voltage problem/ battery drain
 

on my '06 uplander with the 3.5L and it has around 227k miles then lately if it sits for a few days then the battery is almost dead. I unhooked the battery and it doesnt go low when unhooked. I did a parasitic drain test and it has right about 10 mw of draw which is far below the maximum allowed of 50 mw . So i'm wondering if whatever is draining it takes a day or two to start draining. Also, i have noticed that when first started, the battery voltage is about 14.6 V but the longer it runs the lower the voltage goes. after 5 mins, it's down to 13.2 V which is barely above the normal battery voltage and i've seen it even get down to 12.8 V. at that point if i shut it off then the battery voltage doesnt even drop anymore meaning the alternator isnt even working. but it doesnt give me a charging system failure warning. so obviously something is up with the alternator's voltage regulator. I ordered a new alternator for it but am curious as to if anyone else had these problems and if a new alternator solved it or not.

How long have you owned this van?
How old is the battery?
Your charging voltages 14.6, 13.2 and 12.8 sounds normal to me ...
You mean 20 MA, not 20mw

I have had the van for 3 years. the battery is 3 years old. when i unhook the battery for even a week then it stays fully charged but if it's hooked up then after 3 days or so it's nearly dead. How can 13.2 or 12.8 VDC sound normal for a charging voltage? My entire life then the charging voltage for a car has been about 14-15 volts. Yes I meant 10 MA (milliamp).

Your voltages are normal. Charging systems are more efficient than they used to be. Make sure you test the battery current about 20 minutes after taking out the key.

What exactly do you mean by dead? It doesn't start the vehicle? What is the voltage after it 'dies'?

That is strange that now it's normal for a charging voltage to be so low. i did read though that the pcm controls the voltage going to the alternator. my '06 buick lacrosse that's the same year as the uplander has always read about 14.6 V. I tested the battery for parasitic drain by leaving the multimeter turned on for a couple hrs and it still only had 10 MA of drain. I can't understand what would be turning on after a couple days in order to drain the battery. When I say "dead" i mean that when i try to start it after 3 or 4 days then i have dash lights and dome lights but when trying to crank i get a click and "cranking disabled". after trying it a few times then i notice the dome light goes out when i try to crank. check the battery voltage and it's below 11. put a charger on it and it fires right up. I wish i could get this figured out. i dont want to have to unhook the battery everytime it sits.

Bet it's time for a new battery.

I suspect battery. No load at all won't cause battery voltage to drop except over extended time.The MA draw can cause a weak battery issue's such as yours. Have the battery tested, but at 3 years old, myself, i would replace it. Voltage regulator will keep the voltage constant under varying loads, and battery charged. The 13.2 dosen't bother me, but dropping to 12.8 tells me that the VR is a problem.

12.8V is still in the normal range.

ok, i researched fuel economy mode and all of the other modes that this type of charging system can do and i have experienced several of them so it must be correct. Interestingly it was designed to extend battery life, alternator life, and increase fuel economy. Thank you for pointing it out to me! looks like i'll return the new alternator as it is still in the box. truth be told, i wasn't looking forward to attempting to change it anyways as it appears quite difficult. I suppose i could change the battery. i just assumed that since the battery kept it's charge when unhooked, that it must still be good. I also tested the battery with a battery load tester. i kept the battery unhooked and once a day for a few days then i would do a 15-20 second load test (150amp load) and it held steady on the voltage with the load on it. That helped me to assume the battery was still good as it seemed doing that would prove that it still had a good reserve capacity. But maybe i'm wrong and the normal parasitic discharge was more than this several year old battery can handle. I sure hope that's all the problem is is the battery. I will update after i replace the battery and give it a few days or so and see if it gets low in charge or not.

I had a diehard battery last 5 years, no sluggish starts, until that one morning a month and a half ago, nothing.Replace the battery.