What causes battery drain?

[rush91]

I keep having issues with battery drain. The car stays in a storage facility, so i have no access to hook the battery up to the tender I have. I have noticed that the battery slowly drains, which lead to the flickering of my dash lights..... I went to get the car out yesterday, dash lights were dim and i noticed the volts were nil before cranking. Go to start and nothing. So take battery out, its less then 6 months old, and run it up to AutoZone. They test it says yep it is low and charge it for an hour.... Put it back in the car and fires right up, no dash flicker.

Long story short, my question is what could be draining it? The car has a Viper aftermarket alarm, which i never use when i store it. Would it be best to just unconnect the cables when storing it?? Why i havent bought a battery disconnect switch is beyond me

[secondchance]

Slow drain, I believe, is normal. One time, battery was being drained in 3-4 days. It turned out, failed HVAC controller was running the fan even when the car was shut off at very low speed.

[DRM500RUBYZR-1]

Slow drain, I believe, is normal. One time, battery was being drained in 3-4 days. It turned out, failed HVAC controller was running the fan even when the car was shut off at very low speed.

A fully charged battery in a C-4 should not go dead in a week.
That is evidence of an excessive draw.
These cars do not have the complex computer functions found in the newer cars.

Seondchance is spot on with the first thing to check, i.e. the HVAC fan module causing the fan to run 24/7.
Easy enough to check, just listen carefully.
If that is not it, next check that the power antenna motor is not running continuously.
If not, next would be all of the courtesy lights controlled by the door switches and hatch switch.
Don't overlook the Underhood light, map lights, glove box light, etc.
If all of those check out you will need to probe each circuit in the various fuse blocks in search of the circuit with activity when supposedly off.
One month should not kill a C-4 battery, even in the cold, so one week is clearly telling you something is wrong.
Aftermarket radio?
Kill the alarm as well.
Keep us posted.
When the battery was charged did they perform a load test on it?
If not, start with that to make sure that it does not have adead or very weak cell, which can happen to a brand new battery if it discharges completely.
:cheers:
Marty

[Paul Workman]

IIRC, last time I checked, normal "keep alive" current draw (after the courtesy lights timed out and hood lights disconnected) was ~25mA. GM (for the C4) claimed 50mA was acceptable. A good battery will not go flat in a week or even a month with normal parasitic drain*.

That said, disconnecting a battery terminal or installing a cutoff switch as Cliff suggests, is a good idea in a storage area that doesn't have access to power your Battery Tender.

*A volt meter switched and leads configured to read amperes (A) or mill-amperes (mA) will read current draw between a disconnected battery cable and its battery post. NOTE: Temporary surge: After a battery cable is disconnected from the battery for a minute or less, and then when attempting to connect & measure current (one meter lead connected to the battery post and the other connected to the battery cable terminal) there will likely be a momentary surge of current which is simply the electronic components recharging - taking a couple seconds before settling down to a steady state. That steady state current draw is called "parasitic draw" which is normally ~ 25 to 35mA (I find on my ZR-1).
If current draw is more than 35mA or certainly more than (say) 50mA, it is time to go looking (starting with pulling the "fusible links" connected on a common terminal behind the battery to see which one has the excessive drain). And, here's where Marty's post (above) comes in as some of the more likely places to look first!

[32valvesftw]

The write below was useful for me when chasing an Ignition off draw on a Jeep cherokee. The 25 milliamps number is not hard and fast but as Paul noted up to 50 maybe acceptable. This write up is not specific to our cars so keep that in mind as well.

IGNITION-OFF DRAW TEST
Ignition-Off Draw (IOD) refers to power being drained from the battery with the ignition switch in the Off position. A normal vehicle electrical system will draw from 5 to 25 milliamperes (0.005 - 0.025 ampere) with the ignition switch in the Off position, and all non-ignition controlled circuits in proper working order. The 25 milliamperes are needed to supply things like Powertrain Control Module (PCM) memory, digital clock memory, and electronically tuned radio memory.

A vehicle that has not been operated for approximately 20 days, may discharge the battery to an inadequate level. When a vehicle will not be used for 20 days or more (stored), remove the IOD fuse from the Power Distribution Center (PDC) This will reduce battery discharging.

Excessive IOD can be caused by:

Electrical items left on
Faulty or improperly adjusted switches
An internally shorted generator
Intermittent shorts in the wiring.
If the IOD is over 25 milliamperes, the problem must be found and corrected before replacing a battery. In most cases, the battery can be charged and returned to service.

