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Discussion Starter #1 (Edited)
BMW Isetta conversion - components

Hi,

I have an old BMw Isetta (355kg with 11hp).

Can you help me to define the components needed for a 30miles dayride with max. 40 mi/h?

thanks for your help
 

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I would say the best bang for your buck with something that weight and speed would be a mars 1003 and an alltrax 7245 controller or 7234 (a bit slower)

Batteries are a huge question mark, how tight a budget are you under?
 

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Discussion Starter #3 (Edited)
I would say the best bang for your buck with something that weight and speed would be a mars 1003 and an alltrax 7245 controller or 7234 (a bit slower)

Batteries are a huge question mark, how tight a budget are you under?


I think 2000 to 2500$ are OK for batteries. Big problem is the max. axle-load so battery weight should be under 70kg (if engine is max. 15kg).

thanks
Martin
 

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Hi,

I have an old BMw Isetta (355kg with 11hp).

Can you help me to define the components needed for a 30miles dayride with max. 40 mi/h?

thanks for your help
A Mars would be good for you. Please do a little research and find a motor with more or less the same torque (or less than two times) for the tiny engine. Otherwise your tranny would be damaged soon.

Or... go direct drive. Two scooter hub motors would fit perfect for you. Kelly have some kits including almost everything you need. And lithiums is a must for you. Is not a huge pack, so, not so expensive, but it has to be as light as possible, due to the car.

Have a look: http://kellycontroller.com/dual-keb-72v-8kw-regen-kit-p-360.html

Greetings from Spain,

Luis
 

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Thats going to be a toughie to get in under 2500 just for the components and battery:

http://cgi.ebay.com/EMC-RT-72v-Electric-Motor-Drive-Kit-EV-Vehicle-ME0709-/250658677267?pt=LH_DefaultDomain_0&hash=item3a5c6be213#ht_2757wt_1091

Thats most of the drive system,

If you go Lifepo4, the batts would cost that alone. Lead would be a lot cheaper in the short term.

for the amp draw, id say to stick with at least 90ah in thundersky type batteries, your range would be a bit more then your looking for, never a bad thing :)

If you wanted to save just a few bucks you might could go with less of a more expensive battery, the headway 10ah. if you did 50ah total x 72v you would be ok for your range, I believe
 

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Thats going to be a toughie to get in under 2500 just for the components and battery...
He said $2,000 - $2,500 for the batteries only.

Anyhow...if you went with 40 ah CALB lithiums, you'd need 21 to reach 72 volts. That's under $1,200 and about 69.5 lbs. I think that's about 6 kilowatt-hours. (I would check all my figures as I am pretty noobie about all this)

Range is very speed dependent so those more knowledgeable might chime in on whether more would be needed.
 

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they handle weight better then one would think , we had one with me on the shelf , mom dad and sister in the seat ( I was 10 ) . It has a chain drive to a 1 piece axle ( no diff on it ) would be easy for direct drive . should make a great ev .
 

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Discussion Starter #8 (Edited)
I will get "my" Isetta (reversed trike, I have the three wheel version) on friday this week. I have seen it before with some rust on the body (some holes), and some missing parts (i can get without problems). BUT also the engine is missing so my idea was to convert this little car to an EV (without destroying the car: some modification on the floor-plate for the batteries is OK).

I am an electrican and also welding is no problem for me so I think I can do the restauration job alone. But i need help with the electronics and I also do not know if I will need the transmission (gearbox) in my little car )or direct drive with e-motor?).

I will go to my local car test-center to inform me about laws and regulations (voltage level and EMV testing, ...) here in Austria. I am sure there is some knowledge about this topic in this forum.

I want to check if there is a reasonable way to convert my Isetta to an EV (and of course there is also a limited budget an appr. 3600$ overall).
I post some photos when my Isetta arrives and I will start with the restauration job.


I have to thank you in advance for your help.

best regards from Austria
Martin
 

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Discussion Starter #9 (Edited)
Hi,

I started with restoration now. Quite lot to do (cleaning frame, many parts to rebuild , ..).

I also want to start to think about the components in detail:

Targets:
- budget: max. 4000 USD
- range: min. 35 miles
- speed: min. 45 mi(h
- add. weight: 110kg (motor, batt., contr.)

tech. data Isetta 300 export(3-wheeler):
please see attached table (sorry it is in german)

I have attached also some photos ...
Also one photo I found from conversion.

