Car battery change over.

[perfectbite]

I have a gas sipping, 2 wheel drive '91 Geo Tracker that has a computer module which is very expensive. About 10 years ago it went out and the cost for the part alone was about $800. The labour cost was minimal.<p>The present (~12.35V) at least 8 years old battery needs replacing but I don't want to 'shock' this onboard computer. Does anyone have any ideas for 'easing' a new battery's slightly higher voltage in while at the same time maintaining the old battery's voltage to the system or should I just (Full speed ahead and Damn the torpedoes!) disconnect the old battery and connect the new battery?<p>Thank You.<p>[ September 08, 2004: Message edited by: perfectbite ]</p>

[Externet]

Hi.
if you prefer to not interrupt the battery supply at swap, to keep the computer memory unchanged or whatever reason, use jumpers from the new battery positioned nearby to the car battery TERMINALS.
Disconection of the old battery will not interrupt power that way.
Secure one terminal at a time to the new battery keeping contact with the jumper until fastened.
Miguel

[jwax]

Or, plug in one of those cig lighter to cig lighter jumper cables to another vehicle while you do the battery swap.

[jollyrgr]

I have put batteries in and out of cars for years and never trashed a computer or other device for that matter. I have lost station presets but that is about it. If you are unfamiliar with changing a car battery it is quite simple. If you fear you might have a problem there is always the dealer. Most auto parts stores change them for free. Big stores like the "members only" Sam's Club or Super Wal-Mart with tire and battery centers will also change the battery if you buy it from them.<p>If you truly want to change the battery without losing memory in the computer or radio presets you can use the JWAX device. All this is is two male cigarette lighter plugs connected tip to tip, side to side with a long cable. The positive is the center tip. The problem is you need a second car near by to connect to. I have one of these but have never had to use it.<p>Another thing I have seen used but have never used myself is an ordinary nine volt "transistor" battery connected to a cig plug through a blocking diode in the positive lead. The diode blocks car battery power from traveling to the nine volt battery but lets the power from the nine volt battery travel back to the accessories and computer that are normally connected to the battery full time. I have never used one of these things. My cars all have under hood lights and I don't see how this little nine volt battery is going to be doing any good once the main battery is disconnected and the light under the hood starts draining the battery. <p>I have a "jumper box" that is quite useful. When I first got it as a Christmas present I didn't think I would use it. It turns out it has been the most useful car tool I have. This thing is a sealed 12 volt Gel Cell battery in a carrying case. It has two large jumper cable type clamps that connects to your car to give it a jump when the car's own battery is dead. Mine is a simple one that has only the two clamps and a cigarette lighter type plug on it. There are others with flashlights, air pumps, and even 120 Volt inverters. You could get one of these and hook it to the car while you swap the battery. When not being used to jump the car battery this thing can power thermoelectric coolers, power cell phones, run an inverter, etc.<p>WARNING! DO NOT USE AN ORINARY CAR BATTERY CHARGER WITHOUT A BATTERY INSTALLED! These things have a lot of ripple and I could see this damaging a computer. Using a regulated power supply like those used for CB or Amateur radio would do okay.<p>If you do ANY of these you have to be SUPER careful! Normally you disconnect the negative cable first on a car battery. This cable is connected to the car frame and is the "ground" cable. Once disconnected you can safely work with the positive cable. Removing the positive cable with a parallel supply circuit CAN cause problems! If you should touch the positive cable and a wrench to the frame in any way you will short out the parallel circuit. Normally with just the car battery in place this would not be an issue. But paralleling the battery makes the positive cable live with respect to the car body and frame. Any accidental touch to the frame will short the "sneak" supply and maybe damage something. You might consider wrapping the exposed parts of the wrench with rubber. (Slip a piece of rubber hose over the handle.)<p>The body of most cars today is the negative connection. Hooking anything (short of the nine volt battery) up to the system backwards will short out the battery and may cause it to explode. Generating sparks anywhere near the car battery may cause it to explode. When connecting a "jumper" circuit to a car, always connect the positive first and to the battery. If a positive terminal block is provided (very popular on GM vehicles) use that. Then connect the negative jumper wire to something metal and substantial. The hoist point on the engine, the alternator frame, the bracing for the front crumple zone, etc. are fine places. <p>As I said I have worked on cars for years and have swapped batteries on things like old 60's Corvettes with transistorized ignitions (talk about a fragile transistor!) to current model cars and trucks. Not once have I had any problem. If while installing the battery you should hook it up backwards you will probably regret it.