how are you powering your 7980?

[tigman250]

I see a few people are mounting the 7980's on 2.2's, just wondering if the 10A CC Bec is big enough to handle this monster? What is your voltage settings?

[indiana mudcat]

CC BEC set to 8.4 volts. I've heard the 7980 can pull 12 amps, but my thought is if you overdraw the BEC that's still gonna be past the point any other servo would have stalled out.

[tigman250]

Bump,

anyone else running a 7980?

[Krakker]

Got one in mine, It's only set to 7.4V but I'm curious to see how well others are getting them to last on higher voltage. Honestly, I don't think setting it over 7.4V with that much torque is going to be that noticable in a 2.2 rig. (unless your counting bent steering linkages)
There's a thread in here with a servo to BEC connector pins that I'm going to use since it's less weight and clutter in the chassis than a Y harness.

[tigman250]

Originally Posted by Krakker

Got one in mine, It's only set to 7.4V but I'm curious to see how well others are getting them to last on higher voltage. Honestly, I don't think setting it over 7.4V with that much torque is going to be that noticable in a 2.2 rig. (unless your counting bent steering linkages)
There's a thread in here with a servo to BEC connector pins that I'm going to use since it's less weight and clutter in the chassis than a Y harness.

HERE is link to thread

Thanks!

[Walldog]

Originally Posted by tigman250

HERE is link to thread

Thanks!

awesome find, Thanks tigman250

[rustyrooster]

I know this is going to sound insane but stick with me…
I would like to know how LOW of voltage can you run a 7980 at and can you program a CC bec that low?
It seems we are always pushing for more, always running stuff in the red or just below redline...and then stuff breaks.

I currently run an s9157 at 6V and according to Futaba I am getting 425 oz in of torque. My point is if I feel 425 is an acceptable torque value for me and if higher voltage shortens the life of the servo and the lower voltage has longer life, then could I run a 7980 at around 5V, still get 400+ oz in of torque i am used to, and have a servo that is bulletproof as far as burning up the servo motor is concerned since I am not ‘running it close to redline’?

[PipeDreams]

I hear your theroy but a HV servo will normally need a in of 6v to run... some below that start to twitch and just do funny things. Not all but some. If hitec rates it at 7.4 or 6 then it's designed to run for a long long time at that. I have a hobbico cs170 which is basically a hitec 7955 and have been running it at 6v now for 4 years with out any problems! If you stay in they're recommended specs and use EPA's you'll be fine for a long long time!

[tigman250]

Originally Posted by PipeDreams

I hear your theroy but a HV servo will normally need a in of 6v to run... some below that start to twitch and just do funny things. Not all but some. If hitec rates it at 7.4 or 6 then it's designed to run for a long long time at that. I have a hobbico cs170 which is basically a hitec 7955 and have been running it at 6v now for 4 years with out any problems! If you stay in they're recommended specs and use EPA's you'll be fine for a long long time!

That brings up another question I have (getting a bit off topic now) are you hurting anything by not using EPA's, can you use the end of your pot (potentiometer used for steering) travel as the endpoint so you are not hitting a mechanical stop? Is the end of pot same as an EP? or are you doing something funny to the servo?

The original question still stands, is a 10A max CC BEC enough to handle the 7980? I know the numbers say so, any real world experience?

[53 willys]

Originally Posted by tigman250

That brings up another question I have (getting a bit off topic now) are you hurting anything by not using EPA's, can you use the end of your pot (potentiometer used for steering) travel as the endpoint so you are not hitting a mechanical stop? Is the end of pot same as an EP? or are you doing something funny to the servo?

The original question still stands, is a 10A max CC BEC enough to handle the 7980? I know the numbers say so, any real world experience?

when I talked to hitec about my 7980(my 1st 7980 went bad after 1 battery pack) they said the 10amp bec is not enough and the higher the volts the less amps you will be able to get out of the BEC.....they highly suggested I run the CC pro bec.....or a separate 2s lipo...both the pro BEC and a separate 2s lipo is a bit bulky for a comp rig so I continue to run the 10amp CC BEC @ 7.4v (on my new 7980)with out any stalling or problems insight......this is all on 3s.....if I go back to 4s I may start to have issues again???

