In more modern cars with computers managing engines and transmissions how much risk of losing data is there if you have a battery disconnect and leave it disconnected for long periods of time?????

When the computer is disconnected from battery power it can forget it's history and any engine/transmission tuning parameters which will cause it to default back to it's baseline setting.

If you're in a state where you have emissions testing, the computer forgets this stuff w/o battery power and you have to go through several drive cycles for the computer to verify everything is working fine.

I wouldn't think there is any risk of hurting anything if you don't mind the computer taking time/miles to relearn what it needs.

for my car because I don't use it very much I put it on a battery tender like my classic car. they even make solar ones if you don't have access to a plug.

I agree with Andrew on the battery tender because it's better for your battery to keep the plates activated. The power accessories like sunroofs and power windows will need to be re-initialized on some modern cars.You may also have to clean the throttle body and re-learn the throttle motor as well every time you disconnect the battery or it will idle about 400 RPM.

Gus

Ten bucks says that Darius is referring to the 5.7 swap setup in his GTX.

How "observant" of you;-)! Somewhere in this car is a microscopic draw on the battery. Until I can track it down I thought a disconnect would save the battery. I do have a good trickle charger and I will keep that hooked up but I was thinking safer than sorry if I am on a trip and don't have an outlet available, not to mention one more security device....although, one would probably NOT be able to hotwire this car very easily if at all.

You won't lose any long term data by disconnecting the battery with any reasonably modern ECU. If your swap is a Mopar ECU, you might lose some adaptations to fuel trims, which will solve itself soon after getting on the road.

Are you sure the microscopic draw isn't the ECU?

Kevin

I am NOT sure that is not the case but is something I will look at for sure.

Or the solar powered charger that you stick on the dashboard and plug into the lighter socket, as mentioned above. I have seen them for as little as $20.

R.