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The 40 milliamps you measure isn't enough to kill a good battery overnight. But if your battery has enjoyed a series of deep discharge events in its life, it can easily be enough to keep the car from spinning briskly on the starter. Drains seem to live in the 20mA range (mine with no electrical accessories added), and go up from there as other things with memory functions and sensing are added. Failing FET's in the fan final stages, fouled or otherwise contaminated contacts in switch or device can allow small leaks, and those are the toughest to find. Stan's thermography method works if there's enough leakage through a relay to cause local heating; we use that method in lots of electrical equipment and it works, but we typically have more than the few milliamps of leakage to detect.
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I received the mini clamp-on DC ammeter this week, and I played with the ***** and buttons for a bit after putting batteries in it. Then I hooked up my vintage Schumacher battery maintainer to K's 4Runner battery and tried to measure current through the charging harness with the new meter. Nothing. So I need to put a DMM in there to verify current flow, then see if it's the maintainer or the new meter that's actually failed. The maintainer was flaky enough that it was superseded by the CTEK, so my suspicion is that it's finally TU. Won't know until I test it all though. A monster's work is never done.
Have you tested the open-circuit voltage of the battery after you try cranking it a little? It should have 12.3 or so at rest, and recover to that after some load. The Toyota dealer has a test that has headlights on for 60 secs, and looks at recovered voltage after another minute. If it doesn't come back to as-found voltage in that minute, the battery needs replacement.
Battery failure modes include slow deterioration from discharge/recharge cycling, and also a "short" in the plates in a cell due to sulfation. It's not really a short, more like fouling that keeps a cell from working but not like having a solid bypass path. A dead cell drops the terminal voltage to about 10 at rest, with almost no current capability due to high total internal resistance. If you are seeing 10 or so at rest, the battery is toast.
I test (and record) the specific gravity of the cells as part of the annual electrical maintenance protocol. That reading offers a little advanced warning of condition and impending failure. The little floating-ball testers are a few dollars at POLAPS. In your case, you'll want to test with the battery fully charged, then rest for a little bit to make sure all outgassing is done. The specific gravity tells us how much of the acid has been spent making a contaminated lead oxide that won't change back to lead when charged completely.
One of the best test items I have bought is a DC clamp meter, mine is cheap a Craftsmen 82369 http://www.sears.com/craftsman-digit...p-03482369000P mine was about half the Sears price of $60 from ebay. Not great, not Fluke, once zeroed does show 10ma with some consistency. A joy to watch it on my wife's Lincoln, clamp the battery lead, zero the meter, and over 15 min the current stages down to nothing (less than 10 ma showing on the meter).
No such luck on either of my 928's, so I bought a couple "side mount" battery disconnect switches, which work pretty dandy between the ground strap and the ground wingnut on the body (not on the battery). I do have to open and close the rear hatch each time I turn the switch on or off, but so far batteries stay good much much longer.
With too much other work to do on the cars, I decided to install a cut-off switch inside the car. Sure, it means that the clock is always out but I can live with that for now.
Naturally I don't have a picture but I put it where the fader button can be found (floor, next to emergency brake). Actually, it's proven to be quite convenient.
Voltage no load (approximate numbers):
12.60V to 12.72V is about 100% charged
12.45V is 75% charged
12.30V is 50% charged
12.15V is 25% charged
So if the battery went from fully charged to 11.8 (nearly drained) in 24 hours with nothing being connected, that indicates a bad battery.
You should get WEEKS (at a minimum) before that happens if the battery has no external drain.
Well, I'm at a loss for closure at this point. As a last measure I fully charged the battery then let it sit unconnected.
After 24 hours the voltage only moved from 12.6 volts to 11.8 volts. Seems to indicate the problem is not the battery.
Randy--
Your testing seems to show that the problem --IS-- in fact your battery. If it drains on its own, disconnected from the car, replace it.
We sometimes forget that the tired/failing battery symptoms can show up slowly, then suddenly the charging system that has been struggling to maintain voltage in a battery that won't take it, isn't enough any more. Battery ends up needing replacement, plus the alternator that's been overworked isn't far behind. When the new battery is in, make sure you are getting full (13.8+) volts at the battery terminals with engine running at 1500 RPM.
If it's not holding 12.3+ after being charged, it's not that good.
Autozone: If it's not a potential warranty expense for them, the battery will test weak or bad. If it's new enough that they might need to do a full replacement with no co-pay, "It tests fine. It just needs to be charged."
That cheap specific-gravity test tells you what you need to know. If the battery has been charged and still fails the gravity test, no amount of additional charging can deliver rated capacity any more.
Add one of those cheap little eye-dropper style specific gravity testers to your arsenal. You get to see the battery deteriorate long before it gets critical. Replace it before it's a serious issue, and before it takes the rest of the charging system with it to failure.
Try the local Walmart for battery testing. When I replaced mine there last year the computerized test equipment they used in evaluating the old battery gave a very comprehensive and detailed printout of the battery condition. But I do have a hydrometer in my tool box.
A worthwhile investment is also a good quality battery charger/maintainer. I use the Optima D1200 which analyzes the battery before charging it. Probably the best charger/maintainer I've used to date: https://www.amazon.com/Optima-Digita...N%3DB009M3PQFA
now go for a drive,
Park it,
then wait 20 mins ,
NOW it would be a good time to shoot your CE panel with the IR gun,
with a fresh battery you should be able to see any warm relays .
if you dont find any,
then you should be able to sleep well.
Glad its back to motoring
NOTE roll the windows down and have the cover off the CE panel so you can reach into the car without opening any doors, verify that the rear door edge lamps are also out
You really do still want to test for parasitic losses even with the new battery installed. Just so you know exactly what you are facing as you move forward. In my opinion anyway.
01-17-2017, 08:05 PM
