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[HotRodHoose]

Right, but if I run in series and then switch to parallel I will get a better acceleration with the same top end, right?  I am trying to get great performance and still have a pretty decent range.  Maybe running in parallel the whole time will be good enough.  I have to run a lot of testing and comparisons so maybe I will try that out as well, run all parallel compared to parallel and series and see how it compares.  I will post all of my findings after I conduct all of the tests, but I can't conduct them until October, Blah, because of school.

[picasso]

This has been covered on a few other EV forums. I will try and dig up the link. Switching the motor is the way to go for a kick of top speed.

[HotRodHoose]

That would be awesome if you could find that link, I appreciate you even trying.  That would be a lot of help, thanks a lot.

[picasso]

here is the link. Some other posts on the same forum about switching, this seems to be the main one. Most of these are smaller bikes. For the EV motorcycle world we would need a much larger switch.

http://endless-sphere.com/forums/viewtopic.php?f=2&t=9215


Some nice stuff on that forum about pack design and pack parts sources.

[Bogan]

had breif read of that thread picasso, 249 posts so i only had a look at the first page. I noticed they were talking about switching between wye (star) and delta configurations, this is applicable only to ac motors, as they have 6 terminals, hotrodhoose is planning to run two DC motors which have only two terminals each. Unless they talk about parrallel series switching later in the thread?

[picasso]

My bad I did not see the part about the dual motors. That topic is also covered on the same forum. The problem with that side of things is double the parts needed on the bike. I havnt seen it don e with a single controller before.

[Bogan]

yeh in theory it shud work, as both motor will be running loaded so back emf differences between the motors (probly very tiny, but there none-the-less) should be negated, though im not sure, will do some more research and get back to you

[Bogan]

yip ive had a think about it some more, and putting two identical dc motors in parallel should work, the slight difference in back emf will sort itself out by pushing more current through one of the motors, and as they will be the same sort of motor this back emf difference and therefor the current will be neglidgeable.

with regard to switching between series and parallel, i dont think it is necessary, the controller can supply whatever current you want to two motors in parralel, so there is no need performance increase to use a series configuration (series may have some infintesimal eficiency gains at mid speed riding) but i dont think it is worth it. However im no expert, there may be some aspect of it ive forgotten about.

[HotRodHoose]

Yes I do remember in electricity class, talking about the three phase connections with wye and delta in AC.  So If I run in parallel only and not switch to series, we are talking more batteries then, so that I can get the full 72v or no?  If I run in parallel in the beginning and then switch to series for more of like 35mph and above do you think that is a more attainable setup if I am aiming for 75mph and a 25mile range?

[Bogan]

no, no more batteries, in parrallel motor wiring you would need less batteries than for series. You dont want to switch to series at higher speeds because with motors in series configuration each motor only gets half the total voltage, so runs slower than parallel where each motor gets all the total voltage.

[HotRodHoose]

I meant run them in series at first then switch them to parallel after a certain speed, or do you think its not even worth it at lower speeds.  If i leave them in series will i get better acceleration at low speeds than with parallel or is it not even going to be that noticeable?

[Bogan]

no, putting them in series would not increase the acceleration, because with motors in series or parralel the acceleration is dependant on the current flowing through the motor, not the voltage applied, and with them in parralel each motor gets the full pack voltage so it is easier to maximise the current through the motors

[HotRodHoose]

So it would be better just to run them in parallel the whole time and not worry about a switch from series to parallel.  In that case is the extra motor going to help out and give me my top speed of at least 75mph?

[Bogan]

yeh parallel the whole time. Extra motor will help with top speed, and accelleration, you have double the kW to play with!

[HotRodHoose]

Ok thanks, so what is everyone having the most luck with as far as controllers go?  I found a motor but cant seem to find a controller that I really like.