Issue with BQ2004E

Hi Jean,

 When INH is low, the bq2004E/H suspends all charge actions, drives all outputs to high impedance.  

 It looks like the battery is not detected; it can be a mistake in the schematic. Can you please compare your schematic with our EVM and see if there any differences.

 http://www.ti.com/product/BQ2004E

 Then make sure that all the pins are getting the right voltages. Specially BAT & SNS pins.

 Thanks!

Tahar

Hi Tahar,

Thanks so much for your answer!

My supervisor of charge stay in mode "fast charging" now.

When I don't put any batteries in my charger, LED1 and LED2 light on during 1/2 second and light off during 1/2 second. I don't see this state in the BQ2004E's datasheet. Is it a normal state of my LEDs?

Best regards!

Jean

Hi Jean,

 No, that is not normal for the LED indication. When the battery is absent, both LED should go LOW.  

 Please see if the SNSE and BAT pins are “0V” when the battery is removed.

 Send us some picture plots will help too.

 -Tahar

Hi Tahar,

I take a picture of my system with and out batteries. I take a movie of the comprtment of my LEDs too.

I have 0V between SNS and ground but I have 4.1V between BAT and ground.

I don't understand why I have a voltage between BAT and ground.

I attached 2 pictures and 1 movie with this post.

Best regards and thanks so much for your help!

Jean

I can't post my movie, it's so heavy.

Sorry. Put I attached the second picture with this post.

Best regards,

Jean

Hi Jean,

 That is the root cause of the issue then. BAT pin voltage, should represent a # of cells potential for the battery. There is a short with something in you circuit. Please find that out and correct it. Please use the EVM as your reference.

 Tahar

Hi Tahar,

I looked your EVM schematic and I compared with mine. I found one big difference, the value of RB1 and RB2. In your EVM, you use 200K Ohm for RB1 but my value of RB1 is 0 Ohm and RB2 is 390K Ohm  because in the datasheet, it's write : RB1 / RB2 = (Nomber of cells / 2) - 1. So, I would like to charge two cells of 1.2V and 600 mAh each. If I want that I need RB1= 0. Is it true?

It's all right now about the LEDs when batteries aren't present. I put a resistor (2.2K Ohm) in parallel between BAT+ and DC. With this, LEDs don't light when batteries are off. But I always have around 4V at Vbat. I think it's normal because when I switch on my charger, the BQ2004E tries to detect if a battery is available or not. For that it send current so the voltage is 5V ( Vbat >= Vmcv) and after with my capacity (100µF) Vbat stays arround 4V. When I look Figure 3 in the datasheet, the only condition for " Battery absent" is Vcell >= Vmcv. I don't understand why you tell me taht it's necessery to have Vbat=0V because if Vbat = 0V, Vcell < Vmcv.

And I looked with your EVM that it's possible for the user to configure the board for a special number of cells. If the user want to charge 2 cells, he needs to use RB25 = 4M Ohm?

On your EVM, page 3, it's writting: Vdc "maximum input voltage" : Minimum: 2.0+ Vbat (or 15V)  /   Maximum: 18+ Vbat (or 35). My question is: Is it possible to have Vdc = 5V on my surpervisor of charge if Vcc = 5V? Or    Do I need to have Vdc = 2V + Vbat?

After resolving my first problem when batteries was not present, I tried to charge my batteries and when I put my batteries in my charger the cycle begins. Between 20 min and 45 min, I have a "fast charging" indication and after I have a "Charge complete" indication. But when I test my batteries I don't have 600 mAh. So the charge is not complete (I totally discharge my batteries before charging). I choose TM1 and TM2 for charged at C/4. In my case, 600 mAh / 4 = 125 mA. I program the BQ2004E with Ireg = 0.125A because I choose Rsns = 1.5 Ohm. 

I read on a forum that charge a 2 NimH cells is not possible with the BQ2004 but it's possible with the BQ2003. Is it true? Because it's the only difference between BQ2004 and BQ2003 is the equation.

I attached my new schematic with the new value of my capacity and INH pin to high and R17/ D6 add.

Best regards,

Jean.

You should be fine with 5V and with this charger. You can try other (03) for better performance.

Ok. Thanks so much for your answer.

When you said "try other(03) for better performance", what did you mean?

Now I try to charge and I tell you if I have an other problem with the time of charge.

Best regards,

Jean.