I am running a Grayson MJ3 motor on my Hawk Sky. I have an 1800mah 3s 11.1V battery and a 2200mah 3s ll.l V battery. Both get hot but the 1800mah literally melts the velco off on some flights....usually when I sit on the throttle real hard. Why does the little battery (1800) get soooo much hotter than the 2200? The motor is so hot I can't touch it for a few min after flights. What is the deal? Thanx
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Smoking Hot Battery????
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RE: Smoking Hot Battery????
You are simply drawing more power than the battery can deliver, and that the motor should handle. All batteries have internal resistance, and current flowing will heat that resistance; generally, low-C rated batteries have higher internal resistance, as do smaller mAh batteries. You don't mention the C ratings, but if that 1800 is a 10C battery, it is rated to provide only 18A; drawing that much current will heat it up. Also, that heat has to go somewhere, so if the battery fits tightly in the foam, with little air flow, the heat is trapped, making the problem worse. The motor gets hot for the same reason, which is why they have maximum current and Wattage ratings; if it is getting hot, it is drawing too much of both. Did you change the prop? Did you measure the power drawn by that motor?
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RE: Smoking Hot Battery????
Originally posted by WintrSolYou are simply drawing more power than the battery can deliver, and that the motor should handle. All batteries have internal resistance, and current flowing will heat that resistance; generally, low-C rated batteries have higher internal resistance, as do smaller mAh batteries. You don't mention the C ratings, but if that 1800 is a 10C battery, it is rated to provide only 18A; drawing that much current will heat it up. Also, that heat has to go somewhere, so if the battery fits tightly in the foam, with little air flow, the heat is trapped, making the problem worse. The motor gets hot for the same reason, which is why they have maximum current and Wattage ratings; if it is getting hot, it is drawing too much of both. Did you change the prop? Did you measure the power drawn by that motor?
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RE: Smoking Hot Battery????
Originally posted by trying2flyOriginally posted by WintrSolYou are simply drawing more power than the battery can deliver, and that the motor should handle. All batteries have internal resistance, and current flowing will heat that resistance; generally, low-C rated batteries have higher internal resistance, as do smaller mAh batteries. You don't mention the C ratings, but if that 1800 is a 10C battery, it is rated to provide only 18A; drawing that much current will heat it up. Also, that heat has to go somewhere, so if the battery fits tightly in the foam, with little air flow, the heat is trapped, making the problem worse. The motor gets hot for the same reason, which is why they have maximum current and Wattage ratings; if it is getting hot, it is drawing too much of both. Did you change the prop? Did you measure the power drawn by that motor?
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RE: Smoking Hot Battery????
Originally posted by WintrSolOriginally posted by trying2flyOriginally posted by WintrSolYou are simply drawing more power than the battery can deliver, and that the motor should handle. All batteries have internal resistance, and current flowing will heat that resistance; generally, low-C rated batteries have higher internal resistance, as do smaller mAh batteries. You don't mention the C ratings, but if that 1800 is a 10C battery, it is rated to provide only 18A; drawing that much current will heat it up. Also, that heat has to go somewhere, so if the battery fits tightly in the foam, with little air flow, the heat is trapped, making the problem worse. The motor gets hot for the same reason, which is why they have maximum current and Wattage ratings; if it is getting hot, it is drawing too much of both. Did you change the prop? Did you measure the power drawn by that motor?
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RE: Smoking Hot Battery????
The 1800 can pump out less amperage as compared to a 2200 even when both are 30C. I'll do the math. This will likely illuminate the issue the best. The bottom line is the batteries are heating up because the prop/motor combination is drawing more amperage than the battery can handle creating a potential dangerous situation.
1800mAh = 1.8Ah
1.8Ah x 30C = 54A
54A is the highest possible sustained amperage which can be drawn from this battery.
2200mAh = 2.2Ah
2.2Ah x 30C = 66A
66A is the highest possible sustained amperage which can be drawn from this battery.
Personally, I like to leave 50% overhead. If the plane draws 45A, I want a 2200mAh 30C battery which can handle 66A.
As batteries age or are abused, the IR (internal resistance) climbs which effectively lowers the C rating. There is no way you can stop this. IR will climb as they age. If you run your batteries below 3.7V per cell (measured at rest after you land), you will raise the IR and potentially kill your battery. Storing your batteries fully charged or under charger will cause IR to go up. They should be stored at 3.85V per cell (or so). So 30C may not be 30C depending on how the batteries were treated or how old they are.
Hopefully this clears it up a bit. Your best friend is a watt meter if you are going to do any changing of props, motors, etc. You can find them here: http://www.motionrc.com/power-meters/
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RE: Smoking Hot Battery????
