battery not holding charge

[xsalfior]

Here are the symptoms

I boost the ca,r let it idle, shut if off, and a couple of days of sitting and the battery is dead. The alternator is new, the battery is new, we disconnected my amps and it still won't hold a charge. I posted my car for sale here and now I am having this problem so any help would be greatly appreciated.

[Azi]

after you boost the car, how long do you let it run for? its prob best to buy a trickle charger for the battery. but its kinda hard to figure out. you might have a draw somewhere, thats draining the battery. check lights, and anything else like wires that you may have touched.

[y2jay]

you need to drive it and not let it idle, unless u idle for 40 mins.

i usually just drive aroundon the hwy for 30mins or so, and its good to go.

[Kocakola]

yeah what they said. I was told never to drive it immediately though, but I don't know if thats true. Normally I just let it idle in my driveway for 30-40 min then go to tim hortons. and back or something

[Nutella]

something might be on drawing current. If you can get a multimeter with ammeter function up to 20AMPS, then I would try measuring the current.
I've done this to verify there was no current leak.

-disconnect negative cable of batt.
-set ammeter to measure maximum current (20A)
-connect ammeter positive lead to negative battery terminal post
-connect ammeter negative lead to dangling negative batt cable.
Observe reading -should be close to zero (but not 0.0 since stereo memory draws a tiny bit)

Crappy tire has multimeters with 20A current measurement capabilities.
If the current draw is more than 20A it will fry the meter.

edit: just to add, did you get the new batt tested for charge holding? Just b/c its new, dont mean its good. the shop where you got it can do a quick test with their equip.

[thekid]

If there were a problem with your alternator, than after you gave the car a boost, it wouldn't stay on long as the car would draw out any remaining power and it would stall. So either the battery isn't holding a charge or something is drawing power behind the scenes.

[Aitch]

Although all of the above may be true, I think the main problem is that you boost it, and only let it idle for a short time. This does very little to actually charge the battery. In fact if you were to try and start it on its own just after boosting it, it would probably not start either. Give it a good charge first!

[red-i]

also.. unless it's a good deep cycle battery, most batteries wont' hold their charge as well after being completely drained, i think?

yeah.. after you boost drive it around for a good half hour for sure. you need to give the alternator time to charge it back up.

[xsalfior]

all great advise, thanks you guys were right after driving it around the battery is fine now. Should have tried that before posting.