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RX voltage display - 10/25/2004 7:29:10 PM   
BillS


 

Posts: 3050
Joined: 9/6/2004
From: Greensboro, NC, USA
Status: offline 		RX voltage display

Would anyone besides me like to have the RX voltage displayed on the transmitter? I believe it would be 100 X safer for people and for airplanes. It is almost unheard of to lose and airplane because of low transmitter voltage (transmitters with displays). Normally transmitter voltage is checked at a glance after turn on, just before take off, and just after touchdown. Receiver voltage is checked, well … maybe sometimes. Why? Checking requires a series of user actions rather than a simple glance.

If receiver voltage were as easy to check as transmitter voltage most low voltage RX crashes would not exist.

Please understand that the concern is not about my crashes but it is about the other fifty to a hundred people in the club. Any out of control crash represents a safety hazard to everyone. And yes there are some technology issues to be resolved and it would take a few years for the general technology to be in everyone’s hands.
       Post #: 1

RE: RX voltage display - 10/25/2004 7:49:19 PM   
Mike01


 

Posts: 643
Joined: 12/29/2003
From: Brooklyn, NY, USA
Status: offline 		This may start a flame war, but I don't think you can tell the condition of a TX or RX pack by monitoring votlage...not under such a small load.

I just did a little test with TX packs. I have 8AA 2100 MAH NiMH batteries in my best radio...they are at about 75% charge (plenty to go) and show 10.2volts (the radio gives you battery voltage). I know they are at about 75% charge based on how long ago I charged them and how much I've used them, along with how long they have been sitting around. If I charge them now, they will take about 500mah...25%.

I have an 8 cell NiCD TX pack that was discharged to .9 volts per cell about two months ago. I just plugged that pack into the radio and it too showed 10.2 volts per cell for about 10 minutes before I got bored of looking at it.

I know from my experience at the local flying field (what a nightmare) that you airplane guys are paranoid to the point of being neurotic about every little detail of your models, including battery condition. If I was you, I would just peak the packs prior to every use and forget about monitoring voltage...but that's just me. Then again, if I was you, I would throw all of the glow planes into the trash and fly foam electrics, then you could actually relax and enjoy your day instead of running around like headless chickens clucking about how tight your lockwashers are on your landing gear.

RX voltage might be easier to check, because the load is greater, but it's still a tiny load. I wouldn't trust the results in either case. Think about it...a discharged pack sitting for two months showing 10.2 volts for ten minutes! That's 1.275 volts per cell!

< Message edited by Mike01 -- 10/25/2004 8:09:59 PM >

(in reply to BillS)
       Post #: 2

RE: RX voltage display - 10/25/2004 8:38:08 PM   
famousdave


 

Posts: 2263
Joined: 9/16/2003
From: Bradenton , FL, USA
Status: offline 		Mike 01 is correct.

The only way to see battery state is by using a fixed load with the servos not moving. It is not the voltage you are looking for but rather the change in voltage or "voltage drop" under max load that gives you an indication of charge state. Also - servos are a dynamic load (i.e always changing) monitoring voltage during flight would not do much good as the mean load and therefore, mean voltage would be constantly changing. (ever see the voltwatch.. it is useless as it reads constant when nothing is moving and lights flash everywhere under load). It is easy to monitor transmitter voltage as it is always under full load and that load does not change.


I have never lost a battery in flight do to undercharge, nor has anyone I know (I hang out with some pretty knowledgeable and experienced large scale flyers) I have seen battery and regulator failures and that is why we all carry two batteries and two regulators. Just like flying a real plane, there are certain things you must do each flight.. checking battery state under a fixed load (.5 amp for 1/4 scale or smaller and 1 amp for giants) is one of them. Checking just prior to every flight is the only real way you will ever know if you have enough juice left to fly.

Personally, I never worry about battery packs. I have two on every plane I fly, and I religiously check voltage every flight and I know my battery charge state at any given time. My H9 Meter is in my pocket at the line and its the last thing I do before starting. Checking voltage is really simple too - use a switch charge jack or spend $1.99 on an external charger jack to move the battery lead to an accessible location.

I think it is more important to develop discipline like full scale pilots do, rather than rely on gadgets to bail us out of predicaments... Ever try to look at your transmitter when flying.. not easy and not too safe....

