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4.8V versus 6V for receiver battery?

Old 09-10-2007, 11:36 AM
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nk1851
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Default 4.8V versus 6V for receiver battery?

Why would one choose 4.8V over 6.0V for receiver battery, or visa versa?
Also, the same question on NiCd versus NiMh?
Thanks
Old 09-10-2007, 11:38 AM
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Charlie P.
 
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Default RE: 4.8V versus 6V for receiver battery?

The 4.8v gives you longer flight time but less servo torque. If you need the added torque go for 6.0v, otherwise the 4.8v would be the better choice. NiCad/NiMH are no difference there (I prefer NiMH as they are more forgiving for charging from partially drained).

If you want longer flights at 4.8v go for a pack with more milliamp hours (maH).
Old 09-10-2007, 11:46 AM
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Default RE: 4.8V versus 6V for receiver battery?

Unless you are using huge servos, multiple servos on each control surface or digital servos that require the extra power or fly in competition, keep with the 4.8v.

Hogflyer
Old 09-10-2007, 11:47 AM
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Default RE: 4.8V versus 6V for receiver battery?

Why does a smaller battery give more time than a bigger battery. Also doesn't a 6.0 volt battery also give you faster servo response?
Old 09-10-2007, 12:41 PM
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Electrolight
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Default RE: 4.8V versus 6V for receiver battery?

Charlie P thats BS.

The only difference between a 4.8 volt and 6 volt batterie is the six volt gives you more torque. (mostly for bigger servos)
As far as how much time you have till the batterie is dead, that depends on the maH rating. ( The higher the maH rating the longer the batterie lasts)
An the difference between a NiCd and a NiMh Is that the NiMh usually has, on average, a higher maH rating. And they are much more forgiveing when charging partially charged. And NiMh are slightly heavier.

These are the main differences. Good luck

Electrolight
Old 09-10-2007, 01:02 PM
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Default RE: 4.8V versus 6V for receiver battery?

Yes, it is true that the 6.0 volt battery will give you a faster servo response time as well as more torque. I use a 6.0v battery on my UltraStick because I wanted a faster servo.. It is also true that the 6.0 volt battery will run to depletion faster than a 4.8 assuming they are both the same capacity (mAh).. The rule of thumb that I've heard is to get a 6.0v battery that is has 25 percent more capacity than what you think you would need in a 4.8v.. This is a ballpark number, but works most of the time.. I've been happy with a 1200mAh 6.0v battery in my stick running 7 servos.. All depends on what type of flying you are going to be doing. If its just a trainer, you want the servos to be slow, but if you want to "amp" the up a bit give the 6.0 a try!

John.
Old 09-10-2007, 01:06 PM
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Default RE: 4.8V versus 6V for receiver battery?


ORIGINAL: jollycub

Why does a smaller battery give more time than a bigger battery.
Ohm's law, as the voltage goes up so does the current if the load stays the same.

The problem with that is we don't have a static load.

In actual practice a 4.8v pack lasts between 5 and 7 percent longer than an equivilent 6v pack.

Old 09-10-2007, 04:14 PM
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Default RE: 4.8V versus 6V for receiver battery?

Nice thing regarding 4.8v is all of your std chargers will work with them. I'm just moving up to my 2nd model (an UltraStick 40) after 3 years on our trainer and looked at 6.0v stuff but decided to stick with 4.8v.

NiCDs are also a bit more durable than NiMH but the latter typically comes in higher capacity. For a std 4 servo aircraft, a NiCD works just fine. It came time for me to replace the stock 600mAH NiCD in my trainer so I chose an 1100mAH NiCD pack (also 4.8v). My son and I flew 8 times the other week and I still had plenty of battery left. That was over 90 minutes of time in the air! We were getting tired and hungry - I don't see why you'd need more for a sport RC model.

Dave Thacker has some good advice on 4.8 vs. 6.0 and NiCD vs. NiMH on his Radical RC site.
Old 09-10-2007, 05:11 PM
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Default RE: 4.8V versus 6V for receiver battery?

