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HomeRC & PowerAircraftHelicopterRadio - Servo - Gyro - Gov - Batt › Thinking about going back to NiMH... You guys have any comments?
04-26-2010 08:42 PM  8 years agoPost 21
eppler

rrApprentice

Baytown, TX

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From futaba
Can I use 6v (5 cell) receiver packs with my Futaba receiver/servos? Will I get increased performance from my equipment? Are there any drawbacks to using 6 volts?
All Futaba systems are designed to operate on either 4.8 volts (NiCD 4 cells) or 6 volts (Alkaline 4 cells OR NiCD 5 cells), except certain servos which are specifically labeled for use at one voltage or the other only. Some manufacturer's systems are not designed for and do not operate well on 6 volt, but most Futaba equipment handles the increased power input and provides increased performance, speed and torque.

Please note that while 6 volts provides you more torque and speed from your servos, it also provides you a significantly shorter run time for the same milliamp hours of capacity and may shorten the life of your servos proportionally. This sounds confusing, so it may help to compare the current in the battery to water in a bucket. If you have four small holes in the bucket, the water will come out at a certain rate. Add a fifth hole the same size, and you're supplying more water (increasing the current and therefore making the servos stronger AND faster); however, the bucket empties 25% sooner than when it only had four holes.

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04-26-2010 08:43 PM  8 years agoPost 22
ncarbon

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Kalispell Montana

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Tail Step Down
So if you run A123 straight, what tail step down can you use for a BLS251?

Ned

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04-26-2010 08:45 PM  8 years agoPost 23
n808

rrVeteran

Seattle, WA - USA

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The Spektrum 5.2V mini-regulator, or two 0.8V step downs in series (or an AR7100 receiver)

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04-26-2010 10:26 PM  8 years agoPost 24
T Koffler

rrVeteran

Cayuga, NY 13034

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Does futaba make anything for a step down? I'm sure that if they have gyros, servos, receiver, ect... They should surely have a recommended power (battery) system right?

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04-27-2010 02:04 AM  8 years agoPost 25
Wingman77

rrProfessor

Pulaski Tennessee

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LOL eppler, that is only true if you are working the servos very hard and using the extra power available... under the same conditions a higher voltage pack will last longer, think about it the energy has to go somewhere and if the servos are wasting it like you say then they would melt.

I know my 8717's are drawing much less current now that they are on 8v, yes they are capable of pulling more than they were before but why would they? they are not doing any more work.

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04-27-2010 04:52 PM  8 years agoPost 26
ncarbon

rrApprentice

Kalispell Montana

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What I did
To run my A123 and use a Futaba Tail servo, I bought a Castle Creations CC BEC 10 amp and re-pinned it and created a pass through signal wire. It regulates it at 5.1v. FYI

Ned

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04-27-2010 10:14 PM  8 years agoPost 27
Brian C

rrNovice

Houston, TX

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Todd, your not the only one looking at the regulator issues. I have recently tested several setups, using the Oscope to see what the voltage really does. You would be surprised at how much the voltage varies, even on a battery. You might also be surprised at how poor the standard RC connector is at doing it's job, there really only good for 2-3 amps. Switch harnesses are also not up to the task. A really good regulator setup with heavy wire from the battery and dual wire/connectors to the receiver gives the absolute highest average voltage, but, a high discharge rate NiMH with 18-16 gauge wire to a Dean's Ultra connector and dual wires/connectors from the Deans to the receiver comes really close (you use the Deans as the switch). Actually, if you have the regulator set at 5.2 volts, the first flight on a fully charged 4.8 volt NiMH will give you the same average voltage or just slightly better. After a few flights you are still only 0.2 volts lower that the regulator setup. Is a regulator worth the extra cost, complexity, you have to make your own decision. I not sure flying the heli I could notice any performance increase with any of the setups(I run 4.8V rated servos). Sanyo 1950FAUP NiMH work well, Elite 4/5A 2000 MAH NiMH weight slightly less and hold voltage under load a little better than the Sanyo's.

Brian

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04-28-2010 01:16 AM  8 years agoPost 28
T Koffler

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Cayuga, NY 13034

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Well, I called Futaba today and told them what I was running for radio gear. I asked what would be a recommended power sytem. He said without a doubt a 4 cell NiMh.. And that 9252's should never see anything over 6.0 volts.. I asked what would be a good regulator if I decided to use a lipo rx pack.. He said that they do not recommend lipo's for use with any of their recievers... Hmmm..

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04-28-2010 05:04 AM  8 years agoPost 29
Heliflyer69

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Northen Cali

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Im still using 4.8v JR xtra 4500mah nimh packs avail from heliproz or rons.

I leave em on the std wall charger (trickle)that comes with the tx. Always topped off and rdy to fly.

I use a JR deluxe switch harness, and check em under a load before every flight.

Knock on wood! I never have battery issues and the setups are KISS.

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04-29-2010 03:08 AM  8 years agoPost 30
Gearhead

rrMaster

Vt

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Nimh
anyone have problems with their Nimh reaching their Rated Capacity ??
I have had 4 Nimh Packs for my planes, three 2700 Packs and one 1900 Pack and not one of them reached their Rated Capacity,

other than that I have nothing bad to say about them..

Jim
Buzz Buzz Buzz

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04-29-2010 04:15 PM  8 years agoPost 31
Four Stroker

rrElite Veteran

Atlanta

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Batteries seldom reach their rated capacity. 90% is about all you can expect.

