High battery voltage (1 Viewer)

[TOYTACO11]

I was cleaning up some wiring mess under the dash of my FJ80 prior owner had a mess under there from a security system, and wiring up radio with speakers and whatnot..

After I got done everything works fine got back from a 30 min drive doing some errands shut truck off keyed it back on to check a few things and noticed that my Main battery voltage was 16-17v with the truck not running just keyed on….

What could cause this when the truck isnt running…. Any ideas??

 

[ChargedSHOTaco]

I was cleaning up some wiring mess under the dash of my FJ80 prior owner had a mess under there from a security system, and wiring up radio with speakers and whatnot..

After I got done everything works fine got back from a 30 min drive doing some errands shut truck off keyed it back on to check a few things and noticed that my Main battery voltage was 16-17v with the truck not running just keyed on….

What could cause this when the truck isnt running…. Any ideas??

Probably overcharged. Likely bad alternator regulator.

 

[TOYTACO11]

Probably overcharged. Likely bad alternator regulator.

When i key it off it goes right back to the normal 12v it should be so dont think its the alternator

 

[ChargedSHOTaco]

When i key it off it goes right back to the normal 12v it should be so dont think its the alternator

What are you measuring the voltage with?

 

[TOYTACO11]

My dual battery monitor… im really just curious what could cause this to happen… Ill find out what it is tomorrow when I go digging for it but never seen this before so wanted to ask

 

[Shipwreck]

Check it tomorrow with a multimeter at the batteries. Check with ignition off, ignition on but engine not running, and then with engine running.

 

[TOYTACO11]

Check it tomorrow with a multimeter at the batteries. Check with ignition off, ignition on but engine not running, and then with engine running.

Will do

 

[LandLocked93]

Key off - "12V"
Key on - "16 - 17V"
Engine not running either way.
Not possible AND accurate at the same time.

If it's 16V while engine running, alternator voltage regulator is bad. It is replaceable and highly recommend replacing sooner than later.
Anything over/under rest voltage with engine off - 12.4 to 12.8V - the batt is s***e.

 

[jonheld]

You have a dual battery system in this vehicle. In order for the battery voltage to increase, the batteries have to be hooked up in series rather than parallel. If that's the case, then you should see close to 25 volts, assuming both batteries are charged. I suppose it's possible for a dual battery controller to do this, but I have no experience with these units.

As stated, you need to put a real meter across the battery terminals. It is not possible for a single battery's voltage to increase without the alternator charging the battery simply by turning the key ON. It should decrease as there is now a small load on the battery.

A fully charged battery at rest should read 12.6 or 12.7 depending on the type of battery. Flooded cell batteries are typically on the lower end. With the engine running after startup, it should read 14.4. It will slowly decrease depending on the state of charge of the battery.

 

[TOYTACO11]

Key off - "12V"
Key on - "16 - 17V"
Engine not running either way.
Not possible AND accurate at the same time.

If it's 16V while engine running, alternator voltage regulator is bad. It is replaceable and highly recommend replacing sooner than later.
Anything over/under rest voltage with engine off - 12.4 to 12.8V - the batt is s***e.

I agree Im fixing to go out and figure it out ill keep you all updated

 

[TOYTACO11]

You have a dual battery system in this vehicle. In order for the battery voltage to increase, the batteries have to be hooked up in series rather than parallel. If that's the case, then you should see close to 25 volts, assuming both batteries are charged. I suppose it's possible for a dual battery controller to do this, but I have no experience with these units.

As stated, you need to put a real meter across the battery terminals. It is not possible for a single battery's voltage to increase without the alternator charging the battery simply by turning the key ON. It should decrease as there is now a small load on the battery.

A fully charged battery at rest should read 12.6 or 12.7 depending on the type of battery. Flooded cell batteries are typically on the lower end. With the engine running after startup, it should read 14.4. It will slowly decrease depending on the state of charge of the battery.

I do have dual battery system with the add a battery kit from blue sea. My guess is the battery monitor has crapped our or maybe the two battery wires are touching slightly or something… fixing to go figure it out will let you all know what i come up with

 

[TOYTACO11]

Key off 12v
Key on 15v engine not running on main battery with second battery totally disconnected

 

[Fj80oregon]

Can you verify with a volt meter on the battery. Maybe your monitor is glitching?

 

[TOYTACO11]

Can you verify with a volt meter on the battery. Maybe your monitor is glitching?

That was checking at the battery with a multimeter

 

[Fj80oregon]

With the truck running I’m guessing?

 

[Marvelicious]

That was checking at the battery with a multimeter

View attachment 3549420

Are you checking the batteries disconnected? If they read lower when physically disconnected, it would point to some sort of issue with the isolator failing and running them in series somehow.

 

[Shipwreck]

Key off 12v
Key on 15v engine not running on main battery with second battery totally disconnected

What about while the engine is running? We need this data. Disconnect any accessories wired to the main battery and check voltage accross the terminals while engine is running.

12v is low for a healthy, charged battery at rest.
Shorted cells in a battery should cause voltage drop, rather than increased voltage, but who knows!?

If the alternator is overcharging, it is possible to have a residual surface charge for a short time. You can turn on the lights for a minute or two to dissipate surface voltage after shutting off the engine; but it doesn't seem like that is your issue.
Do you have any capacitors in your stereo or lighting systems?

 

[smritte]

you don't have a solar panel do you?

 

[TOYTACO11]

With the truck running I’m guessing?

With the key on was not running

 

[TOYTACO11]

you don't have a solar panel do you?

No solar panel