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Old Sep 18, 2012, 01:41 PM
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Originally Posted by vespa View Post
a scope may not be fast enough to measure this...Fluke meters even have a "fast min/max" capture...
You're comparing a multimeter's response to a 1GS/s digital storage scope? I assume you're kidding. My direct observations stand as stated above. Re: the Castle BEC's problems there have been reported cases where their voltage seems to fold back* when subjected to some loads that should not have caused a drop.

* voltage drop that stays dropped (i.e. load memory) even after the load is removed.

If you'd like to debate the tech issues of measurement techniques I'm very happy to continue this offline. Always willing to learn more. .
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Old Sep 18, 2012, 02:21 PM
GER 3788
Joined Feb 2012
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Hey all....

I am using the BECs with a 2s 450mAh Lipo

The size of the voltron is not an issue.

Here CC BEC: 30x15x10 (old version without big CAP)
Here Voltron: 18x42x11mm.

Somehow I will get it in, otherwise I will sell em and go for a linear technologies voltage regulator..letīs see.
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Old Sep 19, 2012, 01:34 AM
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Quote:
Originally Posted by vespa View Post
Chris, a scope may not be fast enough to measure this though it looks as though yours is trying -- but you dismiss the readings as artifacts? Try the test with a multimeter that captures minimums. Fluke meters even have a "fast min/max" capture which is really fast (maybe too fast) and can give pretty shocking numbers (excuse the pun). The faster the measurement, the wilder the readings become, so it's really only useful to measure on a timescale that is similar to that of the capacitors in your RX and servos. I was easily able to produce "slow min/max" readings well below 3V with a glider powered by 2A LiFe + CCBEC and they exactly coincided with reboots of servos and/or receiver.
Very interresting Vespa.

Sounds closely related to some other problems CC might be having with their speed controllers. I may need to think about what equipment to use that will measure fast enough.

If I am not mistaking, are there not 2 different situations that can lead to a problem. The first being when the switching reg first powers up and the second when it is subjected to fast changing loads? I thought Matze's problem was due to the first? So really we should try to capture both events in a test. Load the output up with some varying capacitance and impedence caps before applying power to the circuit.

All is not easy for a switcher!
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Old Feb 06, 2013, 02:21 PM
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Friends,

I just discovered this discusison and want to thank you all for an education in servos, batteries, BECs and things that go bump in the night.

Now for the DUMB QUESTION OF THE DAY!

It seems that much of this is driven by a desire to use LiFe or perhaps 2S LiPo packs to drive your receiver/servos. To do this you introduce another device, a BEC. OK.

What was wrong with the 4S and 5S NiCd and NiMh packs that the receivers/servos were designed to use?

I have nothing against the lithium packs, but if you have to introduce a new point of failure into the system to make them work, why do it? Why not just use NiCd or NiMh packs for those radio/servo combos that don't like the higher voltages of he lithium systems. What is the motivation to change?

I am no world class competitor so I do realize I am probably asking a dumb question, but that is how I learn.

When I switched my Supras, Graphite and Ava over to Futaba FASST 2.4GHz I considered going to Lithium of some kind. But the need to add a regulator bothered me, so I stayed with 5 cell 2/3A packs. These are the same cells that electric pilots use to drive their motors so they certainly can handle 10+ amp loads while holding a desireable voltage.

Inquiring minds want to understand the need/attraction of this Lithium/BEC combination if it introduces risk.
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Old Feb 06, 2013, 02:40 PM
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Once you have used a Life pack, you will understand the attraction. They charge super fast, don't self discharge, and never false peak.
Also, because of the charging algorithm, you can easily tell if the pack is near full or not.

