kwblake

Hey Folks. My first question is regarding a Hobbico LiFe battery, (my first), that I just purchased. I was just doing a quick read of the instructions,(Go figure), and read that " A voltage regulator is required to step the battery voltage down to an acceptable level when used as a receiver pack. Most servos have a maximum input voltage of 4.8V or 6.0V." I have done a fair amount of reading in these forums about LiFe batteries, but don't remember reading about anyone using a regulator. So, I guess my question is, do any of you use a regulator with these batteries?

Second question is. What is the third wire on a regular flat plug for. I purchased a few MPI switches, some Futaba servos, a couple of "Y" plugs, and they all have three wire, White, Red and Black. The Futaba wall charger that came with my Nexstar, has two wires each for the Tx and Rx. The Spectrum wall charger that came with my DX 7 has two wires to the TX one black, one black and white, and three for the Rx, one brown, one red and one orange. Also the LiFe battery I just bought has three wires going to the balance plug. Someone please help, and please keep it as simple as possible, as electrical things and I don't seem to have a great understanding of one another. Mechanical is good, Electrical is not good.

Thanks very much

MinnFlyer

My Feedback: (4)

What is the voltage output of your LiFe pack? If it is between 4,8 and 6v, you're good to go. If not, you need a voltage regulator.

Battery packs (Both Rx and Tx) have two wires, black and red (Pos & Neg).

Servos have 3: Pos, Neg and signal The signal wire (white) tells the servo which way to move and how far

You can use a 3-wire extension to a battery, the third wire will just sit there and do nothing (kinda like Congress).

j.duncker

My Feedback: (2)

To regulate or not to regulate, that is the question?

OK It depends on the RX and the servos and any other kit like gyros you are running. I have run PPM Futaba and Futaba digitals at that voltage with only a little jitter when the pack was fresh off charge but I also know that the Futaba gyro is not supposed to tolerate this voltage.

Can you be more specific on the equipement you have, make and model numbers if poss.

The third wire carries the servo position information.

KW_Counter

The small flat white 3 wire plug is so you can balance charge the battery.
Some chargers charge through this plug.
Some charge through the main wires and balance through this plug.
I hope this helps.
Good Luck,
KW_Counter

mike109

G'day

As I read this, the LiFe cell is flat at 2.8 Volts, works between 3.0 and 3.3 Volts and can be charged up to 3.6 volts.

Now I guess you have a two cell pack so it is nominally a 3.3 volt x 2 = 6.6 Volt battery. This is more than the 6 volt limit that many of our receivers and servos can handle. This would be the reason for using a Voltage regulator which would probably reduce the voltage to 5 Volts or so.

This all goes back the to good old days of NiCd battery packs which were 4 x 1.2 volts = 4.8 volts nominally but when fully charged can be around 5.5 volts. This is less than 6 Volts and was probably the reason that the older equipment had a nominal limit of 6 Volts. The newer battery technologies are now pushing this limit. Some older equipment will be able to handle the extra voltage, some will not and the smoke will get out.

I gather there are now some higher voltage receivers and servos which can use the higher Voltage packs with no problems and you may have these or you may not.

Sounds like you need to study the specs of your receiver and servos to see if they can handle 6.6 Volts and if not, then you need a regulator.

Does this make any sense?

As to your second question - three wires on servos etc - As has been said, the red and black (Futaba) are for power and the white is the signal to the servos from the receiver. Some switch harnesses have the third wire but it is generally un used.

As for the three wire connection on your battery pack - you have a two cell battery. It is two 3.3 Volt cells wired in series. The three wires allow your charger to charge each cell individually so that they can be balanced. You can also charge the pack via the two wire outlet but it is better for the battery (if slower) to charge it through the balancing connection.

TimBle

ah the age old debate of regulate or don't regulate.

In short, Life Batteries do not need a regulator in the system because the voltage is not much higher than that of a NimH or NiCAD 6V pack anyway.
These typically operate from around 7.2V dropping very quickly down to around 6.6v and then hit their performance curve all the way too around 5v before they run outof excited electrons quite quickly.

Life batteriestend to sit at 6.6V till they're 90% depleted then start to drop to arounf 6.2v and then they shut down.
So Life's operate within the same range as NiCAD and NiMH. Only problem is they expose the system to a higher overall current which may or may not be good for the electrics in the long term. So I guess usng a regulator is not a bad thing here either but its not strictly necessary and the recommendation from manufacturers is simply due to them being good citizens and advising you on the safest course of action since they don;t knowhow you are going to wire everything.
I have safety used my LiFe batteries without a regulator without issue for months.

jetmech05

I have a li-ion battery in my Python.....I check the voltage before I fly....if it's newly charged it can be as high as 8.4 Volts...therefore I regulate to 5.8 Volts....I re charge when the voltage falls below 7 Volts on a 1 amp load......this takes 3 to 4 weeks flying Sundays 2 or 3 sometimes 4 flights a Sunday......

Now you're getting confused with the number of wires.....first let me tell you that in any electrical circuit there has to be a complete path for current flow....so your wall wart charger and switches has 2 wires....power in and power return to the source whether it be your aircraft battery or the outlet in your wall......

It is also the same for a servo...but the thrid wire is for the signal to tell the servo what to do.......

As far as colors go....brown to black.
hope this helps....gotta go dinner is rerady

kwblake

Thanks for the info.  The equipment I am using is as follows.  Transmitter is Spectrum DX7, Receiver is Spectrum AR7000, Servos are Futaba A3004, and the LiFe battery is 6.6V  1800mAh.  I guess it is up to me to use a regulator or not.  My Pulse XT does not have a smoke unit, and I don't really want one.  Can anyone recommend a good regulator that  I could use if I decide to?

Thanks

Wonder

My Feedback: (7)

I am using the same TX, RX, servos and battery as you are without a voltage regulator.

tw

mike109

G'day

Modern electronics are wonderful things. The ratings put on most devices are conservative. That is, they can handle higher voltages than their specs say. Something rated at 6 volts may happily work at 12 or even more but sometimes the rating is less generous and just a small percentage over voltage will kill the component.

Also, this sort of damage can be cumulative and while a component may not fail immediately it may have a shorter life if run at higher voltages.

As has been said - when these batteries are in their normal operating range, they are not that different to NiCd and NiMh packs but when freshly charged they are well outside the rated values for most receivers and servos. If the engineers who designed the Rx and servos were conservative (and JR/Spektrum engineers probably are) then they would have allowed some "head room" above their specification but if they were not and were using components with tolerances closer to the limit, they there may be problems.

I suspect that in time as more of these cells come into common use, the specs of the equipment will be uprated to accommodate these batteries officially. In the mean time, you either take your chances and hope the engineers were conservative or you opt to be safe and use a regulator.

For what it is worth, I have been using 5 cell Sanyo Eneloop (NiMh) Rx packs with my Spektrum system for about 12 months. When fully charged these packs are near to 7 volts but settle to about 6.8V. no load I have not had any problems with this arrangement. I am using Hitec HS 55, 81, 325, 425, 475 and 645 servos with no problems. So far.