My big questions:
- do I need the original transmission (is it easier to finish the conversion with transmission)?
- if no transmission needed, what about gearreduction in chain case (now 2,3:1)?
- components: I live in Europe (favor to parts I can buy here)
- motor: Perm PM120l or Lynch (Agni 95s) or...??
- controller ??
- batterie: biggest question: Li Batteries for sure but ??? Voltage, Ah ???


thanks for your help
best regards
Martin
 

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My Kirk EV aka. Sparky weighs 330Kg including 125Kg of LA @72V. I use a Mars 0709 but need to keep the max amps down to 210 to prevent it burning the brushes. I have an Alltrax 7234 so controlling things is easy. Your weight would be too much for my motor, I think by the time you had fitted batteries but if you talk to John Fiorenza at Mars he is very helpful. My performance meanwhile is 56 mph! Acceleration is slow off the mark, especially up hill, but OK above walking pace.Range wise I think you would struggle to acheive your target for long term use with FLA. You just won't be able to pack in enough lead, particularly as you have a smallish weight limit.
Of course I could sacrifice top speed for better acceleration, myself, but the range would still be an issue. When I first put it on the road last summer I could get >25 miles, but at too great a cost to mt FLA pack.
Lithium or NiMh? Vectrix seem to do OK with NiMh but I think that the trick is a very good BMS in that case.
Incidently, I use a direct drive-no transmission. It save weight, money, complexity and space. Your greater weight should still be OK without transmission because you speed requirement isn't so high.

Andrew
 

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If I were in your position I would look on the Electric Motorsport website. They have details of the EMC-RT200 motor from Mars. It is capable of 200Amps continuous which would be plenty for your conversion. The best news is that the cost is only $650. Electric Motorsport can supply a kit with controller, wiring, contactor, charger DC-DC converter, fuses etc.
I'm sure that you could source the parts cheaper, but I got everything except the battery side of things from them so that it all came as one package. It is easier to import this way. You only need to pay one payment for import duty. This part is not difficult at all, so please don't feel that you need to buy from a European based supplier.
There are other US based companies who could supply a similar package, so it may be worth looking around on the internet.
EMS now supply Lithium batteries also, which they did not yet have 2 years ago when I was buying, so you could always Email them or even phone them with your requirements.
I would imagine that you are going to need about 200Wh/mile of energy. That means you will need about 10KWh of battery to have a maximum theoretical range of 50 miles. Of course you would only ever use 80% max. of this storage. Still you might be able to do 40 miles.
I am not thinking of upgrading to Litium but if I was I would be prepared to invest a lot in a BMS to protect my investment in batteries. (The thread on this subject in the batteries section is one of the hottest topics of debate!)
$4000 may be a liitle tight to get everything you need.

I think I said above that I would be happy to use direct drive because of your low speed requirement. Transmissions are heavy. I use a 530 motorcycle chain with sengine sprocket from EMS (12 tooth) and a specially made wheel sprocket (46 tooth) for my 24 inch Kawasaki rear wheel. The EMS website will tell you how many rpm per volt you will get. I calculated 60mph @ 72V. This figure was avery good guess, since a full throttle I get voltage drop., hence only 56mph.


My lighter trike uses about 140Wh/mile unless you go very slowly. That is a figure based on experience, not conjecture, so I hope it is helpful.

Keep us informed about your project. I love reverse trike and think your Isetta is a very good choice for conversion. A Mescerschmitt (think my spelling is wrong!) might be even better because you have the rear seat area as an ideal battery compartment, though you would maybe need a ventilated battery box in there.

Andrew.
 

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Here's one fairly simple setup.

Since your max speed is only 40 mph I would estimate energy consumption at 120 Wh/mile. (That's 1.5 times the energy consumption of my motorbike if I average 25 mph).

To get a 30 mile range that means your total energy requirement is 3.6 kWh. To give a decent safety margin I would round that up to 5 kWh.

The simplest setup would be 16 x 100 Ah CALB or Thundersky lithium cells for a total pack voltage of just over 50V and weight of 50 kg.

Combine this with an Agni 95 motor and Alltrax 7245 controller. Both are reliable and relatively easy to install.

I don't know the diameter of the rear wheels, but as a rough guess you would need a gear ratio of around 6:1. It doesn't look as if that can be achieved in a single stage using the existing chain case (not enough room for the large sprocket). You may need to do a two-stage chain reduction. You already have the final stage, so you just need to fit a sprocket to the existing input on the chain case and drive this with the Agni (chain drive) to give a first stage reduction of about 3:1.

