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  1. #1
    RC Racer EclipseMantis's Avatar
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    Compatible servos?

    According to Traxxas, the vxl3s has a bec that does 2.5 amps and 6.0 volts. Does that mean that a new servo needs to have a stall current of 2.5 amps or less??

    Also, if I switch to a Spektrum receiver (and a HV servo), can I bump up the voltage to 9.6 volts? The receiver can take it.

    Lastly, why isn't there a subforum for esc questions?
    Last edited by EclipseMantis; 11-22-2020 at 08:46 PM. Reason: added stuff
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  2. #2
    RC Qualifier NitroBugg's Avatar
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    Most High Voltage servos (Savox as an example) usually run around 7.4v to 8.4v for max torque and speed. Just because a BEC can put out 9.6v, doesn't mean its a good idea to run that much "unless" your servo calls for it. I've seen some upwards of 14v, but check what you will be running first.
    Last edited by NitroBugg; 11-22-2020 at 09:13 PM.

  3. #3
    RC Champion Panther6834's Avatar
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    No matter what any of my servos are capable of running, I never run any higher than 7.4V...and, to be honest, in regards to all of the servos installed in my non-racing vehicles, all of those ESCs have the BEC set to 6V.

    The other hand of the equation is taking into consideration any other accessories...such as LED lighting...you are, or might be, running. Most RC LEDs can only accept up to 6V, so setting the BEC any higher will kill those accessories. I installed multiple LEDs in a (non-Traxxas) crawler, some of which were for up to 6V, while others were for up to 12V. Unfortunately, I forgot about changing the ESC's BEC to 6V...and, within less than 5 minutes of powering up the vehicle, the LEDs that had a 6V max blew out.


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    Last edited by Panther6834; 11-22-2020 at 10:22 PM.
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  4. #4
    RC Racer EclipseMantis's Avatar
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    I'm don't have any lights, nor plans to add them. I do know to check the max servo voltage before doing any changes. I'm more worried about the amp draw, although I don't know if I should be.

    Does the VXL-3s have an adjustable bec?
    Last edited by EclipseMantis; 11-22-2020 at 10:29 PM. Reason: <ERROR_RENDERING>
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  5. #5
    RC Champion Panther6834's Avatar
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    Quote Originally Posted by EclipseMantis View Post
    Does the VXL-3s have an adjustable bec?
    If I remember correctly, no...it's pre-set to 6.v, and non-programmable. That's one of the reasons people (myself, included) switch to non-Traxxas ESCs (especially the 6-letter brand that starts with 'C', and ends in 'e').


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  6. #6
    RC Racer EclipseMantis's Avatar
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    So I can't run a servo at more that 6 volts with that esc? I guess I should have seen that coming. At least it makes it easier to pick a servo! What about stall current?
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  7. #7
    RC Champion Panther6834's Avatar
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    Quote Originally Posted by EclipseMantis View Post
    So I can't run a servo at more that 6 volts with that esc? I guess I should have seen that coming. At least it makes it easier to pick a servo! What about stall current?
    Only thing you really need to make certain of is that any servo you buy can operate on 6V...which almost all can. The only real exception would be servos requiring direct beauty (ie. super high-voltage) power.


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  8. #8
    RC Racer EclipseMantis's Avatar
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    Thanks for your help! Sorry to keep coming back to this, but the vxl-3s has a bec of 2.5 amps. Do I need to worry about that?
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  9. #9
    RC Champion Panther6834's Avatar
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    Quote Originally Posted by EclipseMantis View Post
    Thanks for your help! Sorry to keep coming back to this, but the vxl-3s has a bec of 2.5 amps. Do I need to worry about that?
    Again, that depends on the servo, and any other accessories that are (or might be) connected. Since you said you don't intend to add any Leads, or other accessories, then you should check the servo, and see how many Amps it draws. While the BEC should, at minimum, support what the servo 'needs', it's better if the BEC had the ability to supply higher Amperage (ie. 'overhead'). If I remember correctly, the "rule of thumb" is at least 10% 'extra'. This is one of the primary reasons why people install extremal BECs. Another reason has to do with the previously-mentioned addition of accessories.

    Using one of my favorite configurations as a perfect example, I have one vehicle...a Class 3 comp crawler...with 4-wheel steering. There's a servo mounted on the front axle, as well as one mounted on the rear axle (both extremely fast, and quite powerful). To give them the fastest speed, and the highest power, they need to run at 7.4V. Additionally, one pair of LEDs (the headlights) can operate above 6V. However, the front & rear-facing lightbars, as well as the rear-mounted taillights, all operate at a 6V max (I briefly mentioned the front-facing lightbars in my previous post...the LEDs I 'killed'). After replacing the ones I killed, I was provided a solution for getting everything to work - an external BEC.

    Using an external BEC (which I programmed to operate at 7.4V), and a Holmes Hobbies dual servo adapter, I am now able to power both servos, and the headlights (which are always on), via the external BEC, which receives its power directly from the battery...but, still receives 'signal' from the Rx. Then, in regards to the ESC's BEC, that's programmed to 6V, and provides power to the Rx, front & rear-facing lightbars, and the taillights. Additionally, due to the considerably higher Amperage of the external BEC (15A), is had the ability to provide plenty of power for both servos, as well as the headlights. While not all racers use them, to you will find a fairly large number of racers using external BECs...they don't weight much, and you never have to worry about "glitching".


