Can I buy a plug-in amplifier to provide 14v to a servo from an 11.1 battery?

[smc-93]

I don't even how to search for these answers so I need the insight of someone smarter with electronics than myself.

I have and SHV650 I'm looking to install in a (Traxxas) 3s rig. The specs say the stall torque is 875oz/inch at 11.1v and over 1055oz/inch at 14v.

(1) Being a direct power servo, I don't imagine voltage drop would be as much of an issue as using a BEC so I should still be able to get ~875oz/inch stall torque right?
(2) Is there anything I could plug in between the battery and the ESC to boost the 11.1v battery output to 14v to feed the servo?
(3) Or is going up in battery size/power my only option.

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[islandlife]

You could run the servo off its own small 4s battery?

[Ots]

Not sure what you're asking in 1., but for 2. and 3. Islandlife has it right: if you want 14V you would have to use a 4 cell lipo. Amplifying would not be a solution for this application.

[Steve g]

What rig and what use will this servo see? Id imagine on 3s it'd be fine. Or just go for 4s for the rig. I run 4s hv on my crawlers. Nice little drone batteries fit nicely

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[smc-93]

Originally Posted by islandlife

You could run the servo off its own small 4s battery?

I suppose I could. I didn't think of that when I posted the question. If I go that route I'd have to try to find a small 4s though.

Originally Posted by Ots

Not sure what you're asking in 1., but for 2. and 3. Islandlife has it right: if you want 14V you would have to use a 4 cell lipo. Amplifying would not be a solution for this application.

Question 1 was primarily a question about voltage drop off. I read running with a BEC, you loose a bit of power.

The question I was trying (posted on my lunch break, didn't really proofread to make sure it made enough sense. My bad.) to ask is if I'm using a "direct power" servo, is there still a drop-off? Or would I get the full X-voltage of the battery?

[smc-93]

Originally Posted by Steve g

What rig and what use will this servo see? Id imagine on 3s it'd be fine. Or just go for 4s for the rig. I run 4s hv on my crawlers. Nice little drone batteries fit nicely

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It'd be installed in an ~14 pound TRX-6. HH puller pro, 540XL motor with an 11t pinion, HH Trail Master ESC, currently a Savox 2290sg servo. I'm not sure how many of those details are relevant, but maybe some of you smart guys and gals can recommend a better electronics setup.
It's not a "rock crawler" anymore but definitely a heavy duty trail truck. Eventually it'll be used to pull a 2-car gooseneck trailer as well.

There isn't really an issue running it on 3s if necessary, I thing 875oz/inch is sufficient. I have a battery box specifically sized for a Traxxas 3s, 5000mah, so I can't use a battery that's physically larger. I was only curious about switching to 4s or some kind of amplifier in order to get the most out of the SHV650.

[Panther6834]

Originally Posted by smc-93

I have and SHV650 I'm looking to install in a (Traxxas) 3s rig. The specs say the stall torque is 875oz/inch at 11.1v and over 1055oz/inch at 14v.

Your best bet it's to use an external BEC...say, Castle BB EC 2.0...and program it to provide the wanted power for the servo. Of course, I don't actually know if the Castle BEC 2.0 can do voltage that high, but I'm running to bet there's are probably other external BECs with that voltage ability. If not, there's always the small/separate 4S, as mentioned.


~ More peace, love, laughter, & kindness would make the world a MUCH better place

[HumboldtEF]

Considering the weight I'd say a small dedicated 4S battery for the servo would be a good way to go, a bit of extra weight might not be too detrimental. I setup a SCX6 like this with a 5400 mah main battery and a 1400 mah servo battery and after testing the main battery hits LVC well before the servo battery does which is nice because theres no LVC protection when running a dedicated battery (the primitive way I did it). You could come up with some way to monitor voltage but if you get the right capacity it could help you keep things simple.

On my setup there's a JST coming off the ESC so if I want to keep things simple and run everything off one 3S battery I can which is a nice backup.

[durok]

Castle BEC 2.0 - Adjustable output voltage: 4.75 to 12V, Continuous current: at 10.25-12.0V output: 7A

Better to use direct power as others here have recommended.

[smc-93]

Originally Posted by HumboldtEF

Considering the weight I'd say a small dedicated 4S battery for the servo would be a good way to go, a bit of extra weight might not be too detrimental. I setup a SCX6 like this with a 5400 mah main battery and a 1400 mah servo battery and after testing the main battery hits LVC well before the servo battery does which is nice because theres no LVC protection when running a dedicated battery (the primitive way I did it). You could come up with some way to monitor voltage but if you get the right capacity it could help you keep things simple.

