Has anyone....

It's not that easy. A series connection just freaks out the electronics.

 

I'll take "Void My Warranty" for $2000, Alex.

 

There are kits to add batteries to an existing Prius, most required a AC cord to charge the extra batteries, since the existing charging system is designed for the existing battery.Since 2012 Toyota actually makes a Prius with extra battery power, the Prius PHV.

Plug-In Supply | Plug-In Upgrades for the Toyota Prius
Enginer | Solar Powered Prius Plug-in PHEV Conversion Kit with Lithium-Ion | Hybrid
are examples.

 

not successfully.

 

I do not think that Enginer is still in the business of PHEV assemblies and accessories

 

Batteries increase the potential (voltage) along a circuit path. More specifically, they establish a potential difference at their terminal points. I believe my traction battery is something around 207V. Where it currently exists would also expect 207V. Wiring a second battery in series with it, into the same point in the circuit, would then put 414V at the positive terminal (with respect to the ground) instead of 207V. Not sure that's so good for the rest of the system.

I imagine what you mean is wiring it in parallel, similar to the way car audio enthusiasts might wire in a second 12V in parallel (with or without circuit modifications) for additional power.

 

Why not start with a hybrid highlander, it already has an electric rear wheel drive

 

I like the idea. I saw a golf cart rear end that seems like it would be a good start for adding rwd. I wonder if leaf springs could be used in the rear?

 

I'm not grokking how adding a second battery in series with the original, has any relationship to powering the rear wheels.

Without changes to the battery control electronics, this series connection will end up running the battery cells at half their usual voltage, where they have little usable capacity. Adjust the battery control to charge the cells to normal, and you risk blowing out everything tied to the battery set that is not rated to run at double the normal voltage.

 

Has anyone here on PC actually done this? I searched but couldn't find any.

 

Yes, back when there was no way to buy car from Toyota with a larger battery, many users did.

 

There are various aftermarket shops that can convert your non-plugin Prius to a plug-in.

One example- Upgrades | Boulder Hybrids

 

If you were seriously considering a project, I would not do it with a Gen 1. Gen 2 might make more sense.

 

many have tried, many have failed.

 

I converted my 2004 Prius on 2006 to a PHEV, I was one of the pioneers by those days. Then in 2010 it was called "TOTAL" loss by the insurance Co. I then transfered the PHEV equipment to a replacement 2008 until 2012 when I sold the vehicle. Everything was transferred again to a 2011, my wife current vehicle.
So far, the PHEV equipment was used for about 76k Miles and still driving strong after some batteries maintenance.
I started with few OEM Prius batteries assembly packs them migrated to LiPoFe4.
Yes PHEV conversions can be done having in consideration a lot of patience and dedication; money was not an object for this working experiment but it was a lot of an investment.

 

I assume Plugin Hybrid Electric Vehicle.

 

On my profile signature, on the BMS+ is an explanation of the system operation and all the gadgets needed.
I will recommend you to purchase an already made KIT from a vendor and there are not many around.