Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - DIY "Mild" Plug-in Prius Project: Grid-powering the 12v side w/ deep cycle batteries

bwilson4web · 11-28-2009, 07:23 AM

My first hack was to install a 1 kW, modified sine wave inverter. This schematic shows the 12 VDC system:

The "HVC" is the vehicle inverter operated by the hybrid vehicle ECU. I believe there is a voltage sensor that runs from the trunk mounted 12 VDC battery to the front. The nominal 12 VDC voltage when the vehicle is running is 13.8 VDC. Be careful with the 12 VDC system as several Prius have had their control computers fried by accidental, reverse polarity during a jump.

The measured 12 VDC load runs ~450 W although others have reported as low as 350 W. Regardless, it is a significant load. You can get a feel for it by reprogramming the Graham scanner. Since the maximum, battery module voltage differences are ~0.1 V, they can be replaced for your study:

cycle so the line to be replaced is on the display
tap the middle MODE so the first data item blinks
tap left and right until the first desired value shows up
tap middle MODE so second data item blinks
tap left and right until desired data value shows up
hit middle MODE until back to the select line to display
hit right or left until the line to replace is showing with the original values
hold the right button for a slow count of 3 to replace the displayed values - the new values will show up
if you don't want to keep these values, hit "RESET"
if you want to keep these value, turn the car off and it will save them for the next power on

I would recommend changing to monitor traction battery voltage and current. Then turn the car on, not running, and use the current and voltage to calculate the overhead load of the car. My memory is ~450 W. Turn on the head lights (Ok, the tail lights to work with the daylight running lights) and use brights and the cabin fans to see the additional load. For fun, press the brakes and see the power draw.

I would recommend getting the electrical diagram manual as your circuit road map. Given the 450W, ~ 1/2 hp, 12 VDC electrical load, it should make a significant improvement.

If I can make a table, I'd like to start a separate thread discussing NHW11 mods and the price-performance tradeoffs. Experimentation is good and hopefully this may give some ideas.

Bob Wilson

11-28-2009, 07:23 AM	#2 (permalink)
bwilson4web Engineering first Join Date: Mar 2009 Location: Huntsville, AL Posts: 843 17 i3-REx - '14 BMW i3-REx Last 3: 45.67 mpg (US) Blue Bob's - '19 Tesla Std Rng Plus Thanks: 94 Thanked 248 Times in 157 Posts	My first hack was to install a 1 kW, modified sine wave inverter. This schematic shows the 12 VDC system: The "HVC" is the vehicle inverter operated by the hybrid vehicle ECU. I believe there is a voltage sensor that runs from the trunk mounted 12 VDC battery to the front. The nominal 12 VDC voltage when the vehicle is running is 13.8 VDC. Be careful with the 12 VDC system as several Prius have had their control computers fried by accidental, reverse polarity during a jump. The measured 12 VDC load runs ~450 W although others have reported as low as 350 W. Regardless, it is a significant load. You can get a feel for it by reprogramming the Graham scanner. Since the maximum, battery module voltage differences are ~0.1 V, they can be replaced for your study: cycle so the line to be replaced is on the display tap the middle MODE so the first data item blinks tap left and right until the first desired value shows up tap middle MODE so second data item blinks tap left and right until desired data value shows up hit middle MODE until back to the select line to display hit right or left until the line to replace is showing with the original values hold the right button for a slow count of 3 to replace the displayed values - the new values will show up if you don't want to keep these values, hit "RESET" if you want to keep these value, turn the car off and it will save them for the next power on I would recommend changing to monitor traction battery voltage and current. Then turn the car on, not running, and use the current and voltage to calculate the overhead load of the car. My memory is ~450 W. Turn on the head lights (Ok, the tail lights to work with the daylight running lights) and use brights and the cabin fans to see the additional load. For fun, press the brakes and see the power draw. I would recommend getting the electrical diagram manual as your circuit road map. Given the 450W, ~ 1/2 hp, 12 VDC electrical load, it should make a significant improvement. If I can make a table, I'd like to start a separate thread discussing NHW11 mods and the price-performance tradeoffs. Experimentation is good and hopefully this may give some ideas. Bob Wilson __________________ 2019 Tesla Model 3 Std. Range Plus - 215 mi EV 2017 BMW i3-REx - 106 mi EV, 88 mi mid-grade Retired engineer, Huntsville, AL Last edited by bwilson4web; 11-28-2009 at 07:38 AM..