Possible problem with lipo

[Drift Demon]

i have a Premium Power 2s 20C 4700mah 7.4v lipo. I've had it for about 8 months now. Only recently, 3 months ago, has it started to play up so to speak. Halway through the run, it would loose its punch & cut-off, set to 6volts, would kick in soon after. Every time this has happened, ive put it on the charger, when its fully charged it only reads around 3500, no more & no less. I have never balanced the pack, which i think is the possible culprit because it always peaks at a certain mah from cut-off. I also check the voltage of the pack when its 'empty' before i charge it, it always reads low 7volts, never in the 6volts mark where the cut-off is set. I will be grabbing a balancer sometime next week, but i though i would ask you guys because it might be something other than the pack needing a balance. cheers...

[rccardude04]

I bet one cell is significantly (+/- 0.1v+) off from the other one. When you discharge all the way to 6.0v, one is below 3v and the other comfortably above. When you charge, one will be higher than 4.2v and the other comfortably below. Probably the same cell that's higher at the end of the charge and lower at the end of the run. This is because it will progressively get weaker every cycle and farther out of balance, causing a horrible spiral.


ALWAYS balance your packs. I don't care what anybody else says, not balancing a lipo pack is bad for the battery. Every once in a while is okay on low current apps, but on cars, especially with cheaper batteries, you need to stay on top of it.


-Eric

[spawn_x]

do you recommend running a balancer while using the battery? I balance when I charge, but then had an 11.1 (which I've slowly used up during 2 week period, playing little by little) and when it ran down to 9v, one cell was at 2.92 and others at like 3.10

Is this a problem? I'm using castle max cut-off setting (which I suspect is just a bit lower than I'd like, at 9v) but not sure how sensitive to the 3v thing, hence I'm asking here :D . I charged it up and it took it, been running it for couple days, at 3.92 on average, so I don't know..

Thank you!

[rccardude04]

Using a balancer while running isn't going to do any good. You just need to keep the LVC safely above where it can cause problems. On my 2s packs, I set it to 6.3, and my 3s packs, 9.5. This leaves a safe margin for the weaker cells to stay well above 3v.

I have no idea why, but a lot of companies tend to set their LVCs to BELOW 3v/cell, and it really needs to be slightly above.

And yes, if you have ANY cell below 3.0v at the end of the run, you have a serious problem. My packs all are well above my LVC at the end of the run. I guess if you can feel the pack really lose power before the LVC cuts in, you probably need to set it a bit higher.

With the Mamba Max, you can set "custom" cutoff.

-Eric

[spawn_x]

Using a balancer while running isn't going to do any good. You just need to keep the LVC safely above where it can cause problems. On my 2s packs, I set it to 6.3, and my 3s packs, 9.5. This leaves a safe margin for the weaker cells to stay well above 3v.

I have no idea why, but a lot of companies tend to set their LVCs to BELOW 3v/cell, and it really needs to be slightly above.

And yes, if you have ANY cell below 3.0v at the end of the run, you have a serious problem. My packs all are well above my LVC at the end of the run. I guess if you can feel the pack really lose power before the LVC cuts in, you probably need to set it a bit higher.

With the Mamba Max, you can set "custom" cutoff.

-Eric

thanks, I'll give it a try, don't think I saw any custom setting for the cut-off (doing the "beep" set up, no computer plug, may have to get one..)

Thanks

[rccardude04]

Mamba Max comes with the cord. If you don't have it for one reason or another, you can use pretty much any generic USB cable... you might even have one for your phone. It's so universal that if you just have one laying around and it happens to fit, you can use it.

-Eric

[spawn_x]

Mamba Max comes with the cord. If you don't have it for one reason or another, you can use pretty much any generic USB cable... you might even have one for your phone. It's so universal that if you just have one laying around and it happens to fit, you can use it.

-Eric

mine's the basic version in clear shrink tubing, no heat sink or place for the USB, I need to snatch one of those adapters off ebay that will plug into it, gonna try to get one cheap :D

Thanks

[ElectricThunder]

You don't have a Mamba Max if it's in shrink. You have a Mamba 25/Sidewinder Micro. In that case, you need the cable, but you also need that Rx-wire-to-USB adapter/decoder.

My Mamba 25 (both of 'em) have a custom cutoff voltage; you just need to access it with the castle link software. That's all.

[spawn_x]

You don't have a Mamba Max if it's in shrink. You have a Mamba 25/Sidewinder Micro. In that case, you need the cable, but you also need that Rx-wire-to-USB adapter/decoder.

My Mamba 25 (both of 'em) have a custom cutoff voltage; you just need to access it with the castle link software. That's all.

yup that is the one. the guy at the LHS told me its the same thing but a lot cheaper, and so far he's been right, running it hard but no problems

[ElectricThunder]

The mamba 25/sidewinder micro are not the same as the Mamba Max, if that's what your LHS guy meant.

The mamba 25 and the sidewinder micro are the same. The mamba micro pro is a little different IIRC (I have a suspicion that it's just a heatsinked sidewinder micro though from some pictures I saw).

[rccardude04]

The Micro Pro is rated for 35A where the Sidewinder is rated for 25. It's prolly got a couple more FETs as well as the heatsink.

I still wish they would release car-based firmware for some of their airplane controllers for those high speed runs. You know, brake that isn't just instantly on and a neutral point that's not at full brakes.

-Eric

[ElectricThunder]

You can increase current handling by adding a heatsink (especially a large one like the micro pro has). Didn't exactly see heatsink off pictures though....so who knows what goodies are under there.

They also cannot just add new firmware to turn some of their plane ESCs into car ESCs. The processors on some of the plane ESCs they make just simply won't do that, and the circuit layout isn't conducive to setting it up with car firmware or something. I think the Phoenix ICE lineup has that potential, though it's up to castle to release the firmware.

It'd be interesting if Castle released the source code and then people could make their own firmwares. I guess that'd kinda shoot their exclusive statup algorithm deal in the foot though.

[spawn_x]

I agree about the brake

mine handles an 8000kv motor and 3c lipo and is just warm to the touch, so I guess it should be ok

[Drift Demon]

Because I do not have a balancer at this stage & cannot afford one right now, is there a way to charge each cell individually? I have a 2s 4700 7.4V lipo pack with an align connector for balance plug. I would like to charge each cell individually until i can get funds for a proper balancer...

[guver]

When the battery is full the individual cells can be checked/discharged/charged thru the balance tap. Each pair of adjacent pins is a cell. Keep the rate low because of the tiny wires/pins/connections.

[Drift Demon]

Alright, i think i understand what you mean. The align tap has 3 sets of wires, 1 red & 2 black.

So, if i connect wire 1 to positive & wire 2 to negative, that will give me the first cell? & wire 2 to positive & wire 3 to negative will give me the second cell? is that right? I mean i could wait til next week when im getting a balancer but i would rather address the problem asap...

[guver]

Pin 1 & 2 is cell one , pin 2 & 3 is cell two.

Pin 1 is also the same as the main wire and pin 3 is same as the other main wire.

Plug in 2S with balancer here, the pic is easy to understand. http://www.scriptasylum.com/rc_speed/_lipo.html

[spawn_x]

Damn! killed another 3c lipo.

somehow my transmitter was on when I tried to run my cars yesterday, and naturally the lipo was gone

grr :mad: I know, gotta be more careful, but sheesh, expensive mistakes..