JIMF14D

Just like a nice big Tomcat with lots of fuel and two big motors, right Sluggo?

Ialso forgot to mention that Ihave upgraded my glow model nicads to 1100-1200mah besides the 6volt change.

Jim D

JL1

My Feedback: (93)

Baraacuda, no offense but I disagree with the methodology of your test. Unless the servos are torque loaded to the values they will experience in flight you will not get an accurate reult. You are correct that you cannot us straight Ohms law to calculate the current flow in a motor because of the counter EMF. However, having said that, with reference to the following statement taken from a robotic bulletin board you will see that I am not alone in stating that increasing the voltage will result in a proportional increase in current.

Re:
DC Motor - voltage or current
You can look at dc motor curves at the Mabuchi web site: http://www.mabuchi-motor.co.jp/en_US...ct/p_0304.html
In general, if you double the voltage to a dc motor, the current will also double, and the power input goes up 4X. Depending on where you are at the efficiency curve, output power may not quadruple. For any given voltage, peak power is typically obtained at half the no-load speed times half the stall torque

VF84sluggo

My Feedback: (55)

Jim...lol, you've got that right! No such thing as too much thrust! And the only time you have too much gas is if you're on fire

Sluggo

ira d

I have run planes up to a 120 size on 4 cell packs with no problems bothFutaba and Airtronics 2.4systems you just need to make sure to use a pack with enough
capactiyto do the job. The 6 volt thing came about when Spektrum was having the brown out problems with their early systems and flyers discovered using a
6 volt pack was aquick fix for the problem.

VF84sluggo

My Feedback: (55)

Exactly.

hairy46

My Feedback: (1)

I use 6 volt packs that way if you lose a cell you still have 4.8 and will still fly, if you lose a cell flying 4.8 it will crash!

DougV

Depends on the system you are using and the size of the aircraft, if you loose a cell on a 4.8 pack using Futaba, the throttle channel ONLY will go to fail safe at 3.8 volts to warn you of an issue, but the rx will continue working down to 2.4 volts.

But i use nothing but A123 or LiFe packs now.

Doug

BuschBarber

My Feedback: (2)

Don't the servos stop working below 4.3v? Even if the Rx still works, it isn't controlling anything.

DougV

Well, read again the first part of my post.
I’ve landed an Avistar trainer on 3 cells using a Futaba system, some regular analog servos will go down to 2.9 volts. Now if you are going to use high voltage digital servos with a 4.8 pack then is not going to work.

Doug

BuschBarber

My Feedback: (2)

The Speed and Torque would be so low , most aircraft would be uncontrollable.

DougV

I'm still using 4.8 packs/R617 receiver on two trainers that I use for my kids when they go flying with me. everything else (Helis, Jets and big airplanes) I use A123's or LiPo's.

Hope that helps!
Doug

JIMF14D

I think this topic has transitioned from battery selection to "pilots who walk on water" stuff .......................

2.9 volts, wow!

Jim D

DougV

Nah... it was more like 3.6 volts, but you know what, at least we got a fighting chance to land the model.

Doug

hairy46

My Feedback: (1)

All I use are the digital servos and like the security of the 6 volt gives me, 6 volt is in all my planes since I lost a plane do to losing a cell in a 4.8

VF84sluggo

My Feedback: (55)

I think we're getting side-tracked here.

If I understand correctly, the point of this thread was the OP asking if Futaba 2.4 ghz would work with 4.8v, or if 6.0v was required. While there may be other reasons to use 6v, the answer is that with Futaba 2.4, 6v is NOT required. 4.8v will work just fine.

Now, he did say that it is time to change his packs. Given that fact, if it were me, and barring any servo voltage limits, I would ditch my old used-up 4.8v packs and replace them with 6v (or 6.6 LiFe.)

Just my $.02 worth as a Futaba user.

Sluggo

landeck

My Feedback: (1)

I have been flying 12 planes (60 through 90 size) with R617FS and R6008HS recievers for the past 5 years. Four of them have 6 volt NiCad batteries and eight have 4.8 volt NiCad batteries. I use only analog servos. During that time I have had zero problems. I also use a VoltWatch on most of the planes which is checked before each flight. On the ones without a VoltWatch I check them with an ESV before each flight. The batteries are 1000 MaH through 1500 MaH capacity.

If I were using digital servos I would only use the 6.0 volt batteries of at least 1500 MaH size because of current drain. I never use NiMh batteries for flight packs because of their relatively high internal resistance. I am looking at useing A123 batteries in the future.

Bruce

FSki

I've been disappointed with some of the high capacity (>2000 mah) AA Nimh cells, they suffer large voltage sags when asked to deliver the amps, ok for a lightly loaded plane where the servos don't have to work too hard, but if I can I tend to use 4 and 5 cell Sub C cells as these are able to provide the current without the voltage dropping too much, but you will see fliers using 1s lipo cells on lightly loaded DLG models without any issues.

Most receivers can easily handle higher voltages and its the servos that are designed for 4 cell Nimh/Nicad that maybe the issue, the newer 2s lipo servos that are coming to market will probably see the gradual switch over to 2s lipos in the future, the added bonus that servos designed to operate on higher volts will pull less amps, so a win win all round.

lopflyers

My Feedback: (12)

LiFe 2 cell

bruceal

On my 40 and 60size planes I just use a 4.8 2000MAh Hydrimax pack from Tower. Once in a while I'll cycle them down to .9 V to check the capacity. End of story, simple and affordable.

BuschBarber

My Feedback: (2)

2cell 2500mah LiFe for less than $25 is the best, simplest, and most affordable solution.

bruceal

I will probably go to LiFe batteries eventually. But up till now NiMh has been good with my Futaba. But I do check my batteries after each flight.

BuschBarber

My Feedback: (2)

I have used NiMh for many years since that and NiCad were all we had to use. The fact that NiMh self discharged just sitting on the shelf and the sensitivity to the charge current really frustrated me. When Cycling chargers came out, at least you could get an idea of how close to Capacity your packs were, but I do not know how many times the chargers would False Peak with NiMh and require that I restart the Charge, again.

As I got into electric power and became familiar with LiPos, It was obvious how long they would hold their charge, how light they were, and how fast they were to charge. When I finally upgraded to a quality Lithium charger such as the FMA 4S and 10S, I became very confident in the Handling and Performance of these batteries. Fromeco and Duralite, among others, began offering Lithium Ion Rx packs. I switched to 2cell LiPo Rx packs, with switching regulators, and 3cell LiPo Tx packs. I never was stranded at the field with uncharged or undercharged batteries. I switched to LiFe because I did not need voltage regulators. It is like heaven compared to NiCad and NiMh. I even keep a LiPo pack handy if my cell phone battery gets low and I am not near a charger. I just connect it to the charging jack on the phone.

My Dremel tools, power drills, cell phones, computer tablets, etc., are all Lithium powered. I have never had a Lithium fire. In the rare case I have a crash that damages a Lithium battery, I will store it in a fire proof container for a day, but I can't remember when I ever had to do that. Charging properly and carefully will prevent issues with Lithium batteries.