79 replies to this topic

[cbr6fs]

J450n, on 03 January 2012 - 10:36 AM, said:

Hi Peeps,

Just Read through this and I'm having a "Beaker moment", It apears I was wrongly advised that bec's are only for nitro's,

I'm Using flux motiv esc (7.2v) and standard HPI firestorm servo (6v) and Ansmann Racing 3.1 RX.

Is it still advisable to use a bec with this setup or wait till I have to replace the servo with somthing better?

Cheers

Jason

Bit late sorry Jason but i have only just seen you post.

Really depends on what your after.
If you are not experiencing any problems like glitching or brown outs then i'd wait till you get a better servo.

In my experience there is a gain to be had on pretty much any car and system by using a decent BEC, if a cars steering is not being pushed to the limits though that gain may well not be noticable for the majority of driving.

RoughRiderBX, on 26 February 2012 - 09:22 PM, said:

I run a 6s lipo on my brushless losi 8ight T though i use a hobbyking esc. How do I program it if it isnt an MMM esc?
Jay

Absolutely no idea, last time i looked hobbyking were selling a lot of BEC's so yours ould be one of many.

Your best bet is to contact hobbyking or look on your BEC's order page and see if there is a PDF manual listed.

If not then a quick google search should bring up the answer.




Cheers
Mark

[suicideneil]

^Don't confuse a BEC with an ESC; the BEC is built into the ESC

There is nothing to actually gain from using an external or separate BEC, if your servo(s) is working fine being powered from the ESC's internal BEC- only if you are experiencing power loss or loss of control ( caused by the servo drawing too much current ), or the ESC is running hotter than you expect it to is it worth running an external BEC to power the servos. Ofcourse, if you want the full 6v ( instead of more like ~5.5v ), or you want to run a HV servo ( which needs 7.2v or more ), then it's definitely an idea to run an external BEC capable of out-putting that much voltage & enough current to cope with the servo's needs.

[cbr6fs]

suicideneil, on 27 February 2012 - 02:10 AM, said:

^Don't confuse a BEC with an ESC; the BEC is built into the ESC

There is nothing to actually gain from using an external or separate BEC, if your servo(s) is working fine being powered from the ESC's internal BEC- only if you are experiencing power loss or loss of control ( caused by the servo drawing too much current ), or the ESC is running hotter than you expect it to is it worth running an external BEC to power the servos. Ofcourse, if you want the full 6v ( instead of more like ~5.5v ), or you want to run a HV servo ( which needs 7.2v or more ), then it's definitely an idea to run an external BEC capable of out-putting that much voltage & enough current to cope with the servo's needs.

Problem is Neil there is no "one solution fits all" it really depends on the ESC, car, driving environment, servo, driver, steering components and many many other things.

So your statement is really to vague to be useful.

As an example on CC Esc's their internal BEC's are pretty terrible, but their servo's they fit on their RTR's are even worse so there is very little noticeable gain by fitting a separate BEC.

Fit a decent aftermarket servo though and the Esc's BEC really starts to struggle very quickly.
Many don't notice though as it's still a million times better than the stock servo they had before.

On a touring car for example the extra torque really isn't needed, BUT don't forget if you have a clean consistent power supply to your servo your steering will be more consistent.
Likewise if you bump up the voltage slightly you will have a slightly faster servo.

On crawlers i've yet to see a crawler that didn't experience a MASSIVE gain by fitting a BEC.
Likewise on bigger wheel'd off-road cars like say the ERevo, Savage etc.

Even my Blitz was noticeably better with an external BEC fitted

So it's my opinion that if you have the funds, can put up with the extra wiring and have space available it's a no brainer, fit a BEC.
On my touring cars/drifters i have found a small gain from fitting a BEC, but that small gain is outweighed by having all that extra wiring everywhere IMO, so in this instance i don't bother fitting a external BEC even though there is a small noticeable improvement.

As most of us have a 4 x AA battery holder knocking around in our tool boxes (as used in many Nitro cars) if your unsure then the best bet is to spend 10 mins slapping together a harness, then just try the car running the servo from the 4 x fully charged AA cells.

