Thanks, that reassuring. So the 60C constant and 120C burst is nothing of concern when using a 120A vesc? I didn’t think these batteries were gonna be a problem when I bought them, but I lost all the notes I took when picking them out
12s 6.6ah and 60c Multiply the 60 times the 6.6 and that’s what is said to be the continuous safe amp discharge of ur batteries without them being over drawn. That’s a very high number. The real battery number is lower than that and it’s overrated. Even at half that c rating ,30, times 6.6…200amps about. Way way more than ur motor or ur controller will be able to do and way more than you’ll need
ohhhhh okay so this doesn’t mean that I will be drawing that much 100% of the time, only that I can? That’s good to know if so, I bought these specifically to meet the FAA regulations for 100wh with a max of 3 batteries, which happens to give me 12s. I’m very much relieved, the 3 batteries were $197, I’d be pissed if I couldn’t actually use them.
I looked at the faa regulations and I had it wrong before, you can only take 3 lithium batteries total. The size can be 100 watt hours and if the airline wants it can be up to 160 watt hours. Maybe they aren’t enforcing it exactly as I think people are getting through with more. (3) 4s 6.6ah packs is a nice number to be legal just under the 100watthours and get 12s
People are definitely getting through with more, since theres no real way to know the capacity. My concern is that if for whatever reason my batteries decide to explode, the fire should be easier to control and i wont die…hopefully. im really hoping to squeeze this in a 22 inch board to carry on so that it isnt mishandled, but i need all my parts first to see what kind of real estate we’re dealing with. I think 12s 6.6a is gonna be pretty great regardless of them meeting the faa regulations, only time will tell with this 149kv motor ive got here waiting
I’m experimenting with a kv “downgrade” as well. I have a HK 6374-149kv on the way to go in place of my HK 6374-192kv. Now in theory, these motors are equivalent (same can, same magnets, same iron, same amount of copper). However, if the specs HK posts online is to be believed, the 149kv may be a better choice (hence the experiment).
That is, I compute the motor constant Km for both motors, and the 149kv should be somewhat better. Now, I will still be running 12s, so my top speed will suffer. But I’m okay downgrading from insane, certain death top speed to merely absurd top speed.
More info about Km here… http://www.motioncomp.com/pdfs/Motor_Constant_Great_Equalizer.pdf
Anyhow, Km may be a good sanity check when considering motors changes.
Higher battery voltage and lower kV motor will be more efficient, because the current will be lower. a 300 kV motor and 4S battery is less efficient than a 100 kV motor and 12S battery just by pure heat losses alone. Remember heat loss for the current is I^2 * R, so double your current, quadruple your power wasted as heat.
There is a reason why the energy grid is in the magnitudus of kiloVolts and not in the hundreds, because if it were in the hundreds of Volts you would be melting your airlines by heat losses alone.
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OK, this is true. But which one has more torque for a given wheel RPM? Or when we start from a stand still position?
not true.
it takes less amps to get the same torque from a 100kv motor as it does a 300kv motor. thinner wires but less amps needed. it all balances out and if your battery is sized correctly you can get the same performance out of any motor if the kv and battery are correctly sized. It’s true that the other wires in the system need to be increased in size if it is a heavy amp system and it can be pushing the limit on some esc but the motor itself will get just as hot.
I dont understand you about airlines. Yes powerlines benefit from transforming to volts for distances but a motor isnt a power line.
Each motor, provided that they are otherwise identical (physical size, pole amount, magnet quality, stator quality), except for different gauge motor windings and turns. As long as they have the same amount of copper on the stator. The torque would be identical, but the higher kV, lower battery voltage motor will run hotter and less efficiently due to heat losses caused by higher currents.
I found a good Vedder’s article today, which explains some of the motor characteristics. And he concludes the same thing. “As long as the copper amount is same, the motors have identical power” Chosing the right BLDC motor and battery setup for an electric skateboard | Benjamin's robotics
either will have the same torque from any position. If it’s a high kv it will take more amps, yes, but the winding is thicker so less heat. and if the battery is specd right it will be a low voltage battery with more amps to suit the motor and ultimately be the same energy and performance from battery and motor
that article is right and says that a low kv and high kv will perform the same.
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Two motors identical other than the kv will perform the same regardless of the load if the kv and voltage are matched.
If the rest of the system is the same between two motors the lower kv will have more torque. I’m saying it need not be the case though and if both systems are have optimized battery voltage and kv they’ll have the same performance and total watt hours converted to power and torque
Maybe so u don’t have to use impractical giant gears. Running a 2000kv motor with a 20:1 gear ratio is impractical but running that motor with only 2s and an esc that can put a lot of amps through will give the same performance.
Same range. Same watt hour battery. One w lots of amps one w lots of volts