voltage question... is 13.7-13.9V normal for some cars?

[tcguy85 10+ year member]

i have an 07 scion tc....

does anyone elses car seem to not ever put out anywhere near 14.4 volts normally? like the only time i've ever seen it at 14.4 is when i first start the car in the morning. and by the time i get to work which is about 15 minutes(10 miles) away it's down to about 13.6-13.9v.

also when i'm parked or stopped at a stoplight the voltage is always between 13.2-13.5. i know it's not extremely low but why is it never at 14.4 steadily? i do have a subwoofer with an amp that does 800watts rms but my voltage never drops more than .3 volts when it's at full tilt. the voltage in general just doesn't seem very high.

once again... this is on a brand new 07 scion tc that i bought in august.

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[jmanpc 5,000+ posts]

yeah thats normal.

 

[jacka 10+ year member]

Yep.. that's completely normal. Could be the shitty stock wiring.. Try doing the big 3, it'll give you less resistance so voltage won't drop from alt to battery. That's how mine was. Otherwise 13.8 is just what your alternator is regulated to.

 

[tcguy85 10+ year member]

anything i can do to get it to 14.0-14.4 volts all the time?

 

[WantedIsHere]

i believe vehicles are mostly regulated between 13.6 - 14.4 or so... give or take a few tenths...

 

[tcguy85 10+ year member]

Yep.. that's completely normal. Could be the shitty stock wiring.. Try doing the big 3, it'll give you less resistance so voltage won't drop from alt to battery. That's how mine was. Otherwise 13.8 is just what your alternator is regulated to.

the stock wiring actually looks good, looks like 6 gauge maybe.

 

[WantedIsHere]

i believe your toyota is regulated lower then that... would have to change the regulator... either an external unit, or internal to the pcm or alt.... You will need someone who knows more about toyota to answer this one...

 

[jacka 10+ year member]

the stock wiring actually looks good, looks like 6 gauge maybe.

Well, mine was ~4 gauge and voltage never got above 13.98. Did the Big 3 and now it's about 14.3. Was either shitty stock wiring, or shitty stock connections, or a combination of both.

 

[tcguy85 10+ year member]

Well, mine was ~4 gauge and voltage never got above 13.98. Did the Big 3 and now it's about 14.3. Was either shitty stock wiring, or shitty stock connections, or a combination of both.

so i should do the big three in 0 gauge?

 

[azimuth 5,000+ posts]

so i should do the big three in 0 gauge?

you should.

 

[tcguy85 10+ year member]

you should.

ok, i just didn't think it was necessary since i only have 800 watts and my voltage barely drops. .3 volts is a pretty small drop at full tilt right?

 

[azimuth 5,000+ posts]

ok, i just didn't think it was necessary since i only have 800 watts and my voltage barely drops. .3 volts is a pretty small drop at full tilt right?

you probably don't have to, but the small effort it takes to do the big 3 should really be done anyway. just my opinion.

 

[tcguy85 10+ year member]

ok how many feet of 0 gauge should it normally take? it's just batt + to alt, batt - to frame and engine to frame right? so maybe 8ft? i should have all 3 as short as possible right?

 

[WantedIsHere]

yes as short as you can and 8 feet will probably be more then enough....

 

[phyphoestilic 5,000+ posts]

I'm pretty positive toyota (Scion/lexus) all are regulated att 13.8, my lexus is at 13.8v and I even have a HO alt installed. Big 3 had nothing to do with it (doing big 3 did help voltage drops) but the regulator is set at 13.8v

When u start the engine it's usually at 14.4v's tho, once it warms up it drops down to 13.8v