Healthy Electrical System Voltages?

Bumbo

Bumbo

New member
I measured my 4Runners battery voltage today and thought it was little low...

With the engine running, at idle, what type of voltages should I be seeing?

Does it compensate for temp? It was pretty hot today.

Does that figure change with a full battery?
Does that figure change with a partially discharged battery?

I was expecting to see high 13's to 14.4 volts, but I am generally in the low to mid 13s...

Is this a sign of alternator issues, reduced output?

Thanks
 
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Bumbo said:
I measured my 4Runners battery voltage today and thought it was little low...

With the engine running, at idle, what type of voltages should I be seeing?

Does it compensate for temp? It was pretty hot today.

Does that figure change with a full battery?
Does that figure change with a partially discharged battery?

I was expecting to see high 13's to 14.4 volts, but I am generally in the low to mid 13s...

Is this a sign of alternator issues, reduced output?

Thanks
Click to expand...
I'm pretty sure you read my mind. You might as well have created this thread for me lol

Battling the same issue. On my third Alternator this week. The first two were rebuilt. Now the new one STILL showing very low 13.1

Been searching forum threads all week. This weekend should be fun

Sent from my XT1575 using Tapatalk
 
From the 4Runner Owner's Manual - Specifications: Battery

Open voltage at 20C (68F):

12.6—12.8 V Fully charged
12.2—12.4 V Half charged
11.8—12.0 V Discharged

From the 4Runner Repair Manual - Charging System: On-Vehicle Inspection

http://4runnerclub.com/i/4r_files/f...rfe/charging/charging_onvehicleinspection.pdf

1GR-FE (V6) Engine - Standard voltage: 12.5 to 12.9 V at 20°C (68°F)

1GR-FE (V6) Engine - With the engine running from idle to 2,000 rpm: 13.2 to 14.8 V

http://4runnerclub.com/i/4r_files/f.../07toyrm/07toypdf/07rmsour/4runnerr/02600.pdf

2UZ-FE (V8) Engine - Standard voltage: 12.5 to 12.9 V at 20C (68F)

2UZ-FE (V8) Engine - With the engine running from idle to 2,000 rpm: 13.2 to 14.0 V
 
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I have a 2004 4.0L V6 SR5 4x4...

Just to confirm, that is the 1GR-FE (you have a small type-o?)

With the car running, at idle, I am seeing 13.4v (measured at the battery), but I NEVER see 14.8v.

Even at cruising speeds I generally see about 13.4-13.5v

The only times I see 13.8 or 13.9 is on a very cold day, right when I start the car. Its been doing that a lot less as of late.

Is there a way to boost the voltage, or is buying a new alternator a generally accepted fix for this? Are these signs of early alternator issues, or it is what it is... just an old fatigued charging system?

Basically I am troubleshooting an intermittent issue with an Automatic Charging Relay for my spare battery... seems like I am a couple tenths of a volt short and it either takes forever to combine, or it just never gets there. I already checked ground resistance, all my cables, leads... I am at the point a very small voltage boost of .2-.5v would solve all my problems.

I just don't want to band-aid fix if there are underlying problems...
 
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The charging system will change the voltage depending on the charge state of the battery.If you put a V gauge into a lighter socket and watch it (Or use a monitoring program on your phone etc) You'll see the charging start out at about 14.4 right after starting the car as it is recharging the energy pulled out by the start, it then rops to like 13.7 or even lower after a bit on the highway and stays there.

Also, at idle the V may be lower due to the alternator being at capacity which it pretty much is, measure it while on the highway with a lighter socket tool you can see while driving, or using an ODM monitor program on your phone. Measuring the charge V while running at idle is not super accurate.
 
If your main battery is not running down over a period of days your charging voltage is fine. Too much voltage will boil the electrolyte in your battery and send it to an early grave. More is not necessarily better in this case.

If your combiner circuit is not working, fix that. Don't try to compensate by monkeying with the alternator voltage.
 
2014 Warthog said:
The charging system will change the voltage depending on the charge state of the battery.If you put a V gauge into a lighter socket and watch it (Or use a monitoring program on your phone etc) You'll see the charging start out at about 14.4 right after starting the car as it is recharging the energy pulled out by the start, it then rops to like 13.7 or even lower after a bit on the highway and stays there.

Also, at idle the V may be lower due to the alternator being at capacity which it pretty much is, measure it while on the highway with a lighter socket tool you can see while driving, or using an ODM monitor program on your phone. Measuring the charge V while running at idle is not super accurate.
Click to expand...

I think I am going to discharge the starter battery down to 12.3 volts and try it again, perhaps the starter battery is always full, and never really throws a higher charge voltage.

I have been monitoring the system, and have my meter setup to capture peak voltages (min/max) at startup... I haven't seen anything in the 14.4 area, generally always in the high 13s, but it moves to 13.2-4 pretty fast. The point being, it gets to 13.2 (or lower) pretty fast, even before 30 seconds are up. And those few tenths of a volt caused some issues for me today... The issue being that the ACR didn't see a voltage above 13v, and never combined.

I have anderson powepoles all over the place so keeping tabs on this stuff has been easy...

That said, I am seeing higher voltages when cold.

Mu90obw.jpg

F4YWxVI.jpg


I am using the Blue Sea SI-ACR...
30 seconds to combine at 13.6v or higher
90 seconds to combine at 13v

I just drove 20-30 miles today running errands and noticed my voltage was still at rest on the house battery side. Thats not normal operation... just trying to track it down...

KwgMhC1.jpg
 
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RonJR said:
If your main battery is not running down over a period of days your charging voltage is fine. Too much voltage will boil the electrolyte in your battery and send it to an early grave. More is not necessarily better in this case.

If your combiner circuit is not working, fix that. Don't try to compensate by monkeying with the alternator voltage.
Click to expand...

I actually moved a few things around... and cleaned my contacts.

All my ground resistances looked ok, but I have it wired to the house battery side though the fuse panel. I increased the wire size, fuse size in hopes to minimise voltage drop to see if I can gain a tenth or two.

If that doesn't do it, ill move it and wire directly to the starter. The internal VM inside the ACR is probably getting some lower than actual reading because of this.

Ill keep an eye on it, and see if the problem persists.

I have been doing a lot of testing, and the function of the ACR is working correctly, so its not bad hardware... Inrush current and everything is within spec...

Tmc1JBB.jpg


uFOxKGv.jpg
 
Stock alt I was seeing low 13s. After a 240a alt, big 3 upgrade I typically see 13.6-13.8 across both batteries. On colder days I've seen as high as 14.2. I have dual battery monitors so I can watch it across the ranges. Funny thing I've noticed is that at idle in first gear (foot on brake) it stops charging, but idle in park it hangs out around 13.4-13.6.. not sure if that's because it's a smaller pulley on the alt it my belt is too stretched. First gear resting idle is around 500-600, park idle is around 700

Sent from my Nexus 6 using Tapatalk
 
Drunner97 said:
Stock alt I was seeing low 13s. After a 240a alt, big 3 upgrade I typically see 13.6-13.8 across both batteries. On colder days I've seen as high as 14.2. I have dual battery monitors so I can watch it across the ranges. Funny thing I've noticed is that at idle in first gear (foot on brake) it stops charging, but idle in park it hangs out around 13.4-13.6.. not sure if that's because it's a smaller pulley on the alt it my belt is too stretched. First gear resting idle is around 500-600, park idle is around 700

Sent from my Nexus 6 using Tapatalk
Click to expand...

I'm using a 1inch shorted belt with my high output alternator. I think it's 82.5 inches. I think they say half inch shorter is fine.
 
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