best cheapest 72v 30a brushed motor controller

[daveyjones97]

as the title, i dont have loads of cash but as spring is in sight i need to get a move on with my bike.
basically im after the best value controller with those specs. cheap and reliable is good, but every time i suggest a controller here or elsewhere people tell me its not the best because....
the only slightly flash function i want is the ability to hold max amps without cutting out, though i think most controllers do that anyway. i already have a brushed motor and batteries.
opinions please guys

 

[Ypedal]

Exactly what motor.. and batteries do you have?

 

[amberwolf]

I'd recommend checking with http://4qd.co.uk for brushed controllers, given your assumed location from previous questions.

http://www.4qd.co.uk/prod/index.html

You'll want to ask about how high in voltage the controllers can be made to go from the factory, so you don't have to do the modifications yourself (typically 48V-60V is the higher range they get used at, but I'm sure they can be modded to go higher than that, just like most controllers can).


I've used (and modified) the discontinued 2QD for CrazyBike2's old brushed powerchair motor drive, without any controller problems.

 

[daveyjones97]

thanks amberwolf, i actually emailed 4qd monday, just waiting for a price and his reccommendations. i would like to buy from him as i could drive to him in an hour if i needed any future help with a 4qd controller quickly.
the batteries are almost definately going to be vapextech as i have had several rc packs and various aa batteries from them in the past and not had any problems at all. http://www.vapextech.co.uk/acatalog/Sub_C_Batteries___Leads___Fittings.html
i know nimh arent fasionable but theyre relatively cheap and safe, this is my first ebike project.
the motor will initially be the universal motor here; http://endless-sphere.com/forums/viewtopic.php?f=1&t=35256
if youre in england and see a dog with a dented head, you know it was rubbish and i needed a better motor! :lol: as i said, cash is an issue so i reckon trying the uni motor has to be worth it. so far no one can give me definative on what it will be like on 72vdc. the coils look about 0.8-1mm thick so hopefully it will take the amps. its not going to pull 30a continuously anyway.

 

[daveyjones97]

how hard can it be? i got this short sweet mail back from 4qd today;
"Sorry, we do not make controllers for voltages above 48.

There are several problems. Main one being that high voltage transistors
don't have the same performance so you cannot simply upgrade transistors
etc."

well, i cant knock the guy for sticking with what he knows. some might say i should do that... i also messaged kenny@crstalyte but no reply yet and stumbled across kelly controllers. then i found a thread on es where a guy was saying thier board layout wasnt as good as it could be, something to do with cap location.
this is why ive been so indecisive about trying to make/adapt my own controller but im 99% sure im just gonna buy one now i investigated the minefield of diy esc's for noobs. the kelly i like best is;

http://kellycontroller.com/kds72050e50a24v-72v-mini-brushed-controller-p-760.html

tbh unless i get loads of people telling me my planned setup is crap im just gonna shell out and hope. ive spent months researching all this and im not significantly wiser. i think its time to throw my ass in the pool and see what happens. il just try and collect a few more prices specs and opinions then punish the plastic.

 

[Ypedal]

You are going down the wrong road my friend..... sorry to tell you but best to know now before wasting all that money and all that time.....

first, those batteries are not right... 2nd a universal motor is a bad idea... 3rd there are cheap brushed controllers available but before getting into that.

stop now and step back..

First, what do you need to get done?

- your weight?
- what will this be used for ?
- how far do you need to go ?
- what is your budget ?
..

 

[daveyjones97]

oh dear thats the answer i was dreading ypedal. me and the bike before i mess with it will be around 210lbs, itl be for 8 mile round trip commutes, town and trail riding. some trails are round an old quarry type area, so im after as much torque as poss for hills. torque and relatively light weight led me to the uni motor as well as the possibility of running it through gears as not only do i want it to climb like a mountain goat i want 35mph top speed too.
im quite taken with the weight distribution of a mid mount motor setup too, good for agility on hardcore trails.
a quote from grin cyclery came in at $1600 which i dont doubt is a good price, is $600 more than i can afford atm.

what was the problem with the batteries? i forgot to look at the discharge rate, im guessing that or the fact theyre only 1.2v per cell is the issue?

the motor i have no idea with. hmm i appear to be at square 1 again.

i really need you experienced guys to just tell me what setup i need. i can make all sorts of metal work for mounting a motor and extra gears myself and lace wheels, but the batts, controller and motor choice has me totally stuck.
if it wasnt for the off road use i would just ebay my old car around march and buy the clyte setup grin quoted me, but im worried that trials type hill climbing would kill it.

