1st Person Experience with depleting the 12v battery
 

Was working on getting the garden ready this weekend and had the 12v battery go dead. Since I was actively present while the whole thing unfolded, I though I'd pass along the experience.

I had the back doors and the lift gate open, the switch was in the ACC position and the radio was on. No other drains except at the beginning when the interior lighting was on from closing/opening doors.

I listened to the FM radio for at least 2 hours and then it acted as it if were losing the station's signal. This lasted for about 5 seconds and then everything went black.

I opened the front door and turned the key off/on. No clicks from the relays, no pressurizing from the brake system, and no display on anything. same thing on a few more key off/on cycles.

I went inside and grabbed the plug-in battery charger, attached it to the battery. Cut the switch off/on and nothing. Off/on again and the relays clicked and the FEH started right up. I promptly disconnected the charger. I let the FEH run, it went though several ICE-ON/EV cycles as I finished up my work and listened to the radio. After about 30 minutes, I turned the switch off. Let it sit for 5 minutes and then restarted without an issue. It has restarted at least 5 times since then without issue.

During this whole process (from the radio cutting out until after the last restart) the battery indicator (little glass eye on the battery itself) was a dim RED. I remember it being dim GREEN earlier in it's life. I've had my FEH since August 2007. So the battery is over 42 months old. I'm betting once you factor in lead time from the battery manufacturer and shelf/build time at Ford, the battery is about 4yrs old.

In any case, I'll keep an eye on it and know that a replacement 12v is in my near future. Fair enough.

I also need to check the water fill level in the battery. I'll do that this afternoon when I have access to the vehicle again. I'll also check the RED eye/GREEN eye situation.

Re: 1st Person Experience with depleting the 12v battery
 

I just had to replace mine. No issues starting mine. I was driving up into the mountains and it started hesitating like it was missing. Turned around and when to the dealership as I thought it was fuel related since i had just changed the fuel filter. Service Dept.checked the codes and said it was the 12v battery. I was quite surprised.

It's been about a month and no problems and it runs like a top.

Re: 1st Person Experience with depleting the 12v battery
 

This is a fascinating process for me. Thanks to the
two of you for sharing your experiences. IMO as an
old engineer the 12vdc low voltage battery in the
FEH is being used in a different set of circumstances
then it was primarily designed to do. And that
being supplying a big surge ( 100's of amps ) to
turn a large DC motor to crank a flywheel to start
a car. All of us have experienced the dying car
battery syndrome. Over time the cranking gets
slower and slower telling us that it's time to
change the battery. But in the case of the FEH
the lead acid battery goes over the edge
of it's power curve quickly and you don't know
it's coming till it happens. IMO I would suggest
that as your battery gets to 36-months of age
that about every 6 months just take it into
any of the auto parts stores and they can
check your battery. It's all usually free.
If you have your FEH maintenanced on a regular
basis checking the battery under a load should
be a check off item. The last check for my 06
FEH was at a Ford dealer and they certified it
to 500A cranking power. And they also confirmed
that the charging system is working. My battery
is about a year old.

Just in case I purchased a Peak Portable Power
System 450 Plus.

http://www.peakauto.com/electronics-..._systems.shtml

An extremely useful device not only for starting
the neighbor's car when his battery died, but it
powers lots of other things. Along with the jumper
cables it includes 115VAC, USB and +12vdc outputs.

I gotta start reading the manual better
 

I had thought that the switch in the floor well was for using the traction battery to charge the 12v battery. It turns out that the opposite is true; the switch is used to charge the traction battery FROM the 12v if the traction battery goes flat. I'm not sure how the main battery could go that flat, considering the protections built in.

Re: I gotta start reading the manual better
 

I think, and I'm only guessing here, that if the HV
( traction battery if you wish ) and the LV 12vdc
batteries both go dead then if you connect something
like my Peak Power Station ( 12dc jumper ) to the
LV terminals and go through the 8min recharge process
with the switch in the floor well. Then the HV battery
will be recharged enough that and you can start the FEH.
I think.

Re: I gotta start reading the manual better
 

Yes, that is the way I read the manual. But I still don't know how the HV battery would go that flat.

Re: I gotta start reading the manual better
 

I also am of the understanding that so long as
the LV battery has some juice in it that it takes
very little energy from the HV battery to spin
up the ICE.

Re: I gotta start reading the manual better
 

I found with about 3 weeks' of storage it will go pretty flat. It probably goes even faster in cold climates.
I've also found that an AGM (dry-cell) 12v battery solves these types of issues since they can be deep discharged repeatedly.

Re: I gotta start reading the manual better
 

You are saying the High Voltage battery will go flat in 3 weeks? What is drawing on that voltage when the FEH is not turned on? The electronics are all run by the 12v system.

Here is what the 2008 Owners Manual States:

"Low and high voltage battery – storage

Your vehicle must be started and run for a minimum of 10 minutes once
a month in order to maintain the high voltage battery charge. This will
maintain the high voltage battery but it is not enough to maintain the
low voltage (underhood) battery and additional low voltage (underhood)
battery charging may be required after 60 days.

