What is the Best Receiver Battery?
 

I'm just wondering what everyone thinks is the best receiver battery for nitro/gas airplanes. For years I used NiCds and then NiMhs The last couple years I've been using LiFePO4 but I understand the draw back is that you can't tell how much capacity they have left in them by checking their voltage. I was thinking of making a pack out of 18650 Li-ion batterys but I don't think my computer charger charges them therefore I wouldn't be able to tell how much I'm putting back into them and I think they have similar discharge curves to LiFePO4s. What about Lipo with a bec? If anyone has any input it would be appreciated. Thanks.

I have done Lipos with a BEC ONLY when I can remove it from the plane for charging. Otherwise, I use LIFEPO4's. I make sure I have a full charge at the beginning of the day. I know that the batts will last far longer than I will be flying so I don't worry about it. Never had a problem yet. I also use a BEC with LIFE's when using for engine ignition that ca;;s for 4.8V. I set the BEC output at 5 volts.

I won't use Nicads or NiMh anymore! I have had too many failures. It seems that the newer chargers that say they do Nicad and NimH batteries don't truly detect the PEAK and you end up with a way undercharged battery even though the charger says it is full. Best to have an OLD SCHOOL charger for those packs. You can pick 'em up at swap meets for a couple bucks.

Yes, I agree. Peak detect chargers are generally a bad idea. They are bad for NiCd and worse for NiMH.

The Sanyo/Pansonic 700 mAh AA sized NiCd packs are very robust and will last for many years if charged at C/10. The higher capacity AA sized packs are not nearly as good. And NiMH packs, with the exception of Eneloops (for transmitters) are not nearly as reliable.

If you can live with 700 mAh and charge at C/10 then the Sanyo/Panasonic 700 mAh packs are probably the best choice. If you need more capacity (which most guys do, or think they do) then LIFE seems to be the chemistry of choice.

I'm now thinking I'll make some 6volt packs with the eneloops. Everyone seems to think they are great. I haven't tried them. I used to buy the Life packs from Hobbyking but now their shipping is so expensive it's not worth it. If I could find Life's for a reasonable price I would buy more but I can't. Interesting what you guys are saying about the computer charger for nicd's and nimh's, that never occurred to me.

For the larger models, IMHO, those Eneloop batteries for receiver power are a bad idea. I've run high current tests on them, then can't handle much more than a few Amps before running into voltage sag issues.

If there is an ideal receiver battery, it would be the two cell 2500 Mah A123 battery packs. Only an ounce more than a 5 cell Nih AA pack, but capable of far higher current capability. (If you dead short the A123 battery leadwire to the switch, it will weld the switch contacts and melt the battery wires. And, no damage to the A123 battery pack. Personal experience.) They can be fast charged in 15 minutes with a high powered charger. Once each cell hits 3.60 Volts DC, they're fully charged. They can be charged, and are ready to go next day, next week, next month, or even next year for that matter. They hold their charge for a long long time. About the only way to kill them is to leave the receiver switch on, and run them flat.

I've got six year old 6S2P A123 battery packs used for electric motor powered models, pulling 80 Amps out of them. And after 6 years, and hundreds of flights, they still turn the same motor with the same prop at the same RPM. Right now, my model collection consists of over 100 A123 cells.

I've heard A123's were good. Some questions. They are Lithium Ion? Do they have a steep fast drop off in voltage like the LiFePO4's? Where do you buy them? I think someone told me they tore apart a cordless drill battery to get them. What do you charge them with? I don't think my computer charger has a setting for Li Ion. I do have some large gas models I want power for, as well as small planes. Thanks

Ah, you're in Canada?

I've been buying my bare cells from this place. They want $20 USA for each cell, but if you buy 10 cells, their price drops to a very reasonable $9.30 Each.
http://www.a123batteries.com/product-p/anr26650m1-b.htm

Note that soldering these cells requires a high powered soldering iron. What I use is the Weller 100 Watt temperature regulated soldering iron with a 3/8 inch diameter iron plated tip. PLus I've got a small tin of rosen flux from Radio Shack that is placed on the cell before soldering. I've got other irons, including an 80 Watt iron not temperature regulated. Trying to solder up an A123 cell with that 80 watt iron is a lesson in frustration.

Or, if you want a battery pack ready made, here is one place that sells them. If you have a charger with LCD display that can charge up to 5 or 10 Amps, order the battery pack with the heavy duty Deans wire.
http://www.radicalrc.com/category/A123-Cells-Packs-199

You want their SKU Number: RRC2S2500 battery pack for $45.00.

FYI, they are a direct drop in replacement for the 5 cell "AA" battery packs, so if your servos work OK with the Nih's, they also work with the two cell A123's. The voltage discharge curves of the two cell A123's and the 5 cell Nih packs are nearly identical. Where the big difference arises is when the battery pack is subjected to high currents, or cold weather. At 10 Amps plus, the A123's are unaffected. Not so with the Nih packs. At temperatures of 0 degrees C or so, the A123's are pretty much unaffected. And at zero degrees C, the Nih packs are starting to get marginal in operation. (I've run many cold temperature discharge curves with both the A123's and Nih packs.) The A123's will weigh about one ounce more than the Nih packs.

