Power Issue

[Posterchild]

I've dropped in and asked a few questions, got some great help on this kit and building it. I've got a decent knowledge of building, wiring and programming R/C, however I've hit a problem I can't get past.
Here is the build sheet
XR10 Bone stock
Dual Holmes Hobbies hand wounds
Spektrum RX
Castle BEC
Single Tekin FX-R Pro
Funky dig switch I've previously received help for here.
Battery choices are 3s 1350mAh 20c/ 3s 1250mAh 45c and some 2cell lipos as well.
JR 9100T servo

HERE IS THE PROBLEM......

I've taken it for a couple test runs. @ about 30-45 seconds, it acts as if it is hitting the voltage cutoff while turning or working the servo hard. When I switch batteries and try again, I get the same result.
I believe I have the Speed control programmed properly. I have it set to Zero voltage cutoff now to try and narrow the problem down.
I have the Castle BEC set to allow an output of only 5.1V now.
No idea where to go from here. I'm going to go through the programming of the speed control again, but I'm out of ideas. That's why I'm here.

Short version.
truck acts as if it's hitting the voltage cutoff with full batteries and correct programming. WTF?

[D19er]

remove the dig switch from the picture... process of elimination.. see if problem continues... thats what i would do... good luck man...

[JohnRobHolmes]

Bump your BEC to 6.5v. At 5.1v there isn't much room for the radio to operate, so any dip in voltage from the BEC will brown out the spektrum.

[Posterchild]

Originally Posted by JohnRobHolmes

Bump your BEC to 6.5v. At 5.1v there isn't much room for the radio to operate, so any dip in voltage from the BEC will brown out the spektrum.

I'll give it a shot. Would it help if I bumped the voltage even higher?

[winnerone23]

I Would think depends on what servo you have. If ur servo can take 7.4v, you can go that high.

[Manning]

Are the batteries good? I.e., do they run a different vehicle OK?

[redrokin00XJ]

Is your BEC grounded to the RX?

[Posterchild]

Originally Posted by redrokin00XJ

Is your BEC grounded to the RX?

I am not sure what you mean by grounded. It uses the regular RX plug that goes into the receiver, so I believe so?

[Charlie-III]

Originally Posted by redrokin00XJ

Is your BEC grounded to the RX?

Originally Posted by Posterchild

I am not sure what you mean by grounded. It uses the regular RX plug that goes into the receiver, so I believe so?

Some people run the BEC direct to the servo, thus there is no direct BEC to RX ground unless you add it.

Since you're direct to the RX, then yes, you're grounded.

Does the ESC stop or does everything die? (when it dies, does the steering still work?)
If it's the ESC, is it or the motor hot?

[Posterchild]

Batteries are good, I've tested them in my Losi Comp with no issues.
When it stops working, the whole rig quits. No steering, no forward/reverse, no dig.

[Charlie-III]

Originally Posted by Posterchild

Batteries are good, I've tested them in my Losi Comp with no issues.
When it stops working, the whole rig quits. No steering, no forward/reverse, no dig.

Since you have the BEC direct to the RX, did you remove the red wire that goes from the ESC to the RX?? You should, never have 2 BEC's feeding the same equipment.

As mentioned, I think you need to raise your BEC output to 6+ volts, maybe 6.5 volts.

Do you have any Tamiya or "cheap bullet" connectors in the rig? You may be losing power there.

Also double check soldered connections, you may have a poor one (maybe battery to ESC?) that gives up under load.

[sidehill]

Originally Posted by winnerone23

I Would think depends on what servo you have. If ur servo can take 7.4v, you can go that high.

The 9100 is a 6v servo

[winnerone23]

Originally Posted by sidehill

The 9100 is a 6v servo

Ah, yes it is.. I looked twice an didn't see it in his parts list.. yep, same as my 8711..

So did you raise ur bec yet? Cause I'm having a similar problem.. but not everything shuts down.. my steering just stalls at full lock in a bind.. but my 7950 is 7.4v.. so I'm pretty sure the bec voltage deff needs turned up from the 6, I think, its set at now.

[Posterchild]

OK. Just raised the BEC voltage to 6V then to 6.4V just to make sure. Same end result.
I don't like how the stupid posts are designed on the ESC to solder to. I've checked and double and triple checked the connections. They look fine.
I'm going to swap the RX next, and go from there. Maybe even the servo next?
This stupid thing is driving me nuts.

Just to get things clear on another issue as well.
My BEC connections are as follows.
red/black leads are soldered directly to Deans battery connector
RX lead is intact and is plugged into the "bind" slot on my RX.
Same way had done it in the past with other crawlers.

[JohnRobHolmes]

Do you have another free channel to put the BEC into? I remember some older BECs had problems putting the spektrum RXs into bind mode.

[Posterchild]

Originally Posted by JohnRobHolmes

Do you have another free channel to put the BEC into? I remember some older BECs had problems putting the spektrum RXs into bind mode.

I do not have another slot.
Could I build a splitter, and piggy back another channel? ie. something I can build or buy that I can connect both the BEC and maybe the third channel to and plug it into the AUX port on the RX?

[JohnRobHolmes]

Yes you could do that. Or take out whatever you have on the Aux channel for a bit.

[Posterchild]

UPDATE**
Hadn't had any time (or ambition) to test many theories and come up empty handed again.
That said! With all of your help and a couple accidental stumbles around the site... SUCCESS!!!!!!

I made one of these, So far, so good!

Thanks again for all the advice. It is an older Castle BEC so that very well could have been my issue trying to run it through the bind slot. I suggest this trick for sure!
Now I can devote more time to my scaler KOH buggy!