Battery Pack

[davidjensen]

What do most of you use for 4 cell batteries for your 3+M TD F3X full house ships? I have heard some using very small (600 or less) packs and I just wonder how long they last with 6 digital servo's. I almost ordered a 1400 MAH NiMh custom pack with one cell in front and the 3 in a triangle behind. This pack will be 4+ oz so I need to find out if this is too much weight before I order it.

[IBWALT]

Current batt. technology will allow rx packs of 2000+ mah easily. The only thing you need to be carefull of is building a pack that is to heavy. My thought is I would rather have a big battery and little or no lead in the nose. So when I set up or mock up the radio setup I throw everything in the plane and put it on the c/g machine and see where it balances. Then I use the largest capacity pack that I can get away with and have just a small amount of lead in the nose for the small c/g adjustments that you will need to make at the flying field.

Walt

[Chipwillis]

I use 2 cell Fromeco Li-ions 2400mah, with a mpi 6v regulator.

I have this setup in an Ava, and an Eraser Extreme, and it works like a champ. The Ava, I can fly basically all weekend without charging, but the Eraser I will charge nightly. It doesnt use that much but I like having the batts topped before a day of flying with it.

I am thinking about using a 4 cell 4800 Fromeco for my Supra, if it will fit comfortably in the nose.

Chip

[tewatson]

What do most of you use for 4 cell batteries for your 3+M TD F3X full house ships?

I standardized on 5-cell 1250 MAh NiMH packs (2/3A cells) for my TD and F3B ships. I had noted erratic performance from the larger 2000+ MAh packs, and these 6v packs fit just about anything nicely, charge fairly quick and exhibit consistent capacity. I think the physical config is called 'flat' in battery manufacturer-speak (all cells side-by-side in a row).

If one figures 250-300 MA/hour for the average six-servo plane, that's still three hours of flight time with an adequate safety margin.

Tom

[mlee8249]

I do the same as Chip and have been for about three years without a single problem. What is nice about this set up is that you know you have tons of reserve power. When you're out in the middle of nowhere and must fly a lot, like the F3J Team Selection or the Masters, you don't want to start looking for the charger and car battery every so often. The other part of this set up I like is that I don't have to worry about power on demand. High capacity ni-mh cells are also high impedance cells (normally), and that means you can only demand so many amps and that's it...it then ends up going into voltage depression which could fall below operating limits of the receiver and a resultant shutdown. Nevermind the gobble-de-goop techno stuff. Just make sure that you use high performance cells that do not have high internal impedence for best performance.

Mike Lee

[davidjensen]

I have been using 5 cell packs for many years. I have a 2700 5 cell NiMh in my Muller Esprit and it has been flawless so far. I wonder about the new JR digital servo's on 6V with the buzz they make.

[IBWALT]

I wonder about the new JR digital servo's on 6V with the buzz they make.

I would bet that the JR servos would work very well on 6V. The only problem I ever had with 5 cell packs was with Hitec receivers. Seems they did not like the voltage in a freshly charged 5 cell pack. But a voltage regulator solved that problem.

Walt

[tewatson]

I wonder about the new JR digital servo's on 6V with the buzz they make.

Horizon specifically endorses the use of their radio gear on 6v. I was worried about this too when I was considering the switch to 5 cells.

Tom

[screamin' eagle]

Anyone out there have experience with the Volz digitals in the wing? I maidened a used plane with four of them in the wing and it had a low voltage alarm buzzing on two different 1600mah nimh packs (4xAA) every time I moved the stick. Made me real nervous. Both packs were freshly charged and read over 5.4 volts on my Futaba Battery Checker.

[Jurgen]

I would bet that the JR servos would work very well on 6V. The only problem I ever had with 5 cell packs was with Hitec receivers. Seems they did not like the voltage in a freshly charged 5 cell pack. But a voltage regulator solved that problem.

WaltWalt, can you say what kind of voltage regulator you use on a 5 cell pack? Thanks, Jurgen.

