Battery drain
This could be a wide variety of things. First, charge the battery. Second, lift the positive battery terminal while having an digital ammeter (20A range) connected between the battery post (+) and the removed battery wiring to see what the drain current is in the "store" mode. Change the meter to a lower scale and repeat to actually measure the draining current. If the measurement is under 50 mA or so, that is probably normal due to some low current things tied to the battery even when the system is in the store mode. Leave the battery disconnected for a day or two and take voltage readings over time. The battery voltage will initially decline by 0.5-1V due to the previous charging but after a couple of days of being disconnected, the drop should only be in the tens of millivolts. If the decay is worse, then the battery itself can be either leaking or internally shorted (typically 1 cell or 2V) If the battery goes below 11V when disconnected there is a shorted cell internal to the batteyr and you need to replace it. When you get a new battery, repeat the tests from the start above to identify the problem.
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