Quick Car Question: Changing Battery

I’m about the change the battery on my wife’s car. Can I use jumper cables to connect my battery to her terminals to keep the computers from losing power and resetting?

How old is the vehicle?

I remember reading somewhere that newer cars use nonvolatile memory for most things, and that you only have to reprogram your clock and radio stations after changing the battery.

2007 Chevy Tahoe.

That seems like it would work. I can’t think of a reason why it wouldn’t, but I’ve never seen it done. Otherwise there is a product that you can plug into your cigarette lighter that will keep the electrical system charged while you change your battery.

If you did that, I’d be sure to keep the positive cable/clamp wrapped in something plastic/rubber once you take it off. With the jumper on there, it’s going to be in the way as you try to swap the batteries and you really don’t want that coming in contact with anything metal.

Yes, but it can be a tricky thing to do. The jumper cable ends have to be clamped onto the battery cable ends* before the battery cables are pulled off of the battery, and must maintain that contact until the battery cables are attached to the new battery. Plan it carefully, use string or bungee chords or whatever to hold the cables out of the way if necessary, and most of all don’t let the positive cable terminals touch the negative cable terminals or any metal on the car.

*Hard to get around this for the positive unless there’s a charging post on her car. However, you can connect the negative jumper cable end to a good metal contact point on the engine or body, which should help with the logistics.

Those items are annoyances which one can avoid if power is supplied to the car during the battery change. The biggest worry, though, is an antitheft radio with the reset code long lost, or on a few cars an antitheft system (that prevents it from starting) whose reset procedure is unknown.

Which is exactly what I’m worried about. That’s why I want to use the jumpers to keep power to the car during the change…

Can I infer from this that you don’t know the unlock code?

If you do lose it, sometimes you can reset it anyways. I had a friend with a Blazer that who’s battery died and the radio locked. We did some googling to figure out the procedure. She had to hold down some keys. Get a code. Hold down some other numbers, get another code. Call an 800 number, hit 2 for ‘dealer’, enter the two codes. Receive a third code, enter that into the radio and it unlocked. What seemed odd to me is that it took all of 10 minutes to find this on the internet and execute it, if I can do it, so can the guy who steals your radio.

Thanks for all of the help guys. In the end, I just took the dang thing to the battery store and had them change it out. They used the little power thingie to keep power to the vehicle.

They did mention that my method would have worked unless I managed to tap the pos lead against the car. Which given where it is would have been damn near impossible to prevent.

Better safe than sorry.

I’d guess that one code is from the radio and one is from the vehicle, and that they are compared to each other to determine if that radio matches the vehicle. The third code is given only if they match.

You could do it that way by jumpering from your cable, but be careful to connect it properly. And leave the ignition of the donor vehicle TURNED OFF. You don’t need any extra juice so it’s best to protect the doner car and yours from any feedback issues.

The same thing could be established by plugging a power device into the cigarette lighter. That would be clean and easy. Such devices are available or could easily be constructed. The current draw is minimal from as high as 500MAH for a few seconds before powering down to sleep mode at 50MAH for example.

I have never had a big problem just exchanging batteries. Yes, you lose presets. Yes, sometimes the computer has to go through a learning phase.