Battery Drain (1 Viewer)

[workingdog]

This is happening in a 67 FJ40 with a 2001ish 6.0 liter with appropriate computer.

In the last couple of weeks, my battery won't hold a charge. I drive it, my alternator is putting out 13.4 to 14 volts. I get back. The battery is at 12.6 volts, the next day it's at 11.8 and will barely start the rig. I pulled the battery cable and tested the current flowing. Only 116 milliamps. It reads 0 on the 10 amp scale. So, I was expecting more. My understanding that the computer should draw about 50 milliamps anyway, 116 hardly seems enough to cause what I'm seeing.

What else can I look at?

 

[stevebradford]

Old battery? Get the battery tested.

 

[workingdog]

Newer battery, but that's a good thought. When it went dead a couple of months ago when lights got left on, the shop said it was fine. But maybe it's not.

 

[tls3601]

Lots of jun batteries these days, on number two in last three months. Just replaced VR though and hopefully that does the trick. Parasitic drain somewhere???

 

[1969FJ]

116 milliamps is actually high. 35 milliamps is normal and you are 4 times that. Now, if there are ad-ons like alarm etc. , then maybe 116 will become normal on your vehicle. Look at the youtube attachment as this guy says 50 milliamp draw , a good battery can handle a month of non use.

 

[workingdog]

Thanks. There's a GPS speedo - I need to see if it's contributing to the load. There is no alarm, no radio - nothing fancy, except for the GPS speedo.

 

[workingdog]

It occurs to me that I need to let the drain test run for a while, to give the ECM a chance to shut down. 116 was on power on, which I don't think is fair. GPS speedo is connected to keyed power.

 

[1969FJ]

Correct, hook up the meter , (current as you know) , and wait for a while and look at the draw. I have done a few vehicles with issues and 30 to 50 milliamp was the draw. (stock vehicles).

 

[workingdog]

I tried, it got as low as 90. I'm going to have to start pulling fuses to see if it's the computer or something else.

 

[1969FJ]

Is 90 the final , all night number ? Maybe 90 is correct draw for what you are running. Pulling fuses will certainly tell the story . Good troubleshooting, something is drawing current.

 

[pithicus]

Have you tried disconnecting the battery overnight? then reconnect. It might have a bad cell.

 

[ginmtb]

I was having problems with my battery dying overnight - took forever to figure it out and I'm not sure what the actual cause was. But I cleaned up every stinking ground so they were good and I no longer have that problem. Also, if I end up not driving my car for awhile I plug in one of these:

DieHard Smart Charger and Maintainer

 

[workingdog]

What does disconnecting overnight do for a bad cell?

 

[Jerry D.]

Check your alternator for a bad diode. Look online for how to test, replacement is easy.

Jerry D.

 

[ginmtb]

What does disconnecting overnight do for a bad cell?

Perhaps he's thinking with your battery disconnected and not drawing anything if it loses some charge overnight then it may have some problems.

 

[workingdog]

I'm seeing 13.7 to 14.4 volts in the cab with the engine running - so I assume that the alternator is doing its job. Is it's possible it's not.

 

[Jerry D.]

Been there, done this. Alternator charged fine, battery would deplete in about two days.


"3. Checking for a Bad Diode

Usually, a bad alternator diode will cause your headlights or instrument panel lights to flicker or dim and, sometimes, drain battery power overnight, or in minutes.

* 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."



Also...in another post...

"Just an fyi, a bad diode in the alternator can drain the battery even when the engine is not running. You can check the amount of A/C voltage leaving the alternator by putting your multimeter leads on the battery (Positive lead on +, and Negative lead on -), with you multimeter set on A/C voltage you should read no greater than .5VAC, if you get more, your rectifier bridge on your alternator is bad and needs to be replaced."


Another test, I haven't tried this one, is to remove the belt that drives your alternator and IF the alternator starts to rotate on its own, you have a bad/leaky diode.


My diode/rectifier board was about $18 as I recal, plus my 2 cents...

Good luck

Jerry D.

 

[workingdog]

Awesome.

 

[pithicus]

Disconnecting the battery will give an indication if the battery is losing charge because of a faulty battery/bad cell.

ie if it cranks fine when reconnected the next day it indicates a parasitic drain. If its half flat like you are experiencing it means the battery is draining from a fault internally.