Alternator charging at 13.4v.

[blazian87 10+ year member]

So I just helped do a battery swap and amp swap for my buddies 09 Lexus IS 250 last night. He's been using the same OEM battery since he got it and it's been dying on him on a few occassions. We swapped out the battery with a fully charged and healthy deep cycle XS battery. Resting voltage was around 12.8v before installing it. I checked the voltage with both batteries and it reads 13.4v while the car is running on both scenarios. That immediately made me suspect that the alternator is going bad. The alt location looks like it might be a bit*h to get to and install. I'm guessing that the alt was overworking itself bc of the dying battery and caused some damage. But now that we have the new XS battery in. Everything's working pretty nicely now and car starts up no problem. If we were to just leave the same alt in with the 13.4v, would it damage this XS battery eventually and die much quicker? I don't know if 13.4v is normal for this car but it seems unusually low as I'm expecting it to be in the 14v range atleast while the car is idle and with no A/C and no music.

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[CSCStang]

So I just helped do a battery swap and amp swap for my buddies 09 Lexus IS 250 last night. He's been using the same OEM battery since he got it and it's been dying on him on a few occassions. We swapped out the battery with a fully charged and healthy deep cycle XS battery. Resting voltage was around 12.8v before installing it. I checked the voltage with both batteries and it reads 13.4v while the car is running on both scenarios. That immediately made me suspect that the alternator is going bad. The alt location looks like it might be a bit*h to get to and install. I'm guessing that the alt was overworking itself bc of the dying battery and caused some damage. But now that we have the new XS battery in. Everything's working pretty nicely now and car starts up no problem. If we were to just leave the same alt in with the 13.4v, would it damage this XS battery eventually and die much quicker? I don't know if 13.4v is normal for this car but it seems unusually low as I'm expecting it to be in the 14v range atleast while the car is idle and with no A/C and no music.

It may be regulated that low but it does sound wrong. Go get a load test done on the alt. As long as the voltage is above resting the batt is getting recharged or keeping charge.

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[LosIsATool 5,000+ posts]

My TC charged at 13.4. Singer put a bypass in the alt he built for me

 

[C1500martin 10+ year member]

Chances are thats te factory charging point. As long as its above 12.6 the batteries are getting charged as stang said.

 

[blazian87 10+ year member]

Ahh so it is regulated. I think steve meade had the same problem with his IS F too. I guess that means everything is fine but we'll get it checked out anyway. Thanks guys


btw @CSCStang; how's your recovery doing?

 

[LosIsATool 5,000+ posts]

I think it's a Toyota thing

 

[blazian87 10+ year member]

I think it's a Toyota thing

Yea kinda figured. But doesn't Honda's do the same thing now too? And maybe a few other companies?

 

[CSCStang]

[quote name='blazian87']Ahh so it is regulated. I think steve meade had the same problem with his IS F too. I guess that means everything is fine but we'll get it checked out anyway. Thanks guys


btw @CSCStang; how's your recovery doing?[/QUOTE]
Slow and steady bro. Not as fast as I'd like but it will happen.

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[LosIsATool 5,000+ posts]

Yea kinda figured. But doesn't Honda's do the same thing now too? And maybe a few other companies?

Honda does something different. The ELD

 

[hispls 5,000+ posts]

My model Jeep likes to charge at 13.6 or so from the factory. I bought an external regulator with my first HO alternator.... my new alternator is internally regulated.

 

[n2audio 5,000+ posts]

Did you rev the engine at all?