Flat battery, cant access boot. SLK 230

[Bellendo]

Hello. Advice please. Cars been garaged for 2 years. Battery is flat and am unable to open boot with key lock. Am I correct in assuming that I need to sort the main engine battery out first. Thank you.

 

[Pontoneer]

Hello. Advice please. Cars been garaged for 2 years. Battery is flat and am unable to open boot with key lock. Am I correct in assuming that I need to sort the main engine battery out first. Thank you.

Not sure , but are there jump start terminals under the bonnet - assuming you can get in there ?

Using a chassis ground point and the live wire to the starter motor might be another option , again if you can get access

 

[Chrishazle]

On my SLK280 there is a jump start +ve terminal under the bonnet OS under a red cover, I use that for my battery conditioner and put the -ve on one of the top mount nuts of the suspension close by.