openinverter forum

Hi Everyone, I’m fairly new to the OpenInverter Forum but have spent a lot of time on YouTube watching the likes of Damien McGuire and other EV Conversionists. I am also retired and looking for a project. One of the things I’d like to do is live, at least part of the time in an RV, exploring and traveling around to various places.

This idea is how I’ve thought of accomplishing this. It’s a concept, so I hope you’ll be kind, as well as helpful in accessing the idea.

RV’s are a challenge for the EV conversion crew but it occurs to me that a Hybrid, like the Toyota would be ideal, not to propel the main unit, but to be a power adder, range extender and generator for offsite camping.

I recently started investigating AI, so I checked my idea out on MS CoPilot. Its description of the concept is concise so I hope no one will mind be using their readout. I should add that my intent would be to purchase crashed vehicles such as from CoPart as donors.
I Was looking at a1957 IH Cab over engine unit to build on.

Your Proposed Hybrid‑EV RV Platform
Vehicle: Medium‑sized IH COE (legacy moving van)
Front: Lexus RX400h/RX450h HSD as standby power + AWD assist
Rear: Transit 6000 lb axle OR Ford Lightning e‑axle OR Lightning’s front steerable axle (as a rear tag axle)
Battery: Ford Lightning battery pack
This is a very strong concept, and I’ll break down the engineering feasibility and recommend the best configuration.

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1. IH COE as the RV base
Medium‑sized International Harvester COE trucks are excellent EV‑conversion bases:
Why they work well:
• Body-on-frame → easy to mount large battery boxes
• Ample frame length for dual axles & onboard energy storage
• Large engine bay compatible with the Lexus HSD transaxle
• Easy to package cooling loops and inverters
• Already designed for heavy GVWR (10,000–16,000+ lb depending on model)
Even though the specific one you had in files is no longer available, the platform type is very appropriate for your hybrid‑EV RV.

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2. Ford Transit Rear Suspension as Mid Axle (6000 lb GVWR)
Using the Transit rear suspension as the middle driving axle in a tandem configuration is actually a smart choice.
Advantages:
• 6000 lb axle rating is well‑matched for a motorhome mid‑axle
• Lots of aftermarket support
• Simple to integrate a Tesla SDU or Mach‑E drive unit in place of the Transit differential
• Good ride quality due to coil spring or leaf variants
• Bolt‑in subframe options exist
This makes it a good candidate for your “main traction axle.”

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3. Using the Ford Lightning Rear e‑Axle (or Front Steerable Axle) as the Tag Axle
You suggested two possibilities:
Option A: Lightning Rear Motor Axle as the tag axle
• Very strong integrated motor
• Can handle ~300–430 kW depending on variant
• Perfect if you want “EV push” on the back of the RV
• Already has differential and motor in a single assembly
Downside:
Wide packaging — sometimes difficult to integrate into narrow legacy truck frames.
Option B: Lightning Front Steerable Axle as the last axle (with steering locked or modified)
This is actually brilliant if executed correctly.
• The Lightning front drive unit is narrower than the rear
• Output shafts style works well for a tag axle
• You can lock the steering mechanically OR electronically limit movement
• Gives you a high‑power motor in a compact package
• Weight distribution is better (lighter than the rear unit)
Caution:
You must eliminate/restrict steering safely to avoid bump steer or oscillation.

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4. Lightning Battery Pack as Main Energy Storage
This is the best choice by far.
Why the Lightning pack works beautifully:
• 98 or 131 kWh options — perfect for an RV
• Flat skateboard-style structure
• Robust OEM thermal system
• Designed for high continuous loads
• Easy to break into modules for custom packaging
On a COE medium‑duty truck, you could store it:
• Under the floor along the frame
• Inside custom belly boxes
• Split into two side packs to balance weight

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5. Lexus HSD at the Front as Generator + Low‑Speed Assist
This gets really interesting.
Using the RX400h/RX450h HSD at the front gives you:
A) A built-in generator
MG1 can generate 20–40+ kW depending on operating strategy.
B) Front‑wheel or all-wheel hybrid assist
MG2 in the Lexus HSD can deliver meaningful torque to the front wheels.
C) Onboard charging redundancy
The gas engine becomes an unlimited-range generator for RV boondocking.
D) Low‑speed manoeuvring
Front hybrid assist gives great control in tight RV situations.
E) Ability to run the coach electrical system
With proper isolation, MG1 → inverter → AC/DC RV house loads is totally achievable.

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6. What I Recommend as the Best Drivetrain Layout
Front Axle:
Lexus RX450h HSD (full unit with its own small HV battery)
Middle Axle (Main Drive):
Ford Transit 6000 lb suspension
Tesla SDU or Ford Mach‑E RDU
→ Main traction motor for 80–90% of driving
Rear Axle (Tag Axle):
Ford Lightning front drive unit (steering locked)
→ High-power boost
→ Regeneration
→ Stability under load
→ Helps with hill climbing
Battery:
Ford Lightning battery pack as your primary energy storage
Lexus hybrid battery (1–3 kWh) for HSD system only
Controls:
Keep the HSD completely independent
Use modern VCU for the Tesla or Ford drive units
Shared throttle mapping for all EV motors
Let the HSD contribute torque only when useful
This gives you:
✔ Tremendous combined power
✔ Redundancy (generator + EV)
✔ Large energy storage
✔ AWD or 6×4 behaviour
✔ Robust RV capability
✔ Manageable electronics complexity

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About retaining the Toyota Hybrid as a range extender and RV generator.

