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PV, 120 (Amazon), 1800 General Forum for the Volvo PV, 120 and 1800 cars

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Amazon conversion to Electric

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Old Sep 15th, 2020, 13:10   #11
whitep
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Originally Posted by rangerovering View Post
Do you still need the gearbox? Not just connect direct to the propshaft essentially?
I will use the gearbox to begin with. Then consider options later. I like the idea of gears. My Zoe doesn't have gears. I want to see what its like. So what if it costs more.

To be honest, I don't know how fast a prop shaft would usually spin. So hadnt really considered it.
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Old Sep 15th, 2020, 14:02   #12
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White;

The whole need for a Gearbox comes from needing to keep an internal combustion engine in its quite limited torque range for a given roadspeed...this falls away with an electric motor where high torque is available from 0RPM, and all the way to max RPMs...it all comes down to the motor drive system (typically a variable frequency PWM system, and the most advanced ones have regenerative braking for max efficiency).

I think it's preferred to drive the Driveshaft directly, otherwise shifting would be a major issues (a clutch would be required to decouple the electric engine from drivetrain during shifting), or else...! ...or, it would be put into gear for a high or low speed range before moving, but could never be shifted while moving...

Cheers
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Old Sep 15th, 2020, 20:26   #13
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The regenerative braking makes it more efficient but also more expensive as you have to us AC motors but i imagine a lot of the road going electric cars are using them now...so using one of them is a good idea
But for a very simple set up a DC motor will be fine and cheaper with less wiring too... as always its horses for courses.. but cant wait to follow this project, good luck..
When i was planning mine the batteries became the straw that broke its back... i was only planning on running for about 10 mins all weekend so I could us only 6 batteries....cost over 4000..
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Old Sep 16th, 2020, 10:25   #14
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White;

The whole need for a Gearbox comes from needing to keep an internal combustion engine in its quite limited torque range for a given roadspeed...this falls away with an electric motor where high torque is available from 0RPM, and all the way to max RPMs...it all comes down to the motor drive system (typically a variable frequency PWM system, and the most advanced ones have regenerative braking for max efficiency).

I think it's preferred to drive the Driveshaft directly, otherwise shifting would be a major issues (a clutch would be required to decouple the electric engine from drivetrain during shifting), or else...! ...or, it would be put into gear for a high or low speed range before moving, but could never be shifted while moving...

Cheers
Yes I will be using a clutch too.
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Old Sep 16th, 2020, 10:30   #15
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The regenerative braking makes it more efficient but also more expensive as you have to us AC motors but i imagine a lot of the road going electric cars are using them now...so using one of them is a good idea
But for a very simple set up a DC motor will be fine and cheaper with less wiring too... as always its horses for courses.. but cant wait to follow this project, good luck..
When i was planning mine the batteries became the straw that broke its back... i was only planning on running for about 10 mins all weekend so I could us only 6 batteries....cost over 4000..
Yes, my initial plan was to go down the DC route but the AC motors aren't so expensive anymore and the regen does give a little return. Yes 4000 on the batteries is what I expect to spend. I am picking up second hand parts here and there, I have a brother in the USA who returns in a few months so thats handy... Lots of people doing this over there.

Mine will be a daily driver and I have my Zoe which I will sell which will help cover the expenses.
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Old Sep 16th, 2020, 12:12   #16
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Sounds a good plan, yes the yanks have done a lot with electric cars.
The Tesla motor and diff were not to bad, I was taken by surprise to be honest on the cost of only 6 batteries plus all the control gear, wiring, charger etc etc...
At the time ( Last Year ) I was looking at 18,000 + for 300bhp.. and I would have done all the fitting and wiring as well.. I really loved the idea but could never justify those costs.. ( it was on a race car not my Amazon) as im looking at 350 to 450 BHP for a lot less from a normal turbo engine.
But I'm really looking forward seeing how you get on as the idea did enthral me due to the instant response and torque of the Electric motor, good luck
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Old Sep 28th, 2020, 10:30   #17
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How are things progressing ?
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Old Sep 30th, 2020, 14:43   #18
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How are things progressing ?
I am still waiting for the restoration to finish. I don't think I will get my hands on the car for a couple of months. I doubt it will be finished before Summer next year.

I am scouring the internet often for second hand bits and pieces. I now have a BMS and charger. Also some other bits and pieces like LED headlights etc.

I am talking and planning and biding my time while I wait for the car to turn up.
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Old Sep 30th, 2020, 16:18   #19
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I am still waiting for the restoration to finish. I don't think I will get my hands on the car for a couple of months. I doubt it will be finished before Summer next year.

I am scouring the internet often for second hand bits and pieces. I now have a BMS and charger. Also some other bits and pieces like LED headlights etc.

I am talking and planning and biding my time while I wait for the car to turn up.
Send me a list of what you need, I have a mate who is a principal engineer for one of the big car companies and he's doing a lot of playing about with EV's at the moment and can ask him for you.
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Old Sep 30th, 2020, 17:53   #20
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My first observation would be that grafting the Amazon body on to an existing salvaged electric vehicle platform might be the easier (and long term less expensive) option; but, in re reading the thread I see you explicitly do not want to do that. Fair game! Your car, your choice.

The choice of a series would DC motor drive without regenerative braking would also not be my choice. This is ancient technology that has been in use for a century (electric trolley cars) with the only technology development being high current DC supplies rather than a bunch of switched resistors. Having to deal with brushes does not appeal to me; but, I have not explored the cost difference between AC and DC, so again your decision.

The plan to go forward with a gearbox is the one that I would seriously question. This will depend on the selection of the actual motor and controller; but, unless you grossly undersize the motor (which will kill your top speed) when you look at the torque - speed - voltage relationships of the electric motor I think you will find that you are flying through the 1st and 2nd gears way too fast. I speculate that with a correctly sized electric motor your acceleration times will be slower with a gearbox than without because of the dead time as you shift gears. Be aware that series wound DC motors tend to have a torque curve that is the reverse of a gasoline engine. Very high torque at stall (0 RPM) with the torque dropping off as motor speed picks up - assuming constant voltage. I expect that any electric motor capable of getting the Amazon up past 80 mi/hr will probably shred an M40 transmission in first gear if you apply full throttle.

Do a little math before you select your drive and make the decision on the gearbox. Look at the B18 torque curve between 900 RPM and 5000 RPM and use the gear ratios to determine the effective torque on the output shaft of the transmission in the various gears. Now, as a first pass select an electric motor capable of matching the power output of the B18 if that is your objective. If this is a non highway car then you can downsize the motor appropriately. Have a look at what the stall torque of that motor is. Chances are that at full voltage (particularly if the motor has a short time rating for acceleration) it greatly exceeds the first gear output torque that the B18 can produce at 3000 RPM. Applying that much torque to the input shaft of your transmission is a recipe for turning your transmission into a piece of shrapnel.

Transmissions are a necessity on a B18 internal combustion that has a very positive slope torque - speed curve between 1000 and 3000 RPM. You need to completely change your thinking when dealing with the negative torque - speed curve for a series wound DC motor.

Last edited by 142 Guy; Sep 30th, 2020 at 18:01.
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