"Two 4-pole Motors in Series" for dummies...
- Thread starter augidog
- Start date
You'll get better performance from them at 24V and leaving htem in parallel, but they may not be able to handle that--it's a test you'd have to try...which could result in destruction over time from overheating or brush wear.augidog said:
In parallel (regardless of voltage) they'll not share current equally, so any difference between them (brush/commutator condition, slight winding differences, etc) could cause one to resist a little more and take less current than the other, which will mean the other is producing more power and heating more. But each will get about half the current.
In series each will get about half of the voltage, so the system will essentially act as if it is just a higher-voltage-winding motor.
If they are both physically tied to the same shaft it doesn't change the loading on them no matter which way you do it.
Watts is total power output of the motor, which it can exceed for some amount of time, but how long depends on a lot of factors. So using that as a limit is the safer option.
So if it was essentially a "30A controller" before, you would want a 15A controller max now. But really, you have two 225W motors, for 450W total at 12V. That's 37.5A peak at startup from a stop if you were actually getting their rated power at exactly 12V, but it's more complicated than that due to voltage sag and actual battery voltage, etc. at 24V (really 28V sagging to probably 20-22V under that load), it'd be 18.75A or so. So a 20A 24V controller would generally keep them within a safe rating, most likely. 15A if you want to keep them really safe and be easier on your batteries, but the system will have less oomph (torque).
More speed and more torque at startup because of higher current draw, assuming your controller can supply that current--otherwise really just more speed, and the same torque for longer on the accleration curve. n Really, they'll probably be abotu teh same because you ave the same total power, assuming you keep current on the series motors limited to half of what the parallel arrangement could ahve .
Even though the motors are different, you can pick any system setup at the http://ebikes.ca/simulator and play with the voltages and throttle settings to see what I mean, and then use the System B function to pick the same setup with a controller that has higher amps and compare them.
Trigger throttles are harder to come by, but TNC scooters or similar places might have them. For simple and proven I would recommend http://4QD.co.uk but they are notably more expensive than the cheap Chinese scooter stuff that might work just as well for your applications. I don't know any specific Chinese models, but the 2QD and 4QD will both work for what you want, as will probably some of the Porter models, etc. We'd have to work out what exactly you expect of the setup and waht hte motors can take.
The voltage won't do it, but high current could if the wires are really thin, like 16-18g or smaller. It's unlikely you'll get that in your setup.augidog said:
Sorry, I don't. My first working controller (besides the many I tried to build from schematics on the web and whatnot that usually didn't work at all) was what was left of a burned up 24V ScootNGo controller that I replaced gate drivers and FETs on, eventually seriously upgrading it to a 100V 100A+ capable controller, though I never used it at more than 36V and probably 30A or less (radiator fan motors with rollerskate wheels for friction drive; see my DayGlo Avenger thread's early pages). I didn't monitor usage or antyhing then, so I don't really know.
Most likely it doesn't have current limiting itself, but instead depends on the fuse or breaker to limit the current so it doesn't blow up. So don't use a breaker or fuse that's rated higher than whatever they specify.
Bear in mind that pretty much every manufacturer and dealer lies about capacity, range, power, and speed.
They also expect the rider to contribute significant power by pedalling all the time, to get those ranges/etc., but they almsot never say that--they state their stuff as if it will do the most range at the highest speed by motor only, when really it's either the most range at a low speed, or a really short range at the highest speed, even if you include pedalling for either one. 
So, typically, SLA will only get you about half the Ah it says it will, usually, because the rating is for practically a trickle discharge, and we're practically short circuiting it for what we do.
It's called Peukert's Law, which means that for any battery you get less total power the faster you draw it out. A decent rule of thumb for SLA might be that you get a mile at 20MPH for every Ah at 24V. Depending on conditions and terrain you may get less than that, and depending on the SLA and the current draw you might get more. So don't count on more than say 8-9 miles at 20MPH, maybe a couple more at 17-18MPH, a couple more at 14-15MPH, etc. More if you don't stop but keep cruising, less if you have to stop and start a lot. This is assuming no pedaling.
All of that is guesstimath, because every system is different as is every rider and riding situation.
You're welcome. I learned it all the hard way, for the most part, before I found this place.
I've mostly moved beyond this type of stuff, but I sure learned a lot about it before I did, since I used busted recycled bits of junk nobody wanted for most of my early projects (and I still do for many things). If you wanna see an interesting evolution, poke around my CrazyBike2 thread, and also back in my early Electricle blog on blogspot (from before I came to ES). 24V 31Ah SLA-powered brushed powerchair motors to start with, maybe 15-17MPh top speed for 10-15 miles without pedalling, up thru a small geared hubmotor powered by NiMH and LiFePO4, now with a 4.5KW-burst hubmotor powered by "48V" 66V hot lithium pack (like RC-LiPo type) for 20Ah that could take me up to 35MPH+ if there was somewhere around here taht allowed that, but easily 20MPH for 20+ miles (probably 30, but I havent' verified taht) with no pedalling. And of course, I'm not done with it yet. :lol:
And it's still mostly built from other people's unwanted discards, or used items of various kinds.
Thud
1 MW
I am going to chime in here& ask a question:
you say "sandwiched" on a friction drive set up?
If the motors are not turning in the same direction with regards to brush timing (such as face to face in a sandwich config) Often a brushed motor has a bit of timing built in for a certain directional spin.
you may be building a system that is fighting itself continualy.
all the work will be on the motor trying to spin faster.
(hate to be the guy pointing out potential problems)
all the best.
T
Hey, Your not Augidog from the old motorbikeracing forum are you? (long dead & gone now)
you say "sandwiched" on a friction drive set up?
If the motors are not turning in the same direction with regards to brush timing (such as face to face in a sandwich config) Often a brushed motor has a bit of timing built in for a certain directional spin.
you may be building a system that is fighting itself continualy.
all the work will be on the motor trying to spin faster.
(hate to be the guy pointing out potential problems)
all the best.
T
Hey, Your not Augidog from the old motorbikeracing forum are you? (long dead & gone now)
Maybe, but probably not. Most have an "LVC" (low voltage cutoff) to protect the battery from damage. Sometimes you can override this, but somtimes it is also just how they designed the controler, and other things are dependent on it being above that LVC, too. Those 4QD brand controllers usually have 12V versions.
http://www.4qd.co.uk/prod/12v.html
and they currently even have osme of the old simple 1QD controllers available:
http://www.4qd.co.uk/prod/1qd.html
presently 40.00 UK pounds for hte 12V 35A version.
http://www.4qd.co.uk/prod/12v.html
and they currently even have osme of the old simple 1QD controllers available:
http://www.4qd.co.uk/prod/1qd.html
presently 40.00 UK pounds for hte 12V 35A version.
