R53 sat for 5 weeks. Zero power, nothing, no lights, clock...zero.

Put smart battery charger into action, a good one...the kind that assesses the battery first.

It wont deliver a charge...as though it’s full
or unable to charge.

Tried for 48hrs. Never delivered a charge. Tested on another battery works fine.

What else could be happening?

 

Bad ground somewhere.

 

Some smart chargers won't work on a totally dead battery.
Connect another good battery to the dead one & connect the charger to that.
Once the dead battery has a little life in it, the smart charger will work fine.

 

How old is the battery? At some point they just quit, voice of experience. That dead 4 year old battery was actually 7 years old leaving us stranded away from home 'till a nice man jump started us.
PS: We greatly enjoyed two trips to NZ some time back motoring the North and South islands for a total of 5 weeks. I was informed by the car hire that 'Gentle Annie' was strictly off limits. Would love to see a picture or two of what we missed if you're willing to see what's up there.

 

+1. Some smart devices are too smart for their own good! Try jumping it traditionally off another car. Barring that, take the battery out and have the parts store test it. They should do it for free.

 

I had no idea. I'll take the battery out and have it tested. I did wonder if the battery was beyond repair, I can't guess the age of it but I would wager 6-8 years.

 

6 to 8 year old battery is very unlikely to survive 5 weeks of sitting and being totally discharged.

My advice would be to just replace the battery with a new one.

Be sure the car has not been visited by critters who like to gnaw on things, though.

 

If it's an original BMW battery, the date is stamped into the top of the negative battery post. Mine was 13 years old & still 'working' but I replaced it as a precaution.
You need an H7 replacement - most catalogs show H6.
As Blue R50 suggested, jump-starting the car will get enough life into the old battery to get that charger working - or just drive around until it's charged up.

Not related, but you might enjoy this:

 

Like most everything in life...sooner or later...things die. Including batteries..!
I bought my 05 JWC about a year ago. It had the original battery in it. If it sat for more than about 4 or 5 day's, not enough power to start the engine. With a charger on it, it was fine.
There was a VERY simple fix...install a fresh battery..!

Mike

 

The alternator is only intended to replenish what charge the battery loses from starting the engine plus what it might lose from sitting for a while. (But there is a limit how long the "while" can be.)

The alternator is not intended to resurrect a completely dead battery. The alternator needs battery power to its rotor to allow the alternator to generate electricity. With a dead battery it can't supply enough power to the rotor and the alternator may not put out enough power to operate the car let alone recharge the battery.

In asking the alternator to try to do this one risks a perfectly good alternator for a bad battery.

To the OP: Just replace the battery. Then vow to not let the car sit 5 weeks unused unless you can connect a good battery maintainer to keep the battery topped up.

 

^^This right here. Or disconnect the battery and/or store it inside somewhere warm while the car sits. You may have noticed that long term warrantied batteries (i.e. 48 months or longer) are no longer widely available, if at all. And the ones on the market are a lot more expensive than they used to be. Just replaced mine for this reason, as it had failed and wouldn't hold a charge no matter how long I left it on trickle. Fortunately it was still under warranty - a top of the line $200 'Super Start Platinum' AGM from O'Reilly Auto Parts with just over 2 years passed on the 36 month warranty. Got a replacement freebie and the 3 year clock started over. They're just not made like they used to be; this time it turned out to be a good thing.