Lenovo ThinkPad T530 - charging slowly and system unstable while charging

[krtech23]

Hello, I recently purchased a T530 from a seller, who used it for a couple years without battery, just with a docking station. I bought a new 6-cell battery (non-original, but a very high quality one, from a brand with almost 100% reliability).

The laptop at first didn't want to charge with the included 90 W AC adapter while being shut down, but after powering it on it began "sipping" power. When after 5 hours the battery wasn't 100% charged, I wanted to run AIDA, but the laptop immediately powered off. I tested without battery and with just battery (and no charger), both were 100% stable. When I ran a system stability test on battery, the CPU clock speed was around 3 GHz and temps at 60 °C stable. After plugging the charger, the CPU speed dropped to under 1 GHz along with the temps, then the fan ramped up and the system crashed. The battery was > 70 % charged at that point, so it shouldn't have been just the charger disconnecting.

I had the same results with another 90 W charger. Later I managed to borrow a used original battery from T430, but it was the same with the original 90 W charger.

I've been doing some more diagnostics with a 65 W charger for my ThinkPad E145. In OS, the system is stable, but the charger keeps connecting and disconnecting. The battery indicator on the lid blinks like this: blink - shorter delay - blink - longer delay.

There is an audible click coming from the motherboard while charging with the 65 W charger (only when the battery is plugged in). I removed the top cover to by able to more precisely locate the sound and it seems to be coming from the power mosfet and charger circuit area. There is no visible water damage anywhere on the board and at first glance, none of the components seem to heat up.

Do you think replacing the charger chip would be enough?

[emestee]

Re: Lenovo ThinkPad T530 - charging slowly and system unstable while charging

You should not be replacing anything before you diagnose the problem. The charger controller, the EC and the battery communicate over SMbus. If the EC believes that the battery needs to be charged but the adapter wont have enough wattage to charge the battery and sustain high performance, it will throttle down the CPU (and/or reduce the battery charging current by instructing the charger to limit it), which is consistent with what you're seeing. If you have a protocol analyzer, you can sniff out the SMBus commands and confirm that this is indeed the case. If the EC believes that the system is consuming too much current, it will shut down the board. Similarly, any of the integrated power supplies on the board may detect an emergency condition and withdraw its power good signal, which in turn will trigger EC emergency. What constitutes "too much current" again depends on how much adapter power is available and whether the battery is charging. The on/off triggering of the adapter is the charger triggering the MOSFETs, either because it detects some fault condition or because it is being told to by EC.

The EC determines which kind of adapter it is (ie how much power is available) by reading the central pin of the adapter connector (which is pulled from 19V by a resistor) into an ADC. That is to say, the voltage on the pin determines the type of the adapter. If the ADC read-off circuit is damaged, the adapter will not be identified correctly.

I would begin with making sure that the BIOS in the machine matches the actual model, and then seeing if the BIOS correctly identifies the adapter.

[krtech23]

Re: Lenovo ThinkPad T530 - charging slowly and system unstable while charging

Hi, thanks for your reply. I was planning on diagnosing the problem more thoroughly later (I had too little time to do it up until now).

However, I tried to power it up yesterday and it wouldn't post. After disconnecting power and cmos battery for 30 seconds, on the first power on (from battery only) it gave me incorrect time warning, then died immediately and wouldn't post again.

I will try to fix the bios. If there are any issues after that, I'll post another question after proper diagnostics.

[emestee]

Re: Lenovo ThinkPad T530 - charging slowly and system unstable while charging

I dont think the BIOS here needs fixing. If the machine is able to start, but shuts down very soon after that, you need to look for the reason it does so. This is typical for liquid damage, thermal protection, bad capacitors and so on. You need to perform basic board diagnostics, and find out how the shutdown is triggered.

I will try to fix the bios. If there are any issues after that, I'll post another question after proper diagnostics.