How fast can a 1800W motor go?

Bmr4Karts said:

The safe way to plan a setup is everything is stronger than your motor.

Link to XDAO

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finally we can agree
Yes.. everything bigger than what the motor needs is safe.

scorn001 said:

...In my case - a 48V W controller goes with a 48V W motor. I was understanding that it was a bad idea to use a 48V W controller with my exisiting motor - I'd need to upgrade the motor as well. Certainly one of the 72V W controllers would be an extrememly bad idea?

What are the rules here? It sounds like I can use a larger/more powerful controller with an existing motor?

Contact us to discuss your requirements of POWERFUL MOTOR W ELECTRIC SCOOTER. Our experienced sales team can help you identify the options that best suit your needs.

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Yes you can.. the controller is "kindly offering" Amps to the motor,
it's not force feeding the motor with currents.
So a bigger amperage rated controller is perfectly fine with a small motor.
(it's force feeding voltage though.. so a 72V controller will likey hurt your 48V motor .. different question)

The thing is that controllers (as motors) can be rated either max or constant power..
the max power rating is something you only want to apply for a few seconds,
then it's going to overhead
(and burn out the traces on the pcb, pop a cap, blow a resistor, fry a MosFet... weakest link first)
constant rating is what you want to have matched or exceeding your requirements.
Some list both, some just peak values (sounds more )
So a reliable source is a very good thing to have.
unfortunately internet sellers are not always as reliable as we wanted them to be. Some don't even know what they're selling some just lie in your face. (hence I like to suggest kellycontrollers rather inexpensive and with good quality and honest ratings)

Say if the motor can draw 45 Amps constantly (60 peak) a controller with a constant rating of 50A and a peak of 100A is a good idea..
an "oversized" controller say constant rating of 200A and peak at 400Amps is just running cooler with that same motor attached.
the other way around -a 200Amp motor on a 100Amp controller-
will certainly cause the controller to overheat and die in short order.

a 100peak controller on a 60Amp peak motor cannot be improved with the shunt method!
an "undersized" controller might (if done properly and not just solder blobbed)
at some risk (I too repeat myself it seems.. aaaanyways)

Batteries.. unfortunately the same rules apply for batteries as for controllers..
there's a constant and a peak rating.
the peak is what automotive battery mfgs call CCA (cold cranking amps)
that rating is usually considered to be applied for no more than 30 seconds
(some mfgs claim up to a minute)
Constant discharge rating is nothing you find mentioned on automotive batteries unfortunately.

A rule of thumb is that it's about 10% of the CCA (maybe 15)
and/or in the realms of their capacitance
means a quality automotive battery can be fully drained rather safely over the course of one hour
(a 45Ah battery delivering 45Amps, a 60Ah battery 60Amps, two paralleled 35Amp batteries 70Amps, a 550CCA battery 55Amps and so on)
it's not more than a rule of thumb though.. type matters
wetcells can deliver amps "more easily" than SLAs, more than AGMs, more than Gel cells
and marine batteries more than automotives without overheating.
(batteries too get warm if abused)

Now you got a W motor (let's assume it's mechanical power rating)
it'll draw ~47Amps (about Watts electrical)
with just four batteries in serial for your 48Volts you want 45-50Ah batteries
with a 4s2p configuration of eight batteries 25Ah batteries should do and so on.

If that 300Amps are Cold cranking amps you might abuse them a little too much already.
even at 15%CCA that'd be 45Amps and just on the upper limit at full power...

Easy to tell if you need to worry though..
just check the batteries every now and again if they got hot after a ride.
Or even better.. get a cheap thermometer with a sensor lead
and wedge that sensor between two batteries
I'd not allow the temperature to rise above 55°C (130'ish F)
especially not if kids are near.
I'd feel much better with it not exceeding 45°C (115'ish F)

'sid

finally we can agreeYes.. everything bigger than what the motor needs is safe.Yes you can.. the controller is "kindly offering" Amps to the motor,it's not force feeding the motor with currents.So a bigger amperage rated controller is perfectly fine with a small motor.(it's force feeding voltage though.. so a 72V controller will likey hurt your 48V motor.. different question)The thing is that controllers (as motors) can be rated either max or constant power..the max power rating is something you only want to apply for a few seconds,then it's going to overhead(and burn out the traces on the pcb, pop a cap, blow a resistor, fry a MosFet... weakest link first)constant rating is what you want to have matched or exceeding your requirements.Some list both, some just peak values (sounds moreSo a reliable source is a very good thing to have.unfortunately internet sellers are not always as reliable as we wanted them to be. Some don't even know what they're selling some just lie in your face. (hence I like to suggest kellycontrollers rather inexpensive and with good quality and honest ratings)Say if the motor can draw 45 Amps constantly (60 peak) a controller with a constant rating of 50A and a peak of 100A is a good idea..an "oversized" controller say constant rating of 200A and peak at 400Amps is just running cooler with that same motor attached.the other way around -a 200Amp motor on a 100Amp controller-will certainly cause the controller to overheat and die in short order.a 100peak controller on a 60Amp peak motor cannot be improved with the shunt method!an "undersized" controller might (if done properly and not just solder blobbed)at some risk (I too repeat myself it seems.. aaaanyways)Batteries.. unfortunately the same rules apply for batteries as for controllers..there's a constant and a peak rating.the peak is what automotive battery mfgs call CCA (cold cranking amps)that rating is usually considered to be applied for no more than 30 seconds(some mfgs claim up to a minute)Constant discharge rating is nothing you find mentioned on automotive batteries unfortunately.A rule of thumb is that it's about 10% of the CCA (maybe 15)and/or in the realms of their capacitancemeans a quality automotive battery can be fully drained rather safely over the course of one hour(a 45Ah battery delivering 45Amps, a 60Ah battery 60Amps, two paralleled 35Amp batteries 70Amps, a 550CCA battery 55Amps and so on)it's not more than a rule of thumb though.. type matterswetcells can deliver amps "more easily" than SLAs, more than AGMs, more than Gel cellsand marine batteries more than automotives without overheating.(batteries too get warm if abused)Now you got a W motor (let's assume it's mechanical power rating)it'll draw ~47Amps (about Watts electrical)with just four batteries in serial for your 48Volts you want 45-50Ah batterieswith a 4s2p configuration of eight batteries 25Ah batteries should do and so on.If that 300Amps are Cold cranking amps you might abuse them a little too much already.even at 15%CCA that'd be 45Amps and just on the upper limit at full power...Easy to tell if you need to worry though..just check the batteries every now and again if they got hot after a ride.Or even better.. get a cheap thermometer with a sensor leadand wedge that sensor between two batteriesI'd not allow the temperature to rise above 55°C (130'ish F)especially not if kids are near.I'd feel much better with it not exceeding 45°C (115'ish F)'sid

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