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Old 03-09-2017, 04:17 AM   #1
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Default how much discharge can a motor take

I am wondering if there is a way to work out the maximum discharge that a motor can take I do not have an esc it is currently going staight from a 3.7v 20c lipo battery to a motor and I don't know how many Cs it can take thus I don't want to purchase a battery that discharges any more then the motor can take?
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Old 03-09-2017, 04:19 AM   #2
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I am wondering if there is a way to work out the maximum discharge that a motor can take I do not have an esc it is currently going staight from a 3.7v 20c lipo battery to a motor and I don't know how many Cs it can take thus I don't want to purchase a battery that discharges any more then the motor can take?
many thanks james
Is this a brushed motor? What is it driving?

Limiting power to a motor by selecting a lower C-rated battery isn't feasible due to temperature rise in the battery.
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Old 03-09-2017, 05:54 AM   #3
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Is this a brushed motor? What is it driving?

Limiting power to a motor by selecting a lower C-rated battery isn't feasible due to temperature rise in the battery.
It would have to be a brushed motor. A brushes will not work without an ESC.


As far as telling, you need an amp meter to measure the current. However, I would not use a motor to discharge a battery as it could take the voltage down too low and be dangerous.
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Old 03-09-2017, 06:09 AM   #4
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Also consider that brushed motors are only efficient to a certain percentage, even if you are trying to push the max it can take, does not mean that it is doing so efficiently.

Most manufactureres such as LRP and Orion used to post efficiency numbers in a percentage form.

Best bet would be to get in contact with the manufacturer, as, even if it can take a certain amount (Max) does not mean that it can do that for an extended time. There always is a safety / efficiency net.

And as bdmpastx stated, you dont have any way to regulate voltage cutoff on the lipo right now.

Maybe get a brushed motordyno like Trinities, Shinwa, Indy, APS Motor Master etc
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Old 03-09-2017, 08:05 AM   #5
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Originally Posted by jamesjetrib View Post
I am wondering if there is a way to work out the maximum discharge that a motor can take I do not have an esc it is currently going staight from a 3.7v 20c lipo battery to a motor and I don't know how many Cs it can take thus I don't want to purchase a battery that discharges any more then the motor can take?
many thanks james
You've got things backwards. The current draw of the system is more limited by the ESC and motor than the battery. The C rating of the battery, is what it can handle, and maintain cell health.

More C typically means tougher cells, so that's better in the long run. It also typcially means less voltage sag when you do load up the system.

As long as weight, and size, are not the question, more C is always better.
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Old 03-09-2017, 08:07 AM   #6
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It would have to be a brushed motor. A brushes will not work without an ESC.
Yup, that's what concerned me: trying to connect a brushless motor directly to a battery is not a recipe for success. But I've heard of people that think they can do it.
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Old 03-09-2017, 08:26 AM   #7
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Originally Posted by jamesjetrib View Post
I am wondering if there is a way to work out the maximum discharge that a motor can take I do not have an esc it is currently going staight from a 3.7v 20c lipo battery to a motor and I don't know how many Cs it can take thus I don't want to purchase a battery that discharges any more then the motor can take?
many thanks james
What motor are you going to attach it to.
I doubt there is an old brushed motor that could pull anywhere near the maximum discharge current of a lipo due to their in inefficiency etc.
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Old 03-09-2017, 09:00 AM   #8
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What motor are you going to attach it to.
I doubt there is an old brushed motor that could pull anywhere near the maximum discharge current of a lipo due to their in inefficiency etc.
With to large of a pinion, or stalled, a brushed motor is essentially a dead short. That will draw ~all the current~.
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Old 03-09-2017, 03:50 PM   #9
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With to large of a pinion, or stalled, a brushed motor is essentially a dead short. That will draw ~all the current~.
Doubt a large pinion is going to do enough to max out a lipo.
If you dead short a brushed motor, I'm betting the motor blows long before the lipo gets a chance to max out
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Old 03-09-2017, 10:04 PM   #10
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I smoked one of my 27t trinity brushed motors running lipos, and the motor stopped running long before the lipo got warm.... The comm was glowing red in the end...
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Old 03-09-2017, 10:17 PM   #11
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It depends on how much power you take from it. In stall, motor performs almost as short circuit, taking all current aviable... When it runs without power output, it takes only ~1Amp

You can't fry motor by just running it on high discharge lipol - that's not how electricity works. Discharge rate on battery says what battery can give without damage.
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