slayer battery opinions

I am converting my slayer to direct drive brushless and thought I had my battery issues figured out, but am now second guessing myself.

What I have is stock slayer w/ 1/8 buggy tires
mm with two caps.
medusa 60mm/3100kv
15t and 18t pinions 36t spur
2 speed intact and using mech. brakes

I figured it out for 3s packs, but now am am thinking of 4s or 2s packs in series. The thing I am worrying about is amp draw.
I was looking at 3s 5000mah 20c and 2s 4000 25c batts. Both should handle 100amps cont, but is that enough?

If it helps the roller with just servos and rx is 5-6lbs.

[BrianG]

Well, with a kv of 3100and using the MM, I assume you meant to put the 3s packs in parallel? Otherwise, the total rpm would be kinda high. Assuming yes, two 3s 5Ah packs in parallel nets a total of 10Ah capacity and 200A discharge rating (5Ah X 20C X 2 packs). Yes, that would be fine. I would prefer that over the 4s 4Ah 25C setup. Even on 3s, I would use a UBEC on the MM.

Do you have the motor, ESC, batteries yet? If not, I would suggest something a little different, depending on the tranny setup.

If using the two speed tranny, get a Medusa 36-60-1600, dual 3s 5Ah 20C packs in series (total of 6s) and the MMM instead. You can get away with a smaller motor since the two speed will help with low end torque and top speed.

If using a single speed tranny, I would opt for the Medusa 36-70-1600, dual 3s 5A 20C packs in series (6s total), and the MMM. The taller gearing of the single speed will work better with the 70mm Medusa.

Either way, I'd go for the MMM because; 1) it supports higher voltage and it's better to use higher voltage and lower current for a given power, 2) it has a built-in BEC, which would be about the same price as a MM and a seperate BEC, and 3) the MMM handles more current than the MM.

I have an extra mm sitting around with cc bec connected to it. I just ordered the motor the other day so its on its way. The tranny is using its 2 speed. It was the batteries I was undecided on.
I initially wanted to just run single 3s batteries in this setup as I really am not looking for back flipping power. The possibility of running the 3s in parallel will be there only if I really need the extra amperage, which is what I am unsure of.

In the previous post I meant running a single 3s or 4s battery; or running a pair of 2s batteries in series.

[squeeforever]

Originally Posted by bent70

I have an extra mm sitting around with cc bec connected to it. I just ordered the motor the other day so its on its way. The tranny is using its 2 speed. It was the batteries I was undecided on.
I initially wanted to just run single 3s batteries in this setup as I really am not looking for back flipping power. The possibility of running the 3s in parallel will be there only if I really need the extra amperage, which is what I am unsure of.

In the previous post I meant running a single 3s or 4s battery; or running a pair of 2s batteries in series.

I would just run something like a 3S2P 8000mah pack. Your setup is pretty similar to what I was planning on running. MM, 2 speed, mech. brakes, and a 7XL instead of the Medusa. If I remember right I ran it once or twice and it was quite powerful. I used a TrueRC 3S2P 8000mah pack and no BEC and it was pretty quick. Its sat quite a while and I'm about to get some more stuff to finish it up so I'll know more soon. I might go 4S though. Still not sure, much like you, but I have 2 3S packs so what the hell...

[lincpimp]

Hmm, this is a slayer right?

I currently run a slayer with a hacker 13l (1800kv) on 5s geared for 50mph. A 3700 25c 5s lipo does fine. I run buggy wheels with badlands tires. This truck really does not load the motor very hard, and the quark 125b barely gets warm...

I would say the 3100kv motor on 3s would be fine, but geat a pair of 3000mah or so packs to run in parallel, or a single polyquest 6000 3s 25c pack (my choice). I am guessing a MM will keep up, but an external bec, fan and addl capacitor are mandatory.

I'm curious what the amp draw will be? Wither or not I will have to run batteries in parallel to increase the discharge amperage. I would prefer to just run single packs.

I know this slayer has to be much lighter than a revo.....less plastic and much smaller tires/rims. So I would imagine this setup wouldn't need to be overkill.

[BrianG]

The amp draw shouldn't be too bad since you're using the two speed setup. I would still opt for something rated for around 100A+ though just to be safe.

[lincpimp]

Originally Posted by BrianG

The amp draw shouldn't be too bad since you're using the two speed setup. I would still opt for something rated for around 100A+ though just to be safe.

Always a good idea Brian. 100amps seems to be a good number to aim for for a vehicle this size.

Cool, that's what I wanted to hear. I will order up some 3s soon and see how they work individually and be able to run them parallel if needed.
thanks.

[BrianG]

Hold on a sec. What 3s 5Ah 20C battery are we talking about here? Some may be rated for 20C, but they don't hold up to that in the real world. In reality, they should be realistically rated for something like 15C. And if that's the case, 5Ah won't be enough. If using cells that fall into this category, I would shoot for a 120A value or more to be safe.

[lincpimp]

Originally Posted by BrianG

Hold on a sec. What 3s 5Ah 20C battery are we talking about here? Some may be rated for 20C, but they don't hold up to that in the real world. In reality, they should be realistically rated for something like 15C. And if that's the case, 5Ah won't be enough. If using cells that fall into this category, I would shoot for a 120A value or more to be safe.

Maxcraps? I would go with a neuenergy 5000 3s 25c pack, or the 6000 25c 3s pack from polyquest. Watch out for maxamps, their stuff is overpriced, and overrated. Let us know what batts you are looking at before you buy them...

zippys since i had good results from them and fit the budget.
mostliky the 5k flightmax in either 25c or 30c.

We'll I got the car together and am using a 2s 4000 protek lipo I already had. The car is pretty fun and temps are all quite low...just lightly warm to the touch. Speed is not bad with just a 2 cell...30-35ish I guess chasing cars down the street.
Now I need to find some affordable 3s lipos...