Battery drains instantly(literally) when just starting a heavy application

Acer laptops are fairly notorious for bad battery performance. That said, there re thing syou can do to help the battery but probably not this one.

Lithium ion batteries need to remain at full charge as much as possible. If they sit around with lower charge they will lose their ability to maintain a charge.

First, use a wall outlet as much as possible. If one is available, use it. Don't run off the battery just because you can. Only when a wall outlet is not available should you use the battery, e.g. trains, planes, autos, etc.

When you shut the computer off always leave it on a charger, if possible, to maintain the charge. If it is already fully charged it can sit unconnected for a couple of weeks being unused but don't let it sit for months on end without maintaining the charge. The longer it sits without a full charge the less charge it will accept when you do charge it.

The above applies to all Lithium-ion batteries. It's a consequence of the battery chemistry.

You could also get a battery with a higher amp/hour rating, usually shown as ####mAH or ###Wh. The #'s number being larger means it can store more energy. Get the largest amp/hour rated battery you can for that machine.