Newbie Problem: Battery drained on '86 Carrera, what am I missing
 

I got an '86 Carrera a few weeks ago. I drove it from Maine to Virginia without any problems with the battery. It was parked there for a few days without any problems and then shipped to California.

It got to California on Friday and the shippers informed me that the battery wouldn't stay charged. When I got it, it seemed to hold a charge and I was able to start it a few times without any problems.

I had it parked from Friday evening until Sunday morning and the battery was drained. I feel like I am perhaps missing something obvious like leaving a dome light on.

Could someone do me a favor and list some obvious possibilities to check? Many thanks.

Take a voltage meter and measure the battery at the terminal. You should have around 12V. It might just be an old battery, has it ever been changed?

it must read 12.6+ to crank, our 911's when sitting will lose 6% per day, cumulatively

buy a good charger like cTek or battery minder, the cheaper ones will not help maintain it properly and will eventually cease charging.

after fully charged anddriven daily, you do not need to trickle charge it but if you get either I mentioned above it will help lengthen the life of the battery

That's a lot of power drain.......
 

Jim,

That's a lot of power drain because after 10 days that would amount to 60%. Are you sure of the number? Maybe 0.6%? Please advise.

Tony

Mine sits for 3 weeks to a month with no charger on. Never had to jump it yet.
Have your battery load tested.......may be time for a new one.

I have left mine as well for many weeks without any starting problems. Got to be 0.6%. Other than the clock, what else would be draining battery...maybe factory alarm?

I've left mine for 3 months over a winter many times without any kind of charger, and it starts right up. These cars pull almost nothing from the battery when they sit. If you're losing 6% per day, your battery needs replacement.

Battery Tutorial | ChargingChargers.com


Internal discharge
Batteries are subject to an internal discharge, also called self-discharge. This rate is determined by the battery type, and the metallurgy of the lead used in its construction. Wet cells, with the cavities inside for electrolyte, use a lead-antimony alloy to increase mechanical strength. The antimony also increases the internal discharge rate to between 8% and 40% per month. For this reason, wet cells should not be left unmaintained or uncharged for long periods. The lead used in Gel and AGM battery construction does not require high mechanical strength since it is stabilized by the gel or mat material. Usually calcium is alloyed with the lead to reduce gassing and the internal discharge rate, which is only 2% to 10% per month for the AGM and Gel batteries.
Any battery discharge, including internal discharge, produces sulphation on the battery plates as part of the chemical cycle, and given enough time, this sulphation hardens, causing diminished battery capacity at best, or total loss of function. Routine charging after use, or use of a "floating" charger for long periods of storage (boat batteries, ATVs, etc.) prevents this diminished capacity and maximizes battery life. A large portion (approaching 50%) of lead acid batteries have diminished capacity or become unusable due to sulphation, and never reach their rated lifespan. There are electronic devices (chargers and stand alone devices) for dealing with sulphation, but the best practice is avoiding the situation in the first place with proper battery management, including use of quality 'smart' chargers.
Summation on attaining maximum battery life
From the discussion above, it can be seen that there are several issues pertaining to battery life. Recharging in a timely fashion after use, avoiding total discharge if possible, routine maintenance charging or use of a "float" charger on batteries in storage or out of season (jetski, snowmobile, ATV, etc.) are all things which contribute to good battery life. Avoiding extreme temperatures, especially heat, when possible, and checking water levels in flooded batteries are essential as well. There are some applications which are more likely to reach the end of the cycle life of a battery, and have diminishing capacity as a result. Wheelchairs and scooters used daily and heavily fall into this category.
I have added a page dealing with battery prices and the reasons they are rising and probably will continue to do so for a while. This situation contributes to the reasons to seek maximum battery life.

Check that the door switch is working correctly. I seem to recall that after the ignition is turned off, the power window relay stays energized until the door is opened & closed. If the dome light circuit doesn't activate then the relay stays energized and can drain the battery fairly quickly.

It has a nice looking Interstate Battery that was replaced within the last few years. I have a multimeter (not that I know what I'm doing with it) and I'll check. I'll also try unhooking the battery for a day to help narrow things down.

Anything else like that I should check?

Get in the car, close the doors, turn on ignition and put windows down. Turn off the ignition, open the door and see if the windows still work. From my past time with an '88 the windows have a relay to allow the windows to operate till the door is open.
Something I did not have a chance to check. My issue was the main ground cable needed replacing, alt. was not charging good.

With unknown history, I would have the battery checked before wasting too much time troubleshooting. If you do have a drain, the easiest thing to try is hooking up an ammeter and start pulling fuses.

the most obvious possibility is that the battery died. not holidng charge is a common failure mode. no way any battery loses 6% per day. you wouldn't be able to start car after 4-5 days. any reputable auto parts store will charge & test battery for free. 12.6 volts is fully charged. 12.0 volts is almost completely drained.

if i let mine sit for 3 day my voltmeter reads 11.9. im running a pc680 and have just come to grips that i need to either start the car every few days or disconnect the negative terminal.

When I bought my car in 2001 the battery would go dead in a few days. Turns out the door "plunger switch" (not sure what the correct name for it is) was sticking, so the car never "knew" the driver's door had been opened - all accessories stayed hot. A little WD40 & a new cover for the plunger fixed the problem.