging current up to 4.7 A [charging battery] after several minutes. The status LED blink when current is high in this case.
    The input current was limited up to 1500 mA due Laboratory Voltage Power Supply settings, maximum current: 5 A [not yet tested for this purpose].
    Voltages:
    V_ISET: 0.19 Volt
    V_ACSET: 0.58 Volt
  • 0 in reply to Kedar Manishankar
    Prodigy 30 points

    I think that I should replace chip [U1] by BQ24171. Change "Select" by divider resistors for FB pin. In addition, a circuit to switching ISET pin to less voltage, so limit charging current to battery [instead 4.7 A max].

  • 0 in reply to Nahum Loredo
    TI__Mastermind 24075 points
    Hi Nahum,
    The battery charger IC will regulate on its own in normal operating conditions, so there should be no need for current limiting by supply. The ISET pin controls and regulates charge current to set value, and ACSET pin regulates input current from adapter. Through Dynamic Power Management, IC will reduce charge current if load + charge current > max. input power so that input voltage does not crash. Please check for the following possible error conditions, as STAT will blink: Input overvoltage, Battery overvoltage, timer fault, battery absent. What is voltage of battery (FB pin)? Please also measure voltage on TS pin. Just to confirm, your batteries are lithium-ion and you are referring to 3.7V as nominal charging voltage, and that each cell max charge voltage is 4.2V?