Does anyone know what the normal current draw is when a C5 is shut down? An acquaintance of mine is having a problem with a 2000 vert that is drawing 15 milliamps. The battery will discharge after about 48 hours of sitting. Her local dealer replaced the battery, BCM and passenger side visor (?) and can't find anything else wrong. According to the dealer, though, the normal current draw is about 6-8ma.

I suggested pulling fuses one-by-one to find where the draw is, but the dealer states they've found nothing. They've told this person the next step is to have an engineer from the factory come out, at the vehicle owner's expense.

Is 15ma excessive? If so, any suggestions as to where to look?

Thanks in advance.

 

15ma[.015],won't kill a battery in 2 days.actually 15ma isn't bad.40ma is border line[could kill it,but not in 2 days].if you are mechanically/electrically handy,the best way would be to get a inductive amp meter and hook it around the negative battery cable and see how many miilamps you have.you can also do it with a amp meter with leads hooked up in series and see with the ma's are.only bad thing about this is,when you unhook the negative battery lead to hook up the meter,there is the possibility that you may turn off the load that's killing the battery.just my .02.

 

Info - Battery Parasitic Drain #02-06-03-010A

Here are some rules of thumb that might help relate parasitic drains to how long a battery would last on a parked vehicle.

The Reserve Capacity (RC) rating multiplied by 0.6 gives the approximate available ampere-hours (AH) from full charge to complete rundown. Somewhere between full charge and complete rundown, the battery will reach a point at which it can no longer start the engine, although it may still operate some of the electrical accessories.

Using up about 40% of the total available AH will usually take a fully-charged battery to a no-start condition at moderate temperatures of 25°C (77°F). Put another way, for a typical battery in a storage situation, depleting the available AH by 20 to 30 AH will result in a no-start condition.


Important
If the battery begins storage at 90% of full charge, reduce the available AH accordingly.


The recommendation for maximum parasitic drain is around 30 mA (0.030 amp). A typical drain today actually falls into the 7-12 mA range, even though some vehicles do approach the maximum. Multiply the drain (in amps) by the time (in hours) the battery sits without being recharged. The result is the amount of AH consumed by the parasitic drain. The actual drain may be small, but over time the battery grows steadily weaker.

Here's an example: a vehicle with a 30 mA drain and a fully-charged 70 RC battery will last 23 days. But if that battery is at only 65% of full charge (green dot barely visible), it is going to last only 15 days before causing a no-start.

Effects of Temperature on a Standing Battery
The parasitic drain will be fairly constant over a range of temperatures. The important temperature is that of the vehicle at the time a start is attempted. Colder temperature raises the threshold of a no-start by increasing the residual power needed. When the temperature falls to 0°C (32°F), the battery will be able to put out only about 85% of its normally available starting power, and the engine may need as much as 165% of the usual power to start.

The combined effect of these two factors is to reduce the number of days the battery can stand with a parasitic drain. At 0°C (32°F), the battery can stand only half as long as it could at 25°C (77°F). And at -19°C (0°F), the standing days are reduced to one-fourth.

Temperatures above the moderate climate of 25°C (77°F) increase the battery's internal self discharge. If the battery is in a locale where the temperature is averaging 32°C (90°F), an additional 5% to 10% of the available ampere-hours will be lost in a month due to self-discharge within the battery. At temperatures below the moderate range, self-discharge will be low enough to be negligible compared to the parasitic loss.

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Hope this helps

 

Thanks for the input. Based on what you've both stated, it seems the 15 ma draw is not the problem. This would lead me to questioning the output of the alternator. Does that make sense?

I can't do any real detective work here, as the car is a couple thousand miles away. I'm trying to help, though, 'cause the dealer has given up.

 

Excellent information... thank you for posting it.

My own 1998 C5 is drawing about 25 Milliamps +/- in sleep mode with a brand new Optima Yellow Top battery.

Prior to the new Optima, I was using an Exide battery that I had bought at BJ's. The car would not start after 3 to 4 days of sitting unless I had used a battery maintainer. Eventually, I got low voltage warnings and it started throwing codes. That was the last straw.

I have learned my lesson... the Vette has a fairly healthy parasitic current draw and is not the place to try to use a run-of-the-mill warehouse store battery. I now pay close attention and use a battery maintainer religiously whenever the Vette goes unused for more than one day.

Monk