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Thalass 05-27-2015 01:13 PM

Conversion advice sought.
 
Hey folks. I used to hang around here a few years ago, but life (mortgage and kids, mostly) got in the way and I kinda fell away from the EV scene.

Now things are looking up and I want to finally convert something! Unfortunately it seems my go-to spreadsheets and forum posts have vanished from the internet - and I've forgotten the general rules-of-thumb.


I would like to convert something like a Subaru SVX, and while something like that demands a performance conversion I just want to get on the road. At least to start with. Upgrades are possible in the future!


The SVX has a CoD of 0.29, though my daily commute won't be fast enough for that to be a factor. I'm assuming 300Wh/km. My commute will be a tiny 10km each way, with a decent hill to climb on the way there but coasting downhill on the way home. I bodged up a spreadsheet which informs me that a range of 25km will require a 6kWh pack, 41.6Ah per cell with pack voltage of 144 (80%DoD). LiFePO4, of course. I think the most important thing is keeping up with traffic, for now. In the future I could buy another pack for longer range - ultimately my inlaws live about 150km away, and this is the furtherest I should ever have to go.

I still prefer AC motors on principle, but man they are still expensive! For the initial conversion I'm willing to go with DC, and I would rather like to build a P&S controller myself. I guess I figure if I spread the cost over many years of tinkering my wife won't notice how much I've spent on what should eventually end up as an electric sports car :P


Anyway, have I forgotten anything? Am I being too optimistic? 45 CALB 400Ah cells should cost $2430 before shippping (probably US$, too). By comparison 45 260Ah Voltronix cells would give me enough range to get to my inlaws' house but would cost $15210!

Thanks!

thingstodo 05-28-2015 12:08 PM

Quote:

Originally Posted by Thalass (Post 481174)
Unfortunately it seems my go-to spreadsheets and forum posts have vanished from the internet - and I've forgotten the general rules-of-thumb.

It happens!

Quote:

has a CoD of 0.29, though my daily commute won't be fast enough for that to be a factor. I'm assuming 300Wh/km. My commute will be a tiny 10km each way, with a decent hill to climb on the way there but coasting downhill on the way home. I bodged up a spreadsheet which informs me that a range of 25km will require a 6kWh pack, 41.6Ah per cell with pack voltage of 144 (80%DoD). LiFePO4, of course. I think the most important thing is keeping up with traffic, for now. In the future I could buy another pack for longer range - ultimately my inlaws live about 150km away, and this is the furtherest I should ever have to go.
This calculator is dated, but the info still appears to apply. No new batteries are listed and the range is pessimistic with lithiums ... but besides that ..

EV Calculator

If you stay with a standard transmission, you can still cycle through the gears and keep up with traffic, even if your vehicle is a bit under powered.

I don't think you need to sacrifice power, unless you find a good deal on the motor or controller.

Quote:

I still prefer AC motors on principle, but man they are still expensive!
If you are willing to wait for me to finish testing Paul's AC controller, that may be a lower-cost option for you.

Quote:

For the initial conversion I'm willing to go with DC, and I would rather like to build a P&S controller myself. I guess I figure if I spread the cost over many years of tinkering my wife won't notice how much I've spent on what should eventually end up as an electric sports car :P
I'm not associated with EVTV, but I like their prices on this stuff:
- 100 A-h CALB SE - $95 each seems like a good deal to me, but they are no-warranty and a few years old stock EVTV Motor Verks Store: CALB SE100AHA 100Ah LiFePo4 Cell, Lithium Battery Cells, SE100AHA
- Siemens motor $3500 EVTV Motor Verks Store: 1 Siemens 1PV5135-4WS14 AC Induction Motor, Motors and Controllers, 1PV5135
- Siemens motor adapter $1000 EVTV Motor Verks Store: Siemens B-Face Adapter, Drive Train Components, bfaceadapter

It's the least expensive AC option I've found so far ...

Quote:

Anyway, have I forgotten anything? Am I being too optimistic? 45 CALB 400Ah cells should cost $2430 before shippping (probably US$, too). By comparison 45 260Ah Voltronix cells would give me enough range to get to my inlaws' house but would cost $15210!
You likely know this already, but you did not mention:
- DC/DC converter or 12V pack of LiFePO4 to run accessories
- heater to keep the windshield clear when it's raining. Water heat to use the existing controls in the car or PTC heater cores installed in the ducts to run direct off the pack
- charger is normally expensive
- do you need a power steering pump or a vacuum pump for the brakes?
- fuses and fuse holders are expensive
- you did not mention instrumentation for the pack, voltage and current, maybe amp-hours, perhaps temperature?

Frank Lee 05-28-2015 05:13 PM

All your posts from here are still here.

Thalass 05-28-2015 08:55 PM

Quote:

Originally Posted by thingstodo (Post 481318)
It happens!



This calculator is dated, but the info still appears to apply. No new batteries are listed and the range is pessimistic with lithiums ... but besides that ..

EV Calculator

If you stay with a standard transmission, you can still cycle through the gears and keep up with traffic, even if your vehicle is a bit under powered.

I don't think you need to sacrifice power, unless you find a good deal on the motor or controller.

With an unlimited budge (dreaming) I'd go dual motor direct drive, but... Yeah nothing wrong with keeping the gearbox. Subaru's tend to have many interchangeable parts so even if the donor car is an automatic I could probably find a manual box to fit. Assuming this applies to the SVX.

Quote:



If you are willing to wait for me to finish testing Paul's AC controller, that may be a lower-cost option for you.

I'm fine with that! It'll be months before I can actually start pulling a car apart anyway. I'm pretty good with a soldering iron, even if I'm deficient in the design side of things. I can certainly follow instructions haha.

Quote:


I'm not associated with EVTV, but I like their prices on this stuff:
- 100 A-h CALB SE - $95 each seems like a good deal to me, but they are no-warranty and a few years old stock EVTV Motor Verks Store: CALB SE100AHA 100Ah LiFePo4 Cell, Lithium Battery Cells, SE100AHA
- Siemens motor $3500 EVTV Motor Verks Store: 1 Siemens 1PV5135-4WS14 AC Induction Motor, Motors and Controllers, 1PV5135
- Siemens motor adapter $1000 EVTV Motor Verks Store: Siemens B-Face Adapter, Drive Train Components, bfaceadapter

It's the least expensive AC option I've found so far ...
Those are good battery prices (Oh and that was supposed to be a 40Ah cell price up there, not 400.

Quote:


You likely know this already, but you did not mention:
- DC/DC converter or 12V pack of LiFePO4 to run accessories
- heater to keep the windshield clear when it's raining. Water heat to use the existing controls in the car or PTC heater cores installed in the ducts to run direct off the pack
- charger is normally expensive
- do you need a power steering pump or a vacuum pump for the brakes?
- fuses and fuse holders are expensive
- you did not mention instrumentation for the pack, voltage and current, maybe amp-hours, perhaps temperature?
I actually had forgotten about those things, other than the dc-dc converter. That's kind of embarrassing. As for indication: I was going to hijack the tacho to indicate current draw, and use one of these to drive the old petrol gauge. Failing that: Full instrument replacement with Tesla style LCD screens... I think I'm daydreaming again.

Quote:

Originally Posted by Frank Lee (Post 481363)
All your posts from here are still here.

Woot! I won't look, I was probably saying stupid things. haha


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