Is this okay with lipos??

[yukon635]

For all of you lipo experts, help a dummy out. would it be okay to take TWO 2 cell (7.2v) packs and charge them differently (each with a deans connector on the ends) and then connect them with a y-harness to be ran to the esc's. will the esc's recognize that they are drawing from 4 cells?

also since there are TWO 2 cell packs at 1320 mah each, could i consider that basically like a 4 cell 2640 pack now??

thanks guys just want to check so i dont screw up my electronics.

[Scattman]

I know depending on how the two packs are wired that it is either 7.4 2640mah or 14.8 1320mah.

You running one or two esc's?

[4u2nv]

first thing is 2 cell lipos are 7.4v It all depends on how you wire them. You could either wire them in series which would double your voltage making it a 4s pack (14.8v) or in parallel which would double the capacity and still maintain 7.4v

[yukon635]

Originally Posted by scattman

I know depending on how the two packs are wired that it is either 7.2 2640mah or 14.4 1320mah.

You running one or two esc's?

yeah i am running two esc's

Originally Posted by 4u2nv

first thing is 2 cell lipos are 7.4v It all depends on how you wire them. You could either wire them in series which would double your voltage making it a 4s pack (14.8v) or in parallel which would double the capacity and still maintain 7.4v

oops, yeah i meant 7.4v

so it sounds like ill be okay it just depends on whether or not i want to connect them in series or parallel

[Scattman]

Originally Posted by 4u2nv

first thing is 2 cell lipos are 7.4v It all depends on how you wire them. You could either wire them in series which would double your voltage making it a 4s pack (14.8v) or in parallel which would double the capacity and still maintain 7.4v

Fixed And all I run is lipo's

[readytocrawl]

What are the C rating's?

[yukon635]

Originally Posted by readytocrawl

What are the C rating's?

20C

[Kamikaze]

Hey kevin, you can do that if you want to, wire them in parrallel and you will keep 7.4 voltage and double your mah rating, also you will double the amp draw that you can have. So you will have a 2p2s 2640 mah lipo that will pull 52 amps continuous. I would still charge them sepperate though.

[4u2nv]

If you are running two speed controls I think you are going to need to use one battery for each esc. I don't think you can use a y adapter to connect them all together.

[4u2nv]

Originally Posted by Kamikaze

No, you need to y harness the batteries and then y harness the 2 esc's. 2 reasons, 1 for the combined amp draw, you stick your rear in a hole and need to force it out, with only one battery you only have 26 amps to draw from where as you could have 52. And 2, if one pack dies durring a run, which will happen cause one end is gonna need more juice than the other then you are waisting the added capacity left in the other pack. I have been running dual esc's with much success since '05.

I Never knew that would work that way.... I always run one esc so I wasn't really sure. This gives me a good idea for a brushless race clod

(This should have been post #14 I don't know what's going on here)

[Thorsteenster]

Originally Posted by 4u2nv

If you are running two speed controls I think you are going to need to use one battery for each esc. I don't think you can use a y adapter to connect them all together.

I would recomend that. If your running 2 ESC's and 2 2 cell LiPo's, why bother Y'ing the batteries togther? Just run a pack per ESC.

[yukon635]

Originally Posted by Kamikaze

Hey kevin, you can do that if you want to, wire them in parrallel and you will keep 7.4 voltage and double your mah rating, also you will double the amp draw that you can have. So you will have a 2p2s 2640 mah lipo that will pull 52 amps continuous. I would still charge them sepperate though.

okay i dont know what the 2p2s is but i understand what you are saying about doubling the maH. i just figured if i wired them in series, i would double the voltage (increase in punch and low end torque) but because of the higher voltage, the truck would pull as much mah from them as if they were just 7.4v.

so you are saying that the 52 amps continuous will allow me to acheive more low end torque but still gain more battery mah I think i read all the previous posts right but might not have

[Kamikaze]

Originally Posted by 4u2nv

If you are running two speed controls I think you are going to need to use one battery for each esc. I don't think you can use a y adapter to connect them all together.

Originally Posted by thorsteenster

I would recomend that. If your running 2 ESC's and 2 2 cell LiPo's, why bother Y'ing the batteries togther? Just run a pack per ESC.

