zbook studio g5 weird USBC charging issues

[zbookfan]

I have a zbook studio g5 that I normally charge using a 100w USBC charger that plugs into AC. Its not as fast or powerful as the AC charger that came with the laptop but it works great and I don't ever really need more than 100w and its so much smaller than the stock zbook charger.

Recently I got a USBC power bank that can output at 100W and I want to use it to charge the laptop. It works great for about 10 minutes but then it will start to cut in and out. The screen on the power bank says that its delivering 100W PD then it'll drop to 0w then 100w then 0w then it'll eventually just stay at 0w. If I unplug it then plug it back in it'll restart the cycle. I tried a second power bank that was a different brand and it had similar results which leads me to think that this is an issue with the laptop. But that doesn't explain why it would work just fine using the 100w USBC charger that plugs into AC.

Has anyone else seen this behavior?

[banhien]

@zbookfan 

Its specs

           https://support.hp.com/au-en/document/c06010885#AbT12

It uses NORMAL HP 150W Slim Smart AC adapter. Now you use a 100W charger, what do you expect ? 100W charger won't charge your machine when running all power.  You can see 100W can charge your machine overnight or off a bit faster.

Hope this makes sense.

[zbookfan]

You responded to a question but not my question. Maybe try reading the whole post? My laptop is never running at full power. I would never expect 100w to keep up if it was running at full power. Normally when I need to charge I'm at a coffee shop or something and writing emails, I wouldn't expect to run simulations or renders on limited power. If I am using My 100w USBC AC charger it will go from about 10% to full in a little over an hour which is quite acceptable.

You completely ignored my actual question, why does it cut in and out when its on a 100w power bank VS 100w AC charger. The output power is the same, the cable is the same. It happens on multiple different 100w power banks which leads me to think its something with how the laptop is negotiating the PD power.