Poor fuel economy

Bisco,
No the batteries I linked to are very different size and have very different terminations, no posts simple screws. Therefore they would require some adaptation of the hold down and connections. Their attraction is they are twenty first century technology, LIFEPO4, which is far safer and emits no toxic gasses under any conditions so no vent is needed (notice the main traction battery which is also lithium, but far less tolerant of abuse, has no vent). They also have a far greater charge efficiency, over 95% vs under 50% for lead acid. Also, the pair weighs about half as much as the lead based batteries. These particular batteries incorporate rather complete electronic protection against over-charge, over-discharge, over- current and over-temperature. Unlike the lead acid based OEM and aftermarket drop in replacements, they can deliver their full capacity, 20AH each, repeatedly without degradation. With lead acid chemistry even one discharge below 50% of capacity results in substantial degradation (reduced capacity and shorter life). Actually The PIP probably would do fine with just one of them but one would cost $209 while 2 is $299. Since I cant resist a bargain I'll go for 2.

 

Has anyone really defined an "end of life" condition for the Prius 12 volt battery? Mine apparently cannot be charged above what should be a 50% SOC. All the energy the charging systems try to add to restore 100% SOC is simply wasted as heat in the 12 volt battery. This wasted energy is manifest as both reduced EV range and reduced fuel economy on gas. How much energy is wasted depends on how aggressively the "systems" try to recharge the 12 volt battery. I really should try to measure the charging current but that would mean inserting an ammeter in series with the battery and an unwanted reboot. If I were designing the charging system I would choose constant current charging at 1C meaning the battery would be charged in under an hour from any state of discharge. That would mean that with the 45 AH OEM battery the charging current limit would be 45 amps. I know from Torque that the charging voltage is limited to 14.4 volts. This suggests that with an actual battery at 12.2 volts as much as 100 watts ( 45 amps times 2.2volts) could be being wasted. Assuming Bisco gets his typical 200 WH/Mile ( a crude average by looking at the spread sheet) at 20 miles/hour, he is using 4000W so the 100 W loss represents a 2.5% loss of range. It's a lot harder to come up with a gestimate for gas but it could be similar.

 

− Quote
Sounds pretty reasonable and I'm not all that premature in replacing mine. I let it rest overnight and measured it this morning and it reads 12.09 volts.

 

I may, in fact have no issue, the 2013 might be every bit as good as the 2012. Yesterday, for the first time since I've had the 2013, the roads were dry and the temperature about 65 f. I took a 110 mile round trip to get some rubber covers for my jack-stands so that I will be able to DIY change the transmission lube, which I've ordered. I reset the trip odometer after the coolant temp reached 180f and logged the 110 miles at a displayed 45 MPH and 61MPG with 7.2 EV miles available both at the start and end. It would seem that the near new EP422s extract a much bigger MPG penalty (it could be 10 MPG or even more) on wet pavement while extracting no more than a small penalty on dry pavement. I'm still going ahead with the 12 volt battery replacement, I'm awaiting the arrival of the batteries.

 

I may, in fact have no fuel economy issue, the 2013 might be every bit as good as the 2012. Yesterday, for the first time since I've had the 2013, the roads were dry and the temperature about 65 f. I took a 110 mile round trip to get some rubber covers for my jack-stands so that I will be able to DIY change the transmission lube, which I've ordered. I reset the trip odometer after the coolant temp reached 180f and logged the 110 miles at a displayed 45 MPH and 61MPG with 7.2 EV miles available both at the start and end. It would seem that the near new EP422s extract a much bigger MPG penalty (it could be 10 MPG or even more) on wet pavement while extracting no more than a small penalty on dry pavement. I'm still going ahead with the 12 volt battery replacement, I'm awaiting the arrival of the batteries.

 

I'm still searching for a reason the 2013 is a fuel hog! I just filled up and this tank's HV mileage was 46 MPG worse than I ever got with the 2012! EV mileage is about the same or slightly better. This tank is after oil change, air filter change 51 PSI in the tires which now have about 1500 miles on them and a new 12 volt battery and new brake rotors and pads & the grill is blocked 100% lower and 50% upper. I've been driving more economically as well.
The instantaneous mpg indicator on the dash seems to consistently be quite a bit lower than what I recall for similar speeds and HSI indications. Is it possible I have a bad air fuel sensor and the ICE is running rich? Does anyone know how "TORQUE" computes air fuel ratio because it is reading 14.6- 14.8 under steady state conditions which is just what it should be. There are no diagnostic codes and the cylinder miss counts are zero. Could it be an EGR issue? How can I tell ? What else could cause higher fuel use? Toyota "customer care" is no help!

 

Well I hope I've found the problem! It's too early to be sure, I'll need to put some miles on it with the "fix" but a short test drive was VERY encouraging, the instantaneous fuel gauge on the dash was like I recall the 2012. In I my first post I mentioned a VERY dirty air cleaner (this is a hint). Let's see who guesses what I did to "fix" it. I'll post with the next tanks results and what was done after I've driven a couple hundred miles.

 

They are in and doing just what they should. I posted the details of the installation on a different thread highlighting the 17+# weight saving.

 

I did another short (18mile) test drive, with Torque displaying "volumetric efficiency" trying to use ICE as much as I could. Back in post #4 I talked about a previous drive where I monitored this "before the fix" the readings were from low 30% to 55%. The readings now are a low of 42% and a high of 65%. The highest readings are when the ICE is delivering about 14 hp.

 

CONGRATULATIONS!!! you guessed it! I don't yet have real data on how much the improvement is but I can tell it is substantial. I've only driven 57 miles on this tank, of which 38 were HV miles about 6 of the HV miles were before the "fix", trip A was reset on fill up and it is showing 85MPG which means that the HV miles were at 56 + mpg according to the car's computer which is optimistic by about 6%. My guess is I'll see almost a 10 MPG improvement for $7 of MAF cleaner and all of 15 minutes work.