A lot of guys seem to be using 6V batteries to stay away from reboots of their RX's in their JR/Spektrum systems due to low voltage. Of course, even larger batteries need to be monitored.
Old 09-10-2007, 07:48 PM
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da Rock
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Default RE: 4.8V versus 6V for receiver battery?

About the different times from 4.8V packs versus 6V packs.

The theory says the 6V won't last as long.

In theory, theory and practice are the same. In practice, they are not.

There was an excellent article in a magazine last year or year before. The guy did a reasonably sensible test that compared the two. His findings showed that in our models, 4cell packs and 5cell packs gave almost identical flight times. Why? I think he surmised it was because the added power for the servo caused it to draw less amps.

And if I remember correctly, he said something very smart at the end of the article. Something about not needing to know why to know it worked.
Old 09-10-2007, 08:59 PM
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Campgems
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Default RE: 4.8V versus 6V for receiver battery?

For what it's worth, here is my experiences. I have two planes currently making the trip to the field. Both are using Futaba S3151 digital servos. The first is a 4*60 and I'm running five servos in it. Also 4.8V. The second plane is a Ruperts Dad scratch built and it has six serovos and a 6V battery. Both are Nicads and 1000mah. I also run VoltWatch sticks on all my planes. I can fly the four star as much as I want to fly in a day, usually about three tanks of fuel, or around 40 minutes total filigh time. The Volt watch will show the battery down about 1 or two lights. The Ruperts on Sat had three short flights of about 5 minutes each and when I put it away for the day, I was down three lights. When I got it home, I cycled it from where it was and I had 63 minutes left at a 500ma load. I'm guessing I could have gotten another 20 minutes filght time if I had wanted to.

The comment about being able to use a standard battery charger is something to keep in mind. I only have one 115vac charger that will charge a 6v battery, but I have three or so of the wall warts that will handle the 1000ma batteries OK. If it wasn't for needing more nose weight on the Ruperts, I think I would fall back to a 4.8v battery. I'm not a good enough flyer to be able to tell the difference.

Don
Old 09-11-2007, 01:10 AM
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Default RE: 4.8V versus 6V for receiver battery?

I use 5-cell packs in planes that have high-torque servos, I figure I might as well squeeze all the torque I can out of them! I've also heard of guys using 5-cell packs because you'll still have four good cells if one cell fails (they usually short out when they fail), and thus have plenty of voltage for your receiver.

As far as which one lasts longer, I've heard arguments both ways. You do get more power out of the servos with a 5 cell pack, but then you have more power in stored in a 5 cell pack. Remember, power is in Watts, not Amps. With 2000mAh cells, a four cell pack has 9.6 Watt/hrs of power stored, and a five cell pack has 12 Watt/hrs of power stored. This means you can put out 25% more power with a five cell pack and it will still last as long as a four cell pack (with identical cells).
Old 09-11-2007, 03:48 AM
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Default RE: 4.8V versus 6V for receiver battery?

Keep in mind also that our servos are going to draw what they want, not what's available. So if they don't want it, it doesn't matter if it's there or not.

If they already have more power from the 6V, they're not going to be asking for more juice.
But if they need more power, they're going to try to draw more juice and with 5 cells they're going to have more available.

But if they want more than what's available, they simply do not get it.
Old 09-11-2007, 05:53 AM
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Default RE: 4.8V versus 6V for receiver battery?

Just remember that Power (Watts) = Voltage X Current. The more torque you have, the more power it consumes.

If you use more power, it has to come from somewhere. Increase the voltage, and keep the current the same, then the watts, or power consumed, goes up. So, going from 4.8 volts to 6 volts satisfies that equation requirement. Current may just stay the same, but the voltage has been increased to 6 volts so there is more power available. But there are more variables in this than a simple math equation. Heat is one. You may not feel it, but it's still there and is a direct result of power consumed and consumes power to create heat.

