Parasitic Battery Drain e53

[Makus]

Originally Posted by andrewwynn

If the current draw drops to 40ma after it goes to sleep you don't have a parasitic draw.

Check the vBat at the battery when you attempt to start. If vBat stays high the problem is likely either the B+ terminal loose or a ground or a connection like the starter.

You can measure vBat at the cig lighter as that is always live and takes a different path to the front of the car than the start/alternator cable.

The other thing you should check is the current draw of the starter which should be about 200-250A. If you have a peak reading multimeter you can measure the voltage drop from the B+ under the hood to the pos of the sig lighter. IIRC you multiply the voltage drop by 300 to get amps to the starter eg. 0.75v= 225A.

When a starter begins to fail it will take more and more current up to double. When that happens you lose double the voltage on the wiring and you get slow turning starter it will "feel like" the battery is low. I've seen a dozen cases of somebody replace both battery and alternator when the starter was the actual problem.

A loose ground strap will have the same problem. If it's loose it can have a 4v drop across the connection and suddenly 12v is 8 and a car won't start

it might make sense, while I was charging the battery and it had 13V and I decided to try to start the car and the value dropped to 12.5V or even lower and there was no power to start the car, only at about 13.4V the starter managed to start without a problem

[andrewwynn]

What did the battery drop to while trying?

A couple people on XO have recently come across a loose connection at the B+ under the hood. The schematic is wrong where it shows the cable is continuous and has a tap to the alternator: it actually is discontinuous and is connected on both sides of the firewall and can get loose. It will give the symptom of a dead battery or starter but with the odd exception of normal resting voltage of 12.4 or so.

[Makus]

values ​​that I gave were at rest without start, if I understood you correctly, is it good to check the fastening of the wires, is there nothing or loose? I am wondering grounding because if I have low values ​​(.05-.07) in sleeping mode which could not be able to discharge the battery so quickly, as I wrote, when the battery is fully charged or I run on cables, the car has no problem with starting but after a few hours something will drain the battery

[andrewwynn]

You are saying something will drain the battery but you are also saying the battery has a resetting voltage of 12.4 which is fully charged. Numbers like 13.2 are only right after charging that's not a resting charge.

Your symptoms sound like either a loose connection somewhere can be power or ground side or a defective battery.

[Fifty150hs]

Pull the fuse for your Nav system and see what happens.