Which e bike controller should I pick?

Gupye

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I’m buying a 3000w base power e bike kit. I’m getting a 80A 26ah 72v battery. Should I get a 72v 80A controller to go with it or could I upgrade to a 100a 72v battery and a 72v 100A or would I run into problems. I’m worried that to much watts on a 3000w motor would effect it.can someone help me and tell me if I would run into any problems running a higher amp controller.
 
I need help.would it be ok to install a 80A 72v battery with a 100A controller. Or would that cause problems. Or should I stick with a 80A battery with a 80A controller instead. Please help and tell me if paring a 80A battery and 100A controller will have a negative affect
 
Gupye said:
I’m buying a 3000w base power e bike kit. I’m getting a 80A 26ah 72v battery. Should I get a 72v 80A controller to go with it or could I upgrade to a 100a 72v battery and a 72v 100A or would I run into problems. I’m worried that to much watts on a 3000w motor would effect it.can someone help me and tell me if I would run into any problems running a higher amp controller.

3000W means the motor can run continuously at 3000W without overheating. It can sustain a lot more for shorter periods, but not continuously before the heat builds up and melts the motor. You could either not run full throttle for long periods, or add cooling. In this example, the MXUS 3K motor melts in less than 8 minutes, but can run continuous under the same current when adding Statorade and hubsinks to shed the heat (although 118C is still a little high. Good thing is, you'd only have a half hour of riding at full throttle anyway.
https://ebikes.ca/tools/simulator.html?motor=MX3005&batt=cust_72_0.05_26&cont=cust_100_250_0.03_V&hp=0&axis=mph&frame=mountain&autothrot=false&throt=100&grade=0&wheel=26i&mass=110&cont_b=cust_100_250_0.03_V&motor_b=MX3005_Sinks&batt_b=cust_72_0.05_26&mass_b=110&hp_b=0&bopen=true
 
They're actually different questions, though directly related.

The first question is which controller, both capable of much more than the motor is, to use.

The second question is which battery to use: one just capable (when new) of what the controller may demand of it, or one incapable of what the controller will demand of it.



The second question is simpler: If a battery incapable of the demand placed on it is used, it won't be able to supply the power demanded by the motor/controller under that much load. If it has a BMS with a well-designed and built safety shutoff for overcurrent, it will shutdown all power to the system in this situation. If it is not well-designed/built or doesn't have an overcurrent shutoff, then everytime more power is demanded than the battery is capable of, it will be stressed, or even damaged. Enough stress, repeated, will damage it anyway, over time.

So the answer is: don't use a battery that is less capable than the controller may ever demand.


A better answer is to use one that is more capable, so that it not only does what you want when you first get it, but still does so as time passes, without stress on the battery.



The first question is also "simple" to answer, but the actual answer to how big a controller (and motor) to use requires much more information.

The simple answer is similar to the first one: A controller capable of more power than the motor is may allow the motor to overheat under a load that high, and fail. Don't use a controller capable of more than the motor is.

The more realistic answer starts with what E-HP said here:
https://endless-sphere.com/forums/viewtopic.php?p=1731084#p1731084
and gets more complex from there, depending on your usage scenario.

If your usage is always running it at it's max power, you need a motor that can easily handle the power your usage will require. That depends on the speed you want to go, how quickly you want to reach that speed (acceleration), how often you have to accelerate (stop/start traffic, continuous riding, etc), the terrain you ride on (hills? what degree slope? how "long"?), what the surface conditions are (mud, sand, gravel, paved road, forest, etc), wind (small breezes, constant high winds, gusts, etc)). All of those directly affect how much power the motor must output, which itself directly affects how much the controller must provide, and how much is drawn from the battery.

The simulator at http://ebikes.ca/tools/simulator.html can help you see how this works, if you go there, read the entire page for the instructions on what everything means/does, and then play with various setups under conditions you will be riding in.


If your usage only sometimes needs it to be at max power, then depending on conditions and usage, you may be able to use a less-capable motor, which sees some peaks of power over it's capablities, but mostly is used at less than it's capablities, so the heat doesn't build up to damaging levels.

The battery still has to be as good as or better than the controller, and the controller still has to be good enough to handle the peaks of power required.
 
amberwolf said:
They're actually different questions, though directly related.

