This was originally posted on www.g35driver.com, it should hold true for the Z community as well:

Hopefully none of you are like me, but, if you are, dead batteries are an all too common occurance. I bought my G35 coupe on 9/11 of 2003 and since then I've managed to put a whopping 14K on the odometer. This means, the car sits, a lot.

This also means, that most of the time, I have to jump my car before I can drive it, on those days I do want to get it out, even with my Optima red top battery!

So, today I went to my local Sears and found an external battery charger/maintainer for $30! I was pretty excited about finding this, but once I opened the box I got even more exicted. This little charger comes with 3 different ways to charge the battery - large alligator clips, cigarette adapter, or two wires with ring terminals on them. The cigarette adapter would be great, but it won't work on our car (the outlet is off when the car is off). So, I decided to permanently install the wires with ring terminals.


Here is the box it came in


Here is the unit sitting on my garage floor!


Here is the plug I chose to use (I've already cut the black wire, it did have a ring connector on it)



I started by removing the battery cover (pop out 4-5 plastic clips and pull up on it). I hooked the ground wire up first. Instead of going to the battery, I went to where the battery is grounded. If you follow the wire on the (-) terminal of the battery you'll find that it bolts to the inner fender. I removed one of the 10mm bolts and put my ring terminal through the bolt, then reinstalled the bolt. Now, the wires weren't going to be long enough to do what I wanted to do, so I grabbed some 20ga black wire I had laying around. I soldered on about 15" of wire.


Here is the black wire connected


Close up of ground


For the power side, I removed one of the nuts on the positive terminal. The ring terminal on the supplied red wire wasn't big enough, so I used a small file to slightly enlarge it. I put the ring terminal (attached to the red wire) on the positive stud and reinstalled the nut. Next, since there was no fuse supplied with the wiring, and I happened to have a fuse holder laying around, I soldered the fuse holder to the end of the red wire (about 8" from the battery). I then soldered about 15" of 20ga red wire (once again, had some on hand) to the other side of the fuse holder. There was a spot in my firewall where my wideband O2 sensor wiring passes through in to the engine bay, so I routed the red and black wire through the same passage. Once the red and black wires came together I covered them in black electrical tape for a clean look.


Here you can see the red wire, connected to the fuse holder, connected to the battery terminal and running through the grommet out in to the engine bay.


Another picture of the wiring

I routed the taped black and red wire with the OEM harness that went though the grommet, even running my new wire through the OEM zip tie. Eventually, the OEM harness Y'd off, and I routed my new wire in through the middle of the 'Y'.


Wire routed with OEM wiring


I then solderd the connector that cam with the charger on to my new wiring:


Original connector back together!

I then covered the remaining exposed wiring with black tape, once again for a clean look:


Almost finished!

Once everything was taped up, you could hardly tell I did anything!


Looks stock!!!!


Just like the day I drove it off the show room floor!

Finally, since I don't plan on driving it until at least next weekend, I plugged my new charger in to my new 'stealth' charging plug!!!!!!!!




The charger will charge with (I believe) 2A of current on a 12vdc battery. Once the battery is fully charged it automaticallys switches to 'float' mode, where it maintains the fully charged battery. This results in a battery that is always 100% charged, no matter how long it has set!

I am thinking about extending the plug a bit further so I don't even have to pop my hood to plug it in. My only concern is that that supplied plug isn't going to like the water and salt that Ohio offers, so I am afraid if its expoxed much more then it already is it will corrode and fail to operate.

 

Great mod Kevin. Over the last couple of years, I've seen countless posts by people who have let their Z sit for a week or so and come back to find the battery dead.

 

I found that my amplifiers booster cap was the problem.