[tigman250]

Originally Posted by 53 willys

when I talked to hitec about my 7980(my 1st 7980 went bad after 1 battery pack) they said the 10amp bec is not enough and the higher the volts the less amps you will be able to get out of the BEC.....they highly suggested I run the CC pro bec.....or a separate 2s lipo...both the pro BEC and a separate 2s lipo is a bit bulky for a comp rig so I continue to run the 10amp CC BEC @ 7.4v (on my new 7980)with out any stalling or problems insight......this is all on 3s.....if I go back to 4s I may start to have issues again???

so when your first 7980 died you were running 4s? I assume you were crawling, not bashing?

[PipeDreams]

Gotta remember too that if you don't solder the servo power wires direct to the bec with a servo that big you're getting huge voltage and power lose through the servo connector! That little black connector is only rated for like 5 or 7 amps. I'm sure if you wired the 7980 right to the bec it would work much better.

Yes EPA's are super important! ex. Take the front tires off and turn the the rig and radio on. Now turn full left (hold) and full right (hold) with the radio... do you hear the servo whine still at full steering throw? That means you are giving it signal to turn further but something is stopping the servo form going that far. But because you keep feeding it signal to go further it keeps trying to even though it can't so intern the servo draws huge amps and burns out the motor inside. But with EPA's you turn the end points down to where you hear no humming at full throw in either direction and now the servo never wants to power past where it physically can't go! Now it doesn't pulls huge amps to turn every time you turn the wheel unless it's bound up beside a rock. Make sense?

[53 willys]

Originally Posted by tigman250

so when your first 7980 died you were running 4s? I assume you were crawling, not bashing?

Yeah 4s...and crawler not a basher

Originally Posted by PipeDreams

Gotta remember too that if you don't solder the servo power wires direct to the bec with a servo that big you're getting huge voltage and power lose through the servo connector! That little black connector is only rated for like 5 or 7 amps. I'm sure if you wired the 7980 right to the bec it would work much better.

Yes EPA's are super important! ex. Take the front tires off and turn the the rig and radio on. Now turn full left (hold) and full right (hold) with the radio... do you hear the servo whine still at full steering throw? That means you are giving it signal to turn further but something is stopping the servo form going that far. But because you keep feeding it signal to go further it keeps trying to even though it can't so intern the servo draws huge amps and burns out the motor inside. But with EPA's you turn the end points down to where you hear no humming at full throw in either direction and now the servo never wants to power past where it physically can't go! Now it doesn't pulls huge amps to turn every time you turn the wheel unless it's bound up beside a rock. Make sense?

My 7980 is hardwired...








For the record I don't think 4s had anything to do with the servo failure..I think I just had a faulty servo out of the box...hitec was great and sent me a new servo before even receiving my broken one.

[PipeDreams]

Ya I'd have to agree that it was likely a faulty servo. Gunnar had one that kicked the bucket shortly after getting it too. I'm considering a 7980 for my xr hardwired to my bec on 4s for sure. But then I may also just run a 7950 and save a few bucks. Run it at 8.4 and it'll make tons of power. It's designed for 2s lipo use and at full charge would put out 8.4 volts so why not set the bec to that and call it a day lol.

[rustyrooster]

Originally Posted by PipeDreams

Gotta remember too that if you don't solder the servo power wires direct to the bec with a servo that big you're getting huge voltage and power lose through the servo connector! That little black connector is only rated for like 5 or 7 amps. I'm sure if you wired the 7980 right to the bec it would work much better.