The first question is which controller, both capable of much more than the motor is, to use.

The second question is which battery to use: one just capable (when new) of what the controller may demand of it, or one incapable of what the controller will demand of it.



The second question is simpler: If a battery incapable of the demand placed on it is used, it won't be able to supply the power demanded by the motor/controller under that much load. If it has a BMS with a well-designed and built safety shutoff for overcurrent, it will shutdown all power to the system in this situation. If it is not well-designed/built or doesn't have an overcurrent shutoff, then everytime more power is demanded than the battery is capable of, it will be stressed, or even damaged. Enough stress, repeated, will damage it anyway, over time.

So the answer is: don't use a battery that is less capable than the controller may ever demand.


A better answer is to use one that is more capable, so that it not only does what you want when you first get it, but still does so as time passes, without stress on the battery.



The first question is also "simple" to answer, but the actual answer to how big a controller (and motor) to use requires much more information.

The simple answer is similar to the first one: A controller capable of more power than the motor is may allow the motor to overheat under a load that high, and fail. Don't use a controller capable of more than the motor is.

The more realistic answer starts with what E-HP said here:
https://endless-sphere.com/forums/viewtopic.php?p=1731084#p1731084
and gets more complex from there, depending on your usage scenario.

If your usage is always running it at it's max power, you need a motor that can easily handle the power your usage will require. That depends on the speed you want to go, how quickly you want to reach that speed (acceleration), how often you have to accelerate (stop/start traffic, continuous riding, etc), the terrain you ride on (hills? what degree slope? how "long"?), what the surface conditions are (mud, sand, gravel, paved road, forest, etc), wind (small breezes, constant high winds, gusts, etc)). All of those directly affect how much power the motor must output, which itself directly affects how much the controller must provide, and how much is drawn from the battery.

The simulator at http://ebikes.ca/tools/simulator.html can help you see how this works, if you go there, read the entire page for the instructions on what everything means/does, and then play with various setups under conditions you will be riding in.


If your usage only sometimes needs it to be at max power, then depending on conditions and usage, you may be able to use a less-capable motor, which sees some peaks of power over it's capablities, but mostly is used at less than it's capablities, so the heat doesn't build up to damaging levels.

The battery still has to be as good as or better than the controller, and the controller still has to be good enough to handle the peaks of power required.

so would installing a 80a controller on a 3000w motor replacing with its stock 60a controller it would cause probelms or not from what your saying
 
Gupye said:
so would installing a 80a controller on a 3000w motor replacing with its stock 60a controller it would cause probelms or not from what your saying

There is no yes/no answer, so I'll restate what I said before, which is the best answer anyone can give you (given the little info we have from you so far):


If, based on the original post quoted at the bottom of this post, it's a 72v battery system, then an 80A controller would be 72 x 80 = 5760W.


Simplistically, not knowing any of the conditions under which you'll use it, or how you'll ride, etc., that's more than the motor is designed to handle continuously (assuming it's really a "3000w" motor, since too many places just say whatever they want about the stuff they sell, not what it really is, and we don't know what specific items you're looking at).

Even a 60A controller, running at 72v, is 4320W, which is still too high for continuous use, assuming an accurately rated motor.

To stay within continuous-maximum-usage limits, you'd need to use at most a 42A controller, for a 72v battery system.

If it's a different voltage, then you'd need to calculate power using that instead of 72.

But most systems are not used at their continuous limits, so it's often possible to use a much higher-output controller on a lesser-capable motor, as long as it is not used at that power level very long. For instance, on the right side of my SB Cruiser trike, I'm using a "500W" hubmotor at around four times that, for a few seconds each time I accelerate from a stop to 20MPH. It gets hot quickly doing this, but it only has to provide about 400-500w the rest of the time, or less, so it has time to cool off while cruising at 20mph before I have to do that again. By the time I'm at the end of the couple mile long ride, it's very hot, uncomfortable to touch on the outside, but not at damaging heat levels (is as much as 60C+ inside, though).

It probably couldn't do this for an extended period, but I rarely ride very far these days. If I did 20-mile rides in start-stop traffic, it might get hot enough to damage itself at some point. If I rode on hills, instead of flat streets, or on sand/gravel/etc that takes more motor power to handle, it would heat up more and faster, and probably wouldn't work very long.

