BQ24001: Holding battery charge / timer / charger start up

Hello Larry,

The bq24001 automatically restarts the charge if the battery voltage falls below an internal recharge threshold, 3.9V. 

Best regards,

Nick

Thanks for replying - automatic restart has not been my experience, I am experiencing several problems which may just be 1 problem -

1. If a battery is very depleted (3.0v or less) - the charger will charge at a 0.02mA rate for some unknown time ~ 20 min and stop charging stat 1 (LED blinks)

2. If the battery charges to a full capacity, the (timer?) shuts the charger off and the battery will deplete to voltage cut off. 

I am using a USB source and a large battery. 4400mAhs.  If the battery is LiPol type.   I want to post my schematic but I am not sure how to.   

Hi Larry,

Going to look into this more today on bench.

Thanks,

Nick

Hello Larry,

You can cycle the input power to reset the charge safety timer, there is no option to disable it.

Larry Larson1 said:

Do I have to disable and enable the charge pin

I believe this should also work based on the functional block diagram.

Nick Brylski said:

The bq24001 automatically restarts the charge if the battery voltage falls below an internal recharge threshold, 3.9V. 

There may be a typo in the datasheet here, I do not see this behavior either.

Best regards,

Nick

What do you think about my first question - 

If a battery is very depleted (3.0v or less) - the charger will charge at a 0.02mA rate for some unknown time ~ 20 min and stop charging stat 1 (LED blinks)

Hi Larry,

The precharge safety timer is for 22.5 min (see figure 14). 

0.02mA seems very low, It may be the battery protector causing the issue. Can you share the schematic? Go to insert-> file.

Thanks,

Nick

Hello Nick, 

The insert file can only do a link... How do I send my schematic? 

https://www.dropbox.com/s/62e2loxqlhswtm8/Screen%20Shot%202021-11-18%20at%205.04.23%20PM.png?dl=0

Here is a link to the file 

Any update? 

Hi Larry,

Recommend adding 10uF of capacitance on OUT as seen here: https://www.ti.com/lit/ug/sluu113/sluu113.pdf

The IC will need some output capacitance to operate correctly so this may be the issue.

You may try looking at startup waveforms of IN, OUT, STAT1 (when plugging in adapter). Also with a current probe would be good.

Best regards,

Nick

Hello Nick, 

What is not shown in this schematic is the abundance of capacitance I have on the battery line -  Each Cap is closely coupled to the power supply for the component it powers (shown on different pages) -   There is a modem w/ power supply and several sensors (4) each with their power supplies - 

1.  The modem power supply has 5 times 100uF ceramic caps on the input (Vbat) & 7-times 100uF ceramic caps on the output.

2. The sensors have 3 times 4.7 uF &  10 uF ceramic cap on the input (Vbat) 

So all total there is over 515 uF on the battery.   Is this my issue?  Inrush?   Getting those waveforms. 

Here are the waveforms you asked for - 

www.dropbox.com/.../AAADfsbUCzBV4cFoTFxp_Ikpa

Charger current when connected (0.020A) 

Stat 1 when 5 vin charger is connected - 

Stat 1 when 5 Vin is disconnected 

Vin when 5 V charger is connected 

Vbat when 5V charger is connected - 

Vbat when 5V charger is disconnected

Hello Larry,

The Input/output capacitance must be located close to the the IC pin for it to be effective. 

You may also open up the battery pack and check the protector circuit. Do you have the battery pack schematic to share?

Thanks,

Nick

Would also be good to check IN/ OUT current with a current probe.

Here is the battery protection circuit -

Also, adding 10uF to the output did not change the behaviour of the circuit.  

Any update here?

Hello Larry,

When charging at 0.02mA is the protector activated? You can check resistance between battery negative and P-.

This is a very old device and it may not be compatible with all protectors. How many units are you seeing this issue on?

I would recommend a newer device like bq25170 or bq24040.

Best regards,

Nick

Would you be willing to ship the board and battery pack to us? I could take a closer look.

Thanks,
Nick

regardless of charger connection, the battery terminals read OL on the multimeter.   Yes, I can ship it, can you send me an address? 

I have a bunch of current wave forms - 

Start up - zoomed

start up - 

Scale Amp probe -  

Steady-state blips 

Is there a limit to the size battery this charger can charge?   My current battery is 4400mAh?