7XL and 5S help ?

[JB3231]

I have the Nemesis Blue 7 XLT FD(??????) motor and was running 5S Lipo. I smoked the 5th cell and had to remove it and make a 4S pack out of it for the LST2.

I tried this motor with a 3S pack and there is no top speed at all. Is there a motor from Mike that I can replace this one with to run good on 3S? The 3S batteries are so much cheaper than 5S that it would be worth the switch.

I would like to switch to the MM esc and run 3S. Can the esc handle the amp draw? What motor would be comparitive to the 7XLT on 5S running only on 3S?

7XLT + 5S =50mph
??? + 3S =50mph

I hope this makes sense. Basically I need a hot motor that can compete on only 3S with the 7XLT on 5S.

[squeeforever]

I wouldn't do it...4S minimum for a heavy truck like that...

[MetalMan]

3s really can't supply enough power. It might work if you geared it for about 30mph, but I'd guess that's as much as you could get out of 3s Lipo. 50mph will take at least 5s Lipo.

[jhautz]

I read in a couple other threads that to achieve 50mph in a Maxx requires roughly 1000 watts of power minimum based on others testing. So for rough estimate lets just use 1100wats to give a little margin for error.

Since Watts = Volts x Amps...

In a 5s (18.5v) system to get 1100 watts of power you need roughy 59 amps of constant power.

1100Watts / 18.5Volts = 59.5Amps Constant

In order to get the same 1100Watts of power in 3s (11.1V) you would need a motor and battery system capable of 99Amps constant.

1100Watts / 11.1Volts = 99Amps Constant

Lipos can generate that much output now days so theorectiaclly I would think its possible. But, assuming an optimistically 90% efficient system you would be generating 166% of the heat your current system generates. My suspision is that your current setup of a 7XL on 5s Lipo probably runs on the hot side to begin with. So adding 66% more heat to get rid of you would probably have some issues. Also none of this even takes into account the amp spikes you would see under heavy acceleration, which in a 3s setup would be thru the roof (for all the same reasons).

I'm not thinking its very realisitic.

[JB3231]

What about a 4S setup?

If you price the high Mah Lipos's in 5's they are outrageous (3-4 bills). 4S is as high as I am willing to go.

If I have to , I'll go back to nitro on the truck and just set up a buggy.

[squeeforever]

Originally Posted by JB3231

If you price the high Mah Lipos's in 5's they are outrageous (3-4 bills). 4S is as high as I am willing to go.

Thats not true at all...I have some 3S2P 8000mah packs...2 for $200...I have yet to use them, but I don't think theres anything that can go wrong, especially with the specs they have...

[Serum]

truerc cells?