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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/9/2012 7:03 PM   
rmh



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Status: offline 		Yeh but doing nice fast rudder full swing operations will typically show up -if battery capacity and C ratingis of lower type
I setup new models using a lousy fourcell battery I keep for that purpose - it shows droop easily -if servo is stalled or of a high load.

it sounds goofy but it does work

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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/9/2012 8:38 PM   
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quote:

ORIGINAL: flycatch

The meter is used to measure the capacity remaining in the battery pack under load. This measurement is only valid under a static condition. This means all controls surfaces are in a neutral position. What your seeing is normal and not a measurement of the capacity remaing in the flight pack. The voltwatch was developed for those who did not want to purchase a volt meter such as those sold by; ACE, MPI and Futuba.


I'm sorry but I don't understand that whole post.

The meter measures voltage. It is a loaded measure if servos are moving, it is unloaded if servos are at neutral. In both cases, it measures voltage not capacity. It doesn't matter what kind of meter it is...it measures voltage.

We in turn use voltage to estimate charge state, if appropriate, depending on the battery chemistry. The discharge curves of older chemistries (NiCd, NiMh etc) are steep enough to give the voltage measurement predictive value on charge state.

The reference to the museum is in regard to using the standard voltmeter approach to estimating charge state with the new A123 type chemistries. There, the voltage discharge curves are so flat that you can't predict charge state using a voltage measurement. We do that on recharge by measuring mah put back in the battery etc. There has been tons of discussion about this on RCU.

The reason to use these voltage devides in the plane with the A123 type chemistires is mostly for evaluating how your total system is running under demand. A stalled servo, a bad switch, extensions etc. all could thwart a batteries ability to deliver the required voltage for performace.

Tom


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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/9/2012 8:44 PM   
tomfiorentino


 

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quote:

ORIGINAL: modeltronics

If you were to look at the voltage with the servos moving under load with a storage scope using NIMH batteries you might see something different than what a VOM of voltwatch shows. They are not fast enough to show what is realy going on. I know everyone does not have a storage scope. A VOM and voltwatch averages. Even if they were fast enough your eyes would never catch it. The inrush current of fast servos is enough to cause voltage drops and on top of that even though NIMH batteries have gotten better they still have higher internal resistance than other types of batteries.

Pete


The Voltmagic device is very sensitive and records Peak Low Voltage (PLV) during each flight. Not a storage scope...from what I understand.

After my 50cc experience, I will use a Voltmagic on and of my birds that mean something to me!

Tom


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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/9/2012 9:48 PM   
modeltronics


 

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Status: offline 		Tom,
I just Googled Voltmagic. That is one very good device! There is a lot of good info on the FAQ page. I will be looking into getting one for my large plane.

Thanks,
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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/9/2012 10:30 PM   
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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/9/2012 11:35 PM   
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@all
Thanks for the insights and advice. After a conversation with a gentleman at the field today (whilst running in my engine) he mentioned that at a minimum it would be best to switch to a 6v battery. And I agree. I'm contemplating these two options below. Any thoughts?
 
 
 
@Tom
I'll PM you soon. I'm getting ready to travel for a few days so I'll be unable to talk but, I do want to talk.
 
 
@Charlie. P / flycatch
I was thinking something along your lines that the static state of the VoltWatch 2 is a more accurate reading of what's going on. But to be on the safe side I'm most certainly switching to a 6v pack. I'm continuing to do further testing with my existing (but old) 6v and am finding that these little digital servos really pull juice vs. my Piper Cub standard Futaba S3003 analog set up.
 
 
@p39
I've been using a wall charger for my battery packs since I was flying and have never had any issues. I typically replace my receiver batteries once every 1 1/2 years and the wall chargers have never let me down. I'm also one that charges 12 hours ahead of time, every time, to be safe. I own a Great Planes Triton Jr. that I use for my LiPo's, I'm assuming that this would work well. Again, I've never done much cycling or discharging with my receiver packs.


