Large custom HV battery upgrade help (gen4)

What are you by profession?

A dreamer?

 

Unfortunately, no.
While anything is possible, not everything is practical

 

You''d have to ask someone who knows how to reverse engineer the system. Conversion have been done in the past, I haven't heard of anyone doing it on a Gen 4 yet. And I sure don't know.

Here's what is said to expect from the Gen 3 plugin PiP lithium upgrade pack
What to expect:
The first few months is the break-in period, you will notice the charging limit/capacity gradually increase from stock 15 miles to 30 miles. Based on the new charging limit, you will also gain more EV range as computer learn, adapt and utilize the higher capacity. We have also found the level one charger speed can get more charge into the battery than level two charger, as the onboard charger isn't sophisticated enough to perform trickle charging at higher state of charge.
Warranty:
2 Years, unlimited miles

And this thread has pics of what can happen if done wrong or handled improperly after install.
Add an additional 8Kw battery to double the range | PriusChat

 

Someone who knows would be too smart to waste their time

 

I think those that did that added a BMS for the additional battery though. The OP is considering using the stock one. Even with a matched battery pack, the BMS is not designed to be able to charge 2 battery packs at once.

 

A BMS and if the bms is not equipped with one, a balance board are usually required for lithium packs that match the cell type specs and series / parallel configuration and are tested in most any DIY build configuration.
That's one of the reasons lithium prebuilt packs are still big bucks. Than the packs need to be tested in the cars they are going into to make sure the systems function properly together. And how are tests done in every situation a car is going to be exposed to within it's lifetime and how to categorize feedback for early adopters or alpha beta testers.
It's not a thing to take lightly especially these days. Yet there are still some brave souls that find the challenges exciting and worth the effort it takes to push on. ie; @jacktheripper and mudders linsight project and Peter in the UK has done multiple lithium installs into NiMH insight crz and I believe also a civic, or at least part way there. 3prongpaul also did a Gen3 Prius dual pack. MikeD did a lithium upgrade to his Gen 1 Insight(s). And share his design for the GC01 grid charger that both Hybrid Automotive and Max Volts got their inspiration from, or so the story as I got it goes. I also look up to all these dudes in no particular order.