Smoking Hot Battery????

[trying2fly]

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

[WintrSol]

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?

[trying2fly]

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?

I have no means to measure the power drawn by the motor.  I tried a minor upgrade from a 5x5 to a 6x4  and I took the stock esc out and put in a 30C.  Both batteries are ranked at 30C.??I will say that an inch of the wires from the original set up was smaller than the much larger wires from the battery.  The stock connector was a banana 4mm and I kept it....just clipped the wire to the old esc(18C) and soldered the connector on to the new battery.  Maybe the wire is too small in that one inch length?  What do you think?

[WintrSol]

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?

I have no means to measure the power drawn by the motor.  I tried a minor upgrade from a 5x5 to a 6x4  and I took the stock esc out and put in a 30C.  Both batteries are ranked at 30C.??I will say that an inch of the wires from the original set up was smaller than the much larger wires from the battery.  The stock connector was a banana 4mm and I kept it....just clipped the wire to the old esc(18C) and soldered the connector on to the new battery.  Maybe the wire is too small in that one inch length?  What do you think?

As noted on your other thread, the motor is attempting to draw way more power than your batteries can deliver; the wire is not the issue, it's the high rpm motor. At 30C, the smaller battery is rated to carry about 54A max; I would bet your motor is trying to draw hundreds, and the voltage is dropping very low, somehow saving the ESC. There are many relatively inexpensive Watt meters available - get one. Also, when replacing a motor, make sure you stay near the kV range of the original, or be prepared to go to a much smaller prop. A 2300kV motor is meant to drive a ducted fan, not a prop, because of the high flow rates EDF jets need. I don't know of a prop small enough to use with a motor rated that high, unless you use a 1S battery.

[trying2fly]

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?

I have no means to measure the power drawn by the motor.  I tried a minor upgrade from a 5x5 to a 6x4  and I took the stock esc out and put in a 30C.  Both batteries are ranked at 30C.??I will say that an inch of the wires from the original set up was smaller than the much larger wires from the battery.  The stock connector was a banana 4mm and I kept it....just clipped the wire to the old esc(18C) and soldered the connector on to the new battery.  Maybe the wire is too small in that one inch length?  What do you think?

As noted on your other thread, the motor is attempting to draw way more power than your batteries can deliver; the wire is not the issue, it's the high rpm motor. At 30C, the smaller battery is rated to carry about 54A max; I would bet your motor is trying to draw hundreds, and the voltage is dropping very low, somehow saving the ESC. There are many relatively inexpensive Watt meters available - get one. Also, when replacing a motor, make sure you stay near the kV range of the original, or be prepared to go to a much smaller prop. A 2300kV motor is meant to drive a ducted fan, not a prop, because of the high flow rates EDF jets need. I don't know of a prop small enough to use with a motor rated that high, unless you use a 1S battery.

Wow,  on the forum"RC Power"  they actually have a video out on converting a Hawk Sky like I did.  There is also a video I googled on HawkSky conversion and they both refer to the highly touted MJ3 as the ultimate motor to upgrade to.  They compared to lots of other motors and seem to think this is the answer for fun and speed, espec. if you trim the wings about 3 in. (which I have not done). I just wanted a zippier Hawk Sky??

[Tom]

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/

[Flygirl]

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/

Holy smokes... I'm like worlds worst at math but you just made me understand how to figure out how many amps a battery can handle... Thank you! (best explanation ever)

[STOOPIDMONKEY]

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. LOL

[Flygirl]

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. LOL

Well if that's the case Sean, guess who's gonna be getting my calculation questions? LOL!

[trying2fly]

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/

Holy smokes... I'm like worlds worst at math but you just made me understand how to figure out how many amps a battery can handle... Thank you! (best explanation ever)

Flygirl, if you like to leave 50% overhead and the plane draws 45A.....you want a 2200mah which can handle 66A???

[Flygirl]

RE: Smoking Hot Battery????

Wait a minute.... Is this a trick question? LOL! (Waiting for a question on sentence structure which I'm much better at. LOL!)

[STOOPIDMONKEY]

RE: Smoking Hot Battery????

Wait a minute.... Is this a trick question? LOL! (Waiting for a question on sentence structure which I'm much better at. LOL!)

I think that question was supposed to be directed to Tom maybe seeing as 45+45=90 and the 45A being 50% of the power available out of a 2200mah battery? I dont know but it makes better sense I think lol. I think what you need to make things all up is a 3000mAh 30C battery.

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.

[WintrSol]

RE: Smoking Hot Battery????

Wait a minute.... Is this a trick question? LOL! (Waiting for a question on sentence structure which I'm much better at. LOL!)

I think that question was supposed to be directed to Tom maybe seeing as 45+45=90 and the 45A being 50% of the power available out of a 2200mah battery? I dont know but it makes better sense I think lol. I think what you need to make things all up is a 3000mAh 30C battery.

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.

Not 50% of available current, but a 50% margin over what you need. So, 50% of 45A is 22.5A, therefore you need a 67.5A capable battery; a 2.2Ah 30C battery meets that, if you can believe the C rating for any battery.

[Flygirl]

RE: Smoking Hot Battery????

Boy oh boy do I have a headache..... ;-)

[trying2fly]

RE: Smoking Hot Battery????

Wait a minute.... Is this a trick question? LOL! (Waiting for a question on sentence structure which I'm much better at. LOL!)

I think that question was supposed to be directed to Tom maybe seeing as 45+45=90 and the 45A being 50% of the power available out of a 2200mah battery? I dont know but it makes better sense I think lol. I think what you need to make things all up is a 3000mAh 30C battery.

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.

You got it Flygirl...the math you present now is more to my liking.  A 3000 mah battery would make the math better to me!!!ha

[STOOPIDMONKEY]

RE: Smoking Hot Battery????

Ok I see Winter my bad I misunderstood Tom.