Simple fact is that if you use a 6 volt battery, the servo acts faster and most of that is from the increase in the "electromotive force" or the "voltage" increase of 1.2 volts from 4.8 to 6 volts.

Now with that said, there is a good reason to increase your capacity from, say 900 mah to 1200 mah and that's two fold. To increase the flight time AND/OR to provide the necessary increase in current available for higher torque and more receiver current.

If you take a system with five servo's, change the battery from 4.8 volts to 6 volts, but the same capacity, chances are that they will last just about the same lenght of time before requiring recharge. And, as I said, there will be other current draw issues such as heat (more power, more heat) which will also consume power which may reduce that flight time slightly.

Best thing to do is monitor your battery condition before and after each flight, especially before. If it's borderline..charge it.
Old 09-14-2007, 10:29 AM
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conradj87
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Default RE: 4.8V versus 6V for receiver battery?

may be a stupid question, but how do you know what capacity battery pack you will need??? try them on the ground?
Old 09-14-2007, 10:41 AM
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Default RE: 4.8V versus 6V for receiver battery?

If you get packs made out of AA cells or larger (for standard servos) you should be fine. The higher the capacity, the more flights you'll get out of it. ALWAYS check your batt pack voltage before a flight, either with a loaded voltmeter or an on-board voltage monitor. In general, I use 4-AA cell packs (1000mAh+) for trainers or scale planes with standard servos, 4-A cell packs (2000mAh+) for my Aerobatic/3D planes with standard servos, and 5-A cell (2000mAh+) packs for my Aerobatic/3D planes with high torque servos. Guys with Giant scale planes seem to go with sub-C cells or LiPo cells with regulators.
Old 09-14-2007, 02:12 PM
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Default RE: 4.8V versus 6V for receiver battery?

Usually, the radio system comes with a battery. The capacity of that battery is sufficient for general applications and maybe three flights before charging. Depends on how daring you are, I guess.

Higher capacity (mah ratings) provide more time. So, anything larger than what came with your radio is probably going to be just fine.

I use a Venim 1200 mah 5 cell (6 volt) NiMH battery pack. It weighs about the same as a smaller NiCd pack but lasts longer because of the capacity. I also use Voltwatch to keep an eye on the battery condition before and after each flight. It gives a quick indication of battery charge and lets you know if you are approaching the point where it requires charging.

CGr
Old 10-08-2007, 11:03 AM
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Default RE: 4.8V versus 6V for receiver battery?

Can I keep using my AA Alkaline batts? Servo says Nicad only. If I would go Nimh, can I use AA style, or should I get a pack?
Old 10-08-2007, 11:15 AM
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Default RE: 4.8V versus 6V for receiver battery?

Usually alkalines don't have a very high current drain rating compared to NiMH or NiCd batteries, so you'll get more voltage drop with alkalines under load. In general it's not a good idea to have the spring loaded battery trays for airplanes, I'd recommend getting a battery pack. If you just have standard servos, a pack made up of AA cells is probably fine. If you have high torque servos, you probably should go to A cells or larger in your packs.
Old 10-08-2007, 08:12 PM
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Default RE: 4.8V versus 6V for receiver battery?


ORIGINAL: Electrolight

Charlie P thats BS.

The only difference between a 4.8 volt and 6 volt batterie is the six volt gives you more torque. (mostly for bigger servos)
As far as how much time you have till the batterie is dead, that depends on the maH rating. ( The higher the maH rating the longer the batterie lasts)
An the difference between a NiCd and a NiMh Is that the NiMh usually has, on average, a higher maH rating. And they are much more forgiveing when charging partially charged. And NiMh are slightly heavier.

These are the main differences. Good luck

Electrolight
Thank you for the whitty rebuttal. You really should also fire off a note to Futaba to change the wording on page 10 of the 9CAP/9CAF Instruction Manual:

"5-cell (6.0V) receiver battery packs - All Futaba airbourne equipment (except that which is specifically labeled otherwise) is designed to work with 4.8V )NiCd 4 cells) or 6.0V (Ni-Cd 5 cells or alkaline 4 cells). Using a 6.0V pack increases the current flow to the servos, which accelerates their rate of response and their torque. However, because of this faster current draw, a 5-cell battery pack of the same mAh rating will last approximately 3/4 the time of a 4-cell pack."

