Replaced aux batter now car acts like it's dead

welcome! how many miles on her?

 

I had that issue when installing a new battery. Turns out I needed to put the new battery on a charger to top it off before installing it in the car. Seems as though the battery sat on the shelf too long and needed to be topped off. Wouldn't of been an issue with most cars but as we know the Prius is a special beast.

Also for some reason you need to push the start button on and off a couple of times after installing the new battery. I think there is a particular suggested way to do it...... meaning when you foot is/isn't on the brake pedal when pushing the start button.

 

perhaps a check of the battery connections, including the negative to body point. and press hard on the brake when pushing the power button. does the 'ready' light come on?

 

Interesting puzzle. I would not rule out a high resistance connection somewhere in the power distribution wiring, causing a voltage drop across the wiring under load, while the battery voltage itself is ok. If that's what it is, it has to be in one (or more) of the power distribution circuits not including the circuit the MFD uses to sense battery voltage, since it is sensing the undropped voltage.

If that were the hypothesis, pursuing it would just be a matter of looking at the wiring diagram manual starting in the power distribution section, eliminating the circuits where the problem isn't, and finding the locations to strategically test voltages to spiral in on where it is.

Interesting. What do you mean by "the accessory connector", and what's the source for that being the go-to response?

-Chap

 

I'm also curious as to what you mean by accessory connector?

I'd also start to fear that perhaps you have two or more separate problems despite having changed the Aux Battery.
Maybe the actual act of changing the Aux battery is just bringing forth problems that already were manifesting with the Dash and MFD?

In other words, we're assuming this is somehow connected to the aux battery or changing of the aux battery when maybe it's not.

I really don't have an answer here, other than I think you need to start deciding which arm and leg you want to sacrifice to the dealer.

PS.
The fact that they didn't keep the vehicle on a charger to keep the computer "alive" while changing the aux battery shouldn't matter.
I've never read that this is necessary or even recommended. Disconnecting the aux battery to replace it? Shouldn't result in needing it to be on any "charger" life support during the changeover.

 

That part at least is perfectly normal behavior for the Prius. When you turn on the headlights it automatically dims the multifunction (LCD) display, as is appropriate for night time visibility.

 

Disconnecting the 12 volt will not cause problems. It will lose your radio presets and clock time, things llike that.

Before going to a dealership maybe get a digital multimeter, and see what sort of volts the battery has, report back?