My mpg and my EV mode and charge and discharge characteristics as shown on the vehicles display are leading me to think it's time for a new traction battery, what with 6 yrs and 188k, but I'm not feeling really sure on this.

I'm not getting any check engine lights, I'm continuing to use Amsoil full synth, I'm buying the same fuel as ever, and I'm not just seeing lower mpgs. I've been seeing 30-28 mpg steady for the last year+, and increasing ICE/EV useage ratio, which all are perfectly normal for a declining HVTB. Ford wastes so much of this batteries capability anyhow, so more time spent out of that 40-53% SOC window is just going to turn this into an electro-motive drive ICE vehicle anyhow, at least in my mind.

What do you say? Time for a battery change?

Then, of course, what's the smart route for battery change? I sure as heck ain't gonna drive right into my local Ford dealers service writers carport and say "gimme a new traction battery and installation". I'm not quite comfortable with finding a battery (supposedly) out of a lower mileage wrecked vehicle on Ebay and buying it and swapping it out either,,,, but I'd probably do that before the dealer option....

 

The fueleconomy.gov site, which is very accurate for every vehicle I've ever owned, including our 08 FWD FEH, rates an 08 AWD FEH at 29/28/27mpg city/combined/hwy so I don't see a problem with what you're seeing.

 

No need for hybrid battery change and it is unlikely you are having issues with it based upon the mpg reported. If I am not mistaken, the Prius has an active SOC between 40-60%. Those Honda hybrids that first hit the market had much greater SOC ranges and many owners have voiced misery with the need to replace the hybrid battery at 80,000 miles.

 

Even if the traction battery loses capacity, it helps to estimate the effect. Even with no traction battery capacity, you still have the benefits of the CVT, smaller than normal gas engine, LRR tires, airflow tweaks, engine shut-down and Atkinson cycle gas engine. So the hybrid electric system is only part of the gas-saving aspects of the vehicle. I have no idea what proportion of the gas savings is due to the regeneration system, but an estimate might be 65%. So if your battery loses 15% capacity, that should mean a loss of 15% of 65%, which would be a 10% difference in the mileage benefits provided by all the car's features. Note that this is not a 10% mileage loss, just 10% of whatever the FEH achieves over a non-hybrid. Which would amount to very little.

But then again, you can get used traction batteries for, say, $700-800, so you could balance that plus installation costs against whatever mileage you think you're losing.

And remember that winter gas doesn't have as much energy in it, plus more gas needed to heat up the engine etc.

There are 2008 FEH taxis with 300,000+ miles on them, and there's a 2008 FEH in the US with over 500,000 miles. The owner of the latter reports no loss in mileage.

 

Without a traction battery, the vehicle does not operate.

 

Yes, if it discharges below a certain point, or loses capacity below that point, it can't spin the electric motor used as the starter.

 

What is interesting is I snapped a photo of my vehicle with a SOC at 11! The title of the thread was "record low SOC".

 

11% of what? We do not know.

I'm at 9.5 years and 165,000 miles.

Runs as good as ever. MPG nearly as good as ever... maybe 5% less ( NOT 5 mpg less ).

Battery not as good as new. Battery has ever increasing internal resistance, measured as ever increeasing heat generation. My battery goes up 20 degrees in 10 minites over 5 miles of city drive.

Still, that is no reason to swap out the battery.
When new the battery was programmed to always use only 20% of capacity.
So the battery can weaken by 80% due to age and still drive normally.

Mine does drive normally. Only loss in efficiency is from A/C battery cooling needed almost every day, vs. only occaisionally in the past.