On Sunday my buddy destroyed his plane and we later discovered that the battery was at fault. It was a 4.8V NiMH 750 mil-amp battery, which has just been charged at 800 mil-amps for one hour. He did not monitor the charger, but it seemed to be charging when he plugged it in and was in trickle mode when he returned an hour later. It flew the plane for about 5-minutes then the plane stopped responding to controls and crashed.

After the crash the battery registered over 4V on a volt meter, but when we plugged it into another airplane we realized the battery only had enough power to move the servos a couple seconds until its power was exhausted and they would no longer move. We did not try testing it in the crashed plane because the rx was damaged in the crash.

Any thoughts what the problem with this battery was and what we should do to avoid this problem?

Always check the battery voltage with a loaded volt meter at 1 amp. Most fast chargers are peak chargers. And if you get a false peak the battery isn't fully charged. This is just one of many reasons for a bad battery. Always use a loaded volt meter. Dennis

Testing battery voltage without a load is worthless. The flight battery can appear full when it's actually about dead.

Also, I wouldn;t charge a 750mAh battery at 800mA. it's just asking for trouble in my opinion.

with my glow plane I have a 2.4 Futaba FAAST 7Ch system. The radio was packaged with servos, battery, and futaba charger (not a fast charger). I have been charging both the tx and rx after each flying session or when I notice the tx voltage getting down to less than 9V or so.

am I pretty safe doing it this way, or am I going to eventually end up like my buddy unless I buy more gear to analyze my batteries?

You will be fine charging with the supplied wallwart charger. But get an expanded scale voltmeter that simulates servo load and test before flying. I use an Expert brand LED tester that loads the battery. I use this before I fly for the 1st time and after every flight. When the LED lights get halfway down between the amber between the red and green I top up with the field charger. I make it a regular habit of cycling my batteries once about every 3 trips to the field. Always test them before you fly to make sure that they didn't false peak.

Curt

Look on the side or the front of the wall wart charger. It details the output current for each line (4.8 and 9.6 volt charge lines). That current is displayed in mili-amps. You relate that directly to your battery.

For instance: 1000 mah battery and a 100 mah charge port for the RX. (same applies for the TX battery, by the way).

So, 1000/100 = 10. So it will take a full 10 hours to fully charge a fully discharged battery, plus about 20% or so for overhead, so figure 12 hours for that 1000 mah battery to be charged with a 100 mah charge source current.

There is no real way to know how much your battery has discharged after a flying day, suffice to say that it has discharged. You can guess, but why take the chance. So, just figure to charge it for 12 hours (as shown above) ummm... overnight... perhaps (does that sound familiar by any chance? ) and you just cannot go wrong. Once it is fully charged, it will revert to trickle and maintain.

Futaba claims that their current draw for the TX is 170mA. I would assume that's per hour, by the way. So, they supply a 600 mah battery. Do the math. 600/170 = 3.5 hours of use.. well, that is if you want to trust that it will be ok for 3.5 hours of use. The point is you have lots of TX time with the 600 mah battery supplied. The charger looks like it's TX port is 170 mah. What a coincidence!

Charge it overnight and be safe.

CGr.

You can also get yourself a smart charger. Most of the newer chargers will tell you how long the charge cycle lasted, and knowing the charge rate, you can determine how many milliamps you put into the battery. If you check the voltage at the start of the charge cycle and look at the amount of current put into the battery, you can get a rough estimate of the health of your battery.

If you're concerned, using an expanded scale volt meter or a dummy load on a standard volt meter is your best option, as long as you know where the cutoff voltage should be.

Brad

You're putting a lot of faith in the battery and charger flying blind like that. It's not very expensive to purchase a loaded meter. Think of it as saving $150 woth of plane.

The wall charger works perfectly well. It's a matter of opinion but the wall charger might be better for the battery than a quick field charger.

