Paul,
FWIW, I'm using an older 1200mAh Lipo pack of course @ 11.1 V (3-cell)
You're right. I think I may have first said 1v. But after confirmation, it's been a consistent .7 drop with the 4001. My lipo charger (and most do this) shuts off at 12.6 when fully charged. Plugging in to my test circuit, the lipos charged were at 12.5v. With the diode, the max I've seen on my test circuit/TX is 11.8v but most of the time 11.7 (never above 12v - my goal!). And, it follows it down. Ironically, it's worked out perfectly, because I have a LVA (Low Voltage Alarm complete with LEDs/Beeper) that I found in my supplies added to the test circuit. I used a .2A load – derived from testing my actual transmitters.
The Blue LED is steady with volts above 11.1 or 10.4 on my radio for 4 hours 45 min (compared to apx 2 hours on nicads!!). Below this, the blue LED starts blinking...but you're still plenty safe. (going on up to 2600 mA lipos? Looking at an EASY 9-10+ hours between charges!)
Apx 45 min later @ 10.2 or 9.5 on the radio, the red LED comes on steady and a beep about every 10 sec. I normally fly to 9.6v (typ voltage for eight 1.2v nicads) on my tx. This is where I will recharge at the latest. But, we're still safe for flying. The TX is still fine...but I WILL land ASAP! And here is why..... you have apx 8 min to land without losing transmission. Read on.
After only apx 4 more min, it gets more critical and the alarm lets you know it: Volts 9.9 on lipos and 9.2 on Tx. The red LED is flashing rapidly and the beeper about 3 times a sec!! VERY loud and annoying and for a reason! The radio is then at apx 8.3 and by then has sounded its OWN critical alarm...and that's why I said it works out perfectly even though I didnt plan it that way. I would not fly at this voltage although I accidentally have! But if you will notice, as most batteries do, the final voltage falls off a cliff so to speak and you're living dangerously!!
Apx 4 min later, the volts are @ 9v (where most smart charger/cyclers will discharge to...the lipos are at the MAX suggested low voltage without risking damage). I did not test below that. But with the transmitter, I HAVE seen it fade out below 8.25 when running on nicads.
So all-in-all, I was going to use a regulator, but after reading and getting word from one of Futaba's service centers-Radio South, I was content to use a diode. Even though it may not be necessary, it has proven to work beautifully with this LVA simulating the exact voltage affects...thanks to the .7 voltage drop.
Darral
Sent: Sunday, August 09, 2015 6:37 PM
Subject: [Electronics_101] Re: Need help on a Voltage Regulator
The 1N4001 diode is a basic, silicon rectifier diode and will drop a
constant, 0.7 V through it. That may help sooth your fears, but it is
not a regulator. So the output Voltage will not be constant, It will
just be 0.7 V less than the battery Voltage.
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Posted by: "Darral" <darral@charter.net>
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