[Jurgen]

Anyone out there have experience with the Volz digitals in the wing? I maidened a used plane with four of them in the wing and it had a low voltage alarm buzzing on two different 1600mah nimh packs (4xAA) every time I moved the stick. Made me real nervous. Both packs were freshly charged and read over 5.4 volts on my Futaba Battery Checker.I would not trust 4 AA cells to feed current junkies like Volz, i think the AA has a too high internal resistance to deliver 4 x 0.6 = 2.4 amps without a voltage drop. I dont have Ri numbers of the AA 1600mAh NiMh but i got a feeling the problem is right there. One Volz operating at normal max performance draws 0.6 amps on 4 cells. This can rise to 0.9 amps stall current :eek:
Jurgen.

[davidjensen]

Well I just got done doing a mock up of the Experience Pro X to see what I need for nose weight. I need a battery that is 7+ oz :censored: This will put the ship at near 78 oz AUW:censored: What did I do wrong :( I did use all JR servo's that added maybe 1 oz and 2 skegs that added just under 1 oz so I figured the ship should come in at 74 to 75 oz. My Muller Esprit is a portley 77.25 oz and floats very nicely and has just a few less sq in of wing :mad: so I wonder what it all means? I just ordered a 5 cell 1400 mah NiMh pack.

[IBWALT]

Walt, can you say what kind of voltage regulator you use on a 5 cell pack? Thanks, Jurgen.

Jurgen, I have an MPI ACC139 which regulates to 5.4v. It is several years old and I am sure there is better technology out there. However the MPI has given me good service and still has quite a bit of life in it.

Walt

[mlee8249]

Screaming Eagle,

What you experienced with the 1600-mAh cells is exactly what I was talking about with high impedence cells and voltage depression under load. You just gave a shining example of what happens. Had this depression occurred at a bit lower rate, causing the voltage to touch down to say 3.5 volts, you might have suffered a rx shutdown that would turn your system off for about 2 seconds. Not a problem on the ground, but in the sky, it will definitely reset your pucker factor. Some rx's are less sensitive than others, but take into account that most rx's have a voltage regulator inside them to keep voltage levels smooth to the circuits of the rx only. Power from the battery is passed directly to the servos by the receiver and is not regulated. Most rx designs are built to operate down to the minimum voltage levels of a ni-cd pack, which is .9 volts per cell, or 3.6 volts on a 4-cell pack. That's why they shut down at 3.5 volts. Only a couple of rx mfg's make units that will work at lower voltages. The one that comes to mind is FMA.

When selecting a high performance cell, you can tell if it is high performance if it will accept a fast or rapid charge normally. High impedence cells may take a rapid charge every once in awhile, but not all the time. High performance cells are made to accept a fast and rapid charge all the time. If you go to the Sanyo Battery website, they have tons of info on their products, and will explain what the product code numbers mean as far as performance. For this brand only, a rapid charge cell has the letter R in the product code. e.g. 1200-SCR cell.

Mike Lee

[emersunn]

A four cell nicad 1300 pack will get you through a one day contest on a 6 digi servo ship. The nicads are easy to maintain and are most reliable IMHO.

Go 5 cell if you need more speed.

-and-

Use a Sirius charger! (http://www.siriuselectronics.com/index.php?main_page=product_info&cPath=1&products_id=157)

[Jurgen]

Right on Mike.
Eagle, i use 1250mAh cells now, you might think hey thats less than my 1600mAh but mine can deliver 70 amps if needed without dangerous voltage dip, your AA cells are barbequed by then :)
Jurgen

PS: 5 cells put more current in the circiut than 4 cells, therefore low internal resistance is even more important.

[screamin' eagle]

A four cell nicad 1300 pack will get you through a one day contest on a 6 digi servo ship. The nicads are easy to maintain and are most reliable IMHO.

Go 5 cell if you need more speed.

-and-

Use a Sirius charger! (http://www.siriuselectronics.com/index.php?main_page=product_info&cPath=1&products_id=157)

I just ordered a 5 cell 1600 nimh pack. Guess that was a mistake. :(

I love my Sirius charger and have been using it for the last two years or so.

[Jurgen]

Mistake, yes and no. Now you know its always better to have high current cells, but on the other hand the extra cell might catch up with the rising voltagedrop over the battery's internal resistance.

If it works than it will be an extra cell to cover the voltagedrop over the pack at the expense of energy for the servos. In other words less gain than using 5 highcurrent cells but it might be enuf for you if you only want to avoid the lowvoltage-issue and take peace with that, knowing there is better. If you can change the order in time you might go for the best immediately.
Jurgen.

