apwachholz

@all
I'm getting some odd feedback on my Hobbico VoltWatch and am seeking some insight and assistance.

The Set Up

[*]E-flite 25 Texan (converted to glow) w/.25 O.S. 2-stroke[*]5 Hitech HS-5085MG Digital BB Metal Gear Mighty Micro Servos (ailerons, elevator, rudder, throttle)[*]NiMH 4C 4.8V 2000mAh Receiver Pack[*]Hobbico VoltWatch Meter (set to 4.8V)[*]E-flite 90 degree retracts[/list]The issue
Freshly charged battery (it's new), inspected and not damaged servos (I'm the only owner), proper installation of electronics (done this numerous times), but when I start moving control surfaces (e.g., ailerons, elevator, etc.) the VoltWatch lights up like a christmas tree all the way down to the red. Stop moving surfaces, and then we're solid green. I've seen this before but no so severe and I'm wondering A) Do I need a larger battery to power the servos, or B) Is the VoltWatch damaged? I'm having a hard time thinking that 5 micro servos pull that much juice.

Any assistance would be of great help.

apwachholz

Thought #1:Ummm, I might have answered my own question (I think).... is the Hobbico VoltWatch 2 only for 5 cell packs? Could that be my issue?Again, any and all assistance would be awesome!

Thought #2:I've read that poor gage quality of the power switch wires (battery-2-receiver) might cause issues as well. ???

tomfiorentino

I think generally when folks move to digital servos they move to 5 cell packs. Definitely so in the high torque stuff. Also, if you go to the hangtime hobbies website, there is a nice discussion there on the problems with certain types of NiMh batteries with higher internal impedence that may not be suitable for receiver power in some setups. Mostly on the bigger stuff but I don't know what those Mighty Micro servos are pulling for amps.

As to the switch and wires etc. yes that can definitely effect the power that the servos see. You can test that by plugging the battery directly into the receiver and looking at what the Voltmagic reads in that instance. If the red disappears, you know it was the switch and related extensions etc.

I would still move to a 5 cell pack though....

Hope that helps,

Tom

Nothing is wrong with your voltwatch...it is simply telling you that the voltage the receiver is seeing is below 4.8 volts.

pilotpete2

In a plane that size the 5 cell pack is a weight issue. While 2000mAh is much more capacity than needed for this model, the "C" capability of AA Nimh is terrible. High capacity, but poor ability to deliver the current.
An 1100mAh 2S A123 pack would way less than the 4 cell Nimh and would hold voltage under load battery than any other battery you can put in a plane.
Also, a heavy duty switch harness would be a good upgrade, one with at least 22awg wire, better yet 20awg.
Pete

BuschBarber

My Feedback: (2)

I have used NiCad and NiMh Tx and Rx batteries for many years. There is really no reason to use them any more. Lithium batteries and chargers have evolved to a point where they are safe, reliable, and no more expensive than the NiCad/NiMh equivalents.

I use 3cell LiPo packs in all my Tx's and 2cell LiFe/A123 packs in all my aircraft except the light electrics that use a BEC. They charge fast, hold their charge for months, and are light. I use 2500mah packs in both the Tx and Rx. I recharge once a week, depending upon how many times I fly each pack per day, and it only takes me 15min. If I need more weight, I can use higher capacity packs.

tomfiorentino

Hey Pilotpete2,

I won't argue with any of that!

I was reluctant to point him in the direction of a different chemistry because he may not be set up to do that and/or have a compatible charger etc. etc.

I'm not familiar with the airplane, but if a 5 cell (6 volt) is too heavy, it would seem like he may not have any other option??

Don't know what folks have done with that kind of plane before, but perhaps they were not running digitals...

There is a million combinations out there!

Tom

baronbrian

My Feedback: (13)

Come on guys, a 2000mah battery for a .25 size plane should not be a problem, even with digital servos. I personally don't like the voltwatch things, mostly because I'm colorblind. Don't the voltwatch 2's have a tiny switch on them for 4.8 or 6v operation? Is it possible you have it switched to 6v??

pilotpete2

OK, but he also has electric retracts running off the same battery, hence my concern over the high impedance of Nimh. Actually, a 5 cell 700mAh Nicd would be better than any Nimh for this situation, true not as many flights per charge, but the Nicds will maintain voltage under load much better than the Nimh.
Pete

apwachholz

Oh, for those wondering, attached is a pic of the aircraft. And as for the weight - even with the RX battery shoved all the way up front I still have to add more to get it to balance out on the CG.So far it's at 4lbs 4oz with a required 4.25oz needed to balance it out.

_aw

apwachholz

@All
Not that this is required but, here's a pic of the VoltWatch 2 "in action" (for your reference).

tomfiorentino

Brian....Regarding your comment on the 2000mah battery...I don't think the issue is battery capacity. It strikes me as a voltage problem.

Apwachholz,

I use Voltmagic which is similar. The LED's will jump around somewhat...but not as bad as you are reporting. On the Voltmagic anyway, they are very sensitive so they pick up the smallest variations in voltage that the receiver really doesn't see. That has been my experience with them. So don't be concerned necessarily that the LED's are moving.

However, they don'tmove much on a fresh charge...so I would say you have a problem.

Did you happen to remember to try your whole system by bypassing the switch altogether? I really think you need to do that...not a different switch...but bypass it altogether.

If you want to PM me with your number I would be happy to give you a call. I have some personal history with an issue similar to what you are describing that ended up being the switch harness and extensions. It was on a 50cc bird that had dual batteries, but the Voltmagic picked up a voltage issue that I would have never known about otherwise. Don't ignore what you are seeing!

