mah and runtime for racing 1/8 Buggy?

[jhautz]

Looking for info on what kind of racing run time people who are racing brushless 1/8 buggys get allong with their setup info. I am converting one right now and am trying to decide how big of a battery I should plan for needing in the battery tray.

The local track runs 20 minute mains on 1/8 buggies. Any idea what kind of battery size I would need to get through a 20 miute race?

Im going to be running a Maxtrix w a Mamba maxx on 4 or 5s. I have options as far as motors go so I can pretty much set it up for whatever KV in need. I have a 1700 kv, 2000kv and 2200kv motors.

Also, what kind of speeds should I be targeting for a rather large track. (250ft x 125ft) and a smaller indoor track (125 x 65)

Edit: Correction... Local track runs 15 minute mains, not 20.

[mtucker]

The place I race at also has 15 minute 1/8 buggy mains. I was able to go the distance with my Enerland / Poly RC 5000mAH 4S Li-Po. That is on a Neu 1512 2.5D and a Mamba Max ESC. When I charged up the battery about a week later, I put less than 4AH back in (3700mAH if I remember correctly).

I like the single battery setup to try and keep things light. Of course dual 8AH Maxamps is a great deal, but you do pay a penalty in weight.

The track I go to is a bit on the small side and with my original setup of about 39MPH top speed, I never maxed it out. I think I am about 35MPH right now and that is still plenty for the track. It doesn't seem like over 40MPH does much good unless you have extremely long straight-aways.

Matt

[jhautz]

I'm also planning on running a single pack. I have an enerland 4350mah 5s pack that I was planning on running. According to my estimates I figured that that should be just about enough, but wasn't sure. I am going to buy a 2nd pack and was thinking that I would go w/ the 5000mah, but didn't want to take the extra weight if I didnt need to.

I am guessing that the 5s pack I have will be more voltage than I really need, but I am going to be running a slightly lower kv motor than you so the speeds should be around the same as yours. Maybe slightly higher.

Sounds like the 4350mah will be really close. I guess I'll have to take it out for a practice run and time it to see how long it runs before I buy another pack.

[coolhandcountry]

You may consider like a 6000 mah pack. That may get you in the area you need.

[mtucker]

Unless your system is much less efficient than mine, you should have no problem making the 15 minutes.

You 5S pack has more energy storage than my 4S pack.

3.7V/cell *4 = 14.8V, 14.8V * 5AH = 74 Watt Hours
3,7V/cell *5 = 18.5, 18.5 * 4.35AH = 80.5 Watt Hours

For the comparison to work, you need to have the same amount of power draw. Since you are using a lower KV motor, that seems reasonable as long as it is geared right.

Matt

Edit: Oh ya, that is where I saw the picture of the big 5s Enerland cell...... in your 1/8 Buggy w/ a Outrunner Motor thread. I love my Enerland 4S pack. They just get warm after 15 minutes of racing.

[jhautz]

That makes sense to me. I think I will be OK with this also, but I'm still gonna take it out for a couple test packs before buying another pack, just to make sure. Just a little to close for me to be comfortable without real world testing.

Yea, that outrunner is just an experiment. Not sure how its gonna work. Ita a 2093kv motor, but that is an unloaded value so I am estimating it will be more like 1800 or so loaded. Plus its a much smaller motor than the Nue 1512. If the outrunner doesnt work out, I have a Neu 1515-2.5D that will be going in. Thats a 1700kv motor. but slightly longer than your 1512. Im estimating that either of these will have me right around 40-43. Probably a little hot for a indoor track, but it will be perfect for the outdoor track in the spring.

[starscream]

That sounds like a fairly large track so your runtime will be significantly less than a smaller track. You'll most likely have to test your buggy with the 4350mah 5s pack to see how long you can run before it dumps.
I agree with CC, 5000Ah may get you through 15 minutes on a short track but you'll most likely need at least 6Ah for a large track.

Keep us updated as I am very interested in your results.

Thanks

BTW
What kind of buggies are you guys running?

[jhautz]

Originally Posted by starscream

What kind of buggies are you guys running?

I'm doing a Cen Matrix. Have an Ofna MBX converted, but its not race worthy. Thing breaks every time it runs. Thats why I went w/ the Matrix. Its the beafyest buggy Ive seen.:dft009:

[jhautz]

[

Originally Posted by starscream

That sounds like a fairly large track so your runtime will be significantly less than a smaller track. You'll most likely have to test your buggy with the 4350mah 5s pack to see how long you can run before it dumps.
I agree with CC, 5000Ah may get you through 15 minutes on a short track but you'll most likely need at least 6Ah for a large track.

So you mean the average amp draw over a timed race will be higher on a large track vs a small track? Not sure I understand why. I am thinking that the highest amp draw is the first few seconds after hitting the throttle. And then under hard braking. I would think that there would be more frequent throttle stabbing and hard braking on a small track vs a large track.

What am I missing?