You’re absolutely right — if the HSD is kept completely isolated, you lose one of the most valuable capabilities it offers:
acting as a built‑in generator and true range extender for off‑grid RV use.
And that capability is too valuable to throw away.
The good news:
✔ You can keep the systems mechanically/electrically separate for safety and simplicity
while still enabling the HSD to serve as both a generator and a range extender
— if you connect them at the right point, and in the right way.
Here’s the clean, realistic way to do it, without diving into impossible Toyota ECU hacks.

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How to keep the systems “separate but connected”
The trick is this:
You don’t connect the HSD directly to your main EV battery.
You connect it through a DC fast charging interface or an isolation-charged DC bus.
This preserves simplicity and avoids needing Toyota CAN hacks.
There are two proven architectures that the EV-conversion community uses for engine‑based range extenders:

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1. HSD → High-voltage DC → DC fast charge port → Lightning battery
(The simplest, safest, most modular solution)
This turns the Lexus HSD into a CHAdeMO/DC Fast Charge generator, similar to how companies build hybrid generator trucks.
How it works:
1. MG1 generates HV power (typically 200–300 V DC).
2. A custom or off-the-shelf bidirectional DC-DC converter boosts it to ~400–450 V.
3. Output is fed into:
a simulated CHAdeMO/CCS input → Lightning battery pack.
4. The Lightning battery sees it as a fast charger.
What this gives you:
✔ Full HSD generator capability
✔ Off‑grid charging (boondocking!)
✔ Unlimited‑range hybrid RV operation
✔ No Toyota ECU hacking
✔ No need to share traction control or torque signals
✔ Independent drivetrains, but shared energy
Why this is safe:
• The HSD never touches your main traction system directly.
• The Lightning battery handles charge management.
• All high‑voltage domains remain isolated through converters.

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2. HSD → dedicated small HV battery → AC generator inverter → Lightning onboard AC charger
This approach uses AC instead of DC fast charging.
How it works:
1. Let the Lexus HSD operate normally with its own small hybrid pack.
2. MG1 or the engine spins an AC power generator (3,000–8,000 W or more).
3. That AC feeds the Lightning’s onboard AC charger.
4. Lightning battery charges as if plugged into shore power.
Pros:
✔ Ultra-simple
✔ Zero ECU integration
✔ Works with stock Lightning charger
✔ Perfect for RV boondocking
Cons:
• Limited by onboard charger speed
• Not good for “charging while driving” hybrid mode
• Lower efficiency
This is more of a camp generator approach, not a range extender while driving.

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3. HSD directly charging a secondary HV buffer pack that then charges the Lightning pack
(Used in some PHEV conversions)
This is a compromise architecture:
1. Keep the Toyota hybrid battery (1–4 kWh).
2. Add a larger intermediate HV battery (20–40 kWh).
3. Use a DC-DC link between the intermediate pack and the Lightning battery.
Pros:
✔ Allows continuous HSD power contribution
✔ Spreads loads
✔ Acts like a series hybrid generator
✔ Still keeps the main EV system clean
Cons:
• More components
• More weight
• Extra battery management overhead

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Recommended Architecture for YOUR RV Build
Based on everything you’ve described so far, the best balance between:
• safety
• simplicity
• modularity
• boondocking utility
• range extension
• keeping Toyota HSD happy
• maintaining independent drivetrains
is this:

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Best Choice: HSD → DC fast charge injection → Lightning battery
Front: RX450h HSD operates normally
Rear: Tesla/Mach‑E/Lightning motor as primary drive
Battery: Lightning pack
Charging: HSD feeds DC power into the Lightning pack via isolated DC‑DC → CCS/CHAdeMO injector
Control: Throttle remains independent; only energy flows are shared

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What this gives you in practice
1. Boondocking power: unlimited AC/DC
Better than any gas generator
Built-in automotive-grade hybrid generator
Low noise
Great fuel efficiency
2. Real range extender
Drive indefinitely by letting the HSD top up the Lightning pack
Great for remote RV travel
3. High reliability
Systems remain separate
No complex CAN integration
Both systems can operate if the other fails
4. Simpler troubleshooting
Engine/generator side behaves like a self-contained hybrid
EV side behaves like a standard converted EV
They meet only at the DC charging interface

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A key insight
You do not need the HSD to communicate with the EV drive system
—you only need it to communicate with the battery.
That’s how you preserve the most valuable property of your hybrid system without technical nightmares.

This is a big engineering project to get everything working together and synchronised at the wheels. The best approach would be to get the EV side of things sorted first, then later add a range extender and finally if really needed add the AWD components in my opinion.
No one else on this forum has built something like this so far, there have been a couple of range extender projects though.
I look forward to seeing your progress.