T60 9-cell battery 42T4511 - zero voltage

[Patrik28]

Hi

I got a broken T60/61 9-cell battery, which caused T60 notebook charging indicator to flash rapidly. Also the IBM battery management showed that the battery charge was 0 %, and it was unable to charge up.

The battery cover was disassembled (against all warning texts on the battery), and the cells were measured (in place). They were all OK, Voltage was about 4.05 V in each (which means ~80 % charge). However the voltage will not come to the battery external connectors (see picture below).

I have researched the problem, but couldn't find similar cases. It is common, that some T60/61 (including 42T4511) batteries have died at the same way, but nobody have tried to fix the problem. They just bought a new battery.

So, let me be the first who is writing about the fixing of the problem. I have already another battery to my T60, so the dead battery would end up to recycling anyway. I can take this project as a hobby… like all my Thinkpads.

Firstly I compared the both batteries:
- First day of use: 03/2008 (42T4511 - dead) // 03/2009 (42T4619 - working)
- Charging cycles 148 // 193
- Capacity left ~50% (both)

For me it looks like there could be a blown fuse symptom. There is a white 3x5 mm component, reading SEFUSE D6Y7XA, which seems to be broken. The multimeter showed an infinite resistance over the fuse.

Here is a picture describing the problem (click to enlarge):


And here is a full resolution picture to see more details (3 Mb size)


If the fuse causes the problem, it sure would be reasonable to change it. But is that SEFUSE D6Y7XA some special type of fuse, because no datasheets can be found?
Could someone recommend another similar type of fuse for me to buy and try if it helps.

[RealBlackStuff]

That's not a fuse, but a thermal cutoff device containing an electrical resistor.
http://www.us.schott.com/epackaging/eng ... _type.html

[Patrik28]

OK, should the component be conductive at the normal position?
There might be two solutions:
1. The D6Y7XA has tripped and it is single use only or completely broken.
2. The battery logic has shut down the power chain by controlling D6Y7XA.

Now the cells voltage (~12 V) comes to the left side of the D6Y7XA, reading from my photograps, but stops there. Both conductors at the components right side are at zero voltage.

I'm not 100% sure, that the problem is with D6Y7XA, but quite confident. Surely the fault is with components, not with batterys software.

Edit. SEFUSE D6Y7XA must be some old type, because even the manufacture don't know D6Y-type anymore. Maybe D6X-type has replaced it. But even that type is hard to find in small quantaties.
It looks very bad for my battery fixing plans. Finding another functional battery or pcb could be the easiest solution.

Edit 2. Now it looks better. A chinese company sells complete pcb's to the battery: http://www.1bu8.com/en/Battery-97.html
The price is at a little high side, but still reasonable, 8.3 + 7.99 dollars. However, if I would find just the thermal fuse only from some company, the shipping costs would be high too.

[RealBlackStuff]

From the documentation:
The operating principle is based on the concept that the thermal pellet will melt in the event that the ambient temperature reaches a specific level. Consequently, the electrical current will be interrupted immediately in order to protect the appliance. All types of thermal cutoffs are constructed as one-shot operation devices. The thermal reaction is irreversible once it has occurred, and the thermal cutoff device must be replaced.

[Patrik28]

Well, I think I'll make order for the complete pcb protection board from that chinese guy.

It was hopeless to find that single SEFUSE component. I spent few hours googling potential end-user electronic shops and all I found was few wholesale places. They might have accepted to send a sample, but I didn't wan't to use that option.

I'll update, what happens with the new protection board, when I will get it.

[RealBlackStuff]

D6X and D6Y are technically identical, just the 3 'legs' are differently positioned.
Look for another (T60 or T61) battery.
The thermistors should be the same. Perhaps transfer it over?

[Patrik28]

Yes, I looked for D6X too, but SEFUSE components are extremely rare (D6Y must be some custom made type for Lenovo). Normally eBay would offer quite good selection for small components for Thinkpads, but this time, it didn't found anything. And same result from Digikey, Elfa, etc.

Taking D6X from another (used) battery would be too risky, because so many have been failed. Seems to be a bad desing error, something breaks the component too early. But because the battery usually last more than a year, Lenovo have not called back the 42T4511 types.
I suppose, that even the new protection board will fail inside 3-4 years or <150 cycles. Interesting to try.

ps. I just wonder. I have heard, that some protection boards will lock itself, when cells are removed. Is there some certain rules when installing the new board? Should the cell-tabs be attached in certain order etc?

[RealBlackStuff]

All I know is, that these boards must be under CONSTANT power. If you would remove the battery wiring from the old board to attach that to the new board, the new board will not work. Same goes for swapping out battery cells, you can NOT interrupt power.
You must first put the new board in parallel, and only then remove the old board.