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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/10/2012 12:02 AM   
BuschBarber


 

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quote:

ORIGINAL: apwachholz

@all
Thanks for the insights and advice. After a conversation with a gentleman at the field today (whilst running in my engine) he mentioned that at a minimum it would be best to switch to a 6v battery. And I agree. I'm contemplating these two options below. Any thoughts?
 
 
 
@Tom
I'll PM you soon. I'm getting ready to travel for a few days so I'll be unable to talk but, I do want to talk.
 
 
@Charlie. P / flycatch
I was thinking something along your lines that the static state of the VoltWatch 2 is a more accurate reading of what's going on. But to be on the safe side I'm most certainly switching to a 6v pack. I'm continuing to do further testing with my existing (but old) 6v and am finding that these little digital servos really pull juice vs. my Piper Cub standard Futaba S3003 analog set up.
 
 
@p39
I've been using a wall charger for my battery packs since I was flying and have never had any issues. I typically replace my receiver batteries once every 1 1/2 years and the wall chargers have never let me down. I'm also one that charges 12 hours ahead of time, every time, to be safe. I own a Great Planes Triton Jr. that I use for my LiPo's, I'm assuming that this would work well. Again, I've never done much cycling or discharging with my receiver packs.


I have a Triton and a Triton2 that I used for NiCad and NiMh. I used it initially for LiPos, as well, but it does not offer Balancing. It only charges through the Power Leads. The same is true for my Lithium only Astroflight 109 charger.

I found the FMA 4S and 10S chargers to be some of the best on the market. The display shows me the Total Pack Voltage as well as the voltage of each individual cell. I can charge up to two 5S LiPo packs at a time as well as LiFe/A123 and LithIon. The newer versions of the charger also handle other chemistrieys.

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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/10/2012 2:22 AM   
V2PLUS10


 

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Status: offline 		You may have tried this but maybe you could bypass the switch, as already mentioned, go directly into the rx with the power lead, then start with one servo plugged in, then add one servo at a time. If you have a bad servo(or if this is load issue) this might isolate it. If you have the same problem with one servo plugged into the rx I'd try a different rx if you have one, but first try a different servo as you may just pick the potentially bad servo as the first choice.....I read most of the posts but i did skip a few, so if someone has already mentioned this sorry for the duplicate...

Randy

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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/10/2012 3:19 AM   
Charlie P.



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quote:

I'm continuing to do further testing with my existing (but old) 6v and am finding that these little digital servos really pull juice vs. my Piper Cub standard Futaba S3003 analog set up.


Yes they do.  Stall one out with an improperly set end-point or badly binding linkage and they'll suck the life out of an AA size flight pack very quickly.

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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/10/2012 5:49 AM   
Speedy-Gonzales


 

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Status: offline 		50cc Ultimate bipe, 3600 NiCD on RX, Aerotech IBEC ( ignition), six Hitec 5645 digitals ( aileron/ elev ),one PPP digital 240 in/oz ( rudder ), one spektrum 821 digital ( throttle) . Batt charges to 4200 MaH. No probs with multiple flights per day.

I use the MPi HD on/off switch.

Sanyo Sub C 3600 NiCD 6V pac ( non-regulated except for IBEC )

JR 921 receiver with no redundancy ( one satellite )

JR 8103 with 2.4 conversion module

Bulletproof!


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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/10/2012 9:00 AM   
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Status: offline 		There is no need to switch to Lipo or LiFe etc. There are NIMH batteries made that are low resistance. I have used them for years on Giant scale applications without a single problem. If you have the chargers cyclers etc like I do for NIMH,NICAD etc, then why switch? The safety of LiPos is still questionable as evidenced by the numerous articles, safety warnings about them etc. Look up how many house fires have been started by LiPos and decide for your self. I hope you find an answer to your problem, I don't think your type of battery is to blame.

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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/10/2012 12:06 PM  1 votes
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quote:

ORIGINAL: rcmichael

There is no need to switch to Lipo or LiFe etc. There are NIMH batteries made that are low resistance. I have used them for years on Giant scale applications without a single problem. If you have the chargers cyclers etc like I do for NIMH,NICAD etc, then why switch? The safety of LiPos is still questionable as evidenced by the numerous articles, safety warnings about them etc. Look up how many house fires have been started by LiPos and decide for your self. I hope you find an answer to your problem, I don't think your type of battery is to blame.