[screamin' eagle]

Thanks Jurgen. I think I've successfully changed my order to the Sanyo R 1700 mAh nicd cells. Dang this is confusing...

[screamin' eagle]

I wasn't able to change my order in time, but explained the situation to Mike at Cheap Battery Packs.com (great outfit, by the way) and got the following response:

"The 1650AA cells we carry are high rate cells designed to handle 10-15 amps
of current -- They actually out perform the KR1700AU in output voltage.
KR1700AU is actually not a high drain Nicad. so I would say the NIMH are a
great choice for you."

Wish me luck. :D

[mlee8249]

Eagle,

Don't be confused. Just settle for nothing less than the best. Never be skimpy about radio system components. Especially the battery. I change my batteries every year, no matter what. That's cheap insurance for any plane. I have uys in my vclub who buy $750.00 planes and stick cheap servos and old battery packs in them and then wonder why the plane dug a smokin' hole in the ground. Some got lucky and had some type of failure on the ground and I was able to keep them from trying to fly. And although some people may think that because I am a contest pilot, my mentality is for top notch everything, this is not true only because I fly contest work. I have learned the hard way that to compromise on equipment is simply increasing your risk factor. That doesn't mean that top notch equipment doesn't have failures...they do. But nearly as often as others. There is a certain level of confidence you gain by knowing the equipment you fly with is very dependable and reliable. Just try this: Next time you fly, ask yourself if everything in that plane is absolutely 100% good and working the best that it can. If you do this for each and every plane you own, I'll bet that at least once you will hesitate and think, "maybe not". At that moment, I want you to remember what that feeling was like, and I'll bet it's not pleasant.

Mike Lee

[Jurgen]

Eagle, there is some confusion about the "R" i think.

KR cells are made for maximum capacity in minimum volume, at the expense of higher internal resistance, something we want to avoid here. KR series is bad choice for this purpose. Example: the KR1700AU you mention is 17miliOhm internal resistance. Good for transmitters and other low drainers.

SCR cells are made for maximum performance at the expense of weight and volume, we like performance so SCR is good for the purpose. Example: the N1700SCR (same capacity and chimistry as the KR1700AU !!) is only 4 miliOhm internal resistance.

But if your 1650 NiMh AA-cells are Sanyo (is it sanyo?), then it's likely the HR-AAU cells which have a monster internal resistance of 25miliOhm, a champ in energyloss. In that case the comment of your dealer is to be taken with care. Sanyo is doing a great job putting all their data online so we can check out ourselves, numbers don't lie.

Jurgen.

[screamin' eagle]

Eagle, there is some confusion about the "R" i think.

KR cells are made for maximum capacity in minimum volume, at the expense of higher internal resistance, something we want to avoid here. KR series is bad choice for this purpose. Example: the KR1700AU you mention is 17miliOhm internal resistance. Good for transmitters and other low drainers.

SCR cells are made for maximum performance at the expense of weight and volume, we like performance so SCR is good for the purpose. Example: the N1700SCR (same capacity and chimistry as the KR1700AU !!) is only 4 miliOhm internal resistance.

But if your 1650 NiMh AA-cells are Sanyo (is it sanyo?), then it's likely the HR-AAU cells which have a monster internal resistance of 25miliOhm, a champ in energyloss. In that case the comment of your dealer is to be taken with care. Sanyo is doing a great job putting all their data online so we can check out ourselves, numbers don't lie.

Jurgen.

Wow, there's really a lot to learn here. The 1650 AA cells are NOT Sanyo - luckily...

[Jurgen]

.....The 1650 AA cells are NOT Sanyo - luckily...Your brand can be better than Sanyo's 25mOhm but not too far off i guess, it would be awesome they beat 17mOhm like your dealer suggest.
Jurgen.

[POF]

...but mine can deliver 70 amps if needed without dangerous voltage dip, your AA cells are barbequed by then :)


@70 A the receiver output is barbequed :D

I use 2500 and 2700 mAh Sanyo but as Jurgen says, I can see the voltage drop when my Volz servos are working on a low battery. It seems like this happens when the cells has only 700-500 mAh left. Maybe I should look at the SCR cells?

Remember to use NiCd when flying at winter temperatures. NiMH isn't good at low temperatures.

Anyone got a link to Sanyo datasheets? I can only find a part of their site under construction.

