How much parasitic battery current is normal
 

After changing our routine and not using our Honda Odyssey as much I started having a dead battery. The battery was a few years old so I got a new one. I charged it on my battery tender before installing. Once the van sat for a few weeks the same thing-totally dead. I measured the parasitic battery drain at 80-100ma. That's a 10th of an amp all the time. Did a web search and it's all over the place on this. I pulled fuses and found the culprit but it feeds several circuits. I have a post on the Honda forum I subscribe to. So what is acceptable? Do I have a problem or a bad battery? I don't want to spend a huge amount of time on this. I thought of swapping in the battery from my pickup and seeing if it still drains the battery.

Battery Drain
 

The simple test is to leave the ground cable off for two weeks and then see if it starts....

Maybe it's a bad battery even if new ? .

I've had a few quartz clocks fail and run the batteries dead in a day or two .

I too am keen to learn what the average / allowable parasitic drain is .

On the Benz's we consider 50mA or less ok.

Bigger battery on a Benz. What does the hungry circuit feed?

I know it's draining the battery. I can see the battery voltage declining as soon as I connect the battery.

All kinds of stuff from the gas door sensor to the clock to the power sliding door sensors and anti-theft stuff, etc. I guess it's up to pulling dozens of fuses to isolate. The suspect fuse is 40A and feeds lots of stuff.

Often a big drain is caused by a failing alternator diode, so even pulling fuses may not do the trick. Try disconnecting the alternator and see if that makes a difference.

I considered that but with a amp meter in series with the battery I can see current drop to near zero when I pull the fuse.

The old way of pulling fuses doesnt fully work on newer cars with can bus networks and sophisticated body control modules.

You will need to make a setup to switch between the ammeter on your DMM and direct power (short jumper) so your DMM doesnt fall asleep in the required 40 minutes of sleep time. Then you probe the fuses with a voltmeter and see voltage between the fuse legs. I was chasing my tail really bad on a chevy suburban a few months ago.

It came out to be the blower speed controller - it had a very strange amp pull. it would go from 50ma to 400 ma - the blower would start blowing on its own

new one fixed it up good - and battery amps was back to 30 ma again. On Honda like yours the dark amp pull is under 35 ma just like other japanese cars. However Honda have one more stupidity - they have an incredibly small battery in all their lineup.

I have a setup as you mentioned so I can switch my Fluke in and out without disconnecting the battery. I realize it may take several hrs for the vehicles electronics to go into sleep mode. I have a lot of likely culprits mentioned by the Honda forum. The power sliding doors are very problematic on these and ours have been flaky from new.

To answer the OP, as high as about a hundred milliAmps.

My Honda guys say 50ma max for mine. I did some troubleshooting in the manual last night. It boils down to 1 fuse that feeds so much stuff it would take the rest of my life to troubleshoot. I would have to rip the interior out to get to it all. If I get a likely cause from the Honda guys I will look at it. Otherwise it's a battery tender. If something did not work it would be easier to locate.

The redneck in me would be inclined to introduce a switch on that circuit before the fuse, to shut off the power to that circuit when it's not in use...locate it below the dash, or in the console.

Don't laugh...you wouldn't need to spend hours searching for the issue, and have a simple way to shut it off and save your battery.

I though of that but the circuit is back up memory to lots of stuff that needs to be relearned and reset every time it looses power. It also powers the keyless entry.

Redneck Engineering
 

Don't laugh at this, when I was a young farm boy I learned all manner of "Farm Fixes" and still use some to this day .

Sadly this one is trickier , I wonder of getting behind the fuse box and separating the wires / circuits is possible .