You may have both a duff battery and a duff alternator.
By battery I mean the main battery not the auxiliary/second/small/SS battery although that is almost certainly duff as well.
The cause of duff battery/ies may very well be a duff alternator so that is the first thing to test/check.
Then check the main battery for charge and condition, if it's a bit low (and the alternator is good / fixed / replaced) it may well fully recover with a charge. If not then it is time for a new battery
Best bet is to take the car to a good auto electrician to properly test the alternator and battery.
No need to worry about the secondary battery as it doesn't effect anything other than the SS system but once you have a healthy alternator and main battery it may recharge and fix itself.
Or you can disconnect it or even completely remove it from the car with no ill effects.
If the secondary battery is beyond saving and you really really want a working SS system then you can replace it with an Exide EK151, the OEM battery is simply one of those with a JLR sticker plonked on it.
By battery I mean the main battery not the auxiliary/second/small/SS battery although that is almost certainly duff as well.
The cause of duff battery/ies may very well be a duff alternator so that is the first thing to test/check.
Then check the main battery for charge and condition, if it's a bit low (and the alternator is good / fixed / replaced) it may well fully recover with a charge. If not then it is time for a new battery
Best bet is to take the car to a good auto electrician to properly test the alternator and battery.
No need to worry about the secondary battery as it doesn't effect anything other than the SS system but once you have a healthy alternator and main battery it may recharge and fix itself.
Or you can disconnect it or even completely remove it from the car with no ill effects.
If the secondary battery is beyond saving and you really really want a working SS system then you can replace it with an Exide EK151, the OEM battery is simply one of those with a JLR sticker plonked on it.