My $0.02 anyway..
DP

< Message edited by desertpig -- 10/25/2004 8:50:14 PM >

(in reply to Mike01)
       Post #: 3

RE: RX voltage display - 10/25/2004 8:48:59 PM   
Mike01


 

Posts: 643
Joined: 12/29/2003
From: Brooklyn, NY, USA
Status: offline 		There are allways those foam electics....

The way I know to stop flying is when my battery dies and the plane comes in for a gracefull landing.

(in reply to famousdave)
       Post #: 4

RE: RX voltage display - 10/25/2004 8:54:46 PM   
famousdave


 

Posts: 2263
Joined: 9/16/2003
From: Bradenton , FL, USA
Status: offline 		We all fly foamies too.. but there is a difference between a $300 foamie and a $4500 IMAC plane... pucker factor increases an order of magnatude with each $1000 spent... trust me!!

DP

(in reply to Mike01)
       Post #: 5

RE: RX voltage display - 10/25/2004 9:02:49 PM   
Mike01


 

Posts: 643
Joined: 12/29/2003
From: Brooklyn, NY, USA
Status: offline 		Oh, I know...I probably have more invested in my race car than one of those giant planes with all required equipment.

I got hooked on the RC flying bug too...and I wanted the biggest baddest plane in the universe. Then I realized that I was spending more time cleaning and fussing over my plane than flying. I noticed I hadn't been to the flying field in three months and had no desire to go.

Now I just grab my foamie and go outside, fly a little till the battery dies then toss it in the shed and go watch tv. Nothing to check, nothing to tighten, nothing to do at all except enjoy a bird in the air peak charge some batteries. I'm still on my second set of AAs for my transmitter.

(in reply to famousdave)
       Post #: 6

RE: RX voltage display - 10/25/2004 9:07:07 PM   
BillS


 

Posts: 3050
Joined: 9/6/2004
From: Greensboro, NC, USA
Status: offline 		We have had four major battery related crashes at our field in the past few months. There may be more that I don’t know about.

Many will put in three to five flights and question whether they should fly again. Some fly again some don’t.

Voltage is certainly better than nothing. While voltage may not be a perfect indicator it is the only measurement currently being used by those who check. If the voltage were easily known some could at least avoid the knee on the discharge curve. A take off run might not be started at 4.8 volts. Even the people who check voltage between flights wait until before the next flight to check. In a questionable situation the spotter could be requested to monitor the voltage.

You and I know it is much better to know the capacity and to monitor the total flight time.

If RX read out was on the transmitter there are a few individuals that should occasionally be talked to while they were flying and casually glance at the voltage. The action might help them save an airplane. More important the field would be safer for everyone.

(in reply to Mike01)
       Post #: 7

RE: RX voltage display - 10/25/2004 9:28:08 PM   
BillS


 

Posts: 3050
Joined: 9/6/2004
From: Greensboro, NC, USA
Status: offline 		DP you are one of the savvy people and are not going to have a problem.

Some of us do monitor the transmitter while flying. Often the flight time is checked. It is really not very difficult to make experimental programming changes while in the air provided the radio is put in the correct mode and channel prior to take off. Level flight at mid throttle is reasonably safe to make a mix percentage change or to glance at the flight time or voltage.

By the way voltage will be lowest immediately after the flight.

(in reply to famousdave)
       Post #: 8

RE: RX voltage display - 10/25/2004 10:06:44 PM   
Mike01


 

Posts: 643
Joined: 12/29/2003
From: Brooklyn, NY, USA
Status: offline 		BillS,

I am going to be helpful instead of just making fun of airplane people.

I think it's nuts that you guys fly over and over again on the same RX pack. What's more, I think it's nuts that most airplane people use NiCD batteries with capacities as low as 600mah! I wouldn't use those batteries as paperweights! From I've been told by airplance flyers, they use NiCDs because of their discharge curves...it's easier to tell pack state by voltage (BS).

What I think you should do is what car people have been doing for years....invest in multiple high MAH NiMH battery packs. Tower Has receiver packs in the 1100MAH range for $30. Buy three of these and peak them the night before you go flying...or better yet, bring your peak charger and chare the ones you're not using flying flying the third.

This way, you always go up with a fresh pack and never have to worry about batteries again. As for the TX, just invest in some 2000+ MAH AAs (no reason you can't use those in RX packs as well) and charge them the night before...then enjoy flying all day without looking twice. I leave my radio on all day at the track with those batteries and have plenty of juice left by nightfall.