No, you need to y harness the batteries and then y harness the 2 esc's. 2 reasons, 1 for the combined amp draw, you stick your rear in a hole and need to force it out, with only one battery you only have 26 amps to draw from where as you could have 52. And 2, if one pack dies durring a run, which will happen cause one end is gonna need more juice than the other then you are waisting the added capacity left in the other pack. I have been running dual esc's with much success since '05.

[S1NN3R]

Originally Posted by raptorman57

Thats because you fail to see he's either looking for HIGHER amp draw for more motor or HIGHER voltage for increased wheelspeed. Just depends on how he wires it up.

Either way will work. He will still get the higher amp draw effectively, because each motor will have 26 amps available exclusively instead of sharing 26 amps, which will basically be the same as letting them share 52 amps. Giving a motor more amps that it needs will not give you any more power. You'll only see a power increase if the motor needs more amps that it's getting. For example, if you have a motor that can draw 30 amps and you go from supplying 26 amps to giving it 52 amps, you WILL see a power increase. But if your motor only requires 20 amps, then changing from a battery that gives 26 amps to one that gives 52, you WILL NOT see a power increase. I have not put one of these motors on a meter to see what the amp draw is, but from my experience it's got to be way less than 15, since you can run two of them on an EVX with no problem at all, and the EVX is rated to 30 amps according to the Traxxas guy that I spoke with.

"Y"ing them together will probably increase runtime though, since the batteries will discharge equally even if one motor requests more power, where if they are each run to a single speed control, the rear motor will almost always have a higher load and thus a higher amp draw than the front, which would cause the rear battey to discharge faster.

(edit, how did my post end up above the one I was quoting?)

[Reflection]

Originally Posted by thorsteenster

I would recomend that. If your running 2 ESC's and 2 2 cell LiPo's, why bother Y'ing the batteries togther? Just run a pack per ESC.

Thats because you fail to see he's either looking for HIGHER amp draw for more motor or HIGHER voltage for increased wheelspeed. Just depends on how he wires it up.

[Thorsteenster]

Ah, gotcha. And thats why I haven't built a super yet.

[Kamikaze]

Originally Posted by S1NN3R

Either way will work. He will still get the higher amp draw effectively, because each motor will have 26 amps available exclusively instead of sharing 26 amps, which will basically be the same as letting them share 52 amps.

No, when you drive a dual esc's clod on seperate channels there are alot of times when you are just driving one motor, one of those being to force your way out of a bind. If the packs are sepperate he will only have 26 amps to pull from on one motor, by running them together he can draw from both packs to power one motor out of a bind. 26 amps in not a lot in a super truck, expecialy in a bind. Same goes for servos, I used to run 2 cool becs on my super truck but I y'ed them together befor the went to the rx instead of one for each servo, because one servo will stall at 5.4 amps, so with only 3 amps avalible with each bec having them sepperate would limit each servo to a max of 3 amps, it I y them together and one is loose and the other hung it will divert power from tboth bec to supply the servo with its max amp cappacity. Kevin, just y them together.

[S1NN3R]

Originally Posted by Kamikaze

If the packs are sepperate he will only have 26 amps to pull from on one motor,

I agree with that. Run in parallel will provide double the amps available to either or both motors. I just don't see how a high turn motor like most crawlers are running will ever get near 26 amps. I might be wrong, as I said I've never put one on a meter and stalled it, but since an E-Maxx doesn't draw more than 30 amps in a bind running TWO lower turn motors, I don't get how a single lathe could draw more. If I remember correctly, the Titan motors draw more than double the unloaded amps of a 55T lathe, so how would the lathe then surpass the Titan on loaded amp draw?

Originally Posted by Kamikaze

one servo will stall at 5.4 amps, so with only 3 amps avalible with each bec having them sepperate would limit each servo to a max of 3 amps, it I y them together and one is loose and the other hung it will divert power from tboth bec to supply the servo with its max amp cappacity.

I also agree with that. You benefitted because the servo was stalling at a higher amp draw than your BEC would provide. But if your servo stalled at 2 amps and you wired two 3 amps BECs together, you would have seen no improvement.

I guess I'l have to stall my 55T Wheely King on a meter tomorrow and see what the amp draw is. If it's less than 15, you buy me a Coke, savvy?

[JohnRobHolmes]

Don't run one battery to each ESC, put them in parallel with each other and with both ESCs. This way they discharge at the same time. For a race clod I would recommend a different setup alltogether.