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Battery Draw

Bioscache2

Well-known member
Joined
May 16, 2004
Messages
337
Location
Upper Marlboro, MD
Corvette
2001 Blk Coupe
Recently I've had some problems with my starter seeming a little sluggish on start up. It's been cold so I suspected the battery but autozone tested it and says it was good, just low. I've been monitoring the volts and the car seems to try and be charging the battery a lot at start up (14.5 volts) It will drop off to 14.2 or so after a while but this repeats itself. I hooked up an amp meter to see if the car was drawing any juice while off and it's taking 1.6 amps, which seems excessive. I pulled every fuse I had in the car but nothing affected this, the only amp I left untouched was the airbag amps just in case. The problem is new and I can't figure out what the draw is or what the problem is.

Is 1.6 amps excessive and any suggestions? The battery is about 3 years old and is a premium battery. Recent work on the car was one new coil, and new plugs and wires. It was done by a pretty good shop so doubtful that was the problem, especially since this happens when the car is off. One other item is that if I leave the battery disconnected for a minute or so, then connect it with the meter it jumps to about 16 amps for a split second (digital meter) and then settles down to 1.5 amps pretty quickly (some capacitor I'm guessing). The only aftermarket item is a seat warmer that was installed years ago and we hooked it to a fuse that we pulled to check.
 
Replaced the battery because it's cheap insurance and at 3 years old (with one year spent deployed so very inrequent use) it probably was needed sooner or later.

Still curuious about what the normal parasitic load on the battery is when off and if that is high, what could be causing it since pulling fuses did not work (note, didn't pull the relays, just the fuse. I'm assuming that all relays are protected by fuses).
 
Well, I've been patiently waiting for someone to jump in on this, as I think it's a very valid question. Hopefully someone will come in and answer your question.
 
1.6 amp draw is too much, .16 a is fine hopefully you are on the correct scale on your meter. A 1.6 a drain will usually drain your battery flat in a day or two, depending on the condition of the battery. Normal parasitic battery drain is usually between 40 ma - 50 ma depending on the vehicle. A battery that has sat for a year, even disconnected, will usually be sulfated and no good. I am not sure how your old battery was load tested, but if it was not loaded with a carbon pile tester then it is possible that the old battery was bad. I have seen many "conductive" battery testers say that a bad battery is good.
 
LLC5, thanks for the help. I rechecked it and it was still at 1.6 amps. I agreed with you that the battery probably needed to be replaced regardless and purchased an Energizer one from Sam's club. Before I could measure to see if the draw was still there I had to drive back to MD and it escaped me. Down here I put the car in the shop for an unrelated incident (water pump leaking) and asked them to check on the battery draw. They reported only 18 mA and said that was within the 50 mA spec (as you mentioned). I guess there must have been some internal short in the old battery. Once they fix the waterpump she should be good as new (or as good as a 9 yr old car with 120k miles can be).
 
Normal C5 battery current draw should be .02 amps (20 milli amps)

C5currentdrawsleep.jpg


There are several common things that cause this issue:

- Make sure that the seat multifunction switch is not stuck in an ON position

- Make sure that the dash light / interior light switch is not turned to the fully ON position. Check the car in the dark for lights that don't turn off.

- The Bose amplifier amp relay can stick on

- The head light control module is a current sensing module and if it malfunctions can draw excessive current. If its warm to the touch, that may be an issue.

- Common aftermarket accessories can draw excessive current even if you think there off.

Check all of that and see what happens. Remember. When you cause the BCM to come out of the sleep / security mode (like opening the door), it can take 2-3 minutes for it to drop off all its loads and go back into the sleep/security mode.

BC
 
BC, I haven't had an issue with it since replacing the battery but those are some excellent things to check should it return. Thanks for the post and welcome to the forum!
 
Battery draw is the biggest reason why I'm very hesitant to install an iPod auxiliary on my Z. Right now, I'm just using an FM transmitter. PITA when I get into some areas and need to find an unused station, though.:W
 
HI there,

The truth of battery draw in c5 is that the maximum seen is usually 35 milliamps.

This is dependant on the different modules you have in the vehicle.

As options vary, so does the control modules in the vehicle.

C6 has a specification of 10-20 milliamps because the modules are of a different design and do NOT require the same constant electrical power that c5 does.

Lets be very cautious about options vs vehicle year vs aftermarket accessories when classifying correct draws.

Plus, if you do have aftermarket accessories, you can effectively raise your tolerance by increasing the reserve capacity of the battery itself.

This is another reason why a 78 class battery is so critical to how the c5 operates.

Allthebest, c4c5
 

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