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Planning Land Rover Defender 90

29125 Views 47 Replies 9 Participants Last post by  Kjnevin
Hello all...110% new to the forum and EV cars in general. SO much good stuff to read on here!

Ive had a lot of experience building several IC cars, but want to dive in head first with an EV conversion. In general my mechanical skill level is good, my electrical level not so much (insert mechanical vs electrical engineer jokes here). I'm considering two options, keeping the standard gearbox or getting rid of it and mating the motor directly to the transfer case.

Ive selected a Defender 90 as a conversion vehicle for a few reasons, the body on frame construction helps a lot in the ease of installation of motor, battery brackets etc. even though aerodynamic and drivetrain efficiency are laughable. A large part of it is practicality from a cargo/hose down point of view.

That being said the range I'm looking for isn't huge. This will be mainly my wife's car to commute 50 miles round trip every day in mixed stop and go and 70 mph traffic. So ideally 100 mile range (excuse my ignorance if this is wildly unrealistic).

Performance wise anything that is an improvement on the standard 122 hp (91 kW) / 221 lb⋅ft (300 N⋅m) diesel engine would be welcome.

This is where things get sticky. I haven't selected any components yet, but have read several of the Wiki articles. The 4 steps in sizing a battery seem to me to be excellent if working with a lot of known variables. But...since the existing diesel power of the vehicle is already known, and this takes the vehicle to top speed and gives a certain acceleration, can this not be used as a basis and work backwards from there to reach a needed battery power and energy?

Naturally at a steady cruise speed not all of the diesels 91kW are being used, only a fraction of that. So if anything, in my mind choosing a 91kW motor would give increased performance, albeit a battery to go with it would be unnecessarily large for 100 miles of range. Or just plain not fit in the available packaging space of a Defender 90.

In the end is that a good starting point or not even close?
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I think I have read somewhere that for Range Rover electric they have used electric steering pump from new Mini One which also adjusts the assistance based on car’s speed.
Although a simple pump with no variable assistance would make things easier perhaps.
Any recent steering pump should be able to change pressure to vary assistance. The challenge is telling it what to do, which is usually a CAN communication.

It looks like control the unit in the first BMW Mini might be unusually simple, according to this discussion from a BMW forum:
Mini Electric Power Steering Pump...
That discussion is somewhat questionable, because it states that there is no control logic needed, but includes a document showing that the pump's output pressure varies with steering action. It also mentions response to steering action, but not road speed.

Another article suggests only a simple low/high assist logic, based solely on steering activity:
The electric pump has circuitry which is used to control or "modulate" the power drawn from the car's electrical system as well as control the hydraulic fluid flow according to the steering system demand. This allows the motor to run slower (and draw less power) when there is little or no need for assistance, such as when driving on straight roads or idling in traffic. When the driver turns the steering wheel, the control circuitry built into the pump's motor increases current flow to the motor, making it spin faster and subsequently moving more hydraulic oil through the steering rack at a higher pressure. Sharp turns and tight maneuvering such as city driving, parking and autocross events keep the motor/pump running in an elevated power state. Once the road straightens out, the system returns to a reduced power state to cool off, save power and increase component life.
I also wonder about the motor for this pump - from various Mini forum discussions it appears to be a brushed (presumably PM DC) design, which has wear problems. Surely this thing which runs all the time should be brushless, right?

The whole early BMW Mini setup looks a generation out date in technology to me... but maybe that suits a Defender. ;)
 

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Discussion Starter · #42 ·
Right, and that's my point...I'm not going to get involved with CAN signals to vary pump assistance etc etc...this has to be a conversion with as few variables as possible, and the ones that are inevitable have to be as simple as possible as well.

In any case...I think there's several options for power steering. First things first, motor and battery selection.
 

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Discussion Starter · #43 ·
So battery wise I think I will go down the Leaf route. Theyre available, have all the hardware to connect them, and are not too expensive. I need to check the volume where Ill put them (fuel tank position, and on top of the motor, maybe even along driveshaft). If there is enough space I will try to go with the initial calculation of 100 modules.

The motor I need to select. Im leaning towards connecting it directly to the transfer case though and getting rid of the gear box.
 

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Just spotted aftermarket Electric power steering , page 27 Spring issue LRO Magazine. suits early RRC , 90 & 110 , goes inline in the steering column.
Many of these systems use the Vauxhall Corsa (GM) power steering assembly... I have one for my conversion and hope to eventually have it integrated into the open source inverter software :cool:
 

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Many of these systems use the Vauxhall Corsa (GM) power steering assembly...
Good tip! :) That certainly looks like the same hardware.

For those in North America, the Opel/Vauxhall Corsa has never been sold here under any name. Perhaps the same powered column appears in another model? In any case, lots of cars (including GMs) have electrically powered columns here, and have for many years, even if not exactly the same unit.

For example, EV West offers an Electric Power Steering Unit for Electric Vehicles, which appears to be based on a GM unit (but not the one from the Corsa), and they provide quite a bit of information linked to that page about how it works.
 
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