Newby advice wanted please

Conversion Kits
1

Hello All,
I’m After a little advice please. I’m from the UK and looking to convert a 1995 Skoda Favorit to electric power. Those of you in the US won’t be familiar with this car, but think of a mk2 golf/rabbit and your not far off.

I chose the car as it has a low starting weight of only 895kgs and no mod cons such as power steering/windows/airbags etc, and because I got a 19K miles from new one in mint condition for almost nothing! :slight_smile:

Anyway, this is what I need it to do for the project to be feasible:

  • Top speed of near to 80mph
  • Constant cruising ability at 60mph minimum, (ideally 70mph)
  • Minimum range of around 100miles (at said 60mph)

So this is what I’m thinking so far, an AC system using 144v from 12 approx.75ah lead acid gel type, heavy duty deep discharge batteries, like Exide Maxxima 900DC or Optima Yellow Tops or similar.

I reckon I should get 4 upfront with the motor and control gear, other 8 either under the rear seat and or modified spare wheel area, I’m hoping that allowing for the new kit weight, less the removed engine and component weight, to end up at no more than around 1200kgs.

So what do you all think, can I do this, or am I being far too optimistic on range & speed? My budget is quite flexible, can probably run to around 12K to 13K dollars if need be.

My only concern is that electric cars are here in UK already, commercially built, but they are all very small (and frankly hideously ugly!) and only seem to have a range of about 40 miles and a top speed of 40mph, so how come the professionals can only get this limited ability?:eek:

Any ideas on motor/controller/charger/DC to DC charger/ brake vacuum/guages etc. appreciated also, will be keeping the standard 5 speed manual tranny and clutch and getting custom adapter plate/mounting made up.

Thats all assuming you don’t all tell me I’ll top out at 30 mile range! :frowning:

Regards

Paul

2

well, 144V at 75Ah is 10800 Watt hours. you won’t be able to get 12 75Ah batteries to weigh in under 300kgs/660lbs. Thats a bit of lead. If you use the Exide Maxxima 900DC, they’re just under 50lbs for a total of 600lbs, but only 50Ah.

If you needed 100miles, you would need to take 10800/100 miles and thats Wh/Mile. You’d need to build a vehicle that can cruise at 108 watt hours/mile. Most motorcycles can’t even get that low, so you just won’t get that sort of distance… period. Its not lithium or lead acid issue, its watt hours. You’d need something more along the lines of 150Ah to get that distance, and still, you’d have to cruise at less than 250 Wh/mile.

Now, as far as AC goes, there’s not too many options that aren’t already more expensive than your budget, and thats with no batteries.

Why does it have to be AC? Why 144V? why 100 Miles? You can’t have all 3 and want to run a small car on it.

If you doubled the battery capacity, and got some larger batteries, and went with a series wound motor and a 144V controller (like synkromotive, curtis, zilla or kelly), you could get some pretty good distances, but the thing is, will your car handle 12 12V 150Ah batteries in it? Thats alot of lead.

If you went with 120V lithium, 40 cells, 200Ah a piece, and even at 400 bucks, that’d still work out to be around 16,000 USD. If you did that, that’d be a 24.4kWh pack, and could get you the distance you wanted… but thats not even taking into consideration your budget, or the fact that you still don’t have a controller/motor.

Might back it down to 50Miles, 144V, series motor, controller and use lead, you should be able to do it under 14 or 15 grand. Consider, you still need a charger, some sort of monitoring, maybe balancing, contactors, DC-DC converter and cabling.

3

Thanks for the feedback so far, since posting I have read up further on the subject and realise 100 miles is gonna be hard to acheive :frowning:

I was thinking AC at 144v as it seemed more efficient, but it doesn’t have to be either, I’m happy to go with whatever works best.

If I can get about 60 miles or so per charge using bigger batteries, that will still be OK, but anything under that, it’s just not practical enough, I’m already doing it for love as financially it won’t save me enough to break even for decades compared to my current car I built that runs on Autogas (Propane), assuming I could build it for 13K, which by the looks of it I can’t, plus at least another 3K every 3 years or so on new batteries (like everything else, they cost more over here!:mad:)

I chose this car as although quite lightweight, it is strongly built, I intend to shed as much weight as possible prior to the new kit going in, and will get uprated springs for it. The GVW is 1380kg, so allowing about 160kg for 2 passengers, I can top out weight wise at a max of just over 1200kg, so I’ve only got about 300kg net increase to play with, I’m assuming (dangerous I know!) that the motor and kit excluding batteries will roughly equal the ICE kit weight removed, leaving the 300kg for batts. but I’m still a bit green so please correct me if I’m miles out!

