the laptop turns off when unplugged from AC adapter
Make sure the laptop computer is receiving power. (Is the cord plugged in correctly?). When the laptop battery is installed in the computer and it is properly plugged in to an AC outlet, check to see if the fuel gauge is showing a charge sign. If this does not fix the problem, the laptop battery, the power source in the laptop, or the AC power cord may be defective.
A red DS light usually indicates that the battery is low or that the device is not charging properly. Even after multiple charges, the battery may be worn out or malfunctioning, leading to insufficient power. It could also be a sign of a faulty charging cable or port. Checking these components or replacing the battery may help resolve the issue.
I'm guessing that the BIOS battery on your PC needs to be replaced.
Last time this happen to me, it was a sign of the battery going bad. It kept stop charging at shorter and shorter period until my battery can barely hold 10 minutes worth of power.
The negative terminal of a battery has a - sign and positive terminal has a + sign.
battery sign
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yes, intelligent battery chargers have a temperature sensor that cuts off the current when the battery temperature rises. This is a sign of being fully charged. Cheaper chargers carry on until you switch off,this can cause the electrolyte to boil away and shorten the life of the battery. In extreme cases overcharging can buckle the plates of a battery making it useless.
.... as a stop sign.
Take the battery out, clean the battery pocket, and put the battery back in.
Each battery terminal will have a sign impressed into the plastic case next to it, and the sign will be either "+" or "-".
All you have to do is make sure the battery is correctly positioned inside the laptop, turn the laptop on and plug it in. Mine charges when it's turned off also, but not all laptops have this feature. If your battery no longer charges or does not hold its charge, it might be worn out. Contact the manufacturer of your computer to buy a replacement.