charging auxiliary (alarm) 12V battery

[Renaud]

does any one run an auxiliary battery for other 12V items on your car?
I bought a low Ah Lucas alarm battery new from Tayna and have recently popped it on the LidL charger. It doesnt do what the car batteries do and ramp up the 4 bar levels in the display. It has just risen to 12.8V and no visible bars. No further rise in a 24 h period.
Just wondered if that sounds correct?

Despite all the right stuff that was said above I still don't like your battery not getting more than 12.8 V. It's a sealed lead after all. I don't know that Lidl charger but I would have tried another just to confirm?