[Pav]

Hi all,


I'm thinking of converting my 1960 Isetta into an EV. For background, I'm located in the UK and the Isetta is a 300 3-wheel version.




Basic requirements would be:


55mph max
50 miles range @ 50mph - fag packet calculation @ 160Wh/m and 80% SoC range would put it at ~10kwh battery requirement?


The car weighs about 300kg dry as is, and the original engine put out 13hp at 5,200 rpm max. I can lose about 60kg by removing the engine, fuel tank and the counterbalance weight.




I was thinking as an easy first "dive" into EV conversion to get a Reva GWiz (AC version), and transplant all the bits into the Isetta, mating the Reva motor to the Isetta gearbox.


I'd consider getting Tesla or Leaf module batteries to get 10kwh to replace the lead acids if the proof of concept works...






Some questions to you gurus:


1) Does this sound like a credible plan?


2) Does anybody have the specs or dimensions of the Reva AC motor and controller?


3) I've found Curtis 1238 controllers (@48v 400A) for relatively cheap around here - out of forklifts I believe - but am I right in understanding they can only be used with DC motors?


4) If the Reva one-donor idea isn't great, what would be an alternative within a similar price bracket? I'm conscious that I could probably pick up a whole running car for £1,000...


5) Regarding batteries, would I need 4 tesla modules to get 10kwh @ 48V? If so, it would be cheaper for me to get a full 20kwh Leaf battery pack...




Thanks all!

 

[brian_]

3) I've found Curtis 1238 controllers (@48v 400A) for relatively cheap around here - out of forklifts I believe - but am I right in understanding they can only be used with DC motors?

A DC controller and an AC controller are very different. While Curtis Instruments makes both DC and AC controllers, and old forklift trucks use DC motors (normally brushed and series-field), the 1238 is part of the Curtis AC controller line; it is specifically for induction (AC) motors, with voltage and current limits as shown in that linked datasheet.

Are you sure that they are 1238 controllers?

 

[brian_]

I really wonder about the viability of some of the conversion plans described in this forum, with people expecting unreasonable performance from low-power motors in large cars, but the Isetta seems like a great target vehicle for a modestly sized drive system, presumably with expectations of modest performance.

For inspiration, in case you haven't already seen it, have a look at the Microlino , which is a new (at pre-production stage) EV inspired by the Isetta, and designed to the limits of the Euro L7e "heavy quadricycle" vehicle category. That's the category of the Reva.

 

[brian_]

... the Isetta is a 300 3-wheel version.
...
I'd consider getting Tesla or Leaf module batteries to get 10kwh to replace the lead acids if the proof of concept works...

With the 3-wheeler, the motor ends up on the suspension arm or ahead of the wheel. If it's ahead of the wheel, it's in the original engine space (on the right), and keeping the volume of space between the seat and wheel from being entirely free for battery modules. The length of a Tesla Model S/X modules fits within the width of the car, but I don't know if you can fit the modules in there with the motor. Leaf modules are physically smaller, so they offer more packing options.

 

[Pav]

Brian, thanks for your replies.

I'm trying to be realistic about expectations - given my day job I know all too well about EV limitations in the real world...


Apologies, I got it wrong now that I've had time to check again, the Curtis controllers I found for cheap are actually 1274 SepEx (?) DC controllers.



Incidentally I had a good poke around the Microlino at a motorshow (Geneva?) a couple years ago, pretty cool little thing.


There's quite a bit of room under the seat for modules, I could definitely get two Tesla ones in, maybe not 4 though, but there's still some space above/below the parcel shelf. Would they need liquid cooling in such an application? I'd rather avoid a coolant circuit if I can!


Any other thoughts on whether to go with a Reva donor or to start piecing things together from scratch? (which I imagine will get a lot more expensive quickly)

Much appreciated

 

[brian_]

Apologies, I got it wrong now that I've had time to check again, the Curtis controllers I found for cheap are actually 1274 SepEx (?) DC controllers.

I can't find the 1274 anywhere in the Curtis product line (current or legacy) - perhaps I just missed it - but online references say that it is for SepEx motors. So it would have a main output for the rotor windings and a separate output for the parallel (or "shunt") field winding... still for brushed DC, but not for motors with the field wired in series with the rotor.

 

[brian_]

There's quite a bit of room under the seat for modules, I could definitely get two Tesla ones in, maybe not 4 though, but there's still some space above/below the parcel shelf. Would they need liquid cooling in such an application? I'd rather avoid a coolant circuit if I can!

In packaging Tesla modules, keep in mind that they need to be supported from the edges (so you need space for structure, and a bit of space between them in any stack) and that they're just in a plastic box, so a metal case is also required (at least in the opinion of many).

Tesla provided a liquid heat transfer system for the cells...

• to cool them when under sustained high demand (which you might not have),
• to heat them when they're too cold to work or charge properly (which you might not encounter depending on how you use the vehicle), and
• to even out the temperature of the many small cells.

Just at a guess, I wouldn't want to run these modules without circulating coolant, if only to ensure that there are not individual cells running at inappropriate temperatures. Even minimal plumbing and a pump might work well, without a radiator or heater. The coolant can be circulated through the controller/inverter (or a plate under it); as Duncan says, you can cool your controller with your battery.

 

[brian_]

Any other thoughts on whether to go with a Reva donor or to start piecing things together from scratch? (which I imagine will get a lot more expensive quickly)

Any set of components salvaged from a decent production vehicle has some advantages:

• the set is probably cheaper than the total of buying individual components;
• the components are matched (such as in power and voltage level) to work together; and,
• the components are configured (programmed) to work together.

On the other hand, some OEM systems are difficult to work with outside of the context of the original vehicle. The REVA is probably quite simple (compared to a modern and more capable EV), so this might not be an issue.

Specifically when mating a salvaged OEM motor to an unrelated transmission, making a coupler work with the shafts can be a challenge. Readily available adapters are for plain shafts of industrial motors, while EV motors typically have a splined shaft to work with a specific transmission. I have not idea what the REVA motor has for mounting or shaft design.