Thinkpad power issue

[HCHTech]

I have a Thinkpad P52 (circa 5/19 so out of warranty) that came in with a swollen battery and reports of "power issues". Very expensive when purchased, so client is hoping for repair, but it's not looking good. It's an 8th gen i7, 32GB RAM, 2 x 512GB SSD.

We fitted a new battery (from Lenovo - client insists on OEM parts), no damage was noted during disassembly. Laptop will charge the battery, but not run on it. When you unplug the power cord, the unit immediately powers down. Trying to eliminate the battery as the culprit, we removed the new battery, and laptop will not run at all on AC-only. Once we reinstall the battery, it is detected, and charges fine, but won't run on the battery only. We have tried a known good Lenovo power supply (client provided, they have a fleet of these).

Battery calibration has been run, latest BIOS, etc.

This has got to be a motherboard issue - but the symptom is very strange, so I thought I would ask here. Just for fun, we got a 2nd new battery, but the symptoms remain. Is it toast?

 

[gadgetfixup]

Are you using an authentic charger, not aftermarket? If using a Lenovo charger then best guess is ISL damage.

 

[ThatPlace928]

I have a Thinkpad P52 (circa 5/19 so out of warranty) that came in with a swollen battery and reports of "power issues". Very expensive when purchased, so client is hoping for repair, but it's not looking good. It's an 8th gen i7, 32GB RAM, 2 x 512GB SSD.

We fitted a new battery (from Lenovo - client insists on OEM parts), no damage was noted during disassembly. Laptop will charge the battery, but not run on it. When you unplug the power cord, the unit immediately powers down. Trying to eliminate the battery as the culprit, we removed the new battery, and laptop will not run at all on AC-only. Once we reinstall the battery, it is detected, and charges fine, but won't run on the battery only. We have tried a known good Lenovo power supply (client provided, they have a fleet of these).

Battery calibration has been run, latest BIOS, etc.

This has got to be a motherboard issue - but the symptom is very strange, so I thought I would ask here. Just for fun, we got a 2nd new battery, but the symptoms remain. Is it toast?

Sometimes a bad CMOS battery will cause that problem. I've had 2 that wouldn't power on for anything but, after replacing the CMOS, everything worked great. Just a thought.....

 

[HCHTech]

Thanks - it is an OEM charger (both we tried). I'll have some time later this afternoon to try swapping the CMOS battery - Otherwise, at least I'll have something more-educated to say to the client other than "She's a no-work!"

 

[YeOldeStonecat]

Have ya done the wee little reset button on dee bottom of her?

 

[HCHTech]

Have ya done the wee little reset button on dee bottom of her?

Yes we did that early in the process - I'm afraid it's dead - as far as I know, that button does the same thing as removing the battery. I didn't have a CMOS battery (this one is in a plastic sleeve with a 2-pin connection) so I've ordered a couple of those. Client isn't in a rush, so that will be the last effort when the batteries come in.

 

[ThatPlace928]

Yes we did that early in the process - I'm afraid it's dead - as far as I know, that button does the same thing as removing the battery. I didn't have a CMOS battery (this one is in a plastic sleeve with a 2-pin connection) so I've ordered a couple of those. Client isn't in a rush, so that will be the last effort when the batteries come in.

In a pinch, Walmart sells 2016 and 2032 button batteries. Carefully slit the plastic casing, pull the old battery out, then put the new one in. I keep a dozen of each battery on hand and have had to do this a few times. Customers might not mind waiting but I have a thing about not waiting for parts to arrive unless I absolutely have to. It means I have to hold onto the client's computer longer than I like. I'm just weird like that.

 

[NviGate Systems]

If memory serves some of those shrinkwrap batteries are rechargeable and some are just dumb batteries.

Not sure if they still put rechargeable ones in tech anymore. Best to double check.

 

[HCHTech]

In a pinch, Walmart sells 2016 and 2032 button batteries. Carefully slit the plastic casing, pull the old battery out, then put the new one in.

Yep, I keep a few different ones in stock as well, we have a whole card of 2032s. For units with a pre-packaged battery like the P52, I don't mess around with using the existing packaging with a new battery, I just order the right thing. If it were my device, or we were in a "it HAS to work by 5pm" situation, then I'd look at reusing the packaging, I guess. It hasn't happened yet.

 

[britechguy]

Yep, I keep a few different ones in stock as well, we have a whole card of 2032s.

Worth having around for your vehicle's key fobs, too. Virtually all of the remote key fobs use 2032s. That's the main reason I have spares just sitting around. And if you order them online they can be had very inexpensively indeed.

 

[ThatPlace928]

Worth having around for your vehicle's key fobs, too. Virtually all of the remote key fobs use 2032s. That's the main reason I have spares just sitting around. And if you order them online they can be had very inexpensively indeed.

My supply of 2032s came in handy, when my son needed one for his vehicle key fob. I order enough to supply my son, too, since we both do a lot of the same work.

 

[HCHTech]

Just to close this loop, I replaced the CMOS battery on that Thinkpad and......nothing changed. It will still startup if you remove the battery and drain it either with a long power button hold or the reset slot on the bottom - sometimes it takes more than once through this dance, but when it's running, it seems fine and even charges the battery - still won't run on the battery at all. Client is replacing the unit. Frustrating but there it is - I don't think I've ever seen this collection of symptoms before - but I'll remember it for sure.

 

[Larry Sabo]

Did you update the BIOS as part of your diagnosis/repair? It can be implicated because of EC (embedded controller) firmware glitches that get fixed by updated EC firmware that comes with the BIOS update. The EC controls battery charging in partnership with the battery charging controller.

 

[Philippe]

The EC controls battery charging

Looks like this EC is dead... or maybe the contacts between the motherboard & the battery.

 

[nlinecomputers]

ISL damage

What is an ISL?

 

[gadgetfixup]

Typically if EC is dead, it won't start. I had a similar issue with a ASUS Nitro 5 board that would start and run with battery and charger installed, charged the battery and if that battery was fully charged you could unplug it and it would run off the battery. Shut it off and try to start from the battery wouldn't work, only flashing power light. Turned out a bad buck converter for the USB ports - yeah it was a weird one.

This one sounds more like a bad BQ chip or mosfet between the battery and main power rain. So BQ works with EC to charge the battery, monitors info from the battery to regulate the charging current, and isolates battery current from the main power rail when the charger is plugged in . When the charger is unplugged, the EC doesn't get ACN signal and closes the gate on the moseft between the battery and the main power rail allowing the system to run on the battery. If that mosfet is bad, the gate line to the BQ is bad or the voltage divider resistors used to monitor system current for the BQ are missing or bad that Mosfet will never close and the laptop will never run off the battery. It will charge the battery but never drain the battery.

I've seen a drop of liquid corrode one pin on a BQ chip and cause this exact scenario. Also see a drop of liquid destroy one of the voltage divider resistors and same result, won't run off the battery. Sorin at ERS explains it pretty well in one of this online classes how a charging circuit works. First suspect when it won't run off a known good battery is the BQ chip.