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?

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

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.

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

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.

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. :no:

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.

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

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!

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.

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.

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.

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. :wink:

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.

I am running 1p pack right now, I switched back from my other 7s2p pack, I kinda like it, not as punchy, but the Revo feels more agile.

Oh, and I made a mistake, my Revo is just under 10 pounds actually, not a little over 9lbs.

Well, the higher the voltage of your pack, the higher the potential amp draw, but it depends, it can draw some amps in the right conditions when voltage drops a lot. My pack usually drops to 19volts from 23v nom., but also, I am finding that the nom. voltage is something more like 3.1 - 3.2v/cell for A123... still experimenting!

Your 8T will probably draw about 80 amps consistant peaks, sometimes hitting maybe 90 amps if you really hit on it hard. You should just get an eagletree now, they are cheap... lol, you have spent a lot of money on this R/C stuff, surely you can afford an eagletree! :rofl: Caugh! $90 Caugh!

What is the advantages of running a higher voltage 5S pack 18.5V as to a lower voltage 3S pack 11.1V? Will the higher voltage run lets say a 8xl motor faster? Will this motor run hotter at higher or lower voltage? Will your run time be longer on a higher voltage?
Anyone? I'm new at this just figured I'll ask the questions since there's so many options.

Speaking in terms of systems, higher voltage systems will draw less current than a lower voltage system. That is to say that a system based on 5S lipo turning 30,000rpms will draw less current than a 3S system turning 30,000rpms (all other things being equal). The higher voltage system will run much cooler.

I consider the 8XL and 9XL to be 4S motors. If you want to run 5S, I'd go to a 10XL.

AAngel, if you go with lets say a higher voltage will you still get the speed out of the higher turn motor or will the lower voltage with the smaller turn motors have more power? Can any BL motor take the lower or higher voltages 2S-6S?

offroader,

If you think of power in terms of watts, then yes, a 3S system will be as powerful as a 4S system, if both systems are setup to do the same amount of work.

Not all brushless motors can handle the same voltage. Motors have limitations in terms of how many rpms they can turn before tearing themselves apart.

Although some advocate running motors to higher rpms, I like to keep my setups at around 30,000 rpms. This makes for cool running no matter the ambient temperature or terrain. I run Neu motors, which are arguably the best motors available right now. A 2200kv motor on 4S or 1700kv motor on 5S is a pretty solid setup.

In answering your question, the two systems that I referred to will run about the same in terms of speed, but the 5S system will run cooler, because it will draw less current.

I actually have some 30C FlightPowers which I am dying to test out. I just need an ESC for my G2R! They are the 4500mah versions. Thats right, 135 amps continuous if they prove true to their rating, which I believe they will. The point of getting these is that, if I recall correctly, at lower drains such as 15C or so, voltage stayed as high as 3.6V per cell, which is quite phenomenal.

If I were to suggest batteries, I would suggest FlightPower Packs, the 25C or the 30C - they should be more than enough battery for anything short of a 1:1 car...

Motor question?
 

When using a 3S 11.1V or 5S 18.5V will a 8XL (2084kv) max 83A motor run hotter or a 12L (2050kv) max 51A as you see both of these motors have close to the same kv. Which motor will be more efficient in terms of longer run time and running cooler?

I think that the L can motor will run hotter. It's going to have to work too hard. The XL can will have more torque and will handle gearing better. The 8XL, as far as I'm concerned, is a 4S motor. Running it on 5S will get you heat problems. If you want to run 5S, I'd go to a 10XL.

i just picked up some Neu 30c 5000 Mah Batteries from a buddy of mine and let me tell you... they fricking rock! and in my experiance max amps has some of the worst defect rates of any battery :( (well at least since i started working for a hobby store). granted im only running 4s in my kyosho but there soooo good :)