[Thirtybird]

All I know is, that these boards must be under CONSTANT power. If you would remove the battery wiring from the old board to attach that to the new board, the new board will not work. Same goes for swapping out battery cells, you can NOT interrupt power.
You must first put the new board in parallel, and only then remove the old board.

That's an interesting statement that I've never heard before - what is the reason for the need for constant power?

[Patrik28]

Now I started to wonder, how the new protection board could work, if it is shipped without any power supply attached (the boards are separately sold).

I wrote a question to the seller too, and they gave a convinced answer. "Just attach the good cells and the board will work directly. No problem."
If the seller is right, then the protection board don't need power. I assume they are right...

Edit. I got an answer from ex-Sefuse, now Schott, that they won't sell thermal fuses to consumers because of safety. If a thermal fuse will break, the fault is usually somewhere else. Changing only the thermal fuse will not solve the problem in high probability.

[Binh]

Now I started to wonder, how the new protection board could work, if it is shipped without any power supply attached (the boards are separately sold).

I wrote a question to the seller too, and they gave a convinced answer. "Just attach the good cells and the board will work directly. No problem."
If the seller is right, then the protection board don't need power. I assume they are right...

I assume that the protection board works like a LCD projector lamp. On the first use, when you connect it to battery cells, it starts counting (by blowing some fuses, for example). After starting counting, the protection circuit will not allow to cutoff voltage, i.e. disconnect cells from the board.

[Patrik28]

Problem solved, the battery is back in business.

I just swapped the new control board and the battery started to work like before. The hardest part in the operation was to discharge every cell under 3.60 V in +/- 0.025 tolerance, before changing the new board. Otherwise the protections might have been triggered.

Sorry for forgetting to take pictures from the operation, but the protection board exchange was very simple:
1. Separate the battery covers gently by lifting from the joint around by knife, sharp screwdriver etc.
2. Rip off the tape holding a temperature sensor right next the protection board.
3. Lift the protection board up so, that you can unsolder four quite large cell tabs under it.
4. Lift the board complete off and replace with a new one.
5. If you separated the battery covers gently (without damaging them), it is now easy to assemble. You barely need no glue at all to attach them, but I dropped one drop of super glue to every corner to be sure.

And the customer service was very kind from the protection board seller too.

[dozer]

ahhh....dear Patrik...thank you !!

I have TWO such failed batteries, both of which are virtually brand-new (fewer than 10 cycles)....and zero help from Lenovo. At over $100/each, I was not well pleased with them.

I'd been thinking that the microcontroller in the pack was the problem....it glitched or whatever and decided it was no good any more.

To learn that it's just a blown thermal-fuse simply delights me!

Although the Schott's info quoted by RBS says "all thermal-protectors are one-shot", that's not correct. The type that recycles when it cools is actually quite common. It's often found wrapped into the top-layer of a power-transformer winding, such as the transformer in a battery-charger...and clicks back on when the xformer cools off a bit.

Those are 2-lead devices though...whereas this Schott device has a 3rd lead which takes the current output through a printed-resistor which heats up during overcurrent to melt the pellet the same as a high ambient-temp would.

Off the top of my head though, it seems that it must be being used as a 2-lead device. I mean, if the mfg chooses to use this "overcurrent sensing" resistor, to get both over-temp AND over-current protection, then presumably the normal over-temp only 'output' lead of the pellet is left unconnected.

Patrik, in your examination of the pack, were you able to determine that they were indeed only actually -using- 2 of the 3 leads?

hmm...a memory has just come to mind...I think that there are certain kinds of "slow-blow" fuses that also fuse from over-temp alone, even if the current through them is within ratings. I'm talking about the usual little glass fuses..2-3mm diameter by 12-20mm long.

I'm undecided on whether I'd rather have a self-resetting thing or a permanent-blow type myself. In a Li-Ion pack?...hmm...

Another thought for the self-resetting type...perhaps one of the Raychem parts would do this job? They're very available.

Thanks again for taking the time to make your very informative post Patrik.

dozer

[Patrik28]

Sorry, I can't say how many of the thermal fuses three legs are connected.

The protection board is also a multi-layer type, so it is nearly impossible to track the connections at home. You would need some x-ray devices to see through the board. Because there are wide copperstrips on the top layers blocking the middle conections, when watching the board against light.

But there is no sense to buy an original Lenovo battery for $100, when you can get a new non-Lenovo battery at half price from eBay (even with a year warranty). In my opinion, the Lenovo-brand is not a sign of quality anymore and worth of extra money, like the IBM-brand was before.