Here are some of the more common questions I have answered. If you have a question, just respond to this post and I will do my best to answer it. Thanks everyone so far for their questions.
Q: If I can get the car into EV mode AND there is juice in the additional battery AND I am in park or stopped the system should charge the primary battery, correct?
A: Most of the time – if the BTV of the Prius battery is >235V (as viewed on the Scangauge) the additional battery will supply little or no power. If BTV is 225V or lower the additional battery will provide 10-12 amps (shown as a negative number on Scangauge under BTA). The system will supply less power as the voltage increases. The additional battery provides power based on voltage, it doesn’t care whether the car is in EV mode or not.
Q: There is a green and red light on the toggle switch “request EV mode”. I believe the green light indicates I turned the system on. Does the red light indicate that the system is charging?
A: The green light indicates the system is turned on and supplying additional power to the main battery. The red light means the additional battery is depleted or the system is no longer contributing energy to the car.
Q: Are there any other reasons besides running out of juice in the second battery that the light on the dash would turn red?
A: Yes, if the converter gets too hot and goes off due to thermal reasons. Usually when the red light is on the 2nd battery has been drained.
Q: If the switch is toggled on but the car denies EV mode does the system still charge the main battery?
A: Yes, as long as the additional battery has power.
Q: Is there a way to tell how much juice is in the second battery besides the red charge light in the trunk shutting off?
A: There is no “fuel gauge” per say on the additional battery. Basically the trunk LED should be red when the system is charging from an external power supply.
Q: I thought that when I exceed 33 MPG the system would kick me out of EV mode, but I have noticed that sometimes when I go 34 MPH the Prius computer doesn’t kick me out of EV mode. I assume it is a rounding display error on the Prius gauge and in fact I may not quite be going 34 MPH but rather 33.68 or something like that.
A: It’s possible. There is also a bit of a time lag on the gauges. You could switch your scan gauge to view more specific information that the Prius doesn’t show on its main computer screen.
Q: There appears to be a lag in the Scangauge. Am I reading the gauge wrong or is there really a delay?
A: There is a delay in the Scangauge display. It is about 2-5 seconds.
Q: If everything was just right how long can I drive in EV only mode before draining the additional battery? I know this really depends on driving habits and conditions but is there some sort of approximation?
A: With the system you can drive about 15 total miles in EV mode. But because the system can only trickle charge the primary battery, you will usually only be able to drive 2-3 miles at one time. I have on occasion, when stuck in heavy local traffic, been able to drive most of the 15 miles in EV mode but it only happens when I am stopped frequently or driving very slow which allows the secondary battery to charge the primary battery fast enough to keep up with the power I am drawing from the main battery.
Q: Sometime there is a loud sound coming from the trunk. What is the noise and should I be worried?
A: Mostly no. If there is a whining coming from the truck that means a fuse has tripped. It should stop in 5 minutes or so. If it doesn’t call whoever did your system.
Q: How long will it take to charge the car when the 2nd battery is completely drained?
A: Four or five hours if the second battery is completely drained.
Q: Can I charge the car when it is plugged in?
A: Yes but you have to be very careful not to charge it for too long because the primary battery pack won’t know how to deal with the extra power. 30 minutes is the max you should attempt this. If you are the type of person who gets distracted don’t even attempt this trick.
Q: Why does my engine sound like it is running but the main computer screen shows the engine as off?
A: My programming background makes me think the engineers at Toyota didn’t show actual engine state because it would just be flickering on and off all the time (In geek talk it is called flapping) so when the engine drops below a certain RPM the engine shows as off. Using the Scangauge computer you can view RPMs. It looks like anything under ~1300 RPM doesn’t show on the main screen.
Q: Why does my kill-a-watt not drop to zero when my charging is complete? My meter reads 5.5 watts instead of 0.
A: Large systems like this have a trickle draw for a couple of reasons. It is nothing to worry about but if you want to be very environmentally conscious (more environmentally conscious than buying a Prius and converting it) you can put your charger on a timer.