2010 Prius Electrical Issue (high volt, abs lights)

You sure are you sure you're readings are correct so with it connected and ready what is on the battery terminals with your meter connected what do you see ready with the lights on just in the ready mode you should be seeing you know like 13 and a half to 14 and a half volts i do believe that's what i see on mine and that's with a decently working battery that's about a year old or so and everything else seems to be generally okay i can't imagine seeing 20 volts back there on the 12 volt battery and if it was getting that it should be showing that while the car is ready and your meters connected to the battery in the battery's connected fully to the car this is the 12 volt and at this point you're 12 volt would be like a 17 volt so you should see that 17 volts or whatever you said you had right now ready disconnected and all that i don't really think it's pertinent here me i care about what the battery is in the car connected and ready to be used it's getting charged by the hybrid system or whatever at 14 and a half volts which is what most lead acid batteries need for charging while they're working at least that's the way i understand it

 

This is the kind of situation where if you could post a video of exactly how you did that, it would probably save a lot of back-and-forth. Ideally it would show the state of the car (dash displays, say), what you disconnected, the placement of your meter probes, and the settings and display of the meter. Another reading to check against, such as the one from the Vehicle Signal Check page on the touch screen (if your car has the touch screen) would help too.

 

Given you are seeing some lights and alarms, there must be some voltage. It could be low but is almost never high on this car. If the car goes to Ready you should have at least 10.5 vdc on the battery prior to starting. Lets assume you are measuring the battery when its disconnected, you were not clear on that point.

1. The meter is not correct. It could be a cheap Harbor Freight meter which sometimes reads high.

2. The meter is being used or read incorrectly. You could be on ac volts and reading 20 millivolts.

Try the head unit voltage display.

Realtime 12v Battery Voltage in Off or Running State
Check out your battery status/charging system by using the MFD Service Menu.

1 Press the Start button without the brake pedal.
2 Press and hold the "CAR" button on the MFD while turning the headlights on and off 4 times.
3 Press "Function Check / Setting" field on the screen.
-Function Check / Setting menu will appear.
4 Press "Vehicle Signal" .
-Vehicle Signal Check Mode" screen will appear, showing

Battery 12.2v ---------SPEED 0 Km/h
IG OFF ---------------TAIL OFF
PKB ON --------------ADIM/TCAN BRIGHT
REV OFF

The 12v battery voltage is shown and changes as load changes. Go to Ready and the 12v will rise.

 

Like other posters, I am suspicious of your technique. But there is a DC to DC converter on a board near the bottom of the inverter assembly.