Rx Batteries selection
 

Hi everyone,

I need to buy an RX batteries pack and I have two questions :

1) Is it better to buy a 4.8v or 6v pack ? What are the main Pros and Cons

2) Which one is better : NiMH, Ni-cd, Lipo ?

I will use this pack with a Futaba 2.4ghz 7 channel receiver. Futaba 3004 servos will be use. I want to get plenty of flight time. This will be use in a second plane so no 3D flight. .40 size airplane. I don't mention the plane model because I am not sure in wich on my three plane I will install this pack.

Thank you,
Séb

RE: Rx Batteries selection
 

I've used 6.0v flight packs for many years without any problems. The total flight time is slightly decreased, but the servo strength is increased by about 20%. The pack weighs 20% more. You have no fear of damage using the equipment you describe. Most of our electronics (digital not included) are designed to handle 4.8 - 6.0v packs.

Given the problems and special equipment needed for other types of batteries, I'd stick with Ni-Cads. They're easy to properly maintain and charge and very forgiving of errors in both.

For increased flight times, increase the mAh, not the voltage, of both the TX and RX packs. An "overnight" (14-16 hours) charger output for a Ni-Cad battery is C/10. That is, the battery pack capacity in mAh divided by 10. A 600 mAh pack will require a charger that puts out at least 60 mAh.

For me, 6.0 is the way to go!

Dr.1

RE: Rx Batteries selection
 

I have an Hobbico Accu-Cycle Elite charger in order so I will be ok to charge any type of batteries. However, I wanted at first to buy an NiMH pack because of their greater capacity, price and weight advantage. So, what problems is related to NiMH batteries. I use theses type of batteries in my digital camera with no problem since many years. Let me know.

Séb

RE: Rx Batteries selection
 

Hey seb ! Rare To see another quebecer on these forums!;)

Go for the NIMH the only disadvantage is that they have a slightly lower discharge rate but a .40 sized plane wont be pulling 4 amps anyways....

BTW the accu cycle can charges lipos but it doesnt balance them, And a .40 sized plans are to small to see the advantages of lipos (it starts to pay off around 35% ers)

RE: Rx Batteries selection
 

I think the big problems are with the LiPo. I don't know if the NiMH need a special charger/precautions or not.

Dr.1

RE: Rx Batteries selection
 

Never had a problem with NiMH at all but would not recommend them for high current draw such as 3D electrics but for a receiver battery they can't be beat.
There is really no need for 6V unless you want to squeeze extra torque from your servos.

RE: Rx Batteries selection
 

If you had a Spektrum I'd recommend 6 volt but since the Futaba FASST have a lower cutoff voltage I recommend staying with 4.8 volt packages but increase the capacities over "stock". If you feel you need more speed/torque from your servos then go to 6 volts AND high capacity.

RE: Rx Batteries selection
 

Thanks to all,

I've decided to go with a Sanyo pack, NiMH 2700 maH 4.8 v.

RE: Rx Batteries selection
 

I've recently gotten an Intellipeak Ice Charger/Discharger/Cycler and it pretty much does anything that can possibly be done to a battery but it does it automatically, for example, if you are using a new NiCad battery, it's a good idea to fully charge and discharge it about three times before you use it normally because it kind of "breaks in" the cells. this does that for you, all you have to do is tell it how many cycles, what the low voltage is before recharging occurs, and the maximum voltage before the discharging begins. it's hella awesome, it's ever got settings for all different types of batteries with a selectable amount of cells

RE: Rx Batteries selection
 

I started out using the stock 600mAh 4.8v NiCD which came with my 6 channel radio (Futaba 6XASuper). I use only 4 standard non-digital servos in my trainer and safely got at least 4 flights of 10 minutes each on a single charge.

Once I got experienced and wanted to fly more, I upgraded to a 1100mAh 4.8v NiMH pack. I can put in about 6 flights per charge now plus the NiMH is a bit lighter than the NiCD pack was.

Now I have an electric sport plane and use a 3 cell 2100mAh 11.1v LiPo pack for the RX and motor. I get one 10 minute flight per charge. I can charge the LiPo on the same Triton I charger I use for my NiCD and NiMH packs but I had to buy an expensive balancer. I use a separate BEC for the RX and servos. I can program the BEC to output anything from 4.9 to 9.0 volts but 5.1v is the default.

Summary is NiCDs are the most durable and stand up reasonbly well to a bit of abuse. NiMH will have a higher capacity with a slight reduction in weight but can't tolerate charging abuses very well. They also self-discharge quicker than the NiCD but NiCD must be properly disposed of via a recycler.

LiPo offers the best combination of performance and weight but are expensive and tolerate ZERO charge abuses. You want to see your model (or home) go up in smoke? Overcharge a LiPo pack.