Not all servos must be run with a regulator if using a Life pack.
All Hyperions except the DLG sized DS-09 will take unrelated life.
The DS11 is almost identical to the Airt 809, and it has run happily on life in the aileron position of my 4m Xplorer for 2-3 seasons now.
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Old Feb 06, 2013, 02:46 PM
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It's certainly a legitimate question. There are lots of drawbacks to Li RX batteries: Cost, shape, fire, etc. but here are a few advantages:

- Nickel cells take forever to charge and only stay charged for a few days. Li charge in 10-20 minutes and stay charged forever. So with Nickel you have to plan your flight at least a day in advance, whereas Li batteries can be charged after flying and remain ready to go for years.
- Nickel cells are destroyed if your charger simply looks at them the wrong way and this can lead to crashes due to sudden capacity reduction. Li cells tend to age gracefully, especially LiFe.
- Nickel cells are destroyed if left unattended. Li cells last forever, even in storage, heat, cold, etc.
- Good Nickel cells (e.g. Eneloop) are expensive, can't produce high currents, and don't work well in cold weather.
- Some modern DLG and F3J designs don't use nose weight and/or are very limited in space so Li cells allow for adequate capacity within the constraints.
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Old Feb 06, 2013, 03:11 PM
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Vespa and Target, thanks for your responses. I can certainly see your position. Not something I am going to venture into as putting a regulator in line is not attractive to me at this time. Been doing fine with the 4S and 5S NiMh packs I am using so I will stay with them for now. I just replaced all my NiMh packs.

The 1500 mah 5S 2/3A NiMh cells I am using in the Supras for receiver packs can be charged at 1.5C with no problem, as marked on the packs.

The 4S 2000 mah AA packs I use, in the AVA and Graphite, seem to manage fine on .5 C.

I have not found the need for faster charging than that for my TD flying. And I tend to top them up the night before or that morning as a matter of routine so not a big deal. When flying an ESL contest I top them up over lunch, though I am not sure they really need it.

But I will continue to follow the thread to learn and prepare myself for the transition, some day.
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Old Feb 06, 2013, 03:38 PM
Detail Freak
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Its mainly the ease/reliability of charging for me that makes the difference, and of course the lack of self discharge.
Not having to "form" a pack or cycle it prior to use-an attraction to the eneloop for some, is also a draw.
I have Life in everything now that it fits in (1450 is almost identical size to your packs, and LESS voltage than a 5 cell 2/3 A pack fresh from charge!) and only run a regulator in a plane that has MKS and RDS in it. Every other plane has no regulator, and most have no switch.
My life packs normally read 6.6-6.5v through the data logger with radio on.

I won't change back.

R,
Target
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Old Feb 06, 2013, 03:57 PM
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Like some above, the last few NiXX chemistry batteries have shown very poor forming performance and when you cannot even get the batteries to show anywhere near their advertised specs, I am not trusting them. I have totally gone LiFe with no BEC/Reg and have been totally confident in what I have. Even on a power ship with not even HV servos they are fine and at a peak of 6.6V, that is less voltage that a hot 5 cell NiXX battery and the best part I know the voltage of the cells in the packs.

I do use a 4 cell NiXX pack on the bench to run a servo driver in my bench, the last of any nickel anything in my shop.

Marc
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Old Feb 06, 2013, 04:18 PM
Detail Freak
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Quote:
Originally Posted by aeajr View Post
The 1500 mah 5S 2/3A NiMh cells I am using in the Supras for receiver packs can be charged at 1.5C with no problem, as marked on the packs.
What servos are in the Supra living on 5 x 1500 Elites??

They likely will be just fine, if not better off on a 2S Life.
If you have tail weight on the Supra to balance with that pack, you can likely take it off if you went Life as well...

R,
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Old Feb 06, 2013, 05:00 PM
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In the KC Supra Pro I have JR 378s in the wings and 368s in the fuse. - 58 ounces That went into the air last season. 5 cell pack and Futaba FASST 2.4.

Original KC Supra has Airtronics 94761 digitals all the way around.- 64 ounces Have had this one since 2007. Took it from 4 cell AA to 5 cell 2/3 A when I went to Futaba FASST 2.4 last season, prior to the NATs.

Both get strong winch launches.

I have no weight in the tail of either one.

They have been working just fine. Normally charge them in the shop at 500 mah using a Triton charger. Will top the one I have been flying at the contest at lunch time, just because I have some time, at about 1 amp using a Hitec charger that I keep in the car.

