Battery not charging :: AC power adapter

21 Feb 2010
Posted by Laptop Junction

AC power adapter failure

Common problems why laptop AC power adapters are unable to charge a laptop battery  are:

1.    A dead ID chip – more about this in the ID chip story
2.    High temperature protection
3.    Overload protection or adapter failure

In case of 1) read the story about the dead ID chip. For 2) cool the AC power adapter or reduce the CPU load. For 3) there are three probable causes:

1.    Short circuit on the motherboard causing excessive power draw.
2.    The CPU and/or laptop battery draws too much power
3.    Laptop power adapter is dying

In case the laptop power adapter has a history of buzzing, hissing or cuts out randomly it’s probably because of 3). Replacement might be the best solution.

If the laptop power adapter starts beeping or the green / blue power LED goes off – it probably going into overload protection, which is case 2). Try and reduce the CPU load or remove the laptop battery.

If removing the laptop battery doesn’t help, the motherboard draws all power as in case 1). First thing to check in this case is the DC power jack. If not, the motherboard circuitry around the DC power jack.

If the laptop still runs of the battery, most likely the problem can be narrowed down to the battery charging circuitry on the motherboard.


Laptop AC power adapter design backgrounds

Nowadays laptop AC power adapters are extremely compact and powerful devices. Faster processors and larger battery capacity have pushed designs to the limit. Not to mention market forces to release new laptops even quicker with an even cheaper laptop power adapter.

Inside the DELL-PA-1900-02D2 AC power adaptor - a switching power supply

Inside a DELL AC power adapter - a switching power supply

One of the major concerns is heat – it should stay at an acceptable level even at high ambient temperatures. Stepping the tail of a dual-core laptop in summertime with an empty battery makes a laptop power adapter heat up real fast. Cutting out on high temperatures is not an unknown phenomena – it’s a standard safety criteria.

More-over electronic components age rapidly in continuous heat – it’s not strange for a laptop power adapter to just die when manufactured with cheap components and stressed to the max.  The secret of quality laptop power adapters is engineering time – which means man hours spend on design and testing.

In the end it’s a race with casualties – recalls of laptop power adapters are not unheard of.

Back to the laptop battery charging diagram.