If you notice a gain, have the funds and space and don't mind about the extra wiring then jobs a god un



Cheers
Mark

[suicideneil]

cbr6fs, on 27 February 2012 - 02:34 AM, said:

Problem is Neil there is no "one solution fits all" it really depends on the ESC, car, driving environment, servo, driver, steering components and many many other things.

So your statement is really to vague to be useful.

My statement was clear and precise about when an external BEC is appropriate or not ( worth bothering with )- I didn't offer a 'one solution fits all' piece of advice as it happens.

Quote

As an example on CC Esc's their internal BEC's are pretty terrible, but their servo's they fit on their RTR's are even worse so there is very little noticeable gain by fitting a separate BEC.

Which is exactly what I said.

Quote

Fit a decent aftermarket servo though and the Esc's BEC really starts to struggle very quickly.

The BEC won't 'struggle' in the way you are implying- the steering will either work fine, or the ESC will start cutting out when you work the steering too much or too hard ( which is what I see guys complaining about usually ). The ESC may also run hotter than you expect it to but will still run fine with no loss of control; which is also exactly what I said. Digital servos won't just put out half power if the BEC is struggling- they'll work fine/better based on the voltage they get- if the current supply isn't strong enough then the voltage will drop > no control as the ESC cuts out. Upto that point it'll work fine- never seen anyone complaining about their steering lacking power suddenly, have seen them say the throttle & steering dies until they release both to neutral.

Quote

Many don't notice though as it's still a million times better than the stock servo they had before.

See above.

Quote

On a touring car for example the extra torque really isn't needed, BUT don't forget if you have a clean consistent power supply to your servo your steering will be more consistent.
Likewise if you bump up the voltage slightly you will have a slightly faster servo.

On crawlers i've yet to see a crawler that didn't experience a MASSIVE gain by fitting a BEC.
Likewise on bigger wheel'd off-road cars like say the ERevo, Savage etc.
Even my Blitz was noticeably better with an external BEC fitted

If your steering response is that poor when running the internal BEC then fair enough, but a servo powerful to tax the BEC would be fairly evident so hence the external one providing better power. You'd know if it was the stock servo being weak, or the new servo overloading the internal BEC though ( well, if you posses problem solving abilities and some fairly basic electrical knowledge- some guys are totally clueless so getting upto speed on the basics is a struggle, let alone something more advanced like ohm's law & such ).

Quote

So it's my opinion that if you have the funds, can put up with the extra wiring and have space available it's a no brainer, fit a BEC.
On my touring cars/drifters i have found a small gain from fitting a BEC, but that small gain is outweighed by having all that extra wiring everywhere IMO, so in this instance i don't bother fitting a external BEC even though there is a small noticeable improvement.

As most of us have a 4 x AA battery holder knocking around in our tool boxes (as used in many Nitro cars) if your unsure then the best bet is to spend 10 mins slapping together a harness, then just try the car running the servo from the 4 x fully charged AA cells.

If you notice a gain, have the funds and space and don't mind about the extra wiring then jobs a god un



Cheers
Mark

Remember what I said about the internal BEC's output voltage- you're bound to notice a difference between ~5.5v & 6v as that represents a ~9% increase. Some only output 5.1v, and that's without a load on it; a good friend tested the output voltage of some BECs with an increasing load once and found that it cut out right around the ~4.5v region I believe it was, but by then he was drawing it's rated current too which you would rarely do for a prolonged period. However, given the price of digital servos though you'd notice a night and day difference between a stock ~150in/oz .25sec/60° servo and an upgraded 250in/oz .09sec/60° servo, both running on 5.5v. Provided the internal BEC could cope ( mine copes fine on my MMM with a savox 1256tg in my Gmaxx & a couple Turnigy S8166Ms in my TXT-1 ) then there isn't a whole lot to be gained from running an external BEC in that instance- the improved servo spec more than makes up for ~0.5v difference.

For what it's worth, I find an improved servo to be a better purchase in most cases rather than an external BEC, given how poor most stock servos are ( no arguments there ). If the improved servo is too power hungry though, then it makes sense to upgrade the BEC too in order to make full use of the new servo's abilities ( assuming you really do need that obscenely fast and powerful servo in a 5lb buggy )

[J450n]

Okies, thanx for clearing it up

Cheers

Jason