Battery Cell broken?

[Udjat]

The laptop sometimes doesn't startup (or loops starting up) on bttery.

With connected mains adapter I have run a self test, which fails on the battery pack.

As can be seen on included image one of the cells seems to be nonfunctional, while the others are in good shape still.

Is this issue repairable? It surely indicates a fabrication error and I wonder whether I can get a replacement if repair is not possible...

[Huffer]

The image is not clearing the censors yet. If you just have a zero charge on one cell this is normal and does not necessarily signal a problem. The failing test means the battery needs replaced. Are you under warranty? If not you will have to purchase the battery yourself and we can help you find one. 

[Udjat]

How is it normal that one of the cells has zero charge? I don't think this can be normal wear, the other cells are at almost full capacity.

Something must be broken in the batterypack; it is not just low on charge but it gives no power at all. It may also be temperature related, since we're experiencing a heatwave right now...

[Huffer]

Very normal:

Here is my battery test report and my battery is perfectly fine:

0 % cell

And even if it were a defective cell if you are past warranty that is a way batteries fail and does not make any special case for an extended warranty. You will have to buy a replacement battery which is a normal laptop maintenance item. 

[Udjat]

Well, the design voltage of your battery indicates a 3 series cell pack, and considering the design capacity it has two strings in parallel (3S2P).

So I'm not surprised that only 3 cells give a non zero voltage in your case. (I'm a little surprised though that the software apparently always indicates the battery having 4 cells.)

My pack is a 4S1P configuration, i.e. a design voltage of 14.8 or so.

Strangely, when running the HP battery check tool when the system is fully up, i.e. not the startup diagnostic reported before, the test says its OK.

Also, this morning the battery was working fine for several hours. As I said, I suspect it's not wear but something else. I just hope it is actually the battery pack and not the laptop itself.

[Udjat]

By the way, although the test passes, I see now that the remaining charge is 1mAh. Even stranger...

[Udjat]

So, the battery decided to be OK oon after my last post, and has worked fine ever since. I got three hours plus from a full charge...

Yesterday I had to plug in while working, and charged up to full. After shutdown I pulled the charger plug and the laptop began short startup cycles of just a few seconds. You basically see some leds light up, power led on the side goes white and red and then it resets.

Why would it do his spontaneously from an off state?

When you put the charger in, it returns to the off state. I am puzzled...

The battery diagnostic log shows aain that cell 2 has 0V. Can it be that this cell is badly connected, and when it need to provide current the voltage drops?

[Udjat]

And, testing the battery with a voltmeter and a load it just delivers some 16.5V.

So I guess either the charging circuit inside the laptop is broken or the control chip in the battery is...

[Udjat · Accepted solution]

Discharging the battery out of the laptop, with an external resistor load accross the power pins, shows that the voltage drops to 0 about every 3 seconds. This is excactly the startup/switch off cycle I see when it is inside the laptop.

So my conclusion is that the ontroller inside the battery detects some fault condition and shuts off the output. This only happens when the battery is fully charged, after a couple of hours of discharging the controller does no longer switch the output, apparently the fault condition is gone.

Now the big question is, how do I reprogram the controller to stop charging before it reaches the fault level?

Alternative is to fork out 85 Euros to replace an otherwise healthy battery...