Hey yall, Today Im going to install some HIDs and Im planning on disconnecting the negative lead on the 12v battery. My question is what I should expect to have to reset or lose (as in memory) if I do disconnect the battery. For that matter, how do I disconnect the negative lead? Do I need to get to the actually battery or is there a lead in the fuse box?
Where exactly is the battery located? I was looking under the hood the other day and noticed it's not there... Guess I should consult my owner's manual...
The negative battery cable attaches directly to the car body at the rear of the car, so yes, you need to disconnect the cable at the battery itself. The battery is beneath the cargo floor in the passenger side rear cargo area.
I suppose after disconnecting the battery it is better to leave the hatch door open since it needs electricity to unlatch?
Good point. Will all relevant systems have to be reset? e.g auto window up/down, MPG, radio presets, etc...?
You will have to reprogram the radio pre-sets and the window up/down. The window is easy. The radio can get complicated if you have a lot of stations in memory. Dealers usually wrap the rear hatch "loop" (on hatch door) with duct tape so the hatch doesn't latch closed. Or just leave it open. Any use data the car remembers will be quickly re-learned. Any trouble codes stored will also go away until they are re-tripped.
You also, I believe, have to redo any other changes you made from how it came new. In my case that means getting rid of the reverse beep and setting the unlock to unlock all the doors not just the driver's. I think I may have to reenter the contacts for my cell phone since they won't sync.
As a bit of clarification, you don't disconnect the cable from the battery, you disconnect the cable from the car body which is just a very short distance from the battery. Many times there is a spark doing this, and is another reason for disconnecting there instead of at the negative battery post. It is a 10mm bolt.
Has anyone made a parallel connection with a current limiting resistor and disconnect it last (connect it first) in order to minimize the spark and also locate the spark further away from the battery? What is a good value of resistance to use?
I really don't think this is necessary, just accept the fact that there is a spark when you connect the negative cable to the body. However if you feel the need to do this, a 5 ohm resistor would allow ~2.5A of current flow. The resistor should be able to handle reasonable power.
Actually, I've worried about that sparking too. One thing of course is to make sure the hatch is up when you're working on the battery. And it is an AGM battery, so there is a bit more safety there too. But when you've seen a battery blow up (long ago in a non-Prius) it is definitely worthwhile to have the respect for it.
Well I worked on the car last night before reading more on this thread and I disconnected the negative lead from the battery and not from the body mainly because it was easier with the tools I had in hand. Well, in the process there was a spark or two but no ill effects to the car, battery, or myself to date. ps. HIDs are working beautifully with minimal to no glare as tested by lead car testing several times. I did however turn down the beam trajectory to be on the safe side. I can finally "see the light!"
