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Nov 16, 2019, 04:40 PM
homo ludens modellisticus
Ron van Sommeren's Avatar
Quote:
Originally Posted by ronaldopn
... Yes, too long ESC-battery wires can kill the ESC slowly. ...
Or in minutes, it depends, as they say.
Kill esc contents
  • Two problems
    ◦ Voltage spikes higher than battery voltage: transistor/FET/chip breakdown.
    ◦ Current through input capacitors too high: overheating/popping/exploding.
  • Example four costly controllers consecutively cremated
  • Solution I: simply lengthen the motor wires instead
  • Solution II: add extra capacitors, rules of thumb
    Calculation spreadsheet
  • Capacitor type and polarity/orientation!
  • How & where (not) to add extra capacitors
    As close to or on controller.
  • DIY capacitor pack pictures
  • Capacitor & pack suppliers
  • Expert/manufacturer opinions & their rules of thumb
    They all say the same ... noise_reduction_101, switching_power_supply_design_101.
  • Cause, explanation, water hammer/knock analogy&video, theory
    References
  • Measurements & scope traces

Prettig weekend Ron
• Without a watt-meter you are in the dark ... until something starts to glow, or blow •
e-flight calculatorswatt-metershigh power motor tips&tricksCumulus MFC
Last edited by Ron van Sommeren; Nov 16, 2019 at 07:37 PM.
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Nov 16, 2019, 05:08 PM
Registered User
dhooks6's Avatar
Quote:
Originally Posted by ronaldopn
I took a quick look at the telemetry data from my last flights with the plane.
SBEC is set to 9.0V and I use five 46kg HV servos on the plane. Unfortunately, built-in Frsky RX telemetry does not record current as I thought, only voltage so we can only evaluate voltage drop.
I checked all flights from that day and voltage never dropped bellow 9.0V (it starts at around 9.3V). I did noticed (which is quite obvious) that the voltage drops occur during combinations of high throttle and/or control surfaces inputs (mainly elevator and ailerons).
Also, it seems like the SBEC holds the steady voltage of 9.3V pretty well as cell voltage drops during flight.
Ronaldo

Interesting,. .3v is minimal, would really be interesting to see current.

Are you running 9.3 on 8.4 servos ??
Nov 16, 2019, 06:42 PM
Registered User
Has anyone done testing on servo performance testing with Bec vrs receiver pack? I'm thinking of ditching a 4 year old cascle pro for a 50g 2s950 lipo on a 73 laser. After reading the write up on promoddler site...
Matt
Nov 16, 2019, 07:12 PM
Registered User
dhooks6's Avatar
Quote:
Originally Posted by mattnat
Has anyone done testing on servo performance testing with Bec vrs receiver pack? I'm thinking of ditching a 4 year old cascle pro for a 50g 2s950 lipo on a 73 laser. After reading the write up on promoddler site...
Matt

I wouldn't stress it.

The esc functions the same basic way, chopping up current to modulate power to your motor.

Seems a bit strange to me to say your electric DC motor running the prop can handle *chopped* pulses of electricity but the motors driving your servos can't .

Yes I know there's a difference in controlling current at a given voltage and controlling voltage.

But fact is that a good switching Bec does a wonderful job supplying power to servos .

An there are way more systems set with a bec them a battery.
Nov 16, 2019, 07:49 PM
Registered User
Aeroplayin's Avatar
I still try to use 2x 2S 1300mAh on even my 102" with a buffer instead of an SBEC. But I also use Savox servos that are rated between 480 oz-in (1270's) and 694 oz-in (2290's) on 7.4v. The buffer and the two batts are 173g with Deans. They are cheap, I charge a bunch of them on parallel charges, and swap them out every flight because I can. Even at 27A peaks -- which would only happen if I pin all sticks at full speed -- means a 21C discharge.
Nov 16, 2019, 08:40 PM
Registered User
dhooks6's Avatar
Quote:
Originally Posted by Aeroplayin
I still try to use 2x 2S 1300mAh on even my 102" with a buffer instead of an SBEC. But I also use Savox servos that are rated between 480 oz-in (1270's) and 694 oz-in (2290's) on 7.4v. The buffer and the two batts are 173g with Deans. They are cheap, I charge a bunch of them on parallel charges, and swap them out every flight because I can. Even at 27A peaks -- which would only happen if I pin all sticks at full speed -- means a 21C discharge.
How many servos are you running?


