RC-Monster Forums - View Single Post - How exactly are people getting long run-times?

BrianG · 08.05.2009, 08:03 PM

These are the factors as I see it. Some of these may not apply to you and have already been mentioned:

- Gearing. As said, gearing lower will help a lot. The higher you gear, the more work is being done, so more current will be drawn reducing runtime.

- Cell quality. If you are approaching the cell max capability, you actually get less mAh out of it. Check an eagletree graph sometime. You'll see a 5Ah pack actually getting ~4500mAh of usable capacity if drawn hard. It gets worse the harder you run it. If your pack is rated for 40C and you only pull 20C, you will get more usable capacity.

- Drivestyle. Those heavy starts and heavy acceleration are impressive to watch, but also generates heavy current spikes, which kills runtime. Try to maintain a more constant speed so you accelerate from a faster speed, which reduces those burst currents. This takes good driving.

- ESC settings. Increasing punch control can further help tame those burst currents. This setting basically stretches out the time the ESC accelerates the motor no matter how fast you pull the trigger. The downside to this is you have less "snap" and in-air correction can be a little more sluggish. Hardcore racers generally don't like this. Also, setting your timing to the optimum setting can boost efficiency. So instead of losing power as motor/ESC heat, more of it gets to the ground. The optimum setting depends on the motor though, so you may have to research.

- Terrain. Anything other than smooth and flat takes more power to push through (like grass or beach sand). On the other hand, loose gravel can actually help since grip is less and burst current is lower.

- Weight. Obviously, more weight takes more power to haul around. This is why sometimes simply going to a larger capacity battery is not the answer as those cells are heavier for a given voltage. And lighter tires (unsprung weight) can help a lot as well.

- Voltage being used. Higher voltage on a lower kv motor is more efficient. Higher currents creates voltage drop on any resistances (wires, connectors, FETs, etc). Lower current reduces these drops so efficiency goes up.

	(#8)
BrianG RC-Monster Admin Offline Posts: 14,609 Join Date: Nov 2005 Location: Des Moines, IA	08.05.2009, 08:03 PM These are the factors as I see it. Some of these may not apply to you and have already been mentioned: - Gearing. As said, gearing lower will help a lot. The higher you gear, the more work is being done, so more current will be drawn reducing runtime. - Cell quality. If you are approaching the cell max capability, you actually get less mAh out of it. Check an eagletree graph sometime. You'll see a 5Ah pack actually getting ~4500mAh of usable capacity if drawn hard. It gets worse the harder you run it. If your pack is rated for 40C and you only pull 20C, you will get more usable capacity. - Drivestyle. Those heavy starts and heavy acceleration are impressive to watch, but also generates heavy current spikes, which kills runtime. Try to maintain a more constant speed so you accelerate from a faster speed, which reduces those burst currents. This takes good driving. - ESC settings. Increasing punch control can further help tame those burst currents. This setting basically stretches out the time the ESC accelerates the motor no matter how fast you pull the trigger. The downside to this is you have less "snap" and in-air correction can be a little more sluggish. Hardcore racers generally don't like this. Also, setting your timing to the optimum setting can boost efficiency. So instead of losing power as motor/ESC heat, more of it gets to the ground. The optimum setting depends on the motor though, so you may have to research. - Terrain. Anything other than smooth and flat takes more power to push through (like grass or beach sand). On the other hand, loose gravel can actually help since grip is less and burst current is lower. - Weight. Obviously, more weight takes more power to haul around. This is why sometimes simply going to a larger capacity battery is not the answer as those cells are heavier for a given voltage. And lighter tires (unsprung weight) can help a lot as well. - Voltage being used. Higher voltage on a lower kv motor is more efficient. Higher currents creates voltage drop on any resistances (wires, connectors, FETs, etc). Lower current reduces these drops so efficiency goes up.