So far, no problems.
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Old Feb 06, 2013, 06:55 PM
Detail Freak
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I would say that likely, none of those servos will have problems with an unregulated Life pack hooked up to them.
For sure, the 761's seems fine to me on Life, I have lots of those in my planes currently.
398's should be an upgrade you would be interested in for the one with 378's, should you ever want to get rid of the 378's. The 398's are MADE FOR the Lixx packs, as I'm sure you are aware.

What is your voltage when you first turn on for the first flight?
Ever measure? It may be higher than the Life initially.
Where the difference lies, is voltage under load.
I assume that you went from 4 cell to 5 cell because you were worried about a low voltage dip effecting the Rx?
If that is the case, that is a reason that Life would work for you....
But its acedemic if the voltage of the 5 cell is higher than the Life and that is what you are after.

I used to charge after 10 rounds of F3F also, when I used the round cells. Charging is not that difficult, and is easy insurance. But the truth is, I find the Life packs to be much more relaible than the round cells.
One of the F3F guys in GB was always stating how a 4 cell pack has a 20% better chance of success, since in a 5 cell pack, there is one more cell that can fail in the first place. I never really agreed, a pack is a pack, right? Now, I'm more in agreement, and the 2S life if you buy in to what he's saying, is over 100% more reliable than a 5 cell pack.
I don't know if I see things 100% the same as he does, but I definitely see where he's coming from.

R,
Target
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Old Feb 08, 2013, 10:40 AM
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Difference in Castle 10 A (BEC) Switching Regulators

Since I haven't seen anything in this thread about the difference in Castle 10 A (BEC) switching regulators, I'm posting it here for your information.

I've often looked at the Castle 10A (BEC) switching regulators that I use and noted that they are different. The old one doesn't have the relatively large electrolytic cap mounted on one end that my newer ones do. I've never gone any further than thinking Castle must have changed their design to correct a problem with output noise or loading. After reading some of these posts and checking the cap, it's only a 220uF electrolytic, I have to wonder exactly what it was that prompted Castle to add it and if there are more components to go along with it on the circuit board (making it part of a filter network perhaps).

There hasn't been any problem using them over the years, but I'm using old, slow, wimpy analog servos.

Here's a picture showing the two versions of the regulator.
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Old Feb 08, 2013, 10:54 AM
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Quote:
Originally Posted by Powerbud View Post
...I've often looked at the Castle 10A (BEC) switching regulators that I use and noted that they are different. ... I've never gone any further than thinking Castle must have changed their design to correct a problem with output noise or loading.
Switching regs like the Castle need capacitance on the output to smooth the voltage between regulator "pump pulses." The more current you try to draw for a given amount of output capacitance, the more voltage droop before the next pulse. And the more droop the more voltage output noise.

Switching regs are great when you have a lot more input voltage than the regulated output voltage. However with our LiFe packs the voltage difference is small enough where a good linear regulator runs with basically the same efficiency as a switcher AND you get the benefit of much cleaner power and a lower circuit complexity which translates to better circuit reliability.

For a good linear reg I highly recommend the Voltron 5.4v 6A unit. And no, I'm not a dealer .

Chris B.
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Old Feb 08, 2013, 11:57 AM
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United States, CA, Midway City
Joined Dec 2003
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Quote:
Originally Posted by target View Post
.
One of the F3F guys in GB was always stating how a 4 cell pack has a 20% better chance of success, since in a 5 cell pack, there is one more cell that can fail in the first place. I never really agreed, a pack is a pack, right? Now, I'm more in agreement, and the 2S life if you buy in to what he's saying, is over 100% more reliable than a 5 cell pack.
I don't know if I see things 100% the same as he does, but I definitely see where he's coming from.

R,
Target
Most nixx cells when they fail , fail close. So if a cell does go bad it becomes a 4 cell pack = more reliable if 1 cell goes bad.
One of the biggest benefit for me is the consistent voltage of the Life cells throughout the day. You start at 6.6v, you end up at 6.6v even under load. You can't say that for a 5cell nimh pack. It'll be more than 1v difference depending on flight loads from begining of day to end of day. It may not matter for most of our flying, but I think for competition work (speed in F3B), getting consistent speed/torque out of the servos is very important.
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