Battery drain

What is the acceptable drain on a battery in a modern car that is turned off? How about on a 96 full size 351 Eddie Bauer Bronco?

I would say being able to start after 2 weeks is not terrible by today's standards, less than that is unacceptable. '90s and earlier cars, and some simpler modern cars can go about a month before they start to crank slowly.

It's all about what's running when the car is turned off. An aftermarket alarm will increase the amount of dark current fairly significantly.

This Subaru doc says their spec is 70 mA maximum average. It includes how to measure as well as an insight into how the car goes to sleep.

https://subaru.oemdtc.com/583/measurement-of-dark-current-parasitic-battery-draw-subaru

My 99 BMW will go 6 months easy, on a 5(6?7?) year old battery. Not sure if that's the norm, but I would be disappointed with anything less after that.

buzzboy said:

My 99 BMW will go 6 months easy, on a 5(6?7?) year old battery. Not sure if that's the norm, but I would be disappointed with anything less after that.

Your BMW also has a battery with the reserve capacity of a small submarine 

I generally am happy with 50ma or less.  I have a late model Civic here that only draws 7ma, so maybe that is how Honda gets away with having Group 51 batteries.

One thing to check, for S&Gs, is to connect one lead of a voltmeter (on volts!) to one battery terminal, and touch the other lead around various places on top of the battery.  If you measure voltage anywhere on the case, the dirt on the battery is conductive and adding to parasitic draw.  

So take a hose to your underhood batteries now and then, your batteries will keep longer when parked.

In reply to buzzboy :

Ask me how I can tell it's not an E39 M5 :) And it has the massive battery as well.

I shoot for under 25mA, but that also totally depends on the car.  On my E30, I was lucky to get it under 200mA, but my 67 LeMans sits at a flat zero.  

Easy method to find a leak is to pull the positive cable off the battery (or negative, doesn't really matter) and connect an ammeter between the cable and terminal to see how much juice you're flowing with the key off.  Start yanking fuses and putting them back in one at a time.  You'll find the circuit that is killing things.  You'll get some obvious dips when you pull the radio fuse, or the VATS fuse, but you should be able to find a one that is a smoking gun.  It will at least narrow it down to what is on that fuse.

Thanks. The Bronco's battery goes dead in two or three days. Before I posted about the draw I measured it at 1.5 ma. My son had the battery checked and it was good. I'll clean it up and keep digging.