I ran a Saito 150 on a Giant Big Stick that was breaking in this engine. I used a 2000 MAb battery@6V, for the RX.
It started great, went through all the breakin procedures, and ran one tank of fuel through it at slow Idle ect. The fuel tank I installed was quite large, about 20-24 OZ, cuz Saitos love fuel.
I ran the engine for about an hour following their breakin rules. , slow, medium, fast, back to Idle, no more than 4K rpm's at breakin.
Then I ran the engine medimum , and full, very rich, and varied the times.
After the breakin I looked at the voltwatch, and it was in the Orange, not good. I measured the Battery at 3.4 volts??? This breakin only took an hour, and yes the RX Bttery was fully charged according to the Voltwatch. I did not measure the voltage with the Sentry meter before this took place. So I did not fly the plane, and wanted to get opinions on what could be wrong.

At 6V your radio draws more current than at 4.8V

If you only checked it using your voltwatch, did you make sure it was on the 6V setting rather than the 4.8V setting. If it was on 4.8V and you checked it good at the beginning, you were probably on the back side of the charge curve and most of the battery was probably discharged before you started. Was it a Nimh that had been sitting for a while before you used it? They have a pretty large self-discharge (unless it was an eneloop or similar).
Just some food for thought.
Good Luck,
Curtis

I understand, I think.??? If I put 2 6V batteries on seperate switches, and the first battery serves the RX, The second battery is plugged into a vacant channel, thus delivering 6 volts. If one battery starts to fail, will the second battery pick up the loss?. That is my actual question but I didn't write it down correctly. Let's say the first battery is 6.50 volts, the seond battery is 6.10 volts. They both will show green on the Voltwatch, but are they sharing the power to the RX on seperate swiches?

The stronger battery will power the receiver and drain into the weaker one until both equalize voltage. If one battery were to fail (as in with a dead cell) the weak battery will kill the stronger battery. Best to isolate each pack with a diode to keep the strong pack from getting drained from the weaker one.

IMO,

You need to check your battery with
a loaded voltmeter. I do before every
flight.

Bob

The Voltwatch will do that if it's set up properly. And, in a two battery situation, as the original poster is using, the Voltwatch will give you the average voltage while in-use, which is exactly what a loaded voltmeter will do.

You don't need a diode anywhere. The setup as the OP is using is exactly what I am using on three of my planes and is just fine. In fact, I developed a battery problem in flight where one of the batteries developed a bad cell. I didn't realize anything in flight, then when I landed, I did my usual voltage check (I check the Voltwatch before and after each flight) and when I checked the one battery, it showed RED on the voltwatch (6 volt pack) and the other showed green. When I had them both switched on, the voltwatch was still in the green showing that the good battery was doing exactly what it was supposed to do.

The setup is simple: one battery per switch then each one is plugged into either the battery channel or a vacant channel on the RX (or use a Y connector cable and connect it to a used channel). The check process is also simple. Switch one on, switch two off, check the voltwatch while moving all sticks to maximum, should remain well into the green. Switch one off, switch two on, check the voltwatch while moving all sticks to maximum, should remain well in the green. Both switches on, then check the voltwatch while moving all sticks to maximum, should remain well into the green. Start the engine, the move all sticks to maximum while watching the voltwatch.. should remain in the green. Go fly.

CGr.

Morning CG. Went from building planes to building a boat (ARK) Been raining hard for 3 days. When it approaches 40 days, the ARK better be ready.
2 eggs basted soft, 2 strips not crisp bacon and 2 slices Oatnut toast. Oh, chock full of nuts coffee.

What CGRetired said. very correct. Check out http://www.hangtimes.com/redsbatteryclinic.html for good advice on this.

6v batteries dont discharge that much faster than a 4 cell pack (about 3 to 5 percent assuming two identical capacity batteries with the only difference being the cell count)

Is it a NiMH battery? If you're breaking in the engine is the battery is new? They must be properly form charged and take 3 or 4 cycles before they really start putting out their rated capacity.

The batteries are Nimh and both are new batteries. I am now cyclying both batteries . I did not cycle the first battery, just charged it and it drained very quick. I will use 2 switches and 2 voltwatchs and measure each battery after each flight.

Are any servos "buzzing"?
It's possible, if the battery is actually OK, that your throttle servo was up against a stop during the break-in and was sucking all the electrical goodness out of your battery pack.

You should only need one Voltwatch. Just separate the batteries by 2 individual switches, but plug the VW into an open slot in the Rx, or put on a Y-cable.

C

That's right. Only one voltwatch. Two is just not needed as they both get connected to the same place, electrically, that is, so they would measure exactly the same thing.

One voltwatch, two batteries plugged into either two vacant slots or connected to the receiver via a Y connector, one switch per battery. Turn one on first, check the voltwatch, turn it off, then turn the second battery on, check the voltwatch, turn both on.. fly. Just as I said in my earlier post.

CGr.

I will use only one voltwatch, with the batteries in parrallel. I will also cycle all my batteries, (new Batts) before first usage. Thanks guys for all of your help.