Get you one of these: You and your buddy can share it for $10
http://www3.towerhobbies.com/cgi-bin...?&I=LXNK82&P=7

or put one of these on your plane so you know at a glance: $12
http://www3.towerhobbies.com/cgi-bin...&I=LXHDJ2&P=ML

You can buld a battery discharger for less than $5 from a 12V automotive bulb. That'll let you cycle your batteries.
Or you can get a Triton Jr (or similar unit) and it'll run a cyle automatically. http://www3.towerhobbies.com/cgi-bin...&I=LXMAH9&P=ML

It's so cheap to all but prevent this from ever happening again. For $10 you can protect your plane unless the battery faults in-flight (not very often).

Have fun!

Today I ordered an ESV and one for my buddy who crashed his pulse, we saved a little by ordering two.

I also ordered a volt-watch, 2 NIMH batteries to run together, switch for the second battery, and a proper battery cycler.

the 2 NiMH batteries combined are only a little heavier than the NiCad they are replacing but will have over twice the power.

my buddy is just going to use the ESV and a single battery for now.

I'm an old fuddy-duddy and never charge a battery at more than half of it's rated capacity. I'd rather go two hours for a full charge than one interrupted by a fire.

I recommend a Triton II or Triton Jr.

IMHO 80% of the guys who cry "HIT!" and lose a model are due to faulty battery management and not radio glitches.

Read through Red Scholefield's RC Battery Clinic site. http://www.rcbatteryclinic.com/

I'm more of a C/10 guy for flight packs.

I use both the ICE and older Triton charger. However, I prefer the Ice. It seems to be a bit easier to operate. At least to me it does. However, both are available and get used on a regular basis (like every time I fly). And I too use the C/10 method as a maximum charge rate.

AstroDad: I think I understand your setup. I have a pair of 1200 mah NiMH packs in a few of my planes. I have each battery setup through a switch to separate receiver channels (unused channels). You can also Y connect the battery (through a switch) to a servo channel if you like. The battery + and - are all "ganged" or bussed together (of course, one on + and one on - ) within the receiver so no matter where you put the battery, you will have a connection within the RX.

I put a voltwatch on a vacant channel also. I am not using flaps, gear, and all that other stuff, the basic four channels get used so I have three vacant channels on a 7 channel RX (DC7000 receiver). So, I simply put one battery on one channel, the other on a second channel, then the voltwatch on the last remaining channel. Some receivers have a separate battery slot plus 7 channels. It doesn't matter where you put the batteries and voltwatch.

And, even with two batteries, you only need one voltwatch. You simply turn on battery 1, check operation and available charge by the indicating LED's, turn off battery 1, then turn on battery two and repeat, then turn both batteries on and go fly.

CGr.

CG that is exactly what my plan is! Thanks for all the advice.

I usually fly in the 100 acre field behind my house, so I wanted an AC cycler and ordered Hobbico Accu-Cycle Tx/Rx Battery Cycler.

I have the FAAST 8-ch radio but only need 4 channels for my H9 Arrow that I fly, so I have pleanty of slots for the 2nd battery and voltwatch. I have not seen a voltwatch in person, so I just hope it is not too bulkly.

Hi AstroDad.

No, it's not bulky at all. It's about 2 inches long, 3/4 inches wide, and about 1/8 inch thick.

I usually cut a slot the size of the LED strip in the side of my fuselage somewhere in the radio compartment. Then I paint the balsa with flat black paint, then put the Voltwatch inside the fuselage with the LED's facing outwards (of course.. ) with the green forward, red toward the back. So, you read it left to right. I then take a small strip of clear monocoat and put that over the hole, and voila.. you got your voltwatch mounted, clean and simple. Oh, I tape it to the inside of the fuselage, hold it there, with a strip of 1" Blenderm adhesive tape, available at any good medical supply store. The Blenderm is strong, flexible, and easy to use.

Here are the spec figures from Tower:

Length: 1.65" (42mm)
Width: .63" (16mm)
Height: .16" (4mm)
Weight: .15oz (4.3 grams)
Current Draw: approx 4-34mA

If you look closely enough, on the left side there is a 4.8 volt - 6 volt slide switch to select your battery type.


CGr.

CGR I like the way you have it mounted on the fueslage. I think I will do the same with mine. On my SeaMaster 120 I have two 2500mAh batteries 6 v operating on two seperate switches. Don't want to lose it at Sea. Bet you didn't know we had Seas in MIchigan. Enjoying some vanilla bean coffee with my everything toasted bagel.

