How much battery do I need?

Hey guys,

I've pretty much settled on a power system for my 8ight T.

It's a Neu 1515/2.5d with a Compro 22418 running 6S. I love this setup. Everything runs cool. My question is this. I'd like to shed some weight so I was considering going to either a 4Ah or 5Ah pack and the truerc packs came to mind. I figured that with the higer voltage the C rating might not be that important.

Does anyone have any idea if a truerc 4Ah or 5Ah 6S pack would be able to keep up? How about a Maxamps 6S 4Ah pack?

[lincpimp]

The 6s 4000 maxamps may be ok, but I would go with the 5k packs. The true rc are a little heavier and have lower c rating. How about 3 trakpower packs? Probably too heavy. Maybe some flight poer 25/30c packs. You could go down to the 3700 and still have the discharge capability. Not sure how much power a 1515 can draw though....

Whats the KV?

Do a Flight power 25C pack

There light, you can get them in 3700, or 4900 mah, that would be nice and light

Or they have 30C packs, in a different range of mah

[bdebde]

I've been thinking about flightpower 3700's or 3200's for 6s. Running 3800 li/mn now and they barely get warm, but they are HEAVY compared to the flightpowers.

[zeropointbug]

Yeah, but AAngel, if you keep a higher C rated lipo, they will only run cool, uber cool when ran in higher voltage setups...

I'm just trying to find a cheaper alternative. If I can get away with running a 6S 4Ah pack, then that would make me happy. If I could use the truerc packs, that would make me even happier. I have probably a couple thousand dollars worth of lipos laying around and am ready to go on the cheap.

The FP 6S 3700 looks nice, but I wonder what the runtime would be like.

Whatever I go with, I'd like to stay around 500 grams. At just over a pound it would be perfect.

[zeropointbug]

yeah, 500 grams is nice... my 7s A123 pack was nice and light around 550 grams, and I noticed a difference between that and a 7s2p pack, but had moe power, the 7s pack made the Revo feel more agile for sure though.

I suppose 4000mah pack running 6s will run pretty cool anyways, so yah, why not go for something lighter (and cheaper).

I would like to try out 12s A123 someday, two 6s packs on each side would be nice... then get a GM single speed tranny to free up some room. Only thing, my 'monster' Quark 125 can't do 12s.

In the end, AAngel, it's all up to you.

zpb, it really is too bad that we live so far from each other. You like to experiment as much as I do, although it appears that my experimentation more often winds up making smoke.

I'm going to work with the 6S for a while. I really need to quite spending so much money on this stuff. My next controller, however, is going to be 8S capable, so I'm not abandoning it, just putting it on the back burner.

[zeropointbug]

Ah yeah, but be thankful that we have forums like this one...

LOL, I couldn't imagine myself spending as much as you do on this R/C stuff... it goes to other projects I'm doing, such as my electric Toyota truck conversion, and the like... hehe.

Do you know of a controller that will do 12s A123 AAngel? I am thinking I would use a 1521/2Y as that would get me around 30,000rpm, or maybe a 1515/2Y, but that would rev to 42,000rpm, a lot of power!

[othello]

A Kontronik Jazz 55-10-32 would fit. Up to 43v (10s lipo). 12s A123 would settle quickly below 43v when fully charged. Integrated car program with proportional brake and reverse. The ESC is listed for 55A and 65A for 10 sec. Heli guys do see peaks of up to 120A with 10s = 4KW. At this power levels proper cooling is needed.

I am using this ESC in my 1:8 buggy with 10s1p A123 without issues and it gets only warm to the touch with peaks up to 1600 Watt.

Another option would be to use a flight ESC with a brake servo. HugeOne is using a CC phoenix 85HV in his 12s 1:8 buggy. See this thread.

[Finnster]

The MGM 9032 would work as well. I have one and am trying to finish all the repairs from the bash and reinstall the new motor/esc. THe esc is much bigger than a MM, so some creativity was needed to make it fit nicely.

[zeropointbug]

Oh right! I didn't even think of the MGM esc.... that one should work good I think. thanks.

Othello, I don't like the idea of running an airplane esc in a truck, just doesn't rub me right. Thanks anyways!

I really need to get an eagletree, so that I have an idea of how much battery I need, in terms of C rating.

My whole point is that these controllers are getting expensive. It seems that, as of late, I've graduated to the ~$400 controllers. There just has to be a break someplace. I was hoping that going to 6S would allow me to run the ~$150 battery packs from places like truerc.

If anyone has any idea of what a Neu 1515/2.5d (1700kv) pulls in terms of amps in a 6S configuration in a truggy, please share the info. Maybe I should have gone with a lower kv motor.

[zeropointbug]

Depends how you are gear my friend. My 1512/3D draws up to 75 amps geared for 45mph, on 7s A123 pack. MY Revo is now just over 9 pounds, very light, and accelerates like mad.

So if you can guess on your weight, and speed, then I can guess on amperage, I have taken a few eagletree's on my setup, and have enough experience that I should be close.

My truggy (8ight T) weighs just over 10 lbs, with the 6S 4.8Ah pack. That's why I'm considering going back to 5S. The battery packs that have any sort of capacity are really heavy; and I don't think that there is enough of a voltage difference between 5S and 6S that I can actually start using cells that have less capacity.

zpb, what configuration is that A123 pack? Is it a 1P or 2P? I'm just wondering because your high amp draw may be due to the voltage of your pack dropping, if you are running in 1P configuration.

In all honesty, it's all about the cost of the batteries at this point. I've been using the pricier batteries, but I have to admit that the danger of destroying one while clowning around is always in the back of my mind. For just playing around, I'd love to be able to run a 6S 4Ah truerc pack, but from what you're saying, those packs won't be able to keep up.