Virtually all the dash lights on (and beeping) after using a 1000w inverter last night, please help.

Hello, we’re in Houston with no power still for several days. At first I went to academy and purchased a 300w inverter to run off the 12v battery, that worked great but very limited to a fan and a tv, so I made the mistake of upgrading to a 1000w (2000w peak) jupiter harbor freight inverter in order to save our upright freezer full of food.
Firstly the freezer began working but stopped after 30 minutes. So I unplugged that extension cord and went back to just the fan and tv. The next morning though I check on my Prius and noticed the gas gauge barely moved compared to the previous 3 nights. And I have constant beeping, the brake, ABS, traction control, and about 4 other lights I have never seen before are on. I also noticed that the brake pedal is hard to push. Before switching to the 1000w inverter everything worked perfectly. So I am assuming that an electronic/electrical situation happened. I removed the inverter from the 12v battery, leaving it disconnected for about 10 mins to see if things would go back to normal, but no.
Can anyone help point me as to what to check for first in the fuse block?
It’s a ‘12 Prius V with the Tech package.
Thanks you.

 

Thank you RJ, this was what I was hoping for a road map to troubleshooting it.

With both cables removed, what voltage reading would lead me to know that it is the culprit?

 

I did as you recommended and had the battery tested at Advance, it was done while in the car and it tested good at 12.82v CCA down to 291 from listed 325 CCA.

While at Advance, I had them run codes and the only one that came up was ABS booster bad, which I know was working fine before I attached the higher powered Inverter.

I have tried many times to eyeball that 125v fuse but the angle makes it impossible to see anything but the top edge of the cover. I have a little telescopic mirror but even that is too wide. I may just break the mirror to get a smaller size to allow me to see if it is blown.
My fuse puller from Toyota lost an edge while trying to pull the 20a fuse rendering it useless. I have since bought new micro fuses and a puller that also tests.

 

I had Advance do a diagnostic and it came back as brake booster but I think this is an electrical issue from me hooking up the 1000w harbor freight inberter and trying to run my freezer off of it.

 

Just to post a follow up:
Thank you to everyone here, especially RJParker.

i ended up buying a thinkdiag scanner and it indeed showed the codes C

 

Just to post a follow-up

First thank you to everyone that helped, especially rjparker. Lots of invaluable information in troubleshooting.

I ended up ordering a thinkdiag scanner and the codes that came back were
C1252 and C1256
pointing to the booster/ actuator.
My local Toyota dealer quaoted me $4300.
2 years ago I received a notice from Toyota showing that they would cover all of this during their “campaign” but at that time the actuator was working because my mileage was low. 2 years post campaig and I am now out of the window of that opportunity. I called Toyota corporate hoping for aome partial relief like 1/2 coverage but they refused.

So I took it to an independent toyota repair shop and the quote was $3100. I asked if I supply my own oem toyota parts, they agreed so that saved me $500 in parts. Making it a $2600 job,

They had a terrible time getting the final calibration done, I forget the actual term. Installation was done within 5 hours, but they spent another 5 hours troubleshooting getting the computer to cooperate but it finally got done.

My other car is an ‘03 Lexus LS430 so at least I can use the thinkdiag for that as well.

The cost and complexity of this repair has probably wiped out any gas savings over the years. And at 136k miles, I dread the head gasket issue in the future. My plan was to sell my V later this year and get a RAV4 hybrid but am not sure if I will be facing the same situation in a few years.

thanks again to everyone.