There is an answer here...

Tom

apwachholz

dirtybird

My Feedback: (5)

You have tried everything but the battery. Doesn't that tell you something?
Switch to Ni-cds or a123 and you will fix the problem.
Or just go and fly. It probably wont have any affect on the ability to fly it.

Charlie P.

Relax. I use 2,000 mAh NiMH packs (4.8 & 6v) and the Voltwatch 2 bounces all over when you cycle the servos. When it stays yellow AFTER you stiop - don't fly that pack again without recharging.

rmh

The capacity of the NIMH is not an indicator of how it handles loads .
This is a common misunderstanding
Many 2000ma NiMh have C ratings of 2 or less.
If you want to use NIMH -buy he cells sold to the race car guys - these are designed for high peak loads - go to NO BS batts or similar supplier -look for high capacity AND high discharge rate.
Our own choice for years is A123 -sized for model.
IF I can cause 2 or more segments to change when stirring sticks - I will not use the pack attached PLUS I will check all accociated servos wirings etc..
Typically problem IS the battery. This includes the ENELOOP which a number of flyers are now using -be careful these are great batts but NOT high load capable types.

I use the little Votmeters from EXPERT in 4.8 and 6 volts- these are cheap and disply clearly the voltage depression using 4.8 volt (four cell)packs or 6 volt (five cell) OR A123 packs.
Your voltwatch is similar-however the selected volt reading must match the selected pack.
-

tomfiorentino

Right. I love when guys have a voltage problem so they put in a higher capacity battery. That's like putting a larger gas tank in a car that doesn't have enough power to climb the hill

He has a voltage problem no doubt and it is either the battery or his set-up. A flash of red on a fresh charge is no good; things shouldn't be jumping around that much at all. He tested the battery in a similar setup on the Piper and did not have a problem...at least I think it was the same battery.

So, not withstanding it is probably better all around to move away from that NiMh, I still think he has a problem with his setup.

To diagnosis it though you really need to change one variable at a time to isolate things.

I'm recalling my experience with my Voltmagic in my 50cc, dual A123's for the whole airframe and ignition. I would get yellow PLV on start-up and engine warmup. Turned out to be the switches at the end of the day. I changed that set-up to EC3 cnnectors for the power feed into a powersafe receiver..now I don't see yellow until I have about 4 flights.

My friend Barracudahockey, and others, I know are using one A123 on 50cc with great results...but I'm too chicken to do that right now!

Fun stuff!

tom

rmh

50 cc powered stuff "should " be fine with one 2300 ma pack
However-
your setup and my setups are of course ,not the same .
how to evaluate actual loads is still a mystery to many newcomers and even many long time modelers.
The game of how much power is actually used has changed- A LOT!!
example
i put a fresh charged A123 1100pack in a pattern model with a Spektrum 8000rx -and left the batt attached overnite -
guess how much it took to refill the batt 12 hrs later?

The new rx use more power - the new digital servos use mor power
some new analog use a lot more power - and if longer servo arms are used which allow the servos to effectively "stall" under moderate airloads , the loads simply go off the charts.
As you have likely seen- stall loads are mysteries to some.
wagging the rudder as in trying to learn to hover, can produce overload in some cases.
many of the "my radio browned out" rants , read like the same story -over n over . The user simply had no idea what actual loads were occuring.

better yet they did not care to learn- they simply wanted a system which would not quit -
Same guys are accomplished air guitar players -but would never care to actually learn the real thing.
Signs of the times -unfortunately.
Not just young guys - age has nothing to do with it.

flycatch

My Feedback: (26)

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.

rmh

Any voltmeter , digital or analog can be used to indicate voltage depressions under load.
loaded meters for today's use are simply worthless for battery evaluation.
The stuf sold a few years back with 200 ma/500ma etc loads should stay on the museum shelf

p39

My Feedback: (5)

How are you charging your battery pack? Your wall charger won't do the trick. Also, with NiMH batteries, you don't want to super fast charge them. And they will need a couple of charge/discharge cycles to really reach more of their potential- depending on the cells. You can sure diminish the capacity of some NiMH cells by fast charging them.

flycatch

My Feedback: (26)

Really, they seem to work for me. I fly on 72mhz and power my models with 4S engines so that makes me a museum piece. One thing I want to pass along is that if it is not broke don't fix it.

acdii

Put a DVOM on it and look at the actual volts, as long as the volts are above the cutoff voltage under load you will be fine.

You said this is a conversion, if you still have the ESC and Lipo, unplug the pack, and plug the ESC and lipo in and recheck it. You dont need the motor hooked up, but make sure if it isnt, the leads for the motor are secured and cant touch.  The ESC has a built in voltage regulator and should maintain a constant voltage with the lipo. If once again you see the same results, then the meter you are using is just very sensitive and you should have no concerns.

eddieC

My Feedback: (2)

I've had a Voltwatch let me down, caused the crash of an expensive gas heli because I trusted the VW.  I'll never own or recommend one again.  [:@]

Get a good ESV (expanded-scale voltmeter), something like the Dynamite Sentry, one of the best field gadgets I own! Gives voltage readouts in both digital and bar graph formats while under load, also shows resting voltage so you know what the pack started at. Does Ni-cad, Nimh and Lithium up to 4 cells. Mine was about $30, it's a must-have IMO.

rmh

Loaded meters must have load representing actual loads seen on model
many newer setups using 2.4 and high torque presicion servos used with gyros pull a LOT of momentary current!
our old 72 mhz setups simply are in a different catagory- really don't compare em -you will get totally incorrect info.

modeltronics

My Feedback: (27)

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