Similarly, it gets hotter faster in summer when it's 105-120F out here (and much hotter at street level especially in traffic with no breeze so the hot pavement heats the air which heats the wheel and motor, etc), and doesnt' get as hot as quickly in winter when it's in the 60s at most during the day.

It also gets hotter faster when it's really windy outside, because the wind drags at the trike and slows it down, making the motor use more power to maintain speed.



So whether you can use a small motor on a big controller depends on your specific usage in your specific terrain, riding style, wind/weather, etc. If you are always running it at maximum, then you need a controller and motor matched in capabilities. (or a bigger controller that is programmed down to match the motor and won't exceed what the motor can handle) If you are only using maximum occasionally, you can use a bigger controller without worrying about it too much, depending on exactly how you really use it.


You can see how some of this works by using the simulator at http://ebikes.ca/tools/simulator.html and reading the whole page for instructions, then playing with different setups using settings that emulate your usage and terrain.


Gupye said:
I’m buying a 3000w base power e bike kit. I’m getting a 80A 26ah 72v battery. Should I get a 72v 80A controller to go with it or could I upgrade to a 100a 72v battery and a 72v 100A or would I run into problems. I’m worried that to much watts on a 3000w motor would effect it.can someone help me and tell me if I would run into any problems running a higher amp controller.
 
I need some help. I’m looking to buy a Ebike kit. The one I found has a 40amp controller. I have to buy the battery separate, would it be the best decision to buy a battery with the same bms as the controller (40abms) or should I get a battery with different bms. Please help thank you
 
Gupye said:
I need some help. I’m looking to buy a Ebike kit. The one I found has a 40amp controller. I have to buy the battery separate, would it be the best decision to buy a battery with the same bms as the controller (40abms) or should I get a battery with different bms. Please help thank you

You want a battery pack that can supply at least 40A continuously. The BMS rating isn't necessarily the same thing, since it's downstream of the cells that provide the current. Assuming the BMS is properly sized for the pack, then yes, 40A or greater is best. However, many controllers allow you to set the maximum current, so limiting the controller to something less than the pack's current capability is another option.
 
Many sellers don't understand any of the terms or ratings of the things they sell, so they may misrepresent something accidentally (some may do it on purpose to sell more stuff). This makes it harder to buy the right parts.

A BMS may be rated for how much it's FETs can handle, or it may be rated for how much current it will allow before it shuts off the output to protect the cells. If the seller page doesn't distinguish between these, or give any other info, it's safer to assume a BMS current rating is the maximum the BMS itself can handle, and buy one that has higher rating than you will ever need, so it won't fail or overheat in use.

If the BMS can actually detect current and shutdown for overcurrent (they dont' all do this), then you also need one that won't do that for any normal current draw your system (controller) will place on it (but would if you had a wiring short, for instance).


Then you need a battery pack (the cells themselves) that can easily handle and supply all the current that will be demanded of it, even as it ages. That usually means getting one that can handle more than you need now, so that as cells degrade over time they can still do at least as much as you need them to. That may mean getting a pack that's 25-50% better than you need, to be sure it still does what you want a few years down the line.


So if you have a 40A controller, if that is the maximum it can ever draw (rather than just a continuous rating, with an unstated peak / maximum), then the BMS must be able to supply at least 40A, and it would be better to get one that's 50A continuous tolerant, or more, to give it some headroom for current spikes or bike upgrades later.

In that event, you'd get a battery with cells that, in the configuration they're assembled in, can handle at least 50A (or more), and preferably 60A+, continuously.


Many people don't follow these, and their systems still work, but sometimes they have failures or problems they might not have had if they'd built the system with some headroom. ;)



Another consideration for batteries is the Ah, capacity (completely separate and different from the A amps rating); this is what gives you range. Depending on the speed you go and the conditions you ride under, you could use 40A continuously. An Ah is just how many amps flow in one hour, so if you needed to ride for an hour at 40A load, you'd need at least a 40Ah battery to do that (it's a pretty big heavy battery, up to 35-40 pounds, size of a stack of hardback books).

So if you post up your intended usage and riding style, terrain, etc., we might be able to guestimate the power usage of the system, and how much you'd need to get whatever range you're after.
 
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