Power/Charging Issues Spin513-51-30EU

We don't typically recommend running sans battery, it's kind of like running a desktop without a surge arrestor. It's just fine until it's not, and then it's too late. Right now it sounds as if the problem isn't the battery itself, but the way Windows sees the battery. You can double check that by going into the BIOS and seeing how long it will run on just the battery. If it seems like the normal duration then charge it fully, boot into Windows and let it run as long as it will without the charger. when it's shutdown due to 'low battery' plug it in and wait for it to fully charge plus a half hour or so, then repeat the cycle. Things are supposed to work such that each time you do the full charge/discharge cycle Windows gets better at reading the battery state, until it ends up actually matching the real world. You can also double check the advanced power settings to make sure low battery level and critical battery level are set to reasonable values and actions. If it's set to hibernate on low battery and low level is 85% you'd get similar symptoms.