Quote:
Originally Posted by No one
Of course you can charge the battery without removing it, provided you have the facility! Removing is troublesome: the battery weighs and it's hard to unlock the boot without the battery installed (I don't know if the jump starting terminals under the hood can be used.  The manual, page 35, only suggests reaching from the cabin.).
Here you are (the OEM charger): https://www.realoem.com/bmw/enUS/sho...diagId=03_2939. Just notice the manual, page 263. 
From your description you drive too little to even restore the charge that has been used to start. It's overall bad for the battery to keep it low. I recall the last time I had the warning (so bad, the cabin ventilator was disabled, in a very cold winter weather with frosted windows, I could hardly drive  ) it took a 200 km drive on a fast road to recharge the battery and have the ventilator enabled again. |
I agree. leaving the battery at a low state of charge will reduce it's capacity and not driving far enough won't recharge it sufficiently.
Connect a charger to the underbonnet terminals until it indicates fully charged.
Buy a voltmeter that plugs into the in car power socket so you can monitor the battery and charging voltages.