Total additional weight would be around 70 kg, less the weight of the original engine.

This is the simplest/lightest setup I can see. For higher top speed and better acceleration close to your top speed it would be worth considering higher voltage: 60 to 80V. However this would mean increased battery weight/complexity. You could still use the same motor and controller though.

There's a useful section in the FAQ on the Agni site, under the heading "Is the motor suitable for my vehicle?": http://www.agnimotors.com/home/index.php?option=com_content&task=view&id=31&Itemid=67
 

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MalcolmB,
I disagree with your energy requirement estmate. If a builder underestimates the energy consumption, they will end up with a White Elephant, that is something which cost a lot but does not acheive their goals. My trike needs 140Wh/mile to acheive the performance goals, yet it's frontal area is rather less. (Who knows about drag coefficient?). With my lower weight I would therefore stand by my 200Wh/mile estimate.
I agree with your choice of controller but I would not spend the extra money required for an Agni motor or a Lynch. I would definately go for a Mars for $650.
 

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Hi Duxuk,
My figure does appear low, but it was partly based on the fuel consumption of the original Isetta, which was over 80 mpg.

Even though your trike has a smaller frontal area, I'd be willing to bet that the CdA of the bubblecar is lower than your trike's, since it has a much more slippery shape. I also added a healthy safety margin to my initial energy figure. 200 Wh/mile is what I would expect for an efficient small car (Mini/Fiat 126 etc) conversion at maximum speed of 40 mph.

I definitely don't want to give anyone an over-optimistic picture, but likewise feel it's important not to be over-cautious as that could discourage someone totally.

Malcolm
 

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Discussion Starter #17 (Edited)
Hi,
Targets:
- budget: max. 4000 USD
- range: min. 35 miles
- speed: min. 45 mi(h
- add. weight: 110kg (motor, batt., contr.)

I have attached also some photos ...
Also one photo I found from conversion.

My big questions:
- do I need the original transmission (is it easier to finish the conversion with transmission)?
- if no transmission needed, what about gearreduction in chain case (now 2,3:1)?
- components: I live in Europe (favor to parts I can buy here)
- motor: Perm PM120l or Lynch (Agni 95s) or...??
- controller ??
- batterie: biggest question: Li Batteries for sure but ??? Voltage, Ah ???
Isetta should take extra load (2 persons) of 160kg (350lbs)
- range: minimum 35 miles
- speed: minimum 45 mph

see below technical specification of Isetta 300 (also drag coefficient):

thanks for your setup suggestions
 

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OK, so you changed your original requirements Martin. In that case energy requirements will naturally be higher, somewhere between my estimate and that of Duxuk.
 

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Discussion Starter #19 (Edited)
OK, so you changed your original requirements Martin. In that case energy requirements will naturally be higher, somewhere between my estimate and that of Duxuk.
Hi MalcomB,

yes your right the numbers are different from 1st posting (because of my conversion error).

you wrote:
You already have the final stage, so you just need to fit a sprocket to the existing input on the chain case and drive this with the Agni (chain drive) to give a first stage reduction of about 3:1.

please, can you give me some more details to understand this?

What do you think now for the final suggestion for components?

THANKS al lot for your Help (and for your patience)!!!!
 

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Sorry Duxuk, I didn't notice that the desired range and speed had gone up. My figures were based on the original 30 miles and max 40 mph. Increasing those to a minimum of 35 miles and minimum 45 mph makes a considerable difference. The energy consumption is likely to be somewhere between 150 and your figure of 200 Wh/mile, depending on the passenger load.

Martin
This can certainly be done but it's likely to be more expensive than you hoped. The solution I've given here is the minimum you're likely to need to meet your goals. If you want a greater safety margin you should consider going to larger cells (130 Ah).

You can still use the same motor and controller. The cheapest and simplest battery solution is still to use the Thundersky/CALB 100 Ah. You can use up to 26 cells and still stay within the voltage range of the Alltrax 7245 (90V). I would buy 26 cells but just fit 24 in the Isetta (if you can find space). Keep the remaining two cells as spares or to add to the pack in case your range is not quite sufficient.

It's hard to see details from your photos, but it looks to me as if there is a rubber coupling between the engine and the chaincase/swingarm. Is it possible to remove the engine, drive shaft and rubber coupling, then mount a chain sprocket in place of the rubber coupling? You could then mount the motor a short distance away, with a chain drive to this new sprocket.
 
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