Grayoon

My Feedback: (6)

Ok, i know you get more out of your servo's...more speed and torque, but is there a reason all the radios come with a 4.8 and thats what most shops sell? I have a couple of 6.0v packs here that would work but i am wondering about why the 4.8v? All help is appreciated. Hope that made sense.

Thanks

bob_nj

My Feedback: (62)

Even though it's only a difference of one cell, price may have something to do with it. Sort of the same logic JR uses in selling their radio systems. For instance, from the top of the line JR down, the receivers are single conversion. Personally I would substitute a dual conversion, but to keep costs in line with competition etc. they go that way. Let's hear what everyone else thinks

A.T.

Most systems started out with dry alkaline batteries = 6V and even today many 4 & 6 channel sets still provide a dry battery TX and RX box. However, whilst the 6V gives faster response and more power, dry batteries loose power rapidly as voltage falls.
Nicads start fuly charged at about 5.2V hiold for awhile then drop and hold 4.8V much longer than the 6V dry cells would average out. 5 cell nicxads often cause problems by being "overvoltage" and if connected straight off a fast field charger cause jitters etc and may damage a servo.
Rather than more volts - use more amps. e.g. 1100 Mah in ieu of 500Mah battery pack. e.g. a small car with a flat battery is easily started by truck (12V 80AH battery) parked alongside but the small car 12V 24AH battery) will not start truck. Rather than ballast in a model - use battery packs as per =
http://www.fly-giantrc.org/technical/parallelbatt.html
to balance a model.
see also the sections under batteries and chargers at Alan's Hobby Web Links http://homepages.ihug.co.nz/~atong/
regards
Alan T.

sfaust

My Feedback: (11)

A.T. hit the nail on the head.

6v will give you more speed and torque at the servo than 4.8v
6v will 'effectively' reduce your capacity by 12% to 20%, so you want a slightly larger 6v pack than a 4.8v pack. I.e., a 1200mah 6v pack to replace a 1000mah 4.8v pack. There will be a slight increase in wear on the servos since they are working a bit harder, however, still well within design specs and limits. Manufacturers approve using 6v packs, and many of them rate their servo torque specs based on 6v. Regulators can be used, but most are not using them, citing the added circuits, connections, and lower reliability of not using them. Using 6v helps recover a lot of the voltage loss in the wiring and switches, which reduces the speed/torque even further on a 4.8v system. In fact, using a 6v pack doesn't guarantee that the servos will even see 4.8v. It all depends on the wiring. Receivers are quite happy running at 6v.

Grayoon

My Feedback: (6)

So youcan safely use a 6v pack then? I have heard about the jitter thing after a freshly charged pack, but i usually charge my stuff the night before a flying day and i would think that initial "peak" would wear off after an hour or so and would think the jitters would be gone.

So like i said, i have a couple of 6v packs here and just wondered if they would work ok. THey are 1100 mah and i think they would do just fine, i was just confused about why everyone seems to use 4.8v. I have also seen these little voltage regulators for use with a 5 cell pack. Are these necessary?

Thanks

sfaust

My Feedback: (11)

Many people are flying 6v packs, and most are not using regulators. If you let the pack sit a bit after taking it off charge, you won't get the jitters.

I would say yes, you are safe in using the 6v packs. However, I say that with the assumption that you are using either JR or Futaba, and servos manufactured in the last few years. If not, then it would make sense to verify it with the manufacturer prior to using 6v packs.

Regulators are not required based on the comments from JR and Futaba. In my opinion, its just another couple of components which can fail, as well as the fact that connectors are the largest source of voltage loss in the path, and the circuitry components also have their own failure rates. If the manufacturers say they are not needed, why add the extra components?

Tired Old Man

My Feedback: (1)

Grayoon:

Be careful if you are considreing using 6v batteries with the older Futaba servos. Many of the older style Futaba servos cannot take a 6v input without damaging the servo. Even some of the current servos on the market from various manufacturers cannot handle 6 volts.

