Re two batteries, or other ideas

[Henderson,Eric]

You can go too far with all of this redundancy stuff and still get failures that are much more common.

I have become a bit phobic about batteries with several "failures" and "dodged bullets". At first I developed a regimen where I did a pack-test before and after every flight. Although this was good it did wear out the charging 
jack in the fuselage side. It also DID NOT test the on-board system. Perhaps the word TEST is what needs to be most emphasized!

My most recent "peace of mind" comes from using on-board battery indicators. The $15 string of LED types work well and can be seen on most of my sport planes. The I4C, C-Volt LCD digital unit drains a meager 10 ma and tells you a whole bunch of things while you have the flight pack turned on. It weight approx. 0.4oz and is in all of my pattern or big planes. The big deal here is that the flight system is on, not just the battery undergoing a load test with some external device. What you are seeing is what you will be flying.

It is not cheap @ $40 plus... but has help me spot the following potential disasters that would have cost $1000's.

1. Several bad aileron pots that drew huge ma's when the engine was running. 
2. Bad connectors to battery. One was arching and melting the plastic connector...
3. Bad servo motors.
4. Binding control surfaces (Throttle servo on soft-mount was being stressed as full power moved motor forward - needed 1/16" less opening to fix) drained an amp at full throttle. The Voltage shown tracks the amperage being drawn pretty closely. 
5. Bad wire on servo lead - black corrosion and non conductive..
6. And last but not least, bad battery cells.

I use this digital display because it can handle any RX pack voltage - 8.4v on a Li-ion or 4.8v on a nicad... are all in the range.

One nasty problem (that LCD found of my Focus) was a regulator that was failing during high current draw. I tracked it down by putting an additional C-Volt in an RX slot and operating the flight system with the engine running (tethered of course). The voltage prior to the regulator stayed good but post regulator was erratic. Bye bye regulator - New one was flawless and easy to test.

Also when trying new packs all I do is read the display before and after a flight and log the discharge for each flight, For example my Li-ion come down .2v per flight with a "digital-servo" ship.

They (I4C_ have and LED version that is a bit heavier as well. Worked good in an application where the canopy was a bit too dark for the LCD version.

 - This is one of those "Ounce of prevention is worth a pound of cure" thought processes.

Regards,

Eric.

BTW I'm not saying don't do all the battery back-up stuff if it helps your phobia but that you can also add an integral read-out device..

Breaking news. They now have a version that doubles up as an onboard tach using the same LCD and a hall effect sensor to pick up magnet embedded in spinner back plate - tells you your rpm while ground tuning and give in-flight peak reading.. more toys ---!!!!!

Regards,

Eric.

-----Original Message-----
From: discussion-request at nsrca.org
[mailto:discussion-request at nsrca.org]On Behalf Of tkeithb at attbi.com
Sent: Monday, March 31, 2003 1:44 PM
To: discussion at nsrca.org
Subject: RE: Re two batteries, was Miracle switch failures


> I currently just use one 5 cell NiCd with a RadioSouth 5.1v regulator and 
> it's the best setup I've had in terms of consistent performance.  I will 
> be repeating this on my next plane. 
> --Lance

So what you're saying Lance is that you DO have redundancy, a second plane.

:-)

Keith
> You are right, the backup battery is the simpler (hopefully more reliable) 
> setup.  I understand.
> 
> In my experience with circuit board design, I've found regulators to be 
> more reliable than diodes.  This is not intuitive, since regulators have 
> many internal transistors, but they also have bypass protective circuitry. 
>  If the regulator is wrapped in foam and the connectors are stress 
> relieved so that they can't weaken, then I'd have no problems having a 
> regulator in the circuit.  I
> 
> I currently just use one 5 cell NiCd with a RadioSouth 5.1v regulator and 
> it's the best setup I've had in terms of consistent performance.  I will 
> be repeating this on my next plane. 
> 
> --Lance
> 
> 
> 
>  
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