Regen battery charging working extra well, MPG down...

Time to test your 12v battery.

 

What is your mpg now? The battery will hang around 5-6 blues bars normally, and 7 green bars occasionally, unless you are in mountain terrain. In stop and go city traffic, with A/C on, I notice that the battery goes lower, 3-4 bars often. If you see all green bars and then suddenly 1-2 purple bars, and suddenly back to green, then there is a battery problem. But it will throw a DTC when it's a real issue.

 

I see that you are in San Diego so the weather is great compared to much of the country, but I have to ask - are you using the heat at all?

 

Just keep in mind that the engine will run more to generate heat and while running will also charge the battery. The AC is electric and puts no direct demand on the engine. Just a thought, it would have been a decent idea if you lived some place cold though.

 

There's nothing to relearn. Don't waste your time disconnecting the battery. Your just exposing the car to sparking and surging which the car really really does not like.

You guys will not give up on the CAI.
This is absolutely the wrong car to do this on and you will see no improvements at all, all you'll see is an unhappy engine.

And the other poster was referring to the 12 volt battery getting old and if its the original it needs to be replaced.
Nothing to do with the intake.
When that 12 volt gets old it takes a lot longer to charge it back up and the engine will run longer to do this affecting mileage. In almost any complaint its the first thing that needs to be addressed in this car.

I know your stubborn so the best way to check if that 12 is getting old is to put a standard battery charger on it in 2 amp mode. In a fully charged battery in a Prius in 2 amp mode it should reach zero current draw in about 15 minutes. Anything longer than that and or not reach zero draw at all and the battery is on the its way out.

Use the front jump points.

 

Based on many reports here Aut0 stores and especially the dealer seem incapable of properly testing this battery.
I would be very leery having an autoparts store dude mess with my 12 volt.

Do as I say and buy a charger at Sears. Its very useful. There cheap. You mess with your car alot. Put your car on a charger once a month like alot of us here do. Its very good for the battery and would take the guessing and head scratching out of this equation as you can track the health of the battery over the years.

But I doubt you'll take my advice.

 

10-Watt Solar Panel by Battery Tender: BatteryMart.com

 

Oh that sucks. I see the problem there no ac. So your stuck with testing it.

And the battery tender is ok for periodic charge but regular batt charger is better for this experiment as it has a current meter. I use my regular charger alot more than my tender.

 

Hmmm, from what I have seen and read three things stand out to me. #1, the condition of the 12 volt battery which has been plainly pointed out, #2 changing of the intake - that is definitely going to affect the controls in more than one way which could very well make the engine run more often which will in turn keep the charge high in the traction battery #3, more hilly route will cause the regenerative action to be more agressive which will also tend to keep the traction battery higher.

If it were my car I would go back to the stock intake AND run the test that JDennenburg posted here on Prius Chat.

Weird stuff happening? MPGs dropping? Test The Battery | PriusChat

Please run the test described in the link above and post back with all three of the figures. That will give us a good idea of the condition of your 12 volt battery.

I would almost bet that the combination of the intake being changed and a old/weak 12 volt battery is the source of your problems. Now if you were to say that your MFD was going from full green to full purple or red in just a couple of minutes, I would suspect the traction battery, but since you are not saying that I have to conclude it is due to the modifications that you made and a possible 12 volt battery being weak. I also agree that the standard test that the auto store uses may not detect a weak battery in your Prius. A weak/failing 12 volt battery will cause havoc in your car.

You can't do much about your route, but you can do something about the other two items.

Good luck to you and I hope this info helps you.

Ron

 

The MG's in the prius also perform the function of the alternator in a normal car. That is, to keep the 12V battery topped off and to supply any loading on the 12V system (ECU's lights fans etc). Some of the green arrows you see going into the HV battery are not charging that battery, but merely providing the ongoing power for the DC-DC converter to keep the 12V system running. If your 12V battery is failing then this load can be considerably increased.

Follow Ron's advice above.

 

I think UART hit the nail on the head, please test the battery and post back what the three figures are. I do agree 100% that if the battery is weak/failing then the whole system from the engine to the traction battery to the DC to DC converter is working overtime just to keep that 12 volt battery charged. It would explain why the traction battery is green more, why the boost is less to the assist as the 12 volt is demanding more juice than the assist and why the MPG's are going down because the ICE is running more to keep up with the demands of the electricity being called for. All of the parts have to work in unison for the Prius to run right.

Also with you running the defroster/AC you are adding more load to the 12 volt system and the traction battery which is making matters worse. If you want to get optimum MPG's from the Prius, you really need to have everything working right, and use as little electricity as possible. There are other things I could add to help you improve your MPG, but then I would be getting off topic.

Ron