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6v or 4.8v receiver pack?

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Old 09-02-2005, 10:13 AM
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Bidwin
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Default 6v or 4.8v receiver pack?

If I use a 6v pack instead of a 4.8v pack for my receiver can I draw the 6v pack down below 5.5v and still fly safely? If the answer is "No" please explain why. If the answer is "Yes" then how far below 5.5v is it safe to go? Do the answers differ if using NiMHs vs NiCads? My new plane has 7 servos instead of 4 and my objective is to fly longer between charges. I plan to buy a relatively high capacity (ie 1650mah) NiMH pack for the plane, and if a 6v pack is a better way to go then I'll buy that.
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Old 09-02-2005, 11:33 AM
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exeter_acres
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Default RE: 6v or 4.8v receiver pack?

I never go below 1.2v per call on a RX pack... any lower and the voltage drop off curve is way to steep for my liking

What I have done is on several occasions, I fly my planes for one flight and then field charge, keeping a mental note on capicity of charge...
then average it out... I thin know about how many mAh I use in each flight on each plane.....

I use 1450 or 1650mAh 6v packs in all but my smallest planes
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Old 09-07-2005, 07:01 AM
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Default RE: 6v or 4.8v receiver pack?

When you use 6v, you get less flight time for the same capacity. More volts equals more amps also but better performing servos. That's a trade off. If only flight time is what interests you, you should get the 4.8 volt battery.

Anyways, I agree all the above...
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Old 09-07-2005, 09:31 AM
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Geistware
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Default RE: 6v or 4.8v receiver pack?

I had this same question when I first started flying. After some testing, the answer became clear. I will try to explain it here.
A pack will power a given load down to a specific voltage before the voltage or current delivered is insufficient. THE question then becomes, at a 1 amp load, how much capacity is left in the pack when a 5 cell pack is at 5.0 volts. You may find you have 25%-35% of the packs rated capacity.

I took two packs a verified 2700maH NIMH pack and a 1800maH NiCad pack. Both 5 cells.
I put a 1 amp load on each and discharged it down to 5.5 volts.
I then discharged both packs at 200 ma to see how much was left in each pack.
The NiMH had 1000maH and the Nicad had 250maH.
I could get more of the load out of the NiCad.
It was a larger and bulker pack.
After this test, I started using NiCads for RX.

ORIGINAL: Bidwin

If I use a 6v pack instead of a 4.8v pack for my receiver can I draw the 6v pack down below 5.5v and still fly safely? If the answer is "No" please explain why. If the answer is "Yes" then how far below 5.5v is it safe to go? Do the answers differ if using NiMHs vs NiCads? My new plane has 7 servos instead of 4 and my objective is to fly longer between charges. I plan to buy a relatively high capacity (ie 1650mah) NiMH pack for the plane, and if a 6v pack is a better way to go then I'll buy that.
Thanks,
Bidwin
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Old 09-07-2005, 10:07 AM
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piper_chuck
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Default RE: 6v or 4.8v receiver pack?

ORIGINAL: Geistware
I took two packs a verified 2700maH NIMH pack and a 1800maH NiCad pack. Both 5 cells.
I put a 1 amp load on each and discharged it down to 5.5 volts.
I then discharged both packs at 200 ma to see how much was left in each pack.
The NiMH had 1000maH and the Nicad had 250maH.
I could get more of the load out of the NiCad.
It was a larger and bulker pack.
Am I missing something? You got 1700 maH (2700-1000) out of the NiHM and 1550 maH (1800-250) out of the NiCad. I agree you got a larger percentage of the NiCad's capacity, but I can't see why getting more load 1700 versus 1550 out of a smaller pack, the NiMH, would be a bad thing.
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Old 09-07-2005, 10:21 AM
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Geistware
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Default RE: 6v or 4.8v receiver pack?

You don't get more load.
With the same load, you get less % of rated capacity before you reach your minimum voltage.
In effect, you can get more energy from NiCad chemistry that you can NiMH at higher loads.

ORIGINAL: piper_chuck

ORIGINAL: Geistware
I took two packs a verified 2700maH NIMH pack and a 1800maH NiCad pack. Both 5 cells.
I put a 1 amp load on each and discharged it down to 5.5 volts.
I then discharged both packs at 200 ma to see how much was left in each pack.
The NiMH had 1000maH and the Nicad had 250maH.
I could get more of the load out of the NiCad.
It was a larger and bulker pack.
Am I missing something? You got 1700 maH (2700-1000) out of the NiHM and 1550 maH (1800-250) out of the NiCad. I agree you got a larger percentage of the NiCad's capacity, but I can't see why getting more load 1700 versus 1550 out of a smaller pack, the NiMH, would be a bad thing.
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