My acer aspire was holing a charge before and now does not only works on ac power. it is only 8 mths old

problem in mother board power supply unit check any dry soldering

all batteries that old are bad, replace them for sure coin cell
and just take out big battery now shorted and now the correct AC power pack runs the PC.
do that first.
the charge lamps lie to all owners if the battery shorts,
learn to just remove the big battery some do even forEVER>
if not needing true mobile the battery is just not needed and for sure act 1 ,test #1
the RTC coin is dead too.

that is true those SMD DC jacks are pure trash, and fail easy
buy a PC lacking that jack, good PCs have jack pigtails that do not fail ever, unless the trunk monkey played here.

i mean a plug on the wall

It could be an AC adaptor issue.

It should boot when connected directly to the power outlet through the laptop adaptor. If it is not boot, then the adaptor might not be supplying the needed power to boot it up.

If it is possible, try to isolate the issue. Charge your new battery using another laptop. Then plug it in your laptop to see if it works. If it will work, then it is the AC adaptor of your laptop that is defective. If the charged battery still won't make the laptop boot, then there is something wrong with your laptop hardware. If could be a motherboard issue of your laptop.

ur battery broken down , so can not keep electric

Power
subsystem
• ACPI 2.0 CPU power management standard: supports
Standby and Hibernation power-saving modes
• 71 W 8-cell or 44.4 W 6-cell Li-ion battery pack
• Acer QuicCharge™ technology
(for Aspire 5600 Series):
• 80% charge in 1 hour
• 2-hour rapid charge system-off
• 2.5-hour charge-in-use
• 90/65 W AC adapter

Take out the battery and make sure you can turn on the laptop with just the AC Adaptor hooked up.

If you can then you know the AC Adaptor is good. Try another known good working battery in the laptop, if the battery charges then you know that the old battery is bad.

If the laptop doesn't charge with a know working battery or a new one then you know that the motherboard is bad.

Try taking out battery and plug in power. If it works, battery is faulty. If not,
Try taking out your hard disk plug in power, if it works, hard disk is faulty. If not,
Try taking out memory card, if there's a sound, memory card faulty. If no sound, it's your motherboard that is causing the error.
Note: If machine is under warranty no need to pay for the repairs.

If you dont hear any beeps. Then most likely the motherboard is faulty.

Replacement parts can be ordered from www.acerparts.com

If you need more assisntace, let me know.

are you sure the battery is good? How old is the system and battery? Do you have any way to check voltage at the battery terminals?