BlueSeas said:
My thought with the simultaneous start up is the inefficiency of dragging an unpowered hub motor along for the ride. Say at a low speed 10mph speed, only one motor was active, that would seem to be lots of drag? The QS205 on my recent build basically renders the bike useless for pedaling, except as a backup "get home" strategy. The 9C motor on my first build can be pedaled, but it's still not really practical without some minimal PAS assistance..
In my stuff i just do full throttle or full pas-throttle on startup so it doens't actually matter what the lowest throttle threshohld is on the controllers. Then when i'm at speed it limits throttle so i only get enough power to maintain 20mph (assuming im pedalling fast enough for the Ca to keep me at that speed). The system
But on Craybiek2, i used separate throttles for eahc, not going thru the CA. I could startup with just one motor, and it didnt' really make any noticeable drag to not power the other motor (in the cases where i broke a wheel and used a regual ar one in it's palce for a while, I didn't notice any real difference between one motor powered and one not, and one motor powered and one regualr wheel...though i don't know if i ever noted down CA readings for this, i probably did, and if so those are in the CB2 thread somewhere. ). That was witha 9c in front and a hsr3548 in the bakc.
I don't remeber if the grin simulator also simulates motor drag but you could try it out maybe the trip simulator does, and you could setup a two motor system but only put throttel into one of them and see how it works out? never tried it.
You would lose the capacity monitoring piece of the CA3, .
The only thing you lose is the ability ato the CA to control the throttle of the PR. All the monitoring abilty of the ca is still there, because you would monitor battery current with an external shunt that feeds both controllers.
aFIAK you can t parallel the shunts on two contorllers to monitor both at once with one CA, or else the controllres themselves can't tell houw much power they are uisng. Maybe you could use diodes from each one to the CA so it dcould still see the voltage but the other ocntroller can't, but then there's a diode loss that i don't remmeber if you can adjust out of the CA shunt settings. don't think you can. The hsunt voltage is small. Maybe grin has dealt with this already somehow?
Anyway i use just one standalone grin shunt out of the batery, then both controllers connect to the otuput of that. then the throttle signal and ground are paralleled on both controllers to the ca's throttle output.
But if i had different controllers and one controller that had adjustable internal throttle settings i'd use that one direclty from the throttle, and the other would be processed by the ca first, if I did not need to use PAS (because the PAS has to be processed by the CA first (unless that adjustable controller could also take in PAS and use it directly, but I don't know of any like that, though it doesn't mean there arent' any). Or if I had a separate PAS-to-throttle converter that could just be paralleled with the real throttle signal to the adjsutable controller
I forget what the OP has but if they have a freewheeling motor that could be the unpowered one in any cases hwere there can only be one for whatever reason.
there'sa lot fo ways to setup 2wd, and which one is "better" depends on the specific stuff being used, and the speciric situation it's being used in, and what the rider needs it to do in each sitaution.
For mine the main reaosn i needed 2Wd was reliablity. I needed backup for the times something would go wrong with one motor or the other.
The next reaosn was power. I couldnt'a fford the big stuff, so by necessity i went with dual smaller ones (as wella s reliablity, but if i could've afforded two double-size systems i owuld've done it that way).
So CB2 had about 4kw on tap, half on each end. Needed tthe power for quick acceleartion at stoplights and such even when heavily loaded with cargo or pulling trailer full of cargo or dog, cuz drivers hate being behind anything that isnt' another car and probalby even that. So since most of the time i end up being the first or nearly first stuck at the light, with a line of cars behind me already impatient to go cuz its' red, then when it's green I have to be able to zip out ahead of them all so they don't get pissed and try to run me over. With the power i had i could cross intersection in <4 seconds and be at 20mph full speed by the time i got across, or sooner, so except for the really leadfooted drivers I wouldnt' ahve problems and could be across and out of the way in the bike lane or at least far to the right so they could then pass me without bieng pissed off as much by my existence.
Something else but i dozed off again so can't remmvber what it was.
In SBC the trike the mtoros are both on the back on either side. Never had a matched pair, the closest i had was a 4503 on one side and 4504 on the other, MXUS 3k's. Had matched grinfineon 30as for a while but one was miswired at factory on ebrake connector so that stuff enver worked right and eventually it blew up the 5v regulator because of it, and that's still in a box waiting to be sent back for fix since maybe this time last year, just enver have time and energy to get it done.
Anyway, because the mtoors werent matched then the torque curves were different so you could kinda feel the push moving from one side to the other as acceleration happened up to full speed 20mph, and that was too complex to build something that would compensate for it like a opamp something or other that would fit between ca throttle output and one of the controllers to change the throttle voltage to make that mtoor match the other one.
Mostly the SBc has alwyas had mismatched ocntrollers, and alwyas mismtached mtoros, , except for those few weeks (monmths? can't remmember) that boht grinfineons were mostly working. It's very different motors now, since one of the 450x's failed again and i stuck a stromer ultramotor in it's place (wish I had another just like it for the left side--it's got a lot of power for such a little thing and its' very well made unlike the MXUS crap). The controllers are also mismatched, some random generic 30-40a on the right and the still working grinfienon 30a on the left. Still feel the torque difference but it doesn't cause a problme, it's not enough for torque steeer to be a problem for instance even at full power.
Was gonna finally ahve matched controllers taht could adjust their throttle curves to go with the mismatched 450x's by building a couple Lebowksis (see my thread about it in my signature) but life hit and i didn't finish teh first or start the second, then months later the first 450x died. So i don't have any experience with matched torque / power setups. Maybe someday.