If your vehicle is to be stored for 30 days or longer, the low voltage
(underhood) battery negative terminal must be disconnected. Failure to
do this could damage your vehicle’s batteries."

I don't know if this means it will be depleted, or just begin to lose charge.

Re: I gotta start reading the manual better
 

I would say that the manual is very conservative.
I doubt there is much draw from the LV battery when
the FEH is off. I typically can go a week or more without
using my FEH and don't seem to encounter a problem.
60-days of storage or beyond I would certainly start that
storage period with a fully charged LV & HV batteries.

Re: 1st Person Experience with depleting the 12v battery
 

Actually temperature (heat) depleats the HV battery quicker.

I park for long periods while I am away to work out of state.

I have the SOC read-out on my scan-gauge.

In sub-freezing winter, my HV battery loses about 6% charge per month.
In summer, it is about twice that much. Still nominal in my opinion.

As a safe-gaurd, I always run it for 5 minutes in the driveway before leaving on a long trip to get it to the maximum 53% SOC.

Re: 1st Person Experience with depleting the 12v battery
 

Happened again today... well, almost.

I was finishing up another outside project today and once again listening to the radio (> 1.5 hrs) with the switch in the ACC position. Radio started to go out so I ran to the car (<3 seconds) and went from ACC to ON. ICE fired up and the radio started playing fine again. Must have caught it with that last little bit of power before it dropped below the point of no return.

I'm pretty sure the 12V battery is weaker than it should be and will fail sooner rather than later. I just can't bring myself to change it out before that happens. My wife knows how to jump-start a car...:angel:

Re: I gotta start reading the manual better
 

Yes I've found in 3-4 weeks of storage the vehicle can go in to a no-start condition with both HV and 12V batteries dead. Perhaps making sure the batteries are topped off before storage would extend the period.
I understand all modern vehicles have these issues with long term storage, since they run alarms, computer memory, radio presets, clocks, etc. while they're off.

Re: 1st Person Experience with depleting the 12v battery
 

Chris-

Now that you know what you are doing wrong, STOP DOING IT!
Most people's stock underhood battery lasts 5 years. 6 year in mild climates.

If you turn your key to "On" without starting the car, your HV battery will downconvert 330v to 14v to run all your low voltage stuff. This will work for 45 min to 1 hour. Then, your HV battery will shut down at 35% charge as a safety... to hold enough cranking power in reserve to start the car. After this "click" (you can hear the relays to the big battery open) only your 12v battery is powering your electronics... and you get about another hour, to 2 hours as you describe. THIS IS HARMFUL to your 12v battery. DON"T DO IT!

Lead Acid batteries, like the one under your hood don't like to be deep cycled.
Run them down once or twice, and you need to buy a new one.

The solution is to keep the key to "run", not ACC.
And really "run" the car for 5 minutes per hour is all you need to do to keep everything charged indefinately.

HTH,
-John

Re: 1st Person Experience with depleting the 12v battery
 

Attachment 2922
It is possible to drop your HV battery below 35%SOC but it is not recommended to do so.

Re: 1st Person Experience with depleting the 12v battery
 

If the HV battery "clicks off" at ~35%, you can turn it back on via cycling the key, but this is not recommended.

I've seen mine go down to ~22% and it still started ok.

The purpose of the button under the driver foot well is a bit mis-leading.
It has been discovered that this button uses 12v energy to heat the HV battery pack. The warmer the pack, the more amps it can put out, so may be "just enough" to push a borderline HV pack over the edge to start the car.
No amount of pushing the button can bring back a deeply discharged HV pack.
It is really NOT a 12v to 330v charger.

Before you get any :lightbulb ideas about pushing this button to warm a cold battery before you start your day, think again. Two conditions must be met for the button to even activate. The battery must be A) cold and B) below a certain SOC which is lower than 22%. At 22% the button on my car would not activate, because the car determined it was not needed.

Dang engineers thought of everything!
I speak only for the 2005 which I own and have thouroghly tested.

Re: 1st Person Experience with depleting the 12v battery
 

Even that translates to more than 6 months of storage for the HV battery.

My understanding is that the 12v runs the electronics trickle charging for the electronics, so what is the HV battery being used for that it would discharge?

Re: 1st Person Experience with depleting the 12v battery
 

All batteries self-discharge just sitting there. Even Duracell AA batteries have a shelf life and expiration date. Those are in years.

However, your FEH has 250 "D" batteries welded in serries.
NiMH self-discharges quicker than alkaline.
Plus there are all those taps and welds and sensors that may be sensing at a few milliamps continuously.
But NiMH is rechargeable, while alkaline is not. Hence a trade off.

Lets make up a realistic number, and say 20% charge is needed to start the FEH. Some people park at 40%. Some like myself, make a point to park at 53% before a long trip. (53% is as high as the car will go at idle in the driveway)

At 6% loss per month in sub-freezing, and 12% loss per month in summer, you can re-do the math.

53% -12, -12, -12 gets you to 17% in 3 months of being parked. Car may not start.

If you park at 40% (the lower end the car allows while driving it) you see you probably won't start after 2 months (40% - 12, -12 = 16% ).