Balancer issue BQ 3060

[Elektor89]

Hello Guys,

I am working on an Power Managment System for my Device which consists of 2 Lithium Ionen batteries in series. For that I build up a charger curcuit (BQ24745) almost the same as the reference design (http://www.ti.com/lit/ml/slur112/slur112.pdf)  just left out the optional things (red marked in the attached file). I think that are features that I don't need but I don't understand for what the circuit on the right side is. Maybe someone can explain it to me.  [The charger works fine also without the optional thinks, but maybe it affects the balancer IC BQ 3060 in it's work? (what I don't think)]

As balancer I use the BQ 3060 IC the schematic I build up is also almost the same to reference design. Different in my solution is that the Fuse is not populated this PIN is on ground, PRES (PIN 17) is to ground and the second safety IC BQ29412DCT is not used.

It is important to know that the Balancer have a flash memory (http://www.ti.com/lit/ug/sluu319/sluu319.pdf on Page 89) where the settings are stored for different configuration. For my System I configured the Data-Flash in the Operation Cfg A Register matched to my system as 2 batteries, internal temp sensor and so on.

The whole commands are send from a mega88 microcontroller via the SMBUS to the BQ24745 charger and the BQ 3060 Balancer.

Everythink works alright I can charge the Battery Pack correctly the balancer works during charging if needed and I can power on my system with the Battery Pack or the charger.


But now and that's the Problem I can't solve when my device is powered up just with the battery and I remove the battery and insert it again I can't switched on my system anymore. I think that's a hardware Problem and not software but maybe the is one register in the Data-Flash what I have to set . Can anyone please have a look --> http://www.ti.com/lit/ug/sluu319/sluu319.pdf on Page 89.
Now back to the Problem what I mantion I think it's a hardware/schematic Problem I did't some measurements and find out:

when the system is powered from the battery then remove and insert again I can only switch on my system again when I short  on  BQ3060  BAT ( PIN 1)
 and PACK (PIN 24) together. Then DSG (PIN 2) turns on and my system gets current but why is the DSG PIN turns off when I remove the Battery and don't turns on automatically when I insert again the battery.

Have anyone an idea?

I also notice that when I disconnect the battery for less then 1s I can turn on my system. Is the BQ 3060 back up Power  with the capacitor C214 on PIN 18 RBI?

An other possibility to turn on my system after I removed the battery is when I start charging after that I can remove my power supply and turn on the device with the battery. To me it seems like the BQ 3060 needs VCC on PACK and BAT but in the data sheet and the schematic reference design it's BAT OR PACK otherwise FETs  Q202 & Q203 has no effect and what happend in the case of charging.

Thanks for Help!


       

[Zsola]

Hello!
It's quite a long problem, but I try to help. At least a part of it.

At first, if you have a circuit on a battery, you must use the Q8 transistor part. If you dont use, when charging and the circuit needs some current, it make an error on the battery, so the charger IC will not stop. That causes an error. When you plug in AC, the Q8 separates the battery from your circuit, so the charger can charge it correctly. If you want a charger and balancer only, you can omit that with the SYS part.
On the first picture: left is a filter (wallplug chargers do some noise that you dont want), C10 and C12 buffer/filter I think, without that the charger sense the ripple current, so the charging wont be correct. With Q6 and Q7 the MCU or other part can switch AC or BATT as main power source.

I have never used a balancer, I prefer more simple solutions with 1 cell and a boost converter.
I think that other problems are caused by the missing parts. Anyway, connect-disconnect main (Lithium) batteries during charging and working of the system is not a good idea. In a finished product you can only change batt when its faulty, and in this case, you must power down the system.
If you dont want to add the missing parts, you have to isolate the problem, measure only the charger then the balancer and so on.