Best charger to use with a standard capacity NiCD or NiMH pack is your wall-wart charger which came with your radio system. I see NO advantage for sport flyers to run 6v packs. And 6 volts will limit your charger options.

RE: Rx Batteries selection
 

SebM

If you use that NiMH 2700 mah 4.8 v battery pack in your piper cub, how many times are you planning on flying it? about 100? :eek: Your transmitter batteries will be dead before that receiver battery will.

I use 600 mah 4.8v batteries in my piper cub with S3004 servos and get 7 flights out of it with a 10 tank and a .46 ax engine and still have some charge left over in it when i head home.

I only use a wall charger that puts out 50 ma to charge it up a good 18 hrs before flying.

RE: Rx Batteries selection
 

I was thinking the same thing. I was finding that my stock 700mAh RX battery was running out too fast when it was cold out (2-3 flights), so I upgraded to a 1500mAh NiMh pack, and it is still full after 5-6 flights.

RE: Rx Batteries selection
 

SebM, I think your choice is a good one. Battery capacity is definitely not an area to skimp on. Too little is bad; extra reserve is good.


Hangtimes Hobbies ("NoBS Batteries") http://www.hangtimes.com/sportrxpacks.html has some good info about selecting batteries. They typically recommend NiCad or NiMH cells. The site discusses impedence numbers and how that impacts voltage drop with lots of current draw. With the S3004s it probably doesn't matter as much as it would to someone running powerful digital servos.

Most of my packs are from Hangtimes and they are the 1650mah NiMH, 4.8 volt, variety. I use "standard" ball bearing servos, and nothing I have uses more than 5, so I have plenty of capacity for a day at the field. I still check them (in case something bad happens) but so far it has just been for peace of mind.

RE: Rx Batteries selection
 

Hangtimes (as well as other sources) sells transmitter packs to upgrade their capacity to match the receivers. I gave my brother a 1650 mah pack for his Futaba 9C. When warm weather returns we'll get to give it a workout. This time of year we're not able to get out very much. North Texas winters are pretty mild but the sun is so far South that visibility is poor most of the time.

http://www.hangtimes.com/txpacks.html

RE: Rx Batteries selection
 

I think most guys make 2 or 3 flights then put the volt meter on the receiver battery and think...well, I better quit now. The meter is reading this or that. Why don't you try making your 2 or 3 flights some time and then set there and move the controls till they no longer work and you will find those batteries are still good for longer than you think. I bought a volt meter and found out I don't even use or like it. It might tell me it's at 4.8 or 4.7 but it sure don't tell me how many more flights I can still get out of it before it actually goes dead!

Very seldom does anyone where I fly crash a plane and blame it on actually dead batteries. It's usually pilot error.

I'll take experience over what those volt meters read anyday!

RE: Rx Batteries selection
 

I don't have any Piper Cub. I have a H9 Solo Sports Trainer, a Neptune Seaplane and a GP Super Sportster 40. I have only one batterie pack so I just decided to get a second complete kit ( motor, Rx, batt, servos ) to have at least two planes ready to fly anytime. I don't know yet in wich of theses plane I will install the 2700mah batt. My others pack is a Nicd 1100mah and I can easely get 6 flight. However I fly now in the winter and this drain the rx batterie much faster so a bigger pack is more then welcome. My Tx are kept warm when flying so it doesn't seem to be affected by the cold and the batterie last a very long time.

Séb

RE: Rx Batteries selection
 

Oh, I'm sorry. I had you mistakened for Seb23

http://www.rcuniverse.com/forum/m_6843667/tm.htm

Next time I'll put my brain in gear before I put my mouth into action! lol

Ain't the 1st time it's ever happened and probably won't be the last. :D

Sorry!

RE: Rx Batteries selection
 

My 1650s stay charged longer than I'd ever want to fly in a full weekend. Charged Friday night and at the field all day Saturday and Sunday with no recharge. I didn't count the flights or measure the 'on' time but there was never any reason to think it wouldn't go another time. Would a 600mah pack do the same? I have no idea.

I have gotten some really good deals on receivers and servos. Otherwise I'd probably just buy 4 channel radios, often cheaper than buying a flight pack, and use the 600 mah pack that comes with it. Since I have to buy a battery pack for each model anyway, I guess I'm willing to spend a little extra on batteries.

RE: Rx Batteries selection
 

That sounds about right to me too.

With a 1200mAh pack on a Modeltech Extra 300 I flew 16, 10-14+ minute flights one day before calling it quits, and the meter indicated I could still fly another 3 or more.

I see many here say that the smaller packs are only good for 3-4 flights, but I've never gotten such a low amount of time out of them.