Hi to all!
I bought a Die Hard Charger / Maintainer. 2 amps. Microprocessor controlled fully automatic 5 stage charging. 2 amp 12V. Will this work on my car battery? Or do I need to buy the BMW brand from the dealer. I know this is a dumb question but I just wanna make sure on how to properly hook this up on my '05 545i? Thank you!

 

The handbook gives details ,you connect to the terminals in the engine bay.

 

The positive terminal in the engine bay and ground it anywhere? What will happen if I hook it up directly in the battery that is in the trunk?

 

The manual shows you exactly where to connect the black terminal... there's a "grounding" bolt close to the positive terminal.

 

It will work ... be sure to use the 12v setting; on that particular battery tender it's easy to move that switch by mistake.

I made an extension for the car connection side using low-voltage landscape wire. It is NOT recommended to use an extension cord between the house electrical outlet and the tender itself.

That way I can connect the tender to the car w/o having to be that close to the gizmo. When not connected, I keep the excess wire coiled up and velcro-strapped under the air filter housing.

 

I don't know how much you paid for it but powermax converters has a battery charger/maintainer that I use everyday. I just leave it hooked up 24/7. They do cost more than just a average battery charger but they are much better. Www.powermaxconverters.com

 

Suppose to use under the hood not trunk, positive goes to obvious red positive relay and ground goes to the big screw looking thing off to the right sticking out by itself.