2 suggestions so you do not waste your money on an unecessary battery replacement:
1. A tester that tells you S.O.H. and S.O.C.like this:
https://www.amazon.com/Autool-Bst-100-Battery-System-Tester/dp/B016OFE8FM
2. a desulphating battery charger like this
BatteryMINDer 1500 | 12 Volt Maintenance Charger Desulfator
The desulphating chargers will often rehabilitate a battery that shows only 50% S.O.H. but still take a full charge S.O.C.
If you have 'cooked' the battery by leaving it on an old trickle charger then it is too late.
To test for a frequent low battery problem ,search for "Parasitic Drain".Easy to test with a simple,inexpensive Multimeter.From a recent Post:
How to Find and Stop Car Battery Drains