jimbo3

Frustrated with having to charge the battery before each use after the car sits for a week or two, a friend of mine and I studied the situation and I learned the following:

-At rest, the residual draw is .02 amps (20 mA)
-If you leave the keys in the ignition like I USED to do, residual draw is .09 amps (90 mA). That's almost 1/10 of an amp being drained every hour, or almost 2 amps a day. Results in the loss of about 1/10 of a volt off the battery per day.
-OEM sealed battery is one tough battery to take the abuse I've inadvertantly given it over the past year.
-Battery Maintainer should arrive via UPS today.

-Jim

tj90

Arent typical car batteries rated around 100 amp-hours? According to your calculations, a battery is completely dead in 100/0.02 = 5000 hrs or 208 days. Leaving the keys in kills the batt in 46 days. Assuming that the battery needs to be at least 50% capacity to start the car, means that you have 104 days (23 leaving keys in) before the car will not start.

I must be wrong in my estimates cause this seems optimistic. I start to get worried with the car sitting for more than 2 weeks - maybe the batt is 1) not fully charged 2) aged and sulfated 3) my assumptions may be off or 4) the current draw is more when opening doors, hoods, playing with power seats when cleaning the car in the garage....

TomF

Your insurance company wouldn't like to hear that you leave the keys in the ignition! LOL

Check the draw on your stereo. I can go weeks without any issues at all. An improperly installed aftermarket system can draw the battery down in days.

The maintainer is a great idea, IMHO.

RallyJon

Why the higher current draw with the key in? What specifically is drawing?

jimbo3

Rallyjon- I used to leave the key in without pulling it out after running the engine so I wouldn't have to fool with the d#@% immobilizer on the next start. I suspect the computer or other electonics remain energized. I do not know if, by removing the key and then re-inserting, the draw would be less, but I'll check and report on that, too. BTW- Stereo is OEM and was not on.

TJ90- Batteries typically have about 70 to 80 amps and this one is about 75A. We figured that a good battery should hold enough charge @ .02A discharge rate to start the car after 3 weeks and certainly after two weeks. However, you'd have to count on you battery being in pretty good shape. Plus, starting batteries aren't designed to cycle like that and will wear out prematurely if they are significantly discharged and re-charged enough times. $50 for the maintainer is cheap insurance and I won't have to fool around with a regular charger every couple of weeks.

tj90

I do have an aftermarket stereo with amp and aftermarket alarm etc so my current draw is probably more. Plus rearely a week goes by that Im not monkeying with the car cleaning it etc. Leaving doors open etc.

AOW162435

I replaced my battery earlier this year with the proper Interstate item. A few days ago I was mucking around in the garage and popped my decklid in order to check the oil level. Something came up and I had to leave. A few days later I notice that the decklid is cracked open and I realize that the light has been on for at least two days. I immediately started the car - but the battery was definately low. So I plugged the maintainer in and all's well again.

Mental note to self, stop being so bloody forgetful!

Andreas

Bull

I don't know all that remain energized with the key left in place and not removed, but if you leave the key in the ignition and open the door, you hear the annoying "bong, bong...". If you pull the key out a slight amount past the first detent, the bonging stops with the door open, and I assume all is disconnected.