Originally posted by Tom.MotionRCThe 1800 can pump out less amperage as compared to a 2200 even when both are 30C. I'll do the math. This will likely illuminate the issue the best. The bottom line is the batteries are heating up because the prop/motor combination is drawing more amperage than the battery can handle creating a potential dangerous situation.
1800mAh = 1.8Ah
1.8Ah x 30C = 54A
54A is the highest possible sustained amperage which can be drawn from this battery.
2200mAh = 2.2Ah
2.2Ah x 30C = 66A
66A is the highest possible sustained amperage which can be drawn from this battery.
Personally, I like to leave 50% overhead. If the plane draws 45A, I want a 2200mAh 30C battery which can handle 66A.
As batteries age or are abused, the IR (internal resistance) climbs which effectively lowers the C rating. There is no way you can stop this. IR will climb as they age. If you run your batteries below 3.7V per cell (measured at rest after you land), you will raise the IR and potentially kill your battery. Storing your batteries fully charged or under charger will cause IR to go up. They should be stored at 3.85V per cell (or so). So 30C may not be 30C depending on how the batteries were treated or how old they are.
Hopefully this clears it up a bit. Your best friend is a watt meter if you are going to do any changing of props, motors, etc. You can find them here: http://www.motionrc.com/power-meters/Lauren
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RE: Smoking Hot Battery????
LOL Lauren Math is not like riding a bike, if you don't use it you loose it. Well that's my experience any way. For my engineering degree I had to take lots of math classes, I'm glad I kept all of my books and notes I use them for reference to help my kids do their homework. LOLFlight Risk (Sean)
AMA # 986105
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RE: Smoking Hot Battery????
Originally posted by STOOPIDMONKEYLOL Lauren Math is not like riding a bike, if you don't use it you loose it. Well that's my experience any way. For my engineering degree I had to take lots of math classes, I'm glad I kept all of my books and notes I use them for reference to help my kids do their homework. LOLLauren
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RE: Smoking Hot Battery????
Originally posted by FlygirlOriginally posted by Tom.MotionRCThe 1800 can pump out less amperage as compared to a 2200 even when both are 30C. I'll do the math. This will likely illuminate the issue the best. The bottom line is the batteries are heating up because the prop/motor combination is drawing more amperage than the battery can handle creating a potential dangerous situation.
1800mAh = 1.8Ah
1.8Ah x 30C = 54A
54A is the highest possible sustained amperage which can be drawn from this battery.
2200mAh = 2.2Ah
2.2Ah x 30C = 66A
66A is the highest possible sustained amperage which can be drawn from this battery.
Personally, I like to leave 50% overhead. If the plane draws 45A, I want a 2200mAh 30C battery which can handle 66A.
As batteries age or are abused, the IR (internal resistance) climbs which effectively lowers the C rating. There is no way you can stop this. IR will climb as they age. If you run your batteries below 3.7V per cell (measured at rest after you land), you will raise the IR and potentially kill your battery. Storing your batteries fully charged or under charger will cause IR to go up. They should be stored at 3.85V per cell (or so). So 30C may not be 30C depending on how the batteries were treated or how old they are.
Hopefully this clears it up a bit. Your best friend is a watt meter if you are going to do any changing of props, motors, etc. You can find them here: http://www.motionrc.com/power-meters/
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RE: Smoking Hot Battery????
Originally posted by FlygirlWait a minute.... Is this a trick question? LOL! (Waiting for a question on sentence structure which I'm much better at. LOL!)
3000mAh = 3.0Ah
3.0Ah x 30C = 90A
90A = double the power you might be drawing in this scenario that Tom laid out for us.
Even a 2200mAh 40C battery would work in this scenario.Flight Risk (Sean)
AMA # 986105
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RE: Smoking Hot Battery????
Originally posted by STOOPIDMONKEYOriginally posted by FlygirlWait a minute.... Is this a trick question? LOL! (Waiting for a question on sentence structure which I'm much better at. LOL!)
3000mAh = 3.0Ah
3.0Ah x 30C = 90A
90A = double the power you might be drawing in this scenario that Tom laid out for us.
Even a 2200mAh 40C battery would work in this scenario.
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RE: Smoking Hot Battery????
Originally posted by STOOPIDMONKEYOriginally posted by FlygirlWait a minute.... Is this a trick question? LOL! (Waiting for a question on sentence structure which I'm much better at. LOL!)
3000mAh = 3.0Ah
3.0Ah x 30C = 90A
90A = double the power you might be drawing in this scenario that Tom laid out for us.
Even a 2200mAh 40C battery would work in this scenario.
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