Bear in mind that a freshly charged 6 volt battery pack will sometimes come off the charger at 8 plus volts. This will cause "jitters' in some servos/systems and sometimes gliching with the radio system. If you experience the "jitters" wait for a few moments before flying the the condition to calm down.

Overall, you will probably like the faster servo response and increased torque made available by switching to 6 volts.

Silversurfer

mulligan

Silversurfer,

Where did you get the information/experience on older Futaba servos? I have been told by experienced pilots in my area that using 6V system with older Futabas is no problem. I am weary because I am about to put up my new H9 P-51 with a 6V system and one Futaba 148 servo (on rudder). Ground checks have gone fine so far.

- George

P-51B

My Feedback: (5)

Whats the Difference? 6.0v vs. 4.8v

1.2 Volts!

Geez, I can't believe no one came up with this.



Seriously though, most electronic components used are designed around 6V. Most operate just fine on 4.8v. There are benefits to your servos in the form of speed and torque when using 6V. I use the regulator BVM sells to ensure I get uniform voltage (5.7V if I recall).

I imagine that you get 4.8V packs simply as a cost measure.

sfaust

My Feedback: (11)

If a pack is coming off a charger at 8+ volts, the problem probably lies with the charger! Most batteries will be in the low 7.x range once the charger terminates. All my 6v batteries top at 7.1 and 7.2 using the Alpha 4, or the SuperNova 250s. Let it sit for a few minutes, and its a tad lower. I've never seen anything over 7.4.

mulligan

Peak charge will be about 1.43 V/cell, or about 7.15 V (7.4V is higher than I've seen), which will last only a very short while. By the time you're in the air, you're likely to be below 7V.

- George

P.S. P-51D, I thought of it, but was not brazen enough to post it

Tired Old Man

My Feedback: (1)

Mr. Mulligan,

In reply to your inquiry on older Futaba servos a couple of answers come to mind. First one is that when the older servos were designed and manufactured, 6 volt battery packs were not used or even considered for use. This would have affected the design criteria for electrical supply.

The second is a website called RCFAQ.COM that lists all the older discontinued Futaba servos and the restrictions on voltages for their servos.

I'm sure that there are many older Futaba servos that can be used with higher voltages that 4.8, but personally I would not want to be the one who is guessing that nothing is going to burn out in flight.

If in doubt, I would try to contact Futaba directly with the servo model number and get their opinion. I believe that the 148 is OK at 6v.
Silversurfer

mulligan

Thanks, silversurfer... boy, I wish AMC were still around to help me verify that the 148 was ok (Hint, Hint Hobbico)

- George

Grier

I charged my 6v 1100mah battery during the week with a 70mah charger and was going to leave it on tonight again but when I came back to it after 2 hours or so the rx output led on the transformer was out. The light is on for all my other packs and even when left on for ages (overcharge i know the led still stayed on)
Like some of these posts said, the servos jitter with the 6v pack and even after when i put my 4.8 v pack in straight after (have I done permanent damage or somethin?)

Tired Old Man

My Feedback: (1)

I doubt if you have damaged the 6v pack in any way. I can't see how a 70 mah charger could even try to cause damage. Unless... If there is a possibility that you may have inserted the receiver battery plug into the charger plug reversed, then you could have shorted out either or both the charger and battery.

If that did or could not happen, then it sounds like you are not making a connection at the plug that will enable the charge indicator light, or you have a broken wire in the battery lead.

If the charger still seems to work with all your other battery packs, use a volt meter to check the voltage in the 6v pack. Zero voltage would probably indicate a broken wire. Extremely low voltage would indicate that you may have damaged the battery pack. Also use your voltmeter to verify that your charger is working.

I'm not an electrical expert by any means. I'm certain that you will get a reply from someone that is, and they will either confirm or refute what I have given you. I just gave you the methods I use to check things out. Best of luck.

Silversurfer