DIAGNOSIS
CAUTION: Testing for high-amperage IOD must be performed first to prevent damage to most milliampere meters.

Verify that all electrical accessories are off. Turn off all lamps, remove the ignition key, and close all doors. If the vehicle is equipped with a illuminated entry system or electronically tuned radio, allow the electronic timer function of these systems to automatically shut off (time out) This may take up to three minutes.
Determine that the underhood lamp is operating properly, then disconnect the lamp or remove the bulb.
Disconnect the battery negative cable.
Connect a typical 12-volt test lamp (low-wattage bulb) between the disconnected battery negative cable clamp and the battery negative terminal post. Make sure that the doors remain closed so that the illuminated entry system is not activated. The test lamp may light brightly for up to three minutes, or may not light at all, depending upon the vehicle's electrical equipment. The term "brightly," as used throughout the following tests, implies the brightness of the test lamp will be the same as if it were connected across the battery. The test lamp must be securely clamped to the battery negative cable clamp and the battery negative terminal post. If the continuity between the battery negative terminal post and cable clamp is lost during any part of the IOD test, the electronic timer function will be activated and all tests must be repeated.
After three minutes, the test lamp should turn off or be dimly lit, depending upon the vehicle's electrical equipment. If the test lamp remains brightly lit, do not disconnect it. Remove each fuse or circuit breaker (Refer to Wiring Diagrams for more information) until the test lamp is either off, or dimly lit. This will isolate each circuit and identify the source of the high-amperage IOD. If the test lamp is still brightly lit after disconnecting each fuse and circuit breaker, disconnect the wiring harness from the generator. If the test lamp now turns off or is dimly lit, Refer to Charging System to diagnose the faulty charging system. Do not disconnect the test lamp. After the high-amperage IOD has been corrected, the low-amperage IOD may be checked. It is now safe to install a milliampere meter to check the low-amperage IOD.
With the test lamp still connected securely, clamp a milliampere meter between the battery negative terminal post and the negative cable clamp
CAUTION: Do not open any doors, or turn on any electrical accessories, with the test lamp disconnected or the milliampere meter may be damaged.

Disconnect the test lamp. Observe the milliampere meter. The current draw should not exceed 25 milliamperes (0.025 ampere) If the draw exceeds 25 milliamperes, isolate each circuit by removing the circuit breakers and fuses. The milliampere meter reading will drop when the source of the draw is disconnected. Repair this circuit as required, whether it is a wiring short, incorrect switch adjustment or a component failure.

[Marc Haibeck]

The Viper alarm may draw current full time, even when not armed.

I have removed three Lo-Jack batteries that were causing a full time car battery drain. When the gel-cell back-up battery gets old it shorts and draws excess charging current. On a C4 Lo-Jack's are installed under the black trim panel under the rear of the hatch.

I ran into a Chinese headlight controller that drew a lot of current full time. I installed a used GM module to work around the issue. The module is in the left front fascia area next to the vacuum canister.

[pappy.72]

You could get a battery disconnect or one of these and put it on the outside of your storage.
https://www.amazon.com/Sunway-Solar-Maintainer-Motorcycle-Powersports/dp/B01MYVUSRH/ref=asc_df_B01MYVUSRH/?tag=hyprod-20&linkCode=df0&hvadid=312196574864&hvpos=&hvnetw=g&hvrand=17549604510433591956&hvpone=&hvptwo=&hvqmt=&hvdev=t&hvdvcmdl=&hvlocint=&hvlocphy=1016439&hvtargid=pla-569060464229&psc=1

[32valvesftw]

My concern with those solar panels, I have a very similar one, is that they have no voltage control circuitry. Which makes me concerned about overcharging a battery.

[rush91]

You could get a battery disconnect or one of these and put it on the outside of your storage.
https://www.amazon.com/Sunway-Solar-Maintainer-Motorcycle-Powersports/dp/B01MYVUSRH/ref=asc_df_B01MYVUSRH/?tag=hyprod-20&linkCode=df0&hvadid=312196574864&hvpos=&hvnetw=g&hvrand=17549604510433591956&hvpone=&hvptwo=&hvqmt=&hvdev=t&hvdvcmdl=&hvlocint=&hvlocphy=1016439&hvtargid=pla-569060464229&psc=1

I'm going to invest in a battery shut-off. I think I have a slow drain due to the alarm system...