On my setup there's a JST coming off the ESC so if I want to keep things simple and run everything off one 3S battery I can which is a nice backup.

In order to have LVC for a servo battery I'd probably need a dedicated ESC to regulate the power correct? That sounds like it would quickly get messy.

By "right capacity" do you mean picking the capacities that would get the servo battery close, but not below, the safe voltage once the main battery hits LVC? Then I'd essentially recharg both batteries as a pair.

Sorry for all the questions, electronics have always been a bit of mystery to me.

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[smc-93]

Originally Posted by Panther6834

Your best bet it's to use an external BEC...say, Castle BB EC 2.0...and program it to provide the wanted power for the servo. Of course, I don't actually know if the Castle BEC 2.0 can do voltage that high, but I'm running to bet there's are probably other external BECs with that voltage ability. If not, there's always the small/separate 4S, as mentioned.


~ More peace, love, laughter, & kindness would make the world a MUCH better place

I have a Castle BEC 1.0 (I think. It's the little, blue, ~$20 one) hardwired into the ESC lead to power the Savox at 8v from 3s. The CC BEC 2.0 can't increase the voltage from 11.1 (battery) to 14v (SHV650 maximum) can it?

Which then brings up another guestion. If the HH servo is direct powered from the main or a secondary battery, what do I do with the already installed BEC? Could there be another use for it or should I cut it off and use it elsewhere?

From what I'm gathering so far, it seems having a secondary mini 4s specifically for servo power would be my best option.

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[HumboldtEF]

Originally Posted by smc-93

In order to have LVC for a servo battery I'd probably need a dedicated ESC to regulate the power correct? That sounds like it would quickly get messy.

I was thinking about a cheap simple voltage checker, just leave it connected and it will beep at a certain point. Some people mount them somewhere it cant be seen.

Originally Posted by smc-93

By "right capacity" do you mean picking the capacities that would get the servo battery close, but not below, the safe voltage once the main battery hits LVC? Then I'd essentially recharg both batteries as a pair.

Sorry for all the questions, electronics have always been a bit of mystery to me.

Yeah you got it, thats basically how I've treated it. 5400 mah main battery with a 1400 mah servo battery left me with a good buffer on the servo battery, it was still at a decent charge. You could very likely go with a smaller capacity too, 1200-1000 mah maybe but its hard to say without testing.

Originally Posted by smc-93

I have a Castle BEC 1.0 (I think. It's the little, blue, ~$20 one) hardwired into the ESC lead to power the Savox at 8v from 3s. The CC BEC 2.0 can't increase the voltage from 11.1 (battery) to 14v (SHV650 maximum) can it?

Which then brings up another guestion. If the HH servo is direct powered from the main or a secondary battery, what do I do with the already installed BEC? Could there be another use for it or should I cut it off and use it elsewhere?

From what I'm gathering so far, it seems having a secondary mini 4s specifically for servo power would be my best option.

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A BEC cant raise the voltage it can only regulate it (battery voltage or lower)


I've used BEC's to regulate the voltage going to LEDs or winches but only if its needed.

[smc-93]

Originally Posted by HumboldtEF

I was thinking about a cheap simple voltage checker, just leave it connected and it will beep at a certain point. Some people mount them somewhere it cant be seen.






Yeah you got it, thats basically how I've treated it. 5400 mah main battery with a 1400 mah servo battery left me with a good buffer on the servo battery, it was still at a decent charge. You could very likely go with a smaller capacity too, 1200-1000 mah maybe but its hard to say without testing.






A BEC cant raise the voltage it can only regulate it (battery voltage or lower)


I've used BEC's to regulate the voltage going to LEDs or winches but only if its needed.

Okay. Thank you very much for all the info (Thank you everyone) It looks like I might be looking into a mini pack and a second battery mount then.

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[Steve g]

Why not just get new 4s batteries to run it all? Something like a 3500 to 4000mah 4s would be about the same size and run time as a 5000mah 3s. Then you could also gear it down some and have even better low speed control and a stronger drag brake.
If you go with a separate 4s for the servo, as others mentioned those cheap plug in LVAs work great. I run them in my son's truck so I can easily tell when his trucks hit LVC.
And just to drive the point across, BECs can only lower the output voltage, not increase it. And since they aren't 100% efficient, it's always about 0.2v lower then the input voltage. So a BEC set to 8.4v with a 2s battery at most will be 8.2v (fully charged 2s is 8.4v), and will drop as the battery voltage drops. I know you don't plan on going this route, just wanted to add some more info. Now their are transformers (a buck and boost for example) that can increase DC voltage, but they are large, expensive, and would drain the battery noticeably faster then a normal BEC.