While NiCad and NiMh are still viable sources of power for a Tx or Rx, they are heavy and take a long time to charge. If you forget to charge one day you may be hours away from flying again. They Self Discharge, so just sitting around, they lose capacity. NiMh do not like a Fast Charge and doing so usually shortens the life of the battery.

I can charge my LiPo or LiFe packs and weeks later they are ready to go at a moments notice. If I had to, I could charge, fly, charge, fly forever.

Almost all Lithium fires are do to improper charging. When electrics and LiPos first came out, I saw some smoking LiPos that were improperly being charged, but I have never had a LiPo smoke or burn and I have been using them for over 5 years. We use them in Cell Phones, Laptops, and Tablets. Modern chargers like the FMA brand inform you of Bad Cells, Discharged Cells, Improper Polarity, and Type of Battery Chemistry.

The safety of Lithium cells has vastly improved. The cost of Lithium batteries is no different than NiCad or NiMh. When I am at the flying field I am constantly charging the LiPos for my electric aircraft all day, switching batteries between flights. I have packs from 2cell LiFe (6.6v), 2cell LiPo (8.4v), to 12cell (50volts) and no issues.

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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/10/2012 1:55 PM   
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Status: offline 		Really, the Voltwatch gives you much more reliable information than a loaded voltmeter. It is almost as good as an ocilloscope as that flickering of the LED's happens for a reason (the voltage is momentarily dropping and the LED's are showing how low. If this is the receiver bus that is being measured and you are using 2.4GHz system, that momentary drop into the red may be dangerously close to where Brown-Out occurs. If the Voltwatch is flickering into the red, you DO HAVE A PROBLEM SOMEWHERE. It could be a high battery impedance, a switch with high impedance, to small a gage wire or to long a run between the battery and the receiver. Something is dropping the voltage at the point the Voltwatch is attached and ignoring that information is a risk you must assume. If it is a battery impedance problem, one solution is to put in a parallel battery as this will cut the internal impedance as seen by the load in half. One way to check on whether or not it is wiring or switch problems is to plug the battery directly into the receiver (by pass all associated wiring) and see if the problem still occurs, if not a wiring problem, if so a battery problem.

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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/10/2012 2:46 PM   
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Status: offline 		Its not about 2000mah its about the large load or amps those heavy duty servos are putting on the pack, you need a better battery pack, the demand from the servos are greater than what the pack can provide, i suggest you go to cheapbatterypacks.com and make a custom flight pack with elite batteries they can handle 20-30amps load. The volt watch is not broken but it is telling you exactly what the receiver in your airplane is getting power wise or if it is starving it. its your battery not your voltwatch..its not broken...this can cause a brown out or help you crash an airplane.

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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/10/2012 2:47 PM   
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quote:

ORIGINAL: Rodney

Really, the Voltwatch gives you much more reliable information than a loaded voltmeter. It is almost as good as an ocilloscope as that flickering of the LED's happens for a reason (the voltage is momentarily dropping and the LED's are showing how low. If this is the receiver bus that is being measured and you are using 2.4GHz system, that momentary drop into the red may be dangerously close to where Brown-Out occurs. If the Voltwatch is flickering into the red, you DO HAVE A PROBLEM SOMEWHERE. It could be a high battery impedance, a switch with high impedance, to small a gage wire or to long a run between the battery and the receiver. Something is dropping the voltage at the point the Voltwatch is attached and ignoring that information is a risk you must assume. If it is a battery impedance problem, one solution is to put in a parallel battery as this will cut the internal impedance as seen by the load in half. One way to check on whether or not it is wiring or switch problems is to plug the battery directly into the receiver (by pass all associated wiring) and see if the problem still occurs, if not a wiring problem, if so a battery problem.


you are absoultly right!!!

