Archive of BMW Motorrad Club Cape (2006 - 2019)

I have the same bike but I'm afraid I can't help with the diagnosis.

I believe the Yuasa YTZ14S MF is the official (factory-fitted) battery for the 2013 GSA. I replaced mine earlier this year, after 146 654km on the original, with the Novelbat YTZ14-BS which I bought from my local Battery Centre. 

Motobatt also very good. about R1400 at most dealers.

Not symptomatic of a battery problem, you'll have had several early warnings on cold starts of an ailing battery.
Batteries also no longer suddenly fail, they send a calling card way in advance.
So this leaves you a failing altenator or a shredded poly-vee belt.

check your poly-vee belt that drives the alternator.
The spluttering results from  weakening battery that is not getting charge current. (from the failed drive belt/altenator and the can-buss goes into life support), 
The dash will eventually go blank, as will all electrical functions so spark can survive.
The altneaotr alos send wanring light when it is not happy, and very unlikely to go suddenly on these machines.

Limp to a service Centre and replace the poly-vee belt.
Avoid riding any distance like this.

Recharge battery if you do have to ride further.

Take advantage of your many friends who may have a spare limp-home belt.

This is a wear item replaced at 60 ooo km intervals.

Some off road riders ask for the old belt back to keep in their tool kit for just such eventualities.

If the bike stood for a long time, the belt goes brittle and will gradually start to degrade and disintegrate until it gets too weak, then it will catastrophically self-distruct, which is most likely your event.
Replacing it is a 45 minutes task if done correctly.

I'm sure you'll find a kind sucker to help you.

Go through your address book, the third idiot is probably the suvcker you are looking for.