Hey guys I want to use Lipos on my E-Maxx which has the EVX-2 Esc and uses 2 batteries. I want to use a low voltage cutoff but I dont know if I should use 2 2-cell shut-offs or 1 4-cell shutoff? I plan on using 2 2-cell 500mah lipos. Also can someone advise how they get wired? Thanks in advance!!!


Manny

OK, been there done that - this is what you need to do - use one 2S add on lvc like the novak smart stop (I'm using that one) to protect the lipo that in addition to powering the motors, runs the receiver and the servos. Since it is putting out more than the other (it is always the same side - more on that later), using the lvc on that lipo will automatically protect the other as well.

I had been running 7 cell pacs in my Emaxx and the pacs are put together such that the same batt pac has to go in the same place everytime. I started noticing that one pac was always drained 400-700mah more than the other. Thats the side the BEC is on - the BEC is in the esc and it steps the batt voltage down to 6v and powers the servos and rx. In the Emaxx, the 2 pacs are combined in series fashion inside the EVX esc. There is no where outside the esc where you can find the total voltage so you could use a 4S lvc.

To find the BEC side (the side that runs the rx and servos), plug one pac into any side. Now turn switch on - if the green light comes on, you're plugged into the side that powers the servos and rx (the BEC side) - this is the side that needs the lvc. If the light doesn't come on, you're plugged intpo the side that just runs the motor - this is teh side that doesn't need teh lvc - it goes on teh other side. I don't know if these are wired the same, but standing behind mine, the bec side is the left side. Test yours to be sure you know which side you need the lvc on. Simple, takes about 2 min.

I assumed you are going to use 5000mah - thats what I'm running. Questions let me know, I'll be glad to help.

That was explained very nicely Duster. I use to use 7 cell packs like yours until I melted one of them I solved the drainage problem by running the wires alternately on one side then the other...if you understand what I mean.

Now I use 5000 mah Orion race packs...much better all around.

I thought of doing that and prob is my Emaxx is old enough and been thru enough owners that the esc wires are very short - too short to swap sides. I didn't want to add an extension and more connectors, so I just ran it that way.

I've been using the 30C IB5000s 2S. Def better way to go.

Ok thanks!! That makes sense. I will try it and let you know.

Remembered this, look at #10 - has wiring for lvc for pr of 2S lipos -

http://monster.traxxas.com/showthread.php?t=423790

Thanks to Suicideneil....

Ok well I tried that link but it takes me to an online store selling a charger. Anyway I tried to find the BEC side but when I plugged in one battery and pressed the button on my ESC nothing happens and I got the same results with the other side. Dont forget that I upgraded to the EVX-2 esc. Can I just plug in one battery then see if the steering servo works and if it does is that the BEC side?

No, you turn the switch on - you don't press the button on the esc - its the on/off switch. Plug the batt back in and turn the on/off switch on. If the batt is plugged ito the BEC side, the esc light will come on. If the light doesn't come on, the BEC side is the otehr side.

Sorry I messed up the link, but it is fixed now....

Ok well when I installed the EVX-2 esc it did not come with a switch and the directions state that the button on the esc is the on-off switch so what do I do now?

Just wanted to say that's a fantastic FAQ/link. Thanks!

Sorry, I've only run the orig EVX (little bit less sensitive to overvoltage ).

I wonder if your're getting the esc turned on? I just re-read your earlier note and you said it didn't light up for either side. Then yes, if the strg servo will only work with the batt on one side, I'd be comfortable that was the BEC side. But I'd want to make sure strg servo doesn't work on both sides. Try that - plug batt in and see if strg works, try both sides and hopefully it works on one side and not the other.

Post back and let us know.....

Well I just tried to see if I can find out which battery controls the steering servo by just connecting one battery and I got weird results. If I just try one battery then the light never comes on. If I plug in both batterys then turn on the truck the light comes on and if I disconnect one battery the light goes off right away and the steering servo does not work. When tried unplugging the other battery the light stays on for a few seconds and the steering servo works. What do you think?? There has to be a way of doing this. The EVX-2 comes with the E-Revo brushed version and I know people have used Lipos with that truck.

Its not a metter of using lipos - volts are volts, the esc doesn't care what the source is as long as its dc. You can run lipo without an lvc - I know plenty that do, but they race and they're on a time schedule and are off track way before getting to a lvc cutoff. Now, I'm just bashing and can easily get to having too much fun and forget all sense of time. I need and installed protection that I know works, but I use theolder EVX (3906).

Those results imply that the BEC side was the side that had the batt plugged in when the light stayed on when you unplugged the batt on the other side. Thats the only logical conclusion.

Are your batts in good shape? What I was going to suggest was running them as close to flat as possible, doing lots of turning and maybe shifting. Then on recharge see which batt takes the most - you'd have to keep up with which batt was on which side - all mine are labeled 1 and 2 and 1 is always in the left. My 7 cells pacs have to go the same way and I see a 400-500mah diff in the 2 sides consistently with the BEC side discharging the battery more.

Another thing poss to try - install your lvc as if we are thinking correctly. Then run with a pr of freshly charged lipos. Don't run to the lvc, but maybe half way and see if the recharge amounts supports that the lvc is installed on the side that is taking a little more charge.

Yeah I understand what you mean about the lipos and the erevo/emaxx but I did not fully explain what I meant. I meant that I know I have heard of people using lvc and lipos with these trucks, sorry! Anyway Yeah I will try what you suggested and I also posted the question on the Traxxas forum. I did read that link you posted and that guy does suggest the method that you did and he also mentioned doing it with the EVX-2 so it can be done. Thanks for all the help!!!!!

I pm'ed Neil over on RCM where he hangs out - seems he keeps getting banned on TRX... but I haven't heard back. He has a similar E-Revo FAQ he authored, but the lipo/lvc section is no diff that what he says his EMaxx FAQ.

I guess I'm slow to catch on, but you must have a diff esc - I just realized the EVX-2 I'm familar with is the yellow one (that was advertised as "waterproof") and searching for this one on Tower a blue one pops up. Its the one you are using cause it has no switch, so trx has changed these??