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[Ninomaniac]

Just run it off the main 3s directly. Unless you absolutely need the torque to break steering links or knuckles.

[ferp420]

those holms hobbies servos have enuff torque to pull the treads out of plastic rod ends why bother with a seperate.battery
i have a 1/6th scale 20 pounder and the v3 will still toss the truck around on 3s the new ones have way more power than the old ones and they still have enuff torque to break parts

dont over think it just run direct power to the servo and be happy

[Greatscott]

You are looking for a voltage multiplier, not an amplifier.

But, I am trying to imagine a 1/10 rig where 800oz of torque would not be enough.

[smc-93]

Originally Posted by Greatscott

You are looking for a voltage multiplier, not an amplifier.

But, I am trying to imagine a 1/10 rig where 800oz of torque would not be enough.

That's a fair point. I was only thinking about getting all the bang for my buck and maximizing the servo output. I didn't really think about the "bang" being my steering links being ripped apart.

Originally Posted by ferp420

those holms hobbies servos have enuff torque to pull the treads out of plastic rod ends why bother with a seperate.battery
i have a 1/6th scale 20 pounder and the v3 will still toss the truck around on 3s the new ones have way more power than the old ones and they still have enuff torque to break parts

dont over think it just run direct power to the servo and be happy

That's some good information, thank you. (In my experience) I trust Traxxas plastic, but, I know HH stuff is pretty powerful as well. I don't know that I could trust the plastic that much. Now that you mention it, I might want to pick a few extra rod ends anyway.

Originally Posted by Ninomaniac

Just run it off the main 3s directly. Unless you absolutely need the torque to break steering links or knuckles.

Lol. I do not. 875 is probably plenty.

Originally Posted by Steve g

Why not just get new 4s batteries to run it all? Something like a 3500 to 4000mah 4s would be about the same size and run time as a 5000mah 3s. Then you could also gear it down some and have even better low speed control and a stronger drag brake.
If you go with a separate 4s for the servo, as others mentioned those cheap plug in LVAs work great. I run them in my son's truck so I can easily tell when his trucks hit LVC.
And just to drive the point across, BECs can only lower the output voltage, not increase it. And since they aren't 100% efficient, it's always about 0.2v lower then the input voltage. So a BEC set to 8.4v with a 2s battery at most will be 8.2v (fully charged 2s is 8.4v), and will drop as the battery voltage drops. I know you don't plan on going this route, just wanted to add some more info. Now their are transformers (a buck and boost for example) that can increase DC voltage, but they are large, expensive, and would drain the battery noticeably faster then a normal BEC.

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Upping it to 4s was my next thought but I wasn't sure what the physical size of 4s would be compared to the Traxxas 3s 5000. I don't have room far a physically larger battery.
If I could up it to 4s, I can't gear down any farther due to the motor shaft size. 11 is the smallest I could find that will fit the motor shaft that that doesn't look like it'll explode the first time it's given power. I only found one 9t but there was hardly any meant behind the teeth.
Thanks the info in the plug in LVA, I might still need one in the future.
It sounds like powering through a BEC is out of the question anyway. They can't act as multiplier/transformer to boost power and a transformer would use excess power for very little benefit. Unless you see ripping your truck apart as benefit.

I'll just stick to directly powering the servo from my existing 3s, after considering the damage 1055oz/inch could do to my rig, I think 875 will be plenty.
I'll just have to find a new use for the existing BEC. They can used, tapped from the battery lead, to regulate power to a winch right? I might add a winch further on down road when I get closer to finishing the rig.

[TheLetterJ]

I'm pretty sure you can get small "step up" converters/voltage regulators in the range you need. I don't know about being plug & play, but something like this: https://www.ebay.com/itm/38440421304...3ABFBMxqX0z9xf might work? Those ones are only rated at 2 amps, but they have an adjustable output, and there are higher amperage versions out there if you look around.

[ferp420]

extra rod ends are always good to have around i try to get the long ones for more thread engagement but it dosent always work that way and you can always cut them down
plastic rod ends are a good fuze they usualy break before doing any real damage
you will also want a quality servo horn and steering knuckles there the next 2 week links in the steering on most rigs