Another alternative is to make an external jack for you RX pack and peak it before every flight (should take 15-25 minutes)...that's if you really don't feel like taking the wings off.

< Message edited by Mike01 -- 10/25/2004 10:11:40 PM >

(in reply to BillS)
       Post #: 9

RE: RX voltage display - 10/25/2004 10:58:06 PM   
BillS


 

Posts: 3050
Joined: 9/6/2004
From: Greensboro, NC, USA
Status: offline 		A measuring instrument is needed.

Mike while the information is informative it doesn’t negate the fact that a real time measuring instrument is needed. Unfortunately those who least understand batteries have the biggest need. Those with the least understanding have the most problems, destroy the most airplanes and endanger the most people. Destroying an airplane is unfortunate but it happens.

Endangering the safety of other club members is the real issue. Voltage indication however flawed it may be would make today’s flying 100 X safer.

(in reply to Mike01)
       Post #: 10

RE: RX voltage display - 10/25/2004 11:03:29 PM   
famousdave


 

Posts: 2263
Joined: 9/16/2003
From: Bradenton , FL, USA
Status: offline 		BillS.. I agree with your premise.. that not all people have the discipline or knowledge... I guess I just assume it because it is such a routine part of my flying...

DP

(in reply to BillS)
       Post #: 11

RE: RX voltage display - 10/25/2004 11:38:29 PM   
sfsjkid



Posts: 576
Joined: 12/12/2003
From: fremont, CA, USA
Status: offline 		Bill, our club has a rule that requires a voltage check before each flight. I would do this anyways, and also afterwards. As everyone has mentioned is not the prefect method of measuring state of charge, seems to work for the most part as I don't hear many battery stories at the club.

As for a RX battery checker in the TX, well I have one in my 9Z and use it religously. But I'm thinking you want one that sends real time information? That would be cool if it had real time logging capabilities, but have a feeling that it might be overkill, IMHO, and may give a pilot a false sense of security. A battery check just before the flight may give a good voltage indication, but in flight as the loads on the servos increases, may quickly discharge the batteries to nothingness, especially if one of the cells is marginal. I usually remember the discharge characteristics of each of my planes, and periodically discharge them at the end of the day. In this way, I know how many flights I had, and how much charge I had left.

As for 600 mAhr batteries, I have them in the most of my planes, while other have 1000 and still others have 270's. Just depends on the plane. I've been able to get 10 flights or more, on the 600's depending on the plane with plenty of reserve, as measured on the discharger. Yet, on my 1/8th scale buggy, 600, would only be good for a couple of runs. Additionally, I must add that fast charging before a run will probably work most of the time but may bite, if you have a bad cell.

Sorry for getting long, but in essense, I feel most secure by checking voltage before and after a flight using a loaded meter (for 30 seconds or longer, I might add), and knowing each of my battery packs.

(in reply to BillS)
       Post #: 12

RE: RX voltage display - 10/25/2004 11:41:21 PM   
Mike01


 

Posts: 643
Joined: 12/29/2003
From: Brooklyn, NY, USA
Status: offline 		BillS,

I understand what you're saying, but put yourself in the shoes of a newbie. What is easier for you to understand and follow...

1. You must monitor your battery voltge by completing this checklist of procedures and by installing this add on component that didn't come with your trainer RTF.

Or:

2. Buy another receiver pack, bring your charger to the field, and charge and swap packs each time you go up.

Now add in the fact that option 2 is the ONLY way you can be sure you have an adequately charged receiver pack and I think the option becomes clear.

(in reply to famousdave)
       Post #: 13

RE: RX voltage display - 10/26/2004 12:05:38 AM   
JNorton



Posts: 3137
Joined: 1/29/2002
From: Montague, MI, USA
Status: offline 		I use 4.8 volt 800 and 1100 MAh Nicad batteries in my planes. For monitoring - all my planes have a Hobbico Voltwatch. After flying I'll check the voltwatch. It very accurately reads the "condition" of my batteries. Note - after batteries sit with no load they will read higher, that is why I read the voltwatch directly after landing, and I don't try to wring the last flight out of them! Very worth while investment at $11.00 a plane.

Just my 2 cents.

John

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(in reply to Mike01)