Here is a lot of info on the use of A123's for receiver/servo power.
http://hangtimes.com/a123_batteries_for_giants_faq.html

The only item in hangtimes I don't agree with is the use of a voltmeter to check the charge of the A123 packs. These cells have a flat discharge voltage from 80% to 20% charge, varying only a percent or three in voltage.

But, it's simple to fly with these cells. Just top of your A123's with a proper charger, and fly two or three flights. Then, top the A123's off again and check what your charger shows for Milliampere Hours replaced. The A123's are very efficient in the charging process, so if your charger shows 1130 Mah replaced, you actually used 95% of that 1130 Mah or 1073 Mah. It's been my rule to NEVER use more than 50% of the charge of any receiver battery during a days flying, to give a safety factor of two.

My club members using the two cell 2500 Mah A123's with 30 cc gassers, and using the A123 battery pack for both ignition and receiver are running around 200-250 Milliampere hours per flight. That would allow around 4-5 flights between charging the A123's. Another club member flying a 150 cc gasser with a whole pile of high powered servos is flying with two 2S2P A123 packs in parallel. The 150 cc gasser is using around 700 Mah per flight. Your results can and will vary.

So, if you're using more than 50% of the 2500 Mah rating of the A123 pack, just top it off at the field. The maximum charge rate of the A123's is 10 Amps, limited by the size of the wire used for charging. Topping off a half discharged A123 battery pack with a balancing type charger set to 10 Amps will take 10 or 15 minutes. Once both cells hit 3.60 Volts DC, they're fully charged.

As far as the charger goes, these A123's use the same charge routine as the LiFe's, namely charge to 3.60 Volts per cell. And, your charger should be the balancing type, with an LCD display that shows how many Milliampere Hours were replaced during the charge cycle. Most modern chargers are so equipped.

Hope that helps.

[QUOTE= The maximum charge rate of the A123's is 10 Amps, limited by the size of the wire used for charging. Topping off a half discharged A123 battery pack with a balancing type charger set to 10 Amps will take 10 or 15 minutes.
[/QUOTE]

Nice post with good information. As to charge rate though, while A123's can take 10amps, I know of know balance connector that can take 10amps. Are you talking about an unbalanced charge routine at 10 amps through, say, an EC3 power feed?

Hi Flyelectricmodel Yes I'm near Toronto, Canada. Thanks for the great response. I didn't realized A123's were LiFePO4 I thought they were Lithium Ion. I couldn't find the built packs on that website. I can't see soldering together my own so I will be buying packs. I only recently learned about noting how many Mah's I'm putting back into packs as a measurement of how much capacity was left in them. When you say the voltage discharge curves of A123's are similar to NiMh's does that mean using voltage to measure remaining capacity of NiMh is also inaccurate? Thanks for all the good info.

If your charger is charging the A123 pack though the balance cable, you're limited to around 2.5 Amps charge rate due to the current limits of the balance cable itself. As indicated in my first posting, to be able to charge at up to 10 Amps requires the battery have two charge connections. One of which is a #14 or so Batt Plus/Minus cable that plugs into the higher current output of your charger. The second would be the A123 balance cable that plugs into your chargers balance connector.

With these two connections, you can charge your A123's at any rate from 100 Milliamperes to 10 Amps. Don't matter to the A123's. However, charging at 100 Milliamperes could take a full day.

Before retiring I've traveled to Toronto on business several times. Nice place to visit.

I've got discharge curves of both a 5 cell Nih AA pack and a two cell A123 2500 Mah pack. At a discharge current of 2 Amps, their discharge voltage curve is within a few percent of each other. But, at high currents, like 10 Amps or so, those AA Nih cells pretty much quit, where the A123's are just starting to get going.

Check the Eneloops for receiver power JPG attached. At 6 Amps, their voltage drops below 0.9 Volts per cell almost immediately. A two cell A123 pack will hold 5.6 Volts at 40 Amps. I've measured peak currents of 14 Amps on my Giant Big Stick model with it's seven Hitec 645MG servos.

That's odd, when I clicked on the Radical RC link, I got the wrong web page. Try this one:
http://www.radicalrc.com/category/A123-Cells-Packs-199

As previously indicated, you want the SKU Number: RRC2S2500 part number.

Assuming the use of a proper balancing type charger programmed for LiFe or A123 cells, about the only way do damage these A123's is to run them flat by leaving the receiver switch on for a week. Even then they can be "Jump Started" and still work OK. But I won't use them for receiver power after being run flat.

