Couldn't put my battery charger on my DD

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Originally Posted By: eljefino
harbor freight has an ammeter with prongs that replaces car fuses. Might be useful.


Interesting idea.

I already pulled all the engine compt fuses and saw no changes the 5.35amp draw. Considering parasitic losses are typically 0.1 to 0.75 amps, this is a huge one. When I open the car doors the lights added barely make a change. I turned on the parking lots and/or headlights and was surprised to see the amps DROP to 5.0-5.2...not what I was expecting. Didn't pull any of the engine relays/PCM fuse "blocks," etc as those didn't want to come out easy. Not ready to break anything yet and disable the car. Been there, done that.

Looks like this will turn into more of a research project than I thought. Haven't checked the interior fused circuits yet, but those are much lower draws too. Had the car for 8 yrs now and it's never once stranded me.
 
Originally Posted By: Trav
Just for laughs pull the alternator wire, it may have a bad diode.


Thanks Trav. I ran across this similar 5 amp draw thread on a 1997 K1500. They mentioned checking that too. If a diode is bad, will it also have an improper output with the car running?

5 amp draw

The owner unplugged alternator, starter,and every fuse in the car, and still had the issue. In the end, it looked like it came down to and added wire a previous ran w/o insulating it. It rubbed through and caused a ground path. I bought my car from a senior with 22K miles - I don't think he did a thing to the car ever except drive it. Not likely there's a modded wire hanging out there. But, certainly possible a factory wire could be exposed to the frame somewhere. My wife is out driving the car around so I'll have to wait a while to try again.
 
That's the funny thing they seem to charge normally, put out decent volts and it seems okay until you let the car sit overnight then it has a flat battery, you may get flickering lights and other abnormalities.
When I saw your post it reminded me of a GMC I did that had these same symptoms, when you think about it there are not many things in the car that pull 5A on their own, the fused circuit may be 10, 15, 20A but individual components would be few.
Rear window defoger, blower motor, headlights, fog lights, amplifier, etc can all pull high amps but I would think you would notice something that obvious still being powered after its turned off even alarm systems don't pull 5A unless activated with horn and lights going.

Quote:
* To check for a possible bad alternator diode, switch your voltmeter to a low setting on the AC (alternating current) voltage scale.
* With the engine running, touch the meter probes to the battery terminals.
* Your voltmeter should read 0 AC volts.

Any amount of AC voltage would indicate a bad diode, so you'll need to replace the alternator.
 
I'll try those things too Trav. Thanks.

The alternator is currently keeping the battery in the 12.2v (sits overnight) to 12.4v (right after being driven). That's lousy for only a 1 yr old battery. You'd think, with that car sitting for up to 2-3 days at times that I'd have had problems starting it from time to time. Nope. It runs exactly as it did the day I installed the battery new....and for the entire 8 yrs I've owned it. Never a hesitation in starting during this past winter, down to 10 degF....after sitting for a couple days. For all I know, it could have been doing this for years without me really knowing it. I replaced the battery a year ago because it was 5 yrs old, and would drop to 12.2v shortly after driving it. I just figured it was an old battery. Hmmm, maybe the alternator is in play too (15 yrs old). The only electrical gremlins I know of are intermittent security/door ajar "false" alarms from time to time, esp. in cold weather. My 1997 Lincoln did that for years...and soon after replacing the driver's door/closed-open switch. But, the drain for that has to be miniscule. The rear defogger (wired into the glass) failed early on in that 1997 Linc. Never really use it on this 2002. That could be gonzo too.
 
If set on the 2A setting does it still kick out?

Low on water is serious overcharging from somewhere.
 
Trav, with the car running there is indeed 1.79 amps AC cross the battery terminals. And the DC amps across the battery terminals jumps from 5.4v DC (car off) to 6.20v DC with the car running. Alternator DC output at idle was around 13.5-13.6v DC which seems normal. What seemed odd to me that the alternator output at idle (alternator terminal to body ground) was the same +6.2 amps DC (same as across the battery). From what you said above, the alternator is dying. This could be a good opportunity to change the serpentine belt + pulleys as well. That has seen better days.

Oh yeah. With the top alternator lead removed, the battery DC amps (terminal to terminal) still read 5.4amps DC with the car not running. Should the other lead removed too?
 
Set the VOM to AC volts low scale and see what the volts are. Anything above zero volts indicates a bad diode.
 
Last edited:
Sorry, got AC amps in my head by mistake.

Car running, shows a fairly rapid cycling of AC voltage across the battery of 0.005 to 0.025....median of about 0.017v AC. Never steady. Makes sense I guess with 1.79 AC amps....that should probably be 0 as well.
 