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  10. #10
    RC Champion zedorda's Avatar
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    When it comes to servos there is a general rule to make it really simple. If the servo can do over 300 oz of torque at the voltage you have it set at an external BEC is suggested on stock electronics. With an aftermarket ESC you need to do the math.

    You get about 100 oz of torque per 1 amp of power.
    Last edited by zedorda; 11-23-2020 at 10:31 AM.

  11. #11
    RC Racer EclipseMantis's Avatar
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    Okay, thanks! That's what I was looking for. I think I'm gonna go with the Savox SC-1258TG:

    https://www.amainhobbies.com/savox-s...BoC6Z0QAvD_BwE
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  12. #12
    RC Champion Panther6834's Avatar
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    Quote Originally Posted by EclipseMantis View Post
    Okay, thanks! That's what I was looking for. I think I'm gonna go with the Savox SC-1258TG:

    https://www.amainhobbies.com/savox-s...BoC6Z0QAvD_BwE
    Just know, in advance, that Savox servos tend to draw more power, and they tend to be noisy. If you want more efficient, and less noisy, servos, check out servos from Hitec, Futaba, Reef's, ProTek, & PowerHD. There are others, I'm sure, but these tend to be the best options.


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  13. #13
    RC Turnbuckle Jr. Dcuda69's Avatar
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    Quote Originally Posted by Panther6834 View Post
    Just know, in advance, that Savox servos tend to draw more power, and they tend to be noisy. If you want more efficient, and less noisy, servos, check out servos from Hitec, Futaba, Reef's, ProTek, & PowerHD. There are others, I'm sure, but these tend to be the best options.


    ~ More peace, love, laughter, & kindness would make the world a MUCH better place
    Agree^^ Love my Power HD 23kg. Throws my 2.8 Trenchers around like nothing!

    https://www.ebay.com/sch/i.html?_fro...+23kg&_sacat=0
    Slash 4x4 Ult 2150kv
    Rustler vxl
    Ford GT vxl

  14. #14
    RC Racer EclipseMantis's Avatar
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    If someone knows of a reputable place to get Power HD servos that ships from the US, then I'm in.
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  15. #15
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    Got my powerhd 23kg from Amazon like 3 or so years ago. Was 34 bucks then. Been over volting and abusing it since, only had to buy 1 set of replacement gears so far.

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  16. #16
    RC Racer EclipseMantis's Avatar
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    Amazon doesn't have the one I'm looking for. The Sav÷x servo (yes, I copied and pasted the ÷) gets GREAT ratings. If I get a cap for the receiver, would power consumption still be a problem?
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  17. #17
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    Caps do help, but not if you dont have your end points adjusted properly. You dont want the servo pushing past what your steering actually turns. I'm still in the old mindset of throwing caps on both the reciever and the esc. Probably not necessarily needed with newer aftermarket escs, but wont hurt anything.
    Try the Amazon search without the dots on the o of savox. Or try places like rcmart, RPP hobby, tower hobbies, even horizon hobbies.

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  18. #18
    RC Racer EclipseMantis's Avatar
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    I meant Amazon doesn't have the power hd servo. I will adjust endpoints
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  19. #19
    RC Champion Panther6834's Avatar
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    Quote Originally Posted by EclipseMantis View Post
    I meant Amazon doesn't have the power hd servo. I will adjust endpoints
    That's strange. I just did a quick Amazon search, and three are quite a few Power HD servo listings...at least seven.


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  20. #20
    RC Racer EclipseMantis's Avatar
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    Sorry, should have phrased that better. I was looking specifically for this:

    https://www.ebay.com/itm/Power-HD-6-...-/142096097509
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  21. #21
    RC Racer EclipseMantis's Avatar
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    I did some more looking around, and found this:

    https://www.ebay.com/itm/POWER-HD-B5...fOyox#rpdCntId

    It honestly seems too good to be true. Anyone else have this servo?
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  22. #22
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    That is a good seller. I've bought a lot from them. If you want that specific servo, buy it from them. When on ebay look at who the seller is. That first link you showed was of rcmart, which is another good safe place to buy from.
    I don't have that specific servo though, so no help from me for that.

  23. #23
    RC Turnbuckle Jr. Dcuda69's Avatar
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    Quote Originally Posted by EclipseMantis View Post
    If someone knows of a reputable place to get Power HD servos that ships from the US, then I'm in.
    In my link for the 23kg on ebay, the 1st listing is Gonitro Hobbies in New Jersey. I have bought from them before without issue
    Slash 4x4 Ult 2150kv
    Rustler vxl
    Ford GT vxl

  24. #24
    RC Champion Panther6834's Avatar
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    In COMPLETE agreement...I've ordered from GoNITRO Hobbies before, and had excellent results. The PowerHD servos in my Losi Baja Rey, ProBoat SonicWake, & ProMarine Skater X2, all came from them.


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