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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/10/2012 6:57 PM   
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I can charge my LiPo or LiFe packs and weeks later they are ready to go at a moments notice. If I had to, I could charge, fly, charge, fly forever. 


By fully charging the Lipo battery and storing it for weeks, you're shortening the pack's life. As for 'charge, fly, forever', Lipo's start decaying from the moment they're made, so they have a finite life. I haven't had a pack last more than 3 years, and that's under light use. They also have a finite number of cycles, 100 +- at best.  I've had Nicads last 10+ years, easily exceed 400+ cycles and withstood occasional abuse without having a 'thermal event'.    The A123's are a great alternative.

quote:

Really, the Voltwatch gives you much more reliable information than a loaded voltmeter.  


I disagree, see my earlier post #23. The Voltwatch gives an inaccurate guesstimate of surface voltage, and still a guesstimate if you're testing while moving the sticks. The Sentry device gives digital and bar-graph info under load, and one can stir sticks for greater load if desired.

I agree the OP has high resistance in the circuit or a marginal pack. Us heli guys saw this years ago while using Nimhs (for reduced weight) when the first good digitals came out. Lots of unexpected crashes until it was figured out that the gyro 'browned out' and, with the 3-5 second reset time, a crash was inevitable. 

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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/14/2012 2:18 PM   
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@blhollo2 
Interesting you should mention Elite battery packs. That's the exact battery pack that I was using years ago in the E-flite Pawnee (converted to glow). I simply migrated all the electronics to the Texan, and come to think about it, I never saw this happen. Well, perhaps the pack is shot....? Either way, we'll get an answer....thanks!

@all
Thanks for all the insights. I truly appreciate all the help. I apologize for not responding, however, I've been in Muncie IN at the AMA headquarters for the past few days; of all places. I'll have a few responses coming and I'm hopping that I can get this whole thing figured out. I'll most definately let everyone know the final outcome. Cheers! 

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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/20/2012 3:37 AM   
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I had a good conversation with Tom over the phone and I'm going to try another approach to the whole issue with servo power. I have a Thunder Power LiPo 3cell 1350mAh 11.1v pack that I used for an electric (attached pic) and I'm going to test using that set up. I'm wondering if the digital servos just need more juice pumped out to them and a 13C continuous and 20C burst should do the trick. If not, I give up (not really). I also have been taking a look at LiFe power cells, per your and Tom's advice, and perhaps that might be the way to go. I'm a bit hesitant putting a soft cell (lipo) into a glow powered aircraft vs. a hard cell (LiFe) but, that's just me. Details to come.


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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/20/2012 3:46 AM   
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Status: offline 		Are you going to plug the 3 cell lipo directly into your receiver? I think that without a voltage regulator you will ruin the rx and servos....what kind of receiver are you using?

Even the High Voltage digital servos are only rated for 7.4 volts....

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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/20/2012 4:12 AM   
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I'm going to use a setup that I've used in the past and put a CastleCreations 25 speed controller in between the battery and receiver..... but..... now that I talk about it, I remembered that Hobbico's VoltWatch2 only works with NiCd or NiMH. Grrr...... anyone got a suggestion for a volt meter for LiPo's? 

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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/20/2012 4:21 AM   
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Status: offline 		The CC bec will probably only deliver 5 volts plus or minus a few tenths of a volt, so you will not be gaining much if anything. I think you need to start with your receiver and one servo and the voltwatch. Add one servo at a time and see if the indications on the voltwatch change drastically. That will tell you if you are trying to draw too much from your battery pack...

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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/20/2012 1:34 PM   
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ORIGINAL: V2PLUS10

The CC bec will probably only deliver 5 volts plus or minus a few tenths of a volt, so you will not be gaining much if anything. I think you need to start with your receiver and one servo and the voltwatch. Add one servo at a time and see if the indications on the voltwatch change drastically. That will tell you if you are trying to draw too much from your battery pack...