4

STOP PRESS!! I have found a potentially much better battery solution that should allow me to get nearer to the range I’m after without weighing 5 tons!!:

“Elecsol Carbon Fibre Deep Cycle Battery -110Ah, (LxWxH): 353 x 175 x 190
Weight: 25.2kg.
Cycle life: 1000 cycles to 80%dod.
Guarantee: full 5 year, maintenance free”

or…

“100Ah, (LxWxH): 278 x 175 x 190 mm.
Weight: 19.5kg.
Cycle life: 1000 cycles to 80%dod.
Guarantee: full 5 year, maintenance free”

These seem pretty cost effective at around a £113/£104 each. (about 200/210 dollars) And total weight for 12 @ 110Ah comes in at 302.4kg or maybe 14 @ 100ah at only 273kg! Assuming 3 to 4 cycles a week they should really last 5 years.

Or, space permitting, they have a smaller 70Ah version, (LxWxH): 242 x 175 x 175 mm. It only weighs in at 16kg, each so could possibly run 20 @ 320kg total with banks of 2’s in parallel, to give a total of 140Ah at 120 volts, OK so top speed will be a little lower, but range would be great, yes??

I would very much appreciate your thoughts and recommendations for a kit based on the abopve power source

Wow this is getting addictive! I think I need to read up more…

5

look around for parts on these sites to get an idea:
http://www.electroauto.com/
http://www.electricvehiclesusa.com/
http://www.evparts.com/
http://www.evtradinpost.com/
http://www.grassrootsev.com/
http://www.kta-ev.com/
http://www.cloudelectric.com/
http://www.electricmotorsport.com/

you’ll need (at the least):
Motor
Controller
Main Contactor
Forward/Reverse contactor (if you go series wound/sepex)
Throttle box
144 (or 120V) charger, or 12-14 individual 12V chargers (balances better)
144 (or 120V) to 12V DC-DC converter to run the 12V system/contactors
Some sort of monitoring (volts, amps, state of charge)
vaccuum pump for the brake system (some cars may not use this)
emergency disconnect (optional, but recomended)
cables, battery post connectors
large fuse and fuseholder

6

Frodus,
Thanks so much for all your help so far, I have contacted EVAmerica who have so far sent me a huge amount of useful initial technical advice.

I’ve now measured up properly and established I can house a total of 12 larger 12v batteries in the car, so I’m using a 125Ah version of the Elecsol carbon fibre one.

I’ve also decided on a DC system, without clutch, to save on cost and keep it a little simpler, the penny finally dropped when I thought about it and realised a DC elecric motor shaft runs freely when unpowered, effectively meaning you can change gears as smoothly as with an ICE car with the clutch down!!

So to summarise my thoughts so far:

144v DC system, running 30HP series motor, original transmission and clutchless, 12x12v 125Ah batteries.

Thats it for now

Regards

Paul

7

OK to update you all…

Elecsol batteries appear to be no good! as ever if it seems to cheap to be true it usually is… (see battery thread if you’re interested in why)

I also realised I’m never gonna get near the range I want using 125Ah 12v batts!!, so the new plan (and I think they’ll just all fit in!) is to use 16 8v Trojan T890’s at 190Ah each, (8 in the rear, 8 under the hood) giving a system voltage of 128v. This should give me the KWh pack range I need to get reliably over a consistent 60 mile range if I use an efficient motor and controller, your thoughts on this would be appreciated.

Regards

Paul

8

Seems like you’d get around 25kWh…and if you keep the rolling resistance low, then you should be able to get that 60miles.

Only one thing, what is the weight of each bat, and all bats combined? and what is that going to do to the car’s handling/suspension? Thats a LOT of lead. Adding weight increases drag.

As far as controllers, you could use a Zilla, or a 144V Curtis. Not sure about kelly (not proven, but also low current). I’ve heard about logisystems 156V, but also, 1500+ dollars. I know the company I’m working with, synkromotive, will be coming out with a 156V 600A controller that would work very well, and has tons of options and will integrate nicely.

9

Well it will be right on the GVW or possibly a little over when finished, but I plan to uprate the springs all round to keep ride height and handling reasonable. The batts. are 31kg each, so total of 496kg plus weight of motor and kit, @150kg?, I’ll expect to lose around 200kg from the original ICE kit removal and maybe some additional weight reduction.

I’m basing my logic on there bieng a lot of VW rabbits with around this weight of batteries or even more getting around 60 miles range with good kit, and the Skoda is almost exactly the same kerb and GWV as the VW to start with with slightly more effective front styling for CD factor.