Low voltage right after startup - slowly climbs back to 14-why?

[amartin_72]

I recently noticed that when I start my truck, the voltage is at 12.5 (battery voltage) and takes about 30-45 seconds to get back to 14.3ish. I am wondering if this is only because my batteries are VERY VERY decrepid and if i leave my lights or dome on for more than 3 mins it will not start. I would still think that as long as the alt is spinning i should get 14v sooner than 30-45 seconds. Is this a problem with the alt, regualtor, or just my horrible batteries? I will be replacing my batteries soon anyways.

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[wesl56 10+ year member]

well ya sounds like they may be wearing out... if ur dome light kills em in 3 min then yeaaa

know how old they are?

 

[Prowler573 5,000+ posts]

That is a characteristic of the PowerStrokes, friend (and possibly just turboed diesels in general?). Every single truck, bar none, at my previous job acted the exact same way. This was regardless of which truck it was and whether they had older, well-used batteries, or brand new ones.

 

[amartin_72]

I know my batteries are shot. They are the originals im pretty sure, they are ford motorcraft without any date stamps or markings. But I would think that even if they were say gone I should get 14v with the alt spinning if its working correctly...

 

[amartin_72]

OH THAT just made me realize what it is! It is probably because they have a fuel heating system on the filter and the glow plugs also cycle for what did i read in the manual ...up to 2 mins depending on temperatture. So this is just from the mazzive load the glow plugs are putting on my alt and crappy batteries at startup.

 

[Prowler573 5,000+ posts]

Edit: Looks like you just explained to both of us what is causing the problem (though it isn't really a problem at all, is it?)

 

[amartin_72]

No it was your post that made me realize it haha.