Chris Smith
Posts: 453
Joined: 5/23/2004
From: Berea KY, Clarksville/Adams,
TN, USA
Status: offline
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Joe,
I hate to talk batteries in the Panther thread, but if no one minds I'll make these the last comments in hopes of helping.
Since you know to hold the button long enough for the blue backlight indicating discharge mode, you should be ok.
Using discharge mode is sort of a round-about way to use the BR-2000. Cross check your results a couple of times using another quality checker to be sure. I had friends that thought they were checking the battery under load just by holding the button only long enough for a reading (red backlight) yet only 72mah load was applied. For .40-.60 size models that might be ok. It cost one of them an airplane because they thought the 6.2 was showing with the 1amp applied, yet it was not. The BR-2000 is a bit tricky. I highly recommend the Radio South battery checker for jet dudes. It has a very simple digital meter, it reads any number of cells, and has 3 load settings 500mah, 1000, and 1500mah that are applied as soon as you hit the button. It is also small and reliable.
http://www.radiosouthrc.com/ProESVTester.htm
Once you get the engine back and it checked ok. You may want to do some other checking for piece of mind. Then if there is nothing obvious, go fly.
Here's some thoughts:
I'd worry if a 6-cell 7.2 battery ever went down to 6.4 volts. Even under load could be iffy. Seems like that would be below the min volt ECU threshold too. Could indicate a bad cell. Use the 1.1-1.2 volt per cell minimum rule to indicate each cell is still ok. That battery would go into my ground toy, fuel pump battery drawer marked "not for flight". If your battery goes from a sustained 8.2V under load to around 7.2V in 2 or 3 flights that could be perfectly normal. You would have to know average flight loads to be sure, or just charge between flights to keep it simple.
For Rx batteries seems 500mah load testing should be sufficient for most jets, but you'll have to test using a device that can tell you average amps used over time of flight. Maybe 1 amp would handle worst case unless there is serious binding somewhere. The only magic formula to determine that would be a recorder in-line between Rx battery and the receiver bus during flight, or add a large safety margin to the total of amps each servo draws during set-up.
For ECUs a 1 amp test load may be ok for an ECU battery under flight load and sustained running, but it may not account for the peak loads the battery will see during engine starts with the starter motor, glow plug, etc. All depends on what amps your ECU should be using. Maybe they are really low, but my guess is they can easily approach or exceed 1 amp during engine start. The engine manufacturer should be able to tell you that. Then, if you find your ECU is demanding more, it may indicate a problem such as bad starter motor, bendix, bearings, or other inefficiencies the ECU battery is drained for. But don't assume the worst.
Maybe the ECU software ignors spike or peak loads during start, but not while running. If the battery is on the edge of a minimal charge, weak cell, or there is other intermittant in-line resistance through a connector or switch, the start sequence alone could drain it to the point of marginal amperage yet be ok voltage as far as the ECU sees in flight. Until a larger amperage demand is placed. Then amperage loads would spike and voltage would have to drop in such a case. You wouldn't know until the ECU commands a low volt shutdown due to a momentary battery brown-out. Maybe right at the point of throttle-up and smoke-on for example. The key word is "momentary" which makes troubleshooting hard.
The only way to be sure you know the normal loads your ECU battery is seeing during a flight would be to use an amp recorder in line between the battery and ECU while the engine is running. I would only do that on the ground. But do it for the time a typical flight would be such as 6-7 mins. Guys that do a lot of electric flight have these small meter/recorders that will show and log amps, voltage, watts, time, and average amps, etc. I bought mine specifically to determine what kind of battery loads my Flash with 10 high power digital servos was using. Made a dual Rx batteries believer of out of me. Dual batteries drops the load on each battery in half. So duals are not just good for redundancy. They also help minimize or eliminate brown-outs which probably happens in jets more than we know. We tend to blame the radio RF or engines. I have not used the recorder for looking at ECU batteries, but now I'm curious.
What's hard to account for is battery cell quality and impedance. Some of the larger sub-C and C-cell sizes used in cheaper packs have internal chemistry and impedance characteristics that can act as a choke point when loads spike. Again, the best way to account for that is always top-off the battery between flights and use a good battery checker.
Let's hope the engine checks out ok. That way you can concentrate on the battery and installation troubleshooting. You may never find the smoking gun. But it helps to know you've checked things out. ECUs are like any other computer. Sometimes they do unexplained things and need a re-boot. Luckily those instances are rare.
Good luck,
Chris
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RE: FeiBao F-9-F Panther - 
