earlier this year had dead battery after sitting for a week. 5 year old battery so bought new one
battery still goes dead randomly (overnight), instead of playing radio for a few minutes after key off, dash displays "system off to conserve power"
ran it thru local repair place (ex ford dealer) nothing found. Voltage 14v at 1800 rpm, lights on"
STILL goes dead randomly

I admit defeat, suggestions

 

Do the test below. Even with all this high tech stuff on these trucks, this test still works. Only difference, you will have to set it up and wait about 45 minutes before observing the light. The later trucks do have a lot of stuff that does stay awake and draws current for that time period so make sure everything is off, the doors are shut, the hood light is disconnected, and then wait 45 minutes and then see if you have a bright light. If you do you have a drain somewhere.

 

Yes one, tell us what the vehicle is.

 

I guessed it was the 2012 f150

 

I will try that.
may try an ampmeter also. I assume the remote, the alarm, the radio clock and ? all draw something.
But is intermittent,

 

Your truck will draw a lot for the first approx 45 minutes. After that, you should not have over 70ma or .07 amps draw.

 

You have the FORD BMS System on the truck.

Reference here- https://www.ford-trucks.com/forums/1...y-warning.html

 

BMS, I know what bs is, but whats the m for

autozonk says 6 month old battery is a little weak, but not warrantyable.
my voltmeter still says 14.2 running, but 12.1 when you shut it off. 11.5 in the morning.
i still vote battery, but will try a bms charge.
guy at autozonk says alternator only replaces starting juice, does NOT CHARGE BATTERY
NEED A NEW AUTOPARTS !!!!!!!!!

 

I guess you didn't read the Referring URL I gave.

AUTOZONE is correct. It is not the job of an ALT to replenish a drained BAT. It may burnout the ALT. This system may also not allow the ALT to recharge to that extent to prevent ALT damage.

You have a parasitic drain on the BAT and it must be diagnosed correctly.

 

I am not sure I agree. The alternator can charge a completely dead battery, it's done all the time when someone is jump started. And I have never seen it ruin a properly operating alternator. I am pretty certain someone that needs a jump is jump started, and then the person helping says "you had better turn it back off or you will burn out your alternator" and they are still left stranded.

You do need to run the car for several hours for it to completely charge the battery, but it should charge it to normal levels eventually.

 

You mis-understood. The vehicle being discussed is a late model with the charging system controlled by the BCM. FORD has had a lot of problems with the system. If the BAT is in a low state of charge or is getting ready to fail, the computer will not allow the ALT to try and bring it back up.

If you jump one, the BAT has to be brought back up by a proper charge, diagnosed/replaced and the BMS reset or the computer will not acknowledge what has happened.

I would hate to think what one of these computer controlled system BAT would cost.

Now, just to start an argument as it has been fairly quiet around here, the ALT is designed to maintain a proper charge on the BAT, say from starting, running the lights or listening to the radio, It is not designed to bring a low BAT back to spec. It can, but it can also cause ALT failure.

RING!

...and that's how the fight started...

 

read the thing about bms.
alternator is 75 amp, means it can support a 75 amp load without draining battery. thats truck, boom box radio, and charge travel trailer battery. thats not in trailer now so i can't check voltage, but was 12,5 when daughter put it in her truck. the joys of fatherhood. should be plenty for charging.

thats the way my mercedes works, my gold wing, n my harley. lets not discuss my first motorcycle, voltage would drop stepping on brake with lights off. hodoka dealer said it was normal. but dont step on brakes with lights on

 

I applaud technology, but the more they put into these vehicles, the more I dislike the newer vehicles. I seems like software engineers who have never worked on a car or truck in their life are designing all these features and junk and just make them more unreliable.

Who in the world has time to let their truck sit for 8 hours undisturbed each time the battery has a problem? I can't believe they write that stuff in there. A business needs to make money, they need their delivery vehicles to work, they do not have time for their truck to sit somewhere for 8 hours while the computer "learns" the new battery state of charge. The whole thing is ridiculous.

 

10 amp charger connected to block and +
24 hrs now, and only down to 5amps

 

Jump starting is an emergency, get ya home procedure, when ya really get down to it. In a way I agree with the 'zone. Ideally the battery should be placed on an external charger as soon as practicable after a jump. Even better, would be to swap in a charged battery instead of jumping in the first place. There is potential, at least, for mischief during this process. Even battery explosions are not unheard of. Maybe rare, but I don't want to deal with it if I can help it. A battery that has been run down to dead should also be checked. Defective batteries don't do the charging system any favors. And a defective charging system will result in battery problems sooner or later.

In cold weather in particular after a jump you can hear belts and pulleys groaning - that's the alternator protesting loudly. Given that the manufacturers "size" everything these days on the "barely enough and no more" principle it's just good practice to avoid putting the alternator through the wringer. "Let it idle for a half hour" is not the way to go about it. Chargers are inexpensive, alternators and batteries are not, especially if one has to pay someone else for replacement.