i have a 1992 bmw 325i and the battery has been drained (an interior light was left on while we were on vacation.) i tried jumpstarting it, but got nothing. how difficult is it to change the battery by myself? i've done a lot of home repairs, etc. myself, but i don't know anything about cars. is this project that's difficult to screw up? should i just bite the bullet and empty my wallet at a repair place? or can do the job myself? if the latter, what kind of battery should i use?

thanks in advance.

 

If the battery just went down from leaving a light on it may just need a charge. I expect you may have not made good connections when jump starting or it should have started if the other battery was in good shape.

Try jumping it again and make sure you go + to + with the same cable and - to - with the other cable. If you were jumping from or to a side post battery they are hard to get a good connection. Or take the battery out just disconnect the - terminal first then the + terminal. There will be some type of hold down bolt or bolts to loosen or take off and the battery will lift out. If I remember right yours is in the pasenger side of the trunk. Take the battery to an auto store that will test your battery. Many auto stores do this for free and if you need a new one will install for free if you can get the car there.

Buy an inexpensive tool to clean the posts and the terminals befor you put it back or put a new one in. The auto store will show you how to use it. It is easy.

 

thanks for the response. i've made sure of the hook-ups and i'm not getting anything (although i did the negatives to the negative of the good battery and a metallic piece of the engine of the car with the bad battery.) if i did this wrong let me know.

as for removing the battery, my biggest concern is sparks/electrocution/fire/etc. should i be worried about this when i remove/install a battery? (i assume that both of my cars have covers over the positive terminal of their batteries for a reason.)

thanks.

 

Disconnect the negative battery cable 1st, while leaving the cover on the positive post to prevent a short with the tool you're using. When installing a new battery, hook up the positive cable 1st then put the cover over it. You'll probably see a few little sparks when removing/installing the battery. That can't be prevented.

If you remove/install the positive cable with the negative hooked up, there is a good chance of causing a short (with big sparks) as the negative is connected to most all metal parts under the hood.

I would try jump starting it again if it worked perfectly fine before it got drained. You possibly didn't have a good enough connection, like car nut said, or didn't wait long enough. Normally, when you make the last connection for the jump start, the running engine will die down slightly, indicating a good connection. Also, it sometimes gives you a better jumpstart connection if you, after clamping the clamps on the battery posts, wiggle them around some till you see some shiney metal, and clamp there, and kind of bite the clamps into the posts a little. Also, rev up the engine of the running car to about 3000 rpm for 10-15 seconds before trying to start your car. You might also try hooking the negative cable to a different metallic piece of the engine.

 

You could also call your local tow guy to do the jump (our road service charge is $30). He'll likely use a portable booster box, aka jump-in-a-box (some of which, like the one I use, have an indicator to show that you've made a good connection and also will not permit backward hookups) and will know all the stuff previously mentioned. If he's a nice guy and the jump still won't work, he might even pull your old battery out for you (but don't expect it, work load and insurance worries may prevent that).

 

It could also be that the jumper cables you have are junk. When you have the cables hooked up, try putting on the headlights to see if they are working. If the cables are connected properly and they are in good working order, the headlights should light without a problem.
I've seen plenty sets of 'jumper cables' that could only be called that because they looked like them. They werent capable of actually jumping a car though. Its worth spending a couple extra dollars to get the quality jumper cables that wont let you down.