Battery tests good, goes dead in 24hrs, only .5mA parasitic draw?

Is it possible I have a bad battery that just won't hold a charge?

I have a yellow top optima 850cca in my 1997 Chevy truck. A fully charged battery will go dead in 24-36 hours if left alone. Battery tested ok twice at autozone. I did a parasitic loss test today and am only drawing .5 mA when vehicle is off. I believe .25-.5 is acceptable on a newer vehicle.

Thoughts on what is causing this?

 

Put in a brand new Interstate.

 

It could be an internal issue with the battery. Take it out of the truck and charge it on the bench. Let it sit overnight. If it takes a big charge the next day go to WalMart and get a new Johnson Controls replacement with a 3 year full replacement warranty. If you are still unsure the next morning, stick it back in the truck. If it does not turn the engine over, you know the answer.

 

How many cranking amps does it have is the real question. A battery can have 12 volts or more and be very low on cranking amps. This would give the same symptoms you describe.

 

I think I figured it out tonight. I have an internal short in the alternator. When the single alt wire is hooked up and there is a volt meter on the battery you can watch the volt meter drop .01 every 30 seconds or so. Unhook the single wire, voltage drop stops. Unclear to me why this does not show up when testing for amperage to check for parasitic loss, but it didn't. I stumbled across this potential source while searching youtube videos on parasitic loss testing.

I will swap the alternator and report back on the results.

 

Awesome!

 

Same deal on my GSX... PO swears its the newer quartz clock... Battery loss is .3 (3/10) A on pos and .7 (7/10) A on ground Seems like a lot to me! That's a 1 amp drain. Still running OEM alternator with external regulator. Field points stuck closed maybe?? For now I pull the batt conn when shutting down if even out for breakfast... Bill

 

no way a quartz clock draws an amp.

 

AGREED! I just spoke with my resident exspurt and he informed me the pre Delcotron units (with the external regulator) would get brush dust and short one of the 6 internal diodes causing a ground. Gotta pull it off for a bench test and maybe treat her to a new regulator as well... Theres also the issue of funky radio stuff being wired wrong as well... ws

 

That is the BIGGEST line of horse-ka-ka I've ever heard.! ou: No kidding,and I've been doing alternators & starters since 1980.
Find a new "resident expert".:bglasses:

---------- Post added at 10:07 PM ---------- Previous post was at 09:33 PM ----------

Optimas are garbage,never buy one again.Put a different brand in,Dekka is great,if you can find one.NAPA sells a relabeled unit,ask for it.:grin:

---------- Post added at 10:12 PM ---------- Previous post was at 10:07 PM ----------

Not possible for Milliamps to do that,the battery wont drain that fast.:TU:

 

OK Karnac... whats causing the drain then? 1 amp is like a dome light right? MY RESIDENT EXSPURT suggested pulling the main red wire off the alternator and seeing if the drainage goes away pointing at the diode trio. The other is pulling the plug on the Reg. I need to at least isolate whats going on. So what youre saying is



Am I on the right track? Id really like to put a one wire Delcotron on here and be done with it. Will it fit frame wise? Will it accept the double pulley? Does the main wire still go to the starter post so its keyed? Does it need a fusible link (external)? Inquiring minds want to know. When "off" and disconnected, the battery, fully charged (tried 2 batteries BTW) showed 12 volts on an analog meter. Running, the system delivers about 12.2 Another BTW... I run several self exciting one wire Delcos' on my boats (2-12VDC and 2-32VDC units) and a converted Model T Ford with nothing but success.
The pic above shows the obligatory ammeter that's not connected. I plan on swapping that out to a voltmeter. The temp gage shows 130 at running (actual 185 on an IR gun) and the hood tach on an HEI dist. shows about 1/2 of what it should. The POSPO wired the tach so the red light comes on whenever the key is on. Third BTW... yes, the block to body (firewall) ground strap is on and intact. ws

 

You never stated how old the battery in the car now is. If it approaching the magic age of 5 years or has been charged/discharged a bunch of times it is very possibly the battery itself. The lead plates exfoliate lead particulate which builds up between the plates, shorting them and reducing the area available to accept and hold a charge. It looks like the PO did a lot of funny stuff electrically and figuring that out won't be any fun at all. As far as the current draw goes, .3 Amps will not draw a good battery down overnight. Batteries carry a cold cranking amperage rating, say 350. At that rate a fully charged 350cca battery, feeding a .3 Amp load should last for at least 1000 hours.

 

u need to define your variables used in the formulas..

 

The variables proved themselves via megavars historisis vs the sine wave. Alternator was putting out a good 13.8 with an after market chinaman regulator. Getting both tested today. The PO did a wonderful job wiring up a Kennwood CD player with a graphic equalizer to the Buick 8 track and a Bose amp in the trunk... lots of wire nuts and sticky black tape. Hmmm... Hood tach wired wrong to the HEI and a few dozen sendin unit wires laying bare on the block with mechanical oil and water temp gages installed under the dash. Probably pulled out 20 feet of "Unknown Variables" on the wire side today. Carbs off and going into the shop. Also went junking and found 2 correct 16 inch wiper blades... a banner day Id say! ws

 

:laugh::laugh:

 

Externally regulated Delcos don't use diode trios. You have a heck of a wiring mess to sort out,a couple new harness would cross my mind if it were my project.:grin:

 

Thanks for the input pal! Im a little rusty on this stuff, but I would guess this is in fact an externally regulated unit (?) Has the main BATT post and the two wires for ignition and idiot light. I spent 35 years as a mechanical engineer at a generating station and kinda understand DC stuff but its not my forte'. The PO made the comment that he was proud of the nice clean wiring work he did on this car. Yesterday the ol' Kleins came out and we started to "Improve" his expertise! What a Carneador! (Spanish for "butcher") ws

 

Check your test instrument. Current out on POS should be the same as current in on NEG.
0.3A out on POS should see a 0.3A in on NEG for a total draw of 0.3A.

 

Yeah... I kinda thought so... the chinaman ampclamp isn't TOO accurate on the bottom end of the DC side. Later, I used a Fluke meter with an ammeter and it showed .5 per leg. But still only 10 volts. Ran the car yesterday and verified 13.8 VDC at the battery which sounds OK to me, HOWEVER, I still pulled the alt/reg off for testing today. Took it to the motor parts for testing and they guy said ZERO output. He sent me to a NEW resident exspurt that only does starters and alts from small farm stuff up to oil cooled 350 amp jobs off the metro busses. Heres his take on this job... The alt, being rebuilt already, is a "transitional model that has a delcotron frame but, an EXTERNAL reg. The rectifier bridge showed being bead blasted and probably was done with silica carbide media. "Probably" has a ground in the rectifier bridge path. The reg is also an electronic chinaman job with a PCB and no coils inside. He'll test that as well. If the stator and rotor are good, new parts and bearings will be about $80. That seems fair. If the big internals are bad, he's recommended a different unit with some wiring changes. Not too difficult. Yeah, its a mess on this end, but will be OK when done. With the alt. out of the circuit, no sign of a ground. Its an FM to me (forking mystery). So the carb and charger is off until next week. That gives me time for bigger and better things LOL...
So I put on the correct wiper blades, and it looks like theres a wiper motor problem too. JHC! First of all, is the motor off the switch or a relay? Like the heater fan??? I hit the switch and the blades lift up and down about 1/2 inch. Sometimes they make the full sweep but feels like a funky switch. Either position when working makes one speed and I can hear the motor run. Is that something busted in the wiper transmission?? Ideas? Thoughts?? ws

 

Very interesting equation .. the answer, obviously, is 42