Thanks for the help Trav. From another thread:

I had this very same issue with my Shelby about 15 years ago. The alternator charged fine and the car started fine as long as I didn't let it sit more than a day or so without running. I took the battery out to have it tested and noticed a rather large spark disconnecting it which means there is a load on the battery....on a 30 year old car that has not memory items or loads when the car is off. After some thinking I figured it had to be a diode in the alternator. Took it off, took it apart, and tested all the diodes only to find a bad one in the tri-diode pack. A few dollars later the problem was fixed.

So a failed +diode can flatten the battery with the car off. Odd that I've not seen the car's operational performance degrade to where I could notice it. We don't drive much at nights any more. The 13.5v alternator output is a bit low (normal 13.8-14.8)
 
According to things I've read, a 5 amp draw should kill my battery within 10-15 hrs. Yet I've gone 48 hours quite often w/o any issues in starting. Doesn't make sense. Car batteries typically have a amp-hr rating of 45-60 amp-hours. Apparently, some of that current is not draining the battery.
 
I would disconnect the alternator wire and see if the current draw drops. If it does that will be a good indicator, I don't know if the current draw would be constant or not.
 
I tried that earlier today. And the current didn't drop. Then again....I just realized my Fluke23 series II DMM uses a different port for amps vs. volt/ohms. So all the current readings I took earlier today are all bogus. Only the voltage readings are accurate. So there is some AC voltage showing up across the battery with the car running.

In trying to do the amp readings correctly, I ended up burning up my needle point leads. Obviously, too much current on that 10 amp setting. How dumb is that? Haven't used the Fluke for current testing for over 12 yrs. Never even thought about swapping leads. Stinks getting old. Back to the drawing board. Tomorrow is another day....lol.
 
Did some research on alternator voltage checks, including neg and pos side voltage drop checks as well as parasitic milli-amp draws off the battery. Will try those along with Trav's suggestions, once I have a working DMM again.
 
a deeply discharged battery will cause your charger to bounce off the overload a while till it starts taking a charge.
had one in the 70's for a camper.
had 2 #27 parallel.
and if a light got left on it would run them down to nothing in a week.
the charger would cycle a hour or so then settle down.
i still have it and its still alive.
might even be the same one you have.
if you didnt reverse polarity you might just leave it a while.
ours survived my brother reversing it several times.
but there is a possibility the rectifiers are now shorted in yours.
btw i hooked ours up live to many things.the trick is to hook up + to battery then - to the frame,block,ect away from the battery.
the sparks are not a problem if you dont make them over a possibly gassing battery that might go boom!
 
Originally Posted By: kc8adu
a deeply discharged battery will cause your charger to bounce off the overload a while till it starts taking a charge.


Mine jumped right into overload and then would trip at something above 10 amps with the batt connected in the car. I took the advice mentioned earlier and disconnected the battery, then plugged in the charger power last. That only drew 8 amps which got the battery fully charged up in about 30-45 minutes. It wasn't that deeply discharged. I've had other batteries near death take as long as 4-8 hours. The battery being discharged a bit is only the symptom. There's either a draw down in the car and/or alternator has issues. I'll isolate those a bit more when I get a fresh set of tester leads.
 
Got back to electrical testing again today.

Alternator AC voltage ripple output to the battery was approx 0.010v (8-15 mv cycling). On various sources I read, anything higher than approx 50-100 mv would indicate rectifier diode failure. Mine was well within spec. Other sources suggested 200-300 mv or more would cause problems, especially draining the battery and causing electronic issues in the car.

Battery was 12.29v when I started...somewhat discharged. Started up the car and the alternator was putting out 14.2v under low loads. Turned on AC, head lights, radio, etc. and it dropped to 13.8v which is normal. After a 10 mile drive and turning the car off, battery voltage was around 12.5v. Did a voltage drop check from - and + battery terminals to the alternator + lead and casing and found no voltage drops higher than 0.01v...normal.

The only smoking gun so far is a 1 yr old battery that draws 8 amps from the charger after sitting overnight. It doesn't quite charge up all the way via the alternator putting out 14+ v. My deep cycle battery charger gets it back to fully charged in approx 30-45 min. Maybe it's the battery after all. Will continue to read up and snoop around.
 
either something is not going to sleep or the battery is sulphated.
top it up then switch charger to the 2a range.
leave it charge overnight.
disconnect charger and leave it disconnected from the car 24hrs.
12.6-12.7v battery ok
if it goes back to the 12.2 range its sick.
 
Originally Posted By: kc8adu
either something is not going to sleep or the battery is sulphated.
top it up then switch charger to the 2a range.
leave it charge overnight.
disconnect charger and leave it disconnected from the car 24hrs.
12.6-12.7v battery ok
if it goes back to the 12.2 range its sick.



Thanks. That's sort of along the lines of what I was going to try next. Checking voltage dip on the next startup couldn't hurt...or even a load test at the place I bought it from. I bought 2 similar brand/model batteries from them a year ago. The one on the car that sits in the garage and rarely gets driven has no problem holding 12.60-12.70 volts after 7 days of sitting.
 
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