Both the CC BEC and the CC BEC Pro are adjustable from 4.8v to well over 6v. The CC BEC can handle 10a and the CC BEC Pro can handle up to 20a from the servos. I have used the CC BEC Pro with 3cell LiPos as Rx batteries which charge to 12.6v. I usually adjust the voltage down to 6v unless I have 5v servos in the mix.

http://www.castlecreations.com/products/ccbec.html

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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/20/2012 3:53 PM   
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quote:

ORIGINAL: BuschBarber


quote:

ORIGINAL: V2PLUS10

The CC bec will probably only deliver 5 volts plus or minus a few tenths of a volt, so you will not be gaining much if anything. I think you need to start with your receiver and one servo and the voltwatch. Add one servo at a time and see if the indications on the voltwatch change drastically. That will tell you if you are trying to draw too much from your battery pack...

Both the CC BEC and the CC BEC Pro are adjustable from 4.8v to well over 6v. The CC BEC can handle 10a and the CC BEC Pro can handle up to 20a from the servos. I have used the CC BEC Pro with 3cell LiPos as Rx batteries which charge to 12.6v. I usually adjust the voltage down to 6v unless I have 5v servos in the mix.

http://www.castlecreations.com/products/ccbec.html



Yes, but he is using a CC 25amp ESC with an internal BEC to power his receiver, not a dedicated UBEC...

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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/20/2012 4:06 PM   
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quote:

ORIGINAL: V2PLUS10

quote:

ORIGINAL: BuschBarber


quote:

ORIGINAL: V2PLUS10

The CC bec will probably only deliver 5 volts plus or minus a few tenths of a volt, so you will not be gaining much if anything. I think you need to start with your receiver and one servo and the voltwatch. Add one servo at a time and see if the indications on the voltwatch change drastically. That will tell you if you are trying to draw too much from your battery pack...

Both the CC BEC and the CC BEC Pro are adjustable from 4.8v to well over 6v. The CC BEC can handle 10a and the CC BEC Pro can handle up to 20a from the servos. I have used the CC BEC Pro with 3cell LiPos as Rx batteries which charge to 12.6v. I usually adjust the voltage down to 6v unless I have 5v servos in the mix.

http://www.castlecreations.com/products/ccbec.html



Yes, but he is using a CC 25amp ESC with an internal BEC to power his receiver, not a dedicated UBEC...

OK! He could always turn off the BEC in the ESC and attach the CC BEC or CC BEC Pro and use that instead.

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RE: Digital Servos + 2000mAh NiMH = Huh!? - 6/20/2012 4:08 PM   
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Last Login: 5/24/2013
From: Des Moines, IA, USA
Status: offline 		Respectfully, I've never seen anyone go to so much work to overcomplicate a simple problem. Clearly the voltage if fluctuating excessively when several servos are in operation at the same time. This can only be caused by high resistance somewhere in the various cables / connections or by an inadequate power source. I'd start by tossing that Hobbico 2000 NIMH battery as these have had known problems over the years. While the capacity may be there, the ability to provide adequate current may be lacking (this is probably a high impedance battery). I don't care whether you go to a low impedance NIMH battery such as provided by NOBS batteries and many other companies, a quality NiCd battery or a fairly high "C" rated LiFe battery .... get something that can handle the current demands! Yes even small digital servos can have fairely high current demands! Use a quality, name brand switch and go fly!

Its really that simple! You really don't have to overcomplicate things with a bunch of regulators, overly large batteries, etc. The NOBS website can educate you about the differences between the various battery types and the importance of low impedance, etc. Battery size, weight and capacity do not guarantee a batteries ability to supply adequate current. Stated another way, a battery can only maintain a fairly constant voltage if it can maintain the amperage (current flow) required by the devices it powers. A batteries MAH rating only states how long a battery can supply power to a load, not how much power or work that can be delivered during that time. 2000 MAH NiMh cells are some of the worst for supplying adequate current under load!

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(in reply to apwachholz)
       Post #: 50

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All Forums >> Radios, Batteries, Clubhouse and more >> RC Radios, Transmitters, Receivers, Servos, gyros >> RE: Digital Servos + 2000mAh NiMH = Huh!?
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