Yeah I managed to run one flat. I brought it back to life with a short lead acid charge to bring the voltage up followed by balance charge. I then ran a discharge cycle and a recharge and realized that although the battery still worked it's capacity had diminished somewhat. It's not going to be used on a receiver again. The packs I've used in the past have been the HobbyKing 700mah and 1100mah LiFePO4's for my small nitro planes. I'm going to use dual packs of higher capacity in my gas airplane. I found the pack with that link. Thanks. PS I spent some time in Oshkosh doing test flights when we were getting our Turbine DC-3 worked on.

I would be less worried about the battery chemistry and more worried about the Internal resistance of the battery in question and the application it was being used in. The quality of the cells being used and your management of those batteries. Hangtime Hobbies/ no BS batteries is one of the few sites that posts such information. There are many solutions to the same problem; using any battery chemistry. so I would not get to hung up on the type used. They all have positives and negatives. educating yourself on the subject will allow you to make the best decision for you and your application.

I'm not aware of any RC radio receiver battery with lower internal resistance than the two cell 2500 Mah A123's. At 25 Amps output current, they still have 2.8 Volts DC per cell at their terminals. The voltage is actually a bit higher than the graph shows because of the voltage drop in the Western Mountain CBA III battery analyzer's test leads themselves.

Take a look at the attached A123 "B" cell discharge curve at 25 Amps. The interesting part of this, they will still have very close to the same output voltage at 25 Amps five years from now.

The A123 batteries are an excellent solution for many applications. Having said that, they are not the only solution, and for some situations, complete overkill. Having an understanding of what your dealing with, allows you to make the best decision for your application. Ignorance is going to crash your plane a lot faster then any particular battery chemistry. That was my only point, which there is more then one way to skin a cat. knowledge is your friend. Anybody can find a solution that is complete overkill, the smart man will figure out how to make it work for less money and complexity but still have that rock solid reliability we all want.

Thanks for the tip on where to buy cells, I don't build my own packs but gives me idea of what the battery assemblers are paying for cells.

i have been using Sony VTC4 cells. They have aboyt twice the capacity of A123 cells. They are speced to remain above 3V at 40 amp drain.
You can get them from Amazon:

http://www.amazon.com/s/ref=nb_sb_ss...c4%2Caps%2C203

They solder easily. They have the same voltage as LIPOLY so you need HV servos. I wont use a regulator. Most receivers will take the voltage.Actually they are the same chemistry as LIPOLY so you can use your chargers an checkers.

Out of curiosity, are these also used in those electronic cigarettes?

I think a very similar battery cell is used in my Sears Craftsman NexTec 12 Volt Lithium Ion impact driver and electric drill. I've checked those cells at 30 Amps. Their output voltage at 30 Amps was no match in comparison to the much larger 2500 Mah A123 cells. They only lasted a couple of years, being used once or twice a month. Replacement batteries were a reasonable $24.00 though.

http://www.sears.com/craftsman-12-vo...1&blockType=G1

Yup, those A123's work very well for the larger models. For the smaller models of perhaps 5 pounds or less, the Nih packs will also do the job. The five cell AA Nih packs are about an ounce less weight than the two cell A123 packs.

For electric models, a quality switch mode BEC really does the job. I've got 10 of the Castle Creations 10 amp uBEC's in my various models, ranging from around 400 Watts up to a giant scale model running 3KW. Next year, a 50 cc conversion to electric is in the planning stages. The ESC I've got on hand is the Castle Creations 120 Amp HV Talon unit with its built in high powered BEC. A backup of a two cell A123 battery pack will also go into that model.

Yes they use them in e cigarettes.
You can also get them from a vape shop.
There is a new one.VTC5 that has a bit more capacity.
They also use them in the Tesla automobile

I've been buying similar 18650 cells cheap off Ebay for the Chinese LED flashlights I have. I think I'm going to wire 2 into a pack and see what the actual capacity of them is (the Chinese Ebay ones). I'm don't think I'm looking for large discharge capacity as much as good MaH's. They are lithium ion. Are they what are in laptop computer packs?

Yes they are in Laptop batteries.
Be careful of ebay batteries.I have got fakes from them.
MaH is discharge capacity. You mean discharge capability?
BTW LIPOLY's are lithium ion.

Yes, you are right. I need capacity not high capability....C I'm going to try measuring their capacity with my charger to see.

I agree with you absolutely, You can buy the Futaba 600miliamp pack for about $15 through Tower which is what I use mostly and Hangtime Hobbies for 5 cell packs. The Futaba pack uses the 600aac cells which typically hold 650 mili amps when I cycle them new. These batteries will run 4 to 5 servos for 4 to 5 flights without an issue. Not dropping below 4.8/6.0 volts respectively. They have much lower internal resistance then the higher capacity NiMH cells, last longer and discharge slower. As for fast charging, 1/2C max, I have had excellent luck with the FMA Direct Revolectrix 50 WAtt charger, much better then any other charger for these low power applications. It also makes an excellent trickle charger. Check it out. I use my old Triton Jr to discharge my batteries, it never worked well for fast charging my Nicads. For those 40-60 size sport planes this a real good, reliable, inexpensive solution.