How exactly are people getting long run-times?

[Marvin]

I'd like to know how people are getting over 20 minutes on a single battery without stupidly high capacitys, weight or voltage.

How?!?

I simply cannot get the run-time out of the same batteries as some of you guys.

My current set-up uses a 6S 6100mAh battery to get just over 20 minutes on the track, but as a result the car weighs 4.1kg! That's truggy weight, but it's a buggy!

My original set-up was 4S 4350mAh which would earn me 11 minutes at a push. I can't do battery changes as I'm just not quick enough to make up the time lost to the nitros. Is it a case of gear down to less than the nitro buggies to get a bit of economy?

Have I gone the wrong way? Do I need smaller batteries, and a far lighter car?

Please help! I'm at my wit's end.

[Snipin_Willy]

Wow, 6s 6100 in a buggy, and ~20 min? I have a 5s 5200 in a truggy and I'm easily getting 20 and I know I get 30 min bashing. How freely does the buggy roll with and without the motor pinion engaged?
I saw someone at a track with his pinion way tight against his spur and he was complaining about punch and speed. It could have been his batteries, but the tight mesh certainly wasn't helping.

[Marvin]

It's definately free, there's no binding, and when my rotor failed on Sunday, I took the complete centre diff out (with motor still attached) and I was able to spin the spur/pinion combination like a clutch bell with those really nice 'almost failed' bearings that spin really freely.

I just thought that the tracks we race on in the UK aren't anywhere near as smooth as in the US, and also we have fewer jumps, which don't take that much throttle in comparison to sweeping corners, so presumeably the run time will be less anyway.

[E-Revonut]

5s 4500mah in my truggy get me over 15 minutes on the track. What buggy, motor, battery, and gearing are you running? You may be overgeared. I'm only geared for ~36, 50/15, just a touch faster than the nitros on the straight but enough torque to kill them at every corner

[E-Revonut]

Also.... Throttle control has a big part in runtime! Drive it like a nitro and your run time will suffer. Drive it like a 1/10 stadium truck and you'll gain a couple minutes, you gotta roll on the throttle smoothly, don't keep giving it bursts like a nitro

[Marvin]

Set-up:
D8 - Stock, so not exactly light.
Tekin RX8 w/T8 1700kV - minimum timing
Gearing 15/48 - so according to BrianG's calculator, it should be good for ~39mph
PolyRC 6S 6100mAh battery.

I'm thinking to invest in all the lightweight upgrades, see what it does to my run-time, then drop the battery size a bit. Also I'll probably gear lower (to ~35mph).

[emaxxnitro]

we gear for about 34mph im geared for 32mph right now. i can get 20 min on a 5ah 4s 30c pack. the c rating is also a factor.

[BrianG]

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.

[Gary NJ]

Mine is a D8 at 8 lbs, Tekin 1700 buggy, 4S 4000 35C, 17/40 gear, 0 timing and 70 throttle limiting, very free running drivetrain and very gentle on the throttle inputs. I've done 18 minutes with this combo and didn't hit up against the LVC set at 3.3v/cell.

[Marvin]

So, my action plan then:

1. Gear down a tad.
2. Tame my driving, possibly also using punch control.
3. Lighten the D8.
4. Use lighter cells, of higher quality.
5. Try to use the smoother parts of the track,not so much of an issue recently.
6. Stick with 6S. One question though, 6S on 1700kV? Is it a good idea considering the low current requirement?


Thanks guys, that's been really useful! Just need to put it into practice now.

[emaxxnitro]

Originally Posted by Marvin

So, my action plan then:

1. Gear down a tad.
2. Tame my driving, possibly also using punch control.
3. Lighten the D8.
4. Use lighter cells, of higher quality.
5. Try to use the smoother parts of the track,not so much of an issue recently.
6. Stick with 6S. One question though, 6S on 1700kV? Is it a good idea considering the low current requirement?


Thanks guys, that's been really useful! Just need to put it into practice now.

also clean and lube your bearings every 2 weekends. it helps with the drag

[stum]

I run both an 8ight-t 8ight-b and a e-revo and the truggy and e-revo both get about 12 minutes of run time on 4s 35c 5k packs, the buggy gets about 13. All are geared for at or just under 40mph. I have a 5s 6k pack I run in my truggy for longer a-mains as well, this gets me enough to do a 20min, but not quite enough for 30min typically. One battery swap in a 30min main works out though if it's a smooth swap.. keeping pit time evened out.

[RC-Monster Mike]

Marvin,
Try swapping to the 1400Kv motor on 6s Lipo for starters. The 1400Kv motor is the best option for this voltage IMO, and will be generous in regards to runtime. I would surmise that your driving style is also a factor - I can get the same runtime you get on a 4s 6000mah pack - only 3/4 the battery power(and while I am no pro, I don't suck, either). I use a 1900Kv system on 4s geared for around 40mph in my buggy. The 1700Kv on 6s will suck more power, but the 1400Kv on 6s should be pretty close to my setup.
Someone above mentioned to drive it like a 1/10 truck(meaning smooth throttle input) - this will make a big difference vs the constant "pulsing" that is often carried over from nitro drivers. In nitro, pulsing the throttle is helpful to keep the clutch engaged to a certain degree - in electric, it wastes power and upsets the chassis. Dropping this habit will lower mah usage and temps significantly.
So...swap to 5s Lipo or the 1400kv motor and focus on smooth throttle input and you should see a noticeable improvement in runtime(assuming there is no binding, etc. as also mentioned above).

[Marvin]

I think I may swap to 5S then. Or, if my quick change system works (you've probably received a multitude of emails from me (Simon Turner) about this recently, use the latest one, its got decent files, I had a right problem with getting a normal file type, but I've got it sorted and sent IGES files), I'll be running 4S.

[RC-Monster Mike]

Yes - I got lots of emails with files I couldn't see, but did see the IGES files this morning(though i haven't looked at them yet). :)