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04-29-2010 04:19 PM  8 years agoPost 32
z11355

rrMaster

New England

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I usually dont have a problem w/ that and esp. > 90%

you really *must* charge w/ a C/10 rate though. That is how the battery is specified. It's also a function of the charger's peak detect circuitry and settings.

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04-29-2010 06:21 PM  8 years agoPost 33
Four Stroker

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Atlanta

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And discharge with a C/10 rate if you want to get the rated capacity.

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04-29-2010 06:53 PM  8 years agoPost 34
tadawson

rrElite Veteran

Lewisville, TX

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Mine pretty much always exceed rated capacities when new. I think a lot of this has to do with how aggressive your charger is, and how deep it discharged when you cycle - an early cutoff can cause a battery to show less capacity then it really has.

- Tim

Friends don't let friends become electrotarded . . . .

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04-29-2010 09:27 PM  8 years agoPost 35
rexxigpilot

rrProfessor

Florida

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I can't think of a worse battery chemistry than NIMH! Even Futaba doesn't recommend them. All Futaba servos and RX's I have say to use NiCd only in the instructions. Even their TX's have either LiIon (14MZ and 12Z) or NiCd.

NiMH has poor charge and discharge characteristics compared to the other chemistries. They self discharge faster than any other battery chemistry (I know the Sanyo Eneloop is an exception, but they is a trade in power output for this feature). The NiMH's only advantage over NiCd is they can have a higher energy density and have no memory. At least NiCd's are reliable.

I ditched NiMH in all my aircraft (helis and planks) a couple of years ago. I had too many NiMH packs die for no apparent reason. They were also a pain in the behind. You have to remember to charge them the night before flying. Also, trickle charging them is the only way to make them last, but it takes too long at a fifth to tenth C. IMO NiMH is a bad technology that is now old tech.

I use A123 packs in most of my gear now. Haven't had a problem with them in 2 years of use. I have 9252's in two planks that use A123 packs too. The only thing I do for voltage regulation is a step down for the heli rudder servo.

I plan on trying some of the flat LiFePO4 packs soon. This chemistry is similar to the A123 cells. They should provide all the benefits of the A123 cells, yet fit better in our helis.

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04-30-2010 03:25 AM  8 years agoPost 36
jschenck

rrProfessor

La Vista, NE.

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My Trex-700 and my Vision-50 Competition are running LiFePO4 packs. No regulator, no switch. I put a mini Deans or EC3 connector in line on the positive side to act as a jumper for 'turning off' the receiver. I don't worry about failing regulators, failing switches or the extra wiring.

BUT I chose electronics for these heli's that are specifically rated for a 5 cell NiMH pack - e.g. rated for "6 Volts". What that really means is that the equipment can handle over 7 volts which is the voltage of a fully charged 5 cell NiMH or NiCD. Remember a 5 cell pack has a "stop flying" voltage of 6.0V (4.8V for a 4 cell pack).

The voltage of a LiFe pack is nearly identical to a 5 cell NiMH or NiCD. I now have an even simpler setup with my LiFe RX packs then I did with NiCD because I've eliminated the switch.

LiFe packs are a lot lighter for the same voltage/capacity compared to NiMH and you can slam the charge back in just as fast as most field chargers can push it. 15 minutes max to bring my LiFe packs back to full charge. But with the 3000mah I fly 8 flights (more than a gallon) and I'm only putting 1/2 the capacity back in.

My 9252's will stay with a lipo and an Align 2-1 because they are only rated for 4 cell NiCD (which come off the charger at about 5.8V btw). Align 2-1 puts out 5.8V, runs this equipment just fine. When it's time to buy replacement equipment I'm buying servos known good at higher voltage. I have bought my last 4.8V radio equipment.

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04-30-2010 03:55 AM  8 years agoPost 37
Gearhead

rrMaster

Vt

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""Batteries seldom reach their rated capacity. 90%""

I have to say over the years I have had many NiCds that Cycled out more than their Rated Capacity,, right now I have 4, two-year-old 1900 Packs an every one Cycles more than their Rated Capacity, one Cycles out at 2021 mAh

Jim
Buzz Buzz Buzz

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04-30-2010 07:10 AM  8 years agoPost 38
Heliflyer69

rrVeteran

Northen Cali

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Perfect time to have this discussion
I decided to pull the 9255's out of my 600 and install the align 620's ive had sitting here.

While testing the swash movement i noticed the swash would go hard over, and rx's started flashing when moving the sticks fast.

So, pulled them out and started running some tests.

Going through the switch the 620's caused what i believe is a low voltage brownout. Is this a correct assumption?
Installed a new switch. Much better, but when moving the collective as fast as i could, same problem.
I then bypassed the switch all together. All was good.

Interesting though....my 9255's and 8717's could not cause a brownout going through the switch. Ive heard of align servos drawing as much as 3.5 amps. Pretty amazing....

Switch and battery are 1 yr old, bout 23 gals. I'm not one to pull the canopy every flight. I check my battery through the switch lead.
Looks like my days of running a switch are coming to an end

A pic of my soon to be retired 'ole school way of battery-switch setups...

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HomeRC & PowerAircraftHelicopterRadio - Servo - Gyro - Gov - Batt › Thinking about going back to NiMH... You guys have any comments?
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