If your pulling from both packs that's only 10.5 c
Nov 16, 2019, 10:35 PM
Ronaldo Nogueira
ronaldopn's Avatar
Quote:
Originally Posted by dhooks6
Are you running 9.3 on 8.4 servos ??
Yes
Nov 16, 2019, 10:54 PM
Registered User
dhooks6's Avatar
Quote:
Originally Posted by ronaldopn
Yes
Well we used to run 6v on the old 4.8 servos , I guess this wouldn't be any worse
Nov 17, 2019, 07:34 AM
Registered User
Aeroplayin's Avatar
Quote:
Originally Posted by dhooks6
How many servos are you running?


If your pulling from both packs that's only 10.5 c
I don't think so because it's a buffered parallel connection that draws from the highest voltage source and it's individual capacity while buffering the other from reverse voltage. In fact, you can use two batteries of different capacities or a battery and a BEC.
Nov 17, 2019, 08:36 AM
Registered User
dhooks6's Avatar
I would think that as soon as it pulled down the voltage from highest pack the other would automatically start sharing the load?

I don't know enough about how it works to comment..



When you charge packs do they bothe need charged or is one ran down an other at a higher state of charge?
Nov 17, 2019, 08:50 AM
Registered User
Aeroplayin's Avatar
Quote:
Originally Posted by dhooks6
I would think that as soon as it pulled down the voltage from highest pack the other would automatically start sharing the load?

I don't know enough about how it works to comment..

When you charge packs do they bothe need charged or is one ran down an other at a higher state of charge?
My understanding is that the buffering diode draws from the one battery with the highest voltage just like the powersafe Rx does. They are both drawn down but don't share the open circuit protecting the one battery with the lower voltage. From the Western Robotics website:

"Paralleling connection of either battery packs or battery eliminator circuits is highly not recommended without the battery buffer. This can cause either your battery pack or battery eliminator circuit to be damaged even if there is a slight difference in voltage between the two sources. Battery packs will degrade or even burst in flames dependent on the battery chemistry if they are paralleled, and especially when there is a voltage difference between the two. The battery buffer can protect your battery pack and/or battery eliminator circuit by preventing voltage from feeding back to each other. The higher voltage of the two sources will go through the output of the battery buffer circuit and if the higher voltage source ever drops below the second source, then the second source will take over and vice versa. "
Nov 17, 2019, 01:52 PM
Registered User
Aeroplayin's Avatar
Quote:
Originally Posted by dhooks6
How many servos are you running?
Only five on the 102" because with ailerons are reinforced sheeted foam with eleven flat HD DuBro hinges. One 2290 is plenty but I still have a 1270 on them. Tom wants MORE when he flies it. I'll wait for Black Friday to pick up a few more servos. I got my 1270's for about $65 each a few years ago. No-brainer at that price. Bought a dozen. It used to cost me the same amount to buy 5 JR's for my 50cc.
Nov 22, 2019, 08:43 AM
Registered User
Aeroplayin's Avatar
New shafts and spacers for the next round of StinGRs.... made in the USA.
Nov 22, 2019, 10:16 AM
indywestrc & viehercfliers
Suds's Avatar
Quote:
Originally Posted by Aeroplayin
New shafts and spacers for the next round of StinGRs.... made in the USA.
Very, very nice!
Nov 22, 2019, 08:56 PM
I fly, therefore, I crash!!!
SteveT.'s Avatar
Cool!!

SteveT.
Latest blog entry: My shop....


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