Runtimes, and curious about LiPos...

[Dagger Thrasher]

Hey guys,

As you know I plan to install a twin BL setup in my Dagger sometime soon...it's really aggravating seeing as I planned to have at least half the money by now, but just haven't been able to find a job. I'll get there in the end....:M:

But anyhoo, I plan to run two Feigao 8S motors with Warrior 9918 controllers. I was planning to use two 8-cell NiMh 3300 packs, but now I'm not so sure. I might use 3600/3700's if needs be. First of all, what kind of runtimes could I expect with this setup? I'll be racing with nitros, and need to have a racing runtime of at least 7-8 minutes, preferably around 10.

But just recently I got interested in LiPos batts...I most likely won't be able to afford them, but I'm just curious. What LiPos would you suggest?

Thanks for any help!

[lipomax]

What's a Dagger? Why do you need dual brushless? A single brushless is more than enough power... or is it one of those vehicles that have separate motors for front and rear?

Lipos are approximately 2-3 x the energy density of NiMHs for the weight so given the same weight of batteries, you'll run 2 to 3 times longer!!! Batteries will cost 2 to 3 x more too.

The large polyquest packs will work well, so with the SHD 20C Kokam packs, and the large Thunderpower packs too.

[Dagger Thrasher]

Thanks for your help. Yeah, the Dagger is a twin motor truck with twin front/rear gearboxes, which is why I'm going dual. LiPos do sound tempting...but does anyone know what kind of runtime I'd get with 3300/3600mah NiMhs? I don't want to fork out on LiPos unless I really need to. Thanks.

[RC-Monster Mike]

The 3600 nimh will last quite a while with a dual setup. I couldn't tell you exactly, but as I recall, you are running 8 cells to each system? I would guess you could get 10-15 minutes of runtime, depending on gearing, terrain, etc.

[Dagger Thrasher]

Thanks Mike, that's just what I wanted to hear. You're right with the 8 cells, and I'd be mostly bashing, but with some racing on grass (Maxx tyres and 18:1 FDR). In that case, I'll prolly go with the NiMhs. Cheers!:D

[RC-Monster Mike]

That will be the heaviest wild dagger in existence! also the fastest!

[Dagger Thrasher]

*Evil laugh*

As long as those two 8S' can haul the 16 cells, that's good enough for me!:D

[RC-Monster Mike]

The two 8s motors on 8 cells each will be a pretty insane setup. Make sure your drivetrain can handle this insane power combo!

[Dagger Thrasher]

Heheheh, only driving the thing will tell I suppose. Sorry to drag the thread out, but today I did some maths and worked out the theoretical top speed of the truck with this setup:

On 18T pinions (18.3:1 FDR): 41mph
On 20T pinions (16:1 FDR): 46mph

And that's not incorporating tyre ballooning. Can't wait!:D

[lipomax]

When figuring out speed, you should really take into account the voltage drop. For a good set of batteries, you can expect a 1.2 volt cell to drop down to 1.1 or 1.05 or 1.0 volts if you really jack up the pinion gear size. If you figure that, your speed probably drops to below 40 mph with 18T pinion and probably closer to 40 mph with 20 T pinion.

[Dagger Thrasher]

That's true, I never took that into account, thanks. As stock, the Dagger gearboxes can only accept those two pinions, so only two ratios...but if needs be I can get hold of some Thunder Tech Racing adjustable motor mounts, so then I could use anything between 16T-24T.

Thanks for pointing that out.:)

[ozmatt]

Just one query re lipos, do they have the same discharge rate and nicads or nmih, I have read some stats here in oz re the korams that states the discharge rate and they dont seem to up to the nicads and stuff. www.masterinstruments.com.au
has some info, whats the general consensus with everybody? maybe in the states you can get some trick ones which we cant access here, i'd love to use them (discounting cost of course), but will i have discharge problems when running brushless or brushed?

matt

[RC-Monster Mike]

The newer kokam 3200 SHD packs can handle 64 amps continuous discharge and can handle peaks much higher. I would say that keeps up with the latest nimh technology.

[ozmatt]

Just been on the masterintruments web site, not listed, thanks for the info mike. I'll have to keep my eye out as theres a weight saving.

matt