bq24610 STAT1 on when battery disconnected

Would you monitor or measure the BAT voltage during that condtion?  The stat1 should be not related to the Vsys load with the datasheet figure 1 configuration. Are you connect system load to the battery directly?

VSYS is not directly connected to the battery. We have the system load connected to VSYS and the battery disconnected. (When we connect the battery, it's connected to VBAT.)

But measuring the VBAT terminal with the battery disconnected...we see a 0.06V on VBAT when the system load is on and a 24V on VBAT when the system load is off. The STAT1 LED is on when the system load is on (this means the STAT1 signal is low according to the LED configuration on the EVM schematic correct?). The STAT2 LED is off when the system load is off.

Just for clarification, what does STAT1 depend on? What triggers it to go high or low?

On your first post:

Howevery, when I run the board with a load on VSYS and the battery disconnected, STAT1 goes high. As soon as the VSYS load is disconnected, STAT1 goes low.

On your second post:

  The STAT1 LED is on when the system load is on (this means the STAT1 signal is low ...)

There is a conflict on your first post and second post.

I still can not figure out how is your circuit. Would you share your schematic with us? But , according your second post,  

1. VBAT is 0.06V and STAT1 is low when the system load is on.

2. VBAT is 24V and STAT1 is high when the system load is off.

First, the STAT1 has a correct behavior. VBAT=0.06V, the charge works at pre-charge stage. The STAT1 Led is on. When a battery is fully charged (24V), the STAT1 led is off.

Second, you have to tell me why system load can change a battery voltage if input source is available.

If a stable current is flowing into the battery, STAT1 is low (LED is on).

I'm sorry; the 2nd post is correct. (in the first post i was getting confused since the leds are sunk by stat1)

but as far as the schematic, we're using the same configuration as the evm. we just have changes on resistor values to accommodate a 6-cell pack and a different fast charge charging current.

if STAT1 is dependent on current flowing into the battery, i dont understand how we could get the STAT1 LED to turn on with the battery disconnected.

The STAT1 LED should not be turned on if the battery is absent. Please remove the BATFET and see what happened.

It will be hard for me to remove the BATFET. But I've attached the schematic of the board. Can you please take a look and let me know if anything is wrong? For the most part it's the EVM with configuration changes to the cell count and charging current. We also have a separate circuit coming off of VSYS.

If it is hard to remove the BATFET, please measure the output current sense resistor voltage when the battery is absent.

If the current is higher than termination threshold, the STAT1 LED will be on.

With the battery absent, the voltage across the current sense resistor is 0, so there should be no current going through it.

Just some things I've observed:

• With the load disconnected from the VSYS terminal block and battery absent, VBAT is 25V
• The load on the VSYS terminal block periodically toggles on and off. With the load connected on the VSYS terminal block and battery plugged in, the battery is only being charged when the VSYS load is in an off state

Do you see anything in my schematic that is incorrect? Could the extra circuit coming off VSYS be causing a problem? It's the only difference I can see between my board and TI's EVM (other than resistor configuration values).

Is the STAT1 still wrong? I didn't find something wrong in the schematic. It is very close to the EVM schematic.

• With the load disconnected from the VSYS terminal block and battery absent, VBAT is 25V

It is correct because you set 6-cell output (6x4.2V=25.2V)

• The load on the VSYS terminal block periodically toggles on and off. With the load connected on the VSYS terminal block and battery plugged in, the battery is only being charged when the VSYS load is in an off state

When Vsys have a load, the input voltage drop cause the Vcc voltage lower than VBat. The charger runs at sleep mode and turns off the input FETs. So, you see it on and off.

Increasing the input voltage can avoid the sleep mode on and off.

I tried increasing the input voltage; same result.

After more troubleshooting I've found that when the battery does charge, it only charges at ~400mA.

So I tried disconnecting the PIC portion of the circuit from VSYS. The circuit has been disconnected before the voltage divider. Now the STAT1 LED never turns on. ACSET, ISET1, and ISET2 have been measured and are correct (we see values of .8024V, .257V, .3V respectively). Current through the battery is only 3mA.

Which path does power take to charge the battery? I'm trying to figure out which components could be causing the problem.