I hate when people make something simple..... complicated......

The FEH.... every FEH 2005-2008 turns the gas engine on when the battery falls to EXACTLY 40% ( OR 39.99% ) as self determined and as displayed on the meter(s).

It is thus in the program to turn on the engine each and every time the battery on board computer(s) self generated and self determined battery state of charge falls below exactly 40% as indicated.

Whether this number is the battery's actual true to life SOC was never part of the discussion, becasue it does not matter. When the car thinks the battery falls below 40%, the engine comes on, each and every time, without exception, so long as the key is in "run" and the car is in any "gear" position other than neutral.

Better? ( I think not... but there you go..... )

 

P.S. Battery voltage is NOT the way SOC is determined. It would be a **** poor way to do so. The battery goes from 400 volts during strong brake to 280 volts during strong acceleration in a matter of 1 second without significantly affecting the SOC.

 

You're about right, but when you try to use "exactly" you fail to understand the engineering involved in measuring these things. Once I understood that your post over on Wikipedia was based on observed information and not design information I knew how to discount what you say.

You can say it all you want, put it in as large a set of bolded caps as you want, but you just have observed data with little understanding of what's behind it.

So even though you're about right, you're really just plain... wrong!

 

RE: battery voltage, so how do you think SOC ought to be measured?

The designers also measure the current into & out of the battery. By knowing current you can adjust the voltage offset for current. Since the battery voltage, corrected for voltage drop or rise due to current, is directly related to the chemistry (eg electrochemical potential), it is likely the best, simplest, and most accurate way to calculate state of charge.

You have accurately observed that when charging the battery the terminal voltage goes up & when discharging it, terminal voltage goes down. Recall that Ohm's Law, E=IR, enables you to calculate the voltage to add or subtract from the voltage that in turn reflects the SOC.

Correction of battery voltage for current is a very simple method. When you do it by a computer, for whom a millisecond is an eternity, it becomes the most accurate method.

So tell me again how you would measure SOC?

 

The only thing I failed to see is who is exactly a Troll.
I dislike petty persons.
I will help persons who really care about what they purchased to drive, and are curious as to how it works and why it behaves like it does.
I will exactly ignore petty persons.

Once you learn a little about the chemisty of NiMH battery cells, you will learn how the battery state of charge is approximated. There is only one good way to get the precise state of charge, and the FEH doesn't do that but once per 10,000 miles ( or so, that number is not exact )
The rules for the car's behavior I described in my posts are exact as in "always" and "without exception".

There is no "+/- 2%" as Bill wrongfully suggests.
I suggest he go out and study his own vehicle.

 

Guys,
Now don't make me get my Fluke 787 out, I may have to learn how to use it... So did anybody reach a consensus on whether the "Battery harness recall" improved performance? On a side note, how do the plug-in hybrid cos. get a Prius to go 52 mph on EV only? 3Prong power claims as much and with lithium iron phosphate batts... http://www.3prongpower.com/products.html
Thanks for the input..
M

 

I did not notice any performance change.
I don't think there was any intent for any performance change.
The intent was to prevent a premature / false error condition to develop.
Basically, one of the redundant system checks is being bypassed via a jumper wire.

As far as for "testing" the battery pack, it was built to deliver 236 watt-hours of nominal power per nominal charge*. If your pack is doing that, it is performing as designed.

Ford published that the battery capacity is 5.5 Ah @ 330 volts.
Ford charges the battery to 53% nominal* and insists on a recharge at 40% SOC.

*Brief excursions outside this range are possible under special conditions.

** Even if the SOC as reported is not exact... the range of use IS exact. If the SOC monitor "drifts" and it probably does, (IE the 40% reported is really 39%) the nominal range is always++ 13%.

++ Repeatably observed under 1000's of cycles under 100's of conditions and by numerous vehicles.

It is widely accepted that the SOC is monitored by "counting coulumbs" or counting watt-hours in and out. Due to heat losses, etc, periodic recalibrations are required. These recals are quite common in the Honda Insight but are fairly infrequent in the Ford Escape Hybrid with much more advanced hardware, and software.

The voltage of NiMH batteries is quite stable over much of the SOC range.
Thus, voltage cannot be used to monitor SOC in the middle of the charge, which is where hybrid cars spend most of their useful life. Periodic deep cycles are required to monitor the health of the battery with any accuracy.
It has been observed that Fords may "deep cycle" the pack once per 10,000 miles. My Honda does it more like once per 1000 miles. But my Honda pack is 9 years old and the Ford is 4.5 years old. Both cars give me the same ( or very nearly the same ) watt-hours of output as when new.

HTH,
-John

 

Counting coulombs? This is a joke right?

SOC is a reflection of the reserve chemical energy in the battery. This varies over the life of the battery. There are various things that can degrade the performance of a battery and reduce its capacity.

A standard Pb-acid traction battery begins at 90% of rated capacity, then increases to about 110% for its first 1/3 of life, then begins dropping to 80% at end of life. This is due to such things as impurities in the chemicals and the physical change in volume of reactants as they change back & forth with charge and discharge.

The SOC early in life and late in life can be vastly different with the same numbers of coulombs drawn. To say that you can measure capacity, or SOC, by "counting coulombs" is nonsense.

I'm sorry, but there is so much uneducated speculation in this discussion that it has ceased to be useful.

Don't confuse hours of observation with real knowledge of how this thing was designed to operate. Don't confuse "battery voltage is quite stable" with unchanging. A flat sloping characteristic is as stable as a constant, unchanging characteristic. Claiming a precision that doesn't exist is the realm of charlatans.

Get a clue.

PS For those who might want to excoriate me on what a coulomb is: go look up the SI definition of an ampere.

 

Go take a look at the Wikipedia page on NiMH Batteries:

http://en.wikipedia.org/wiki/Nickel_...ydride_battery

This is a quick skim of the characteristics of this battery. This page will show you just how far off the mark some of the above discussions have been.

Note that the charge & discharge characteristics do not have a zero slope as intimated in one post.

Preventing cell reversal is a very real element of the programming of this car. When you have as many cells as are in this one, preventing the weakest cell from reversing is a big deal. Should one cell reverse the cascade effect would quickly end the life of the battery.

 

Here's a pdf download on NiMH batteries & characteristics.

Of note is the curve on p12 for % discharge vs voltage.

For those of you that can... enjoy:

data.energizer.com/PDFs/nickelmetalhydride_appman.pdf