Ha.. I already mentioned donuts today.. some Starbucks Kamoto Dragon Decaf brewing as we speak!!

I have a very good friend that lives in Grand Rapids, another retired Coastie. He captains the university research boat that goes out in Lake Michigan out of Grand Rapids. We go way back.

I went to Navy Boot camp and Electronics school at good old Great Lakes Training Center north of Chicago, so am very familiar with how darned cold it can get out your way during the winter months. Boot camp was Nov - January, Tech school was March to December.. then they sent me to Submarines in Holy Loch, Scotland. What a life! Went in the Coast Guard after my tour in the Navy. Wanted something different, and different is what I got!!! Wow, what a ride!!

CGr.

Yeah, I mounted it near the switches on the opposite side of the exhaust. Clearly visible.

CGr.

You better hoard your StarbuckI see they are closing 600 outlets. Imagine how many people are going to be in withdrawl. Hummmm!!!! have to start Starbuck anoymous.

Yeah, you're right!! [X(] I gotta head down the corner quick like and get a bag full of Komoto!!!

CG that set up sounds really clean!

I hope I have clearance to do mine similar.

That's great! You won't be sorry with your purchases. I need to learn from you and install a redundant battery.

AstroDad.. on one plane, one that had a removable canope, I actually mounted it in the "dashboard" so the "pilot" could see it. Looked pretty cool. I also cut through the thin ply to make it fit in.

It just takes a little time and careful cutting to put it wherever you may wish to put it. The only 'requirement' is that it is clearly visible when you need it to be visible. Obviously, you can't see this thing from the air. It's not for that. It is a 'before and after' device in which you get the 'warm and fuzzy' that your battery pack(s) are functioning and have a decent and usable capacity to continue flying.

What I also do with mine is this: Upon initial installation, I use it as a tool to check for any binding in the linkages. I turn everything on (this is on the 'bench') and then, systematically move each stick to control each and every conrtol surface plus the throttle, and any other item that may be attached to the battery that causes a load. Moving the sticks will cause the battery draw to change due to servo movement and servo load, and thus the LED's on the Voltwatch will flicker. If I get a hard flicker.. movement to the RED for instance, when moving the rudder, for instance, I know that there is a bind in the rudder linkage somewhere and it needs some attention. The same goes for all other control surfaces.

What is nice with this is especially true for the throttle. We often have a problem with pushing or pulling the throttle linkage to far. So, when we do that, the servo will strain to continue pulling the throttle beyond the stops, so it will begin to draw excessive current when it reaches the throttle stops, full and closed. So, this becomes a tool for setting the throttle servo throw to manage throttle movement and insures that you have full throttle when you move the throttle stick to maximum, and that it closes all the way when you pull it back. AND, the adjustment is made to insure that it does not go any further than that, on either end. Thus, no binding, no excessive current draw from the throttle servo.

I can assure you that there are many RC'ers out there that do not pay attention to that, and as a result, when going to full, for instance, their servo wants to move further than it can based on the linkage adjustment. So, the linkage will flex, or bend, and the servo will strain, and.. yep, you got it.. draw more battery current.

So, it not only gives you that warm-fuzzy feeling before and after each flight, but it also will give you a tool for quickly determining excessive or adequate (acceptable) current draw for adjusting your linkages. Sure, other devices will do the same thing, but none, in my estimation, is as 'cheap' (meaning inexpensive), easy to install, and easy to use as the Voltwatch is. And, it looks kinda cool too!!

CGr.

for my high-wing trainer I have the best access and space on the fuselage below the wing, but it is going to be a pain to see when doing pre-flight because the wing will be blocking my view as I stand above the plane.

I hope I can find room to install it on the top of the fuselage behind the wing, but space will be tight. I might even do a fully external install on top of the fuselage behind the wing. If external, I might build a little aerodynamic structure around it to reduce drag.

here is a photo of my airplane. http://www.hangar-9.com/ProdInfo/Lar...es/HAN2550.jpg
so I am thinking if I have to go external, then on top of the fuselage behind the wing might be the best external location?