Just repeating what I thought I knew.

And I did say: "If you want longer flights at 4.8v go for a pack with more milliamp hours (mAh)."
Old 10-08-2007, 09:15 PM
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Default RE: 4.8V versus 6V for receiver battery?


ORIGINAL: Electrolight

Charlie P thats BS.

The only difference between a 4.8 volt and 6 volt batterie is the six volt gives you more torque. (mostly for bigger servos)
As far as how much time you have till the batterie is dead, that depends on the maH rating. ( The higher the maH rating the longer the batterie lasts)
An the difference between a NiCd and a NiMh Is that the NiMh usually has, on average, a higher maH rating. And they are much more forgiveing when charging partially charged. And NiMh are slightly heavier.

These are the main differences. Good luck

Electrolight
Aside from being disrespectful and beligerant you are simply wrong. When comparing battery characteristics is is the norm to compare packs of similar mah ratings. Charlies post was dead on and yours, as usual, flawed. As for comparing weights that also depends on a number of other factors.
Old 10-09-2007, 05:39 AM
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Default RE: 4.8V versus 6V for receiver battery?

The key factor here is "of equal capacity" or words to that effect. Equal capacity means SAME mah ratings. All Charlie P (and Futaba) said is absolutely correct.

Like anything else, if you want more capacity, well, increase it!! Rocket science, I guess. Want longer flight times? Put a larger fuel tank in the plane. If you want longer battery duration, put a higher capacity battery on board. Simple as that.

When I went from 4.8 to 6 volt, I increased the capacity by about 20% to 25%. I get just about the same number of flights out of a charge as I did before with the added benefit of the faster servo response. I also use Voltwatch and monitor my battery voltage before AND after each flight. But, being a cautious soul, I don't let the battery go down to the point where I would have any question of making it back to the runway. If it looks as though it needs to be charged, I charge it. Call me over-cautious, but I've never lost a plane because of a dead battery pack because I flew just one-more-time.

I've read some posts here where people fly when it is clear that their battery pack is just about depleted. That's taking one heck of a chance. Not only with crashing your plane, but where it may come down. Remember Murphy's Law.. and Murphy is alive and well.

CGr
Old 10-09-2007, 06:10 AM
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Default RE: 4.8V versus 6V for receiver battery?

Going to six volts means that your servos can make more torque, it doesn't mean that they will make more torque. The torque a servo makes is exactly the amount needed to overcome aerodynamic forces, hinge friction, and linkage friction. Since that doesn't change when you go to six volts, neither does the torque the servos need to make. The unloaded amp draw of a permanent magnet DC motor is nearly constant with changing voltage.

So, if your control linkages are binding and stalling your servos near the endpoints of travel, you are going to get shorter battery times with six volts. If everything moves freely, your battery life should not be that much different.
Old 10-09-2007, 10:31 AM
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Default RE: 4.8V versus 6V for receiver battery?

Where did I say anything about torque in my reply?

So, if your control linkages are binding and stalling your servos near the endpoints of travel, you are going to get shorter battery times with six volts. If everything moves freely, your battery life should not be that much different.
That happens with 4.8 volt batteries too. 'Load' doesn't care what voltage the batteries are. Load equals current draw and power depletion, power being voltage and current. If there is a bind, it just doesn't matter what the batteries are, they will deplete faster than if there was no binding.

CGr
Old 10-09-2007, 11:30 AM
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Default RE: 4.8V versus 6V for receiver battery?

Hey CGRetired. are you saying that if I use a 4.8v 2700 mah it will last longer than the 6v 2700 mah that I am using now. If that is true then I will buy some 4.8 batteries. Thanks

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