bq2002 and bq2004 - indicate full charge?

Ok for bq2004, but something is not clear about the test with uC with bq2002.

Ok I have a uC but you're saying me that if I can check that the bq2002 is in trickle status (the train coming cc pin)... I can 

desume that the battery pack is charged.

1) I'm not sure about that: this state (from state machine) can be reached for fault with temperature so the battery could be not cherged.

I'll wait you answer but I'm going to study the bq2004.

What about a fuel gauge?

What's the simpe IC  can I use for NiMH pack ?

Best regards

You can begin a new post in the gas gauge forum to see what nickel fuel gauge they recommend.  Be sure to include the number of series cells that you have.

Your uC should be able to detect the different duty cycles for top-off and trickle charge, so it can see if the IC is in trickle charge. 

You are correct that if there is a fault during fast charge or top off, the charger will terminate charge and move into the trickle charge state.  I suppose your uC could also look at the TS and BAT pins to see if the battery triggered the maximum temperature or maximum charge voltage fast charge terminations.  And you could count the time that the charger is in fast charge to see if it hit the maximum charge time.  Other than this, the charger will exit fast charge only when it detects a proper termination.  After it detects the proper termination, it will move to top off charge.  So, if the charger skips top off, then the battery cannot be guaranteed to be full and also if it reaches the maximum charge time in fast charge, it can not be guaranteed to be full.  But if none of that is true, if it moves from fast charge to top off to trickle charge without reaching the maximum charge voltage or maximum temperature and without hitting the maximum charge time in fast charge, then you can safely assume the battery is 'full'.

Ok.

With bq2004 if i choose "Mode 1" (DSEL=Vss) if I see LED1=H and LED2=LOW i can assume that the battery pack is charged regardless

any events  occurred during is charging?

We need to distinguish between fast charge and top-off charge.  Older NiMHbatteries are not fully charged after fast charge.  That is why there is top-off--to finish fully charging the cell.  With that LED combination, you cannot tell if you are in top off or trickle charge.

You need to determine if your customer who uses your system needs to know if the pack if completely full (top-off complete) or just mostly full (fast charge complete only).  If you need to tell the difference between top off and trickle charge, you either need a fuel gauge or will need to use some logic from your uC as I previously described.

Hi,

I'm using BQ2002T and a uC like you suggested me to check  if the Bq2002 is in trickle state, and so, if the battery is fully charged.

But I have a critical doubt.

I supply the Bq2002 that start in Fast Charge State because VBATT<2V and VTS is 1.6V therefore 0.25Vcc<VTS<0.4Vcc (Vcc is 5V).

With a thermo gun I warmed up the thermistor and at 1.3V(??) of VTS the BQ2002 went in trickle state.

BQ2002 but remains in this state forever even if I cool the thermistor and the VTS returns in the range 0.25Vcc<VTS<0.4Vcc!

Is that right?

I don't think.

Could you help me?

And what about 1.3V for VTS?

Should be 0.225*5V=1.125V. 

Bye

Frank

Once you have exceeded the TCO, you enter the trickle charge state and stay there per the state diagram on page 3.  You must cycle input power to start a new charge.

A better way to run your test is to use a potentiometer in place of your thermistor.  You can accurately and easily measure and change the voltage on the TS pin.

You need to measure your Vcc--don't just assume it is 5.00V.  Then, calculate the range of voltages on the TS pin that would exceed the TCO--this threshold has a 5% tolerance.  Also, make sure you are in fast charge to begin with (look at the LED) and then don't change the TS pin voltage too quickly or you might generate a dT/dt termination instead.  Lastly, confirm you are using the bq2002T, not another version.

Yes I'm using Bq2002T.

In the state diagram seem it can go out trickle state if the temperature fall down 0.25Vcc. 

So if one of terminations occur I can't understand with bq2002t if the battery is full charged. I will know only if it goes in trickle charge and the terminations aren't occur.

Is it right?

if yes, I suppose to change my design.

Chris,

With bq2004 if i choose "Mode 1" (DSEL=Vss) if I see LED1=H and LED2=LOW I can assume that the battery pack is charged regardless

any events  occurred during is charging?

At this point it's not important for my design(fully or most fully) but I'WILL BE SURE that this LED will go ON only with mostly full and not if the temperature is high like bq2002T.

Bye

Once you get into the trickle charge state, you cannot come out of it unless the pack voltage goes above 2V/cell and then back below it.  There are no arrows leaving that state.  You need to power cycle the charger to restart the fast charge algorithm.

On the bq2004 with that LED combination, you can only tell what state you are in, not how you got there.  So, it behaves the same as the bq2002 in this regard.

You should never hit the TCO termination threshold with a healthy battery pack.