 

[Ypedal]

first problem , with the batteries, 3ah will not deliver 8 miles, and those nimh will not enjoy 30 amps for any duration, used as a single cell it might work for a while but having to string 10 of them for ever 12v pack will result in a big headache.... dont trust the capacity claims, they lie.

Much better bet is 5ah or 8ah Lipo cells, they will deliver 30 amps easily....

A brushed, permanent magnet motor is better suited, lower rpm means less mechanical reduction to get the rear wheel turning at a proper speed... vs universal motors.

Used stuff comes along regularly in the market here, a geared hub motor used to drive the cranks ( vs being a hub, spoked ) would be much better, check with cell_man .. since some fabrication is something you can do..

I"m sure this can be done under 1000$, likely well under.

 

[daveyjones97]

ok, thanks. what should be the battery spec wish list? chemistry, c rating manufacturer and stuff?
also anyone want to comment on the kelly controller, good or bad its all welcome.
im still tempted to try the uni motor as noone yet has convinced me it'l be worse than a pm brushed motor, it should pull simalar torque from a low rpm size for size?

 

[REdiculous]

Most uni motors are integrated into a product that's not designed for continuous use so you'll probably want to cut the power rating in half.

There's tons of vacuums with "1000w" printed on the side, but how long do you vacuum?...if you're like me you do about 5 minutes at a time, with little breaks tossed in so you can move furniture or pick up Legos.

We've got a product here that's basically just a 200w uni motor and it literally says, "Do not operate continuously for more than 1 minute at a time." That product is roughly the same size and weight as a 150w continuous duty PM motor I have. :lol:

 

[Ypedal]

I believe Universal motors have very little startup torque, once up to speed you can load them up but from a dead stop they suck.... PMDC motors however :wink:

 

[daveyjones97]

ok, il start looking at pmdc brushed motors. why do you have to half or double everything on a nameplate for the worse?! i used to think gas engines exagerated! i was hoping id get away with it as i wouldnt be pulling full current for long periods but maybe not.
for batteries, any opinions on a123 systems? theyre used in dewalt tools and not too hard to get hold of.
also no ones commented on the kelly controller which is giving me a twitchy buy it now finger

 

[daveyjones97]

after more research on batteries and reading http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=2498&start=0 im sold on a123-m1s. i found a uk supplier http://www.electricwingman.com/6s-a123-battery-pack-lifepo4-triangle-enerland.aspx so i reckon i need 4 packs to get 72v. i'l have to mess about with the packs to end up with 3x7 cell packs, 21 cells total. the es thread above will be learnt word for word when i get the batteries so i end up with a suitable pack and charging system.
the kelly controller looks good for the price, and the gearing is worked out, but on a piece of paper i cant find right now... basically planning on having a kart sprocket mounted to the rear disc mount of my hub, a shaft with a small sprocket on left, large sprocket fixed to a freewheel on the right and the motor drive sprocket on the right. ultimately id like to experiment with deralleur primary gears, a pair of freewheels, but i think thats going to have to wait until the single speed works or not. initially the gearing will be 20mph at 5000rpm. oh and the rear disc will be on the jackshaft too. i might have to make a tiny one up if the 140mm dia is too much of a flywheel.
a suitable motor is being researched, but i might end up trying the uni motor as its free and not worth anything. have to see how the budget pans out. also 1mph will be 250 rpm, so if i give a brief crank of pedal in a low gear off the line it shouldnt suck too badly? i trust your advice, but the budget is mostly wiped by the batteries, charging and controller. i give every es member permission too laugh at me when its crap with the uni motor