Laptop not turning on

I have a hp CQ61 laptop. It was second hand so fairly old. It has never held charge and always needs to be plugged in to stay on otherwise it turns off fairly soon. Whilst charging it has the message "plugged in, not charging". Recently it has had another symbol on the charging icon, I can't remember what and didn't look what it meant (I know I should've on reflection) and when I have been turning it on it has given me a message that "the charging level is low" or something like that but has still turned on and stayed on. It has died a couple times in the past (before this message when turning on etc happened) and all I've had to do was plug it in and wait a couple minutes and it will turn back on.

Now it will not turn on at all. The 3 lights at the front blink 3 times every time I try to switch the power on. The charging light is on. I can't hear fans or anything start when I try to start it. I have tried everything else I've seen online on how to fix such as taking out battery and turning power on etc. Nothing works. The lights also don't blink when I turn it on without a battery in it.

I was basically wondering how to fix it. I assume the problem is the battery and not anything else but I need to know before I buy a new one or if there was a possible way of fixing it without changing battery.

Thanks in advance.