Yes EPA's are super important! ex. Take the front tires off and turn the the rig and radio on. Now turn full left (hold) and full right (hold) with the radio... do you hear the servo whine still at full steering throw? That means you are giving it signal to turn further but something is stopping the servo form going that far. But because you keep feeding it signal to go further it keeps trying to even though it can't so intern the servo draws huge amps and burns out the motor inside. But with EPA's you turn the end points down to where you hear no humming at full throw in either direction and now the servo never wants to power past where it physically can't go! Now it doesn't pulls huge amps to turn every time you turn the wheel unless it's bound up beside a rock. Make sense?

Sorry tigman if we are off topic a bit but i like what is being discussed.
pipedream, what do you do when you are in a bind? if you are bound somewhere between full throw and center and you release the wheel on the tx the servo is now tring to get back to center and is now going to be at a high (max) amp draw correct? It seems ideal if you could match the servo position by steering the controler back in the direction the tires are bound (eliminating the whine even though still technically bound), but what if you can't get it exactly and it is still whining? do we get any credit for tring to get close or because the servo is in a position that does not match controler location it continues to draw max amps? I assume it still draws max amps.

Turning off the controller is going to send servo to failsafe position and again cause it to draw max amps, right?. is there a way to set failsafe modes to 'limp' where it would cut power to the servo if signal is lost? I would be interested in that to help save my stuff from damage. I have a dx3e and am not up to speed on all the fancy stuff out there.

[PipeDreams]

Dx3e has epa's! When you'r crawling and it's bound up or not turning right where the wheel on the tx is not a big deal because it's normally not trying to stay there for a long period of time. As you crawl you are always moving your servo back and forth... More often then not though you are trying to max out the steering to get tight turns thus needing the epa's. The little bit of time it spends bound up or moving isn't enough to burn it out. They are designed to take some struggle but with out epa's you'r making it work much harder then you need to. Just look how often you hold the wheel on the tx at full turn one way or the other! The hard the time the servo is having moving to it's directed position the more amps the servo will draw. Place your crawler on a table and wit it on try turn your tires by hand.. it's tough because the servo is getting signal to stay centered but if you constantly make the servo work by holding it off from it's intended position it will burn out much faster then keeping the rig rolling and letting the servo catch up to where you are instructing it to go. Set your epa's and don't worry just drive! Do you know how to set them?

[53 willys]

I put my 7980 on my xr after my 5955 robo servo at 7v kept stalling! The steering on the xr turns so sharp with vp knuckles and c's and chaotic steering link that I notice the servos have a hard time pulling it back from full lock sometimes....I hope the 7980 will cure the bind up at full lock..

[PipeDreams]

That's odd.. the shorter your servo horn is the more leverage you have and the servo works less. Is your servo horn to long?

[53 willys]

Originally Posted by PipeDreams

That's odd.. the shorter your servo horn is the more leverage you have and the servo works less. Is your servo horn to long?

It's just a standard robtronic servo horn...Maybe I'm just low on coffee but a short servo arm is gonna be less leverage and more work for a servo to move I would think...

[indiana mudcat]

Originally Posted by PipeDreams

Ya I'd have to agree that it was likely a faulty servo. Gunnar had one that kicked the bucket shortly after getting it too. I'm considering a 7980 for my xr hardwired to my bec on 4s for sure. But then I may also just run a 7950 and save a few bucks. Run it at 8.4 and it'll make tons of power. It's designed for 2s lipo use and at full charge would put out 8.4 volts so why not set the bec to that and call it a day lol.

Agreed on the 8.4.

Another point on the 7950 vs 7980 is the larger gears in the 7980, so even if you powered the 7980 at 6.0 vs a 7950 at 7.4/8.4 you still have a much stronger gearset. Gears are what I break in servo's not motors.

53 willy's I notice what your talking about at full left lock, the linkage locks up and you can't move the tire at all by hand, only by the servo arm. I believe thats what caused the gears in my 8711 to go, a shorter drag link seems to help as do longer servo arms. I know shorter arms have more power, but it's about geometery of the linkage not power.