[POF]

Anyone got a link to Sanyo datasheets? I can only find a part of their site under construction.

Aahh: http://www.sanyo.com/batteries/specs.cfm

[Jurgen]

...It seems like this happens when the cells has only 700-500 mAh left. Maybe I should look at the SCR cells?

Remember to use NiCd when flying at winter temperatures. NiMH isn't good at low temperatures.This illustrates that internal resistance is a very living thing, just like the chimistry is something organicaly trough the charge/discharge curve. It is smaller when full and larger when emptying. You may but better don't apply the "voltloss=Ri X current" rule and count on that, but rather use it to compare batteries to eachother, in particular whithin the same brand as they hold on to same determination method. I don't know if Sanyo's method of determing Ri is something standarised and used by other brands, we would like it to be so.
Jurgen.

[Gordysoar]

For those of you who don't know me, I fly rc sailplanes more often, more places in the world with more guys than anyone else on Earth.

For that reason I started flying Volz servos exclusively in my TD contest ships and DS planes about 6 years back. I have been to Volz in Germany and Micheal Volz is now my closest friend in the world, we've done soaring trips a number of times in the world, including Parker and Visalia, Muncie etc.

For those of you who don't get what Volz are about, they were and are the only servos that were created specifically for use in high performance contest sailplanes, versus the other brand servos that can be adapted to work well in rc sailplanes. When Michael created them in the first place, he never even thought about the possibility of them being used in power planes etc.

The original Micro Maxx (now for nearly 4 years, still have about the same torque and speed of today's other brand digitals).

Since they were created for use in RC high performance contest sailplanes the X series which followed were optimized for use with 4 cells, and the digitals still perform perfectly with as few as three cells (a problem for other digis today).

And by the way, JR etc do okay the use of 6 volts, not 5 cells...they aren't the same :-)

Before some one decides that somewhere above has me saying that Volz are 'better' than JR/Hitec/Futa....look back and read carefully, no where do "I" ever say that. All the brands work just fine now days....certainly they work better than our thumbs.

So why did he get the low voltage alarm if the current draw isn't the problem, using a hot pack? The alarm reports that it is seeing low voltage,,,key word 'it' sees.

So if the pack is hot and the servos don't draw excesive current (they'd have to be on FIRE to draw a battery pack down to a low so low that it fires the alarm....feel free to engage logic :-) Heck the wires would melt before the voltage in almost any pack we use today would drop low enough to fire the alarm.

So if the servos can't cause it, and the battery isn't losing voltage, then why is the alarm 'seeing' a tremendous voltage drop?

I know, heck I did an article on it years ago in RC Soaring Digest magazine, years ago.

Yes strong and fast happens with the use and application of energy, and if you compare specs, you'll see that Volz digis are faster, and stronger at 4.8v than the others at 6 volts (or even 5 cells:-)...

So again, if it can't be the servos sucking the batteries down without melting the wires, and the batteries are going dead, why would the alarm report low voltage?

Gordy
Atlantic City today, sky'd out the World's Heaviest Carbon Supra today off a 10' piece of bungee...you?

[cody303]

Gordy,

This tread is about battery performance and high capacity cells. Maybe you should go back and reread it more carefully. No one is bashing on your Volz servos, there is no reason for you to try and defend your servos.

Cody

[Jurgen]

sky'd out the World's Heaviest Carbon Supra today off a 10' piece of bungee...you?In one word: envious (to avoid the word jealous).

We never asked Eagle the voltage alarm trigger point. Are his cells connected together well? What quality wires he have and are the connectors in RX and lead extentions etc, and the switch in good shape? We can't close examine in a forum. One bad solder or sliding-contact can ruine things.

For the sake of Volz glory, haleluyah, i ordered one a few days back but then i saw afterwards they were out of stock at the selling point, grrr, wait, wait, wait...
Note: i wrote "current junkies", that was positive oriented as their current represent power.

Jurgen.

[POF]

Just found this:
http://www.flyquiet.co.uk/smf/index.php?topic=285.0
Same subject.

[Jurgen]

Nice to see (in that forum) they did measurement of internal resistance of AA sized cells and had 23mOhm result, which is very close (next to equal) to the 25mOhm Sanyo give on theirs.
Jurgen.

[POF]

I found this battery that could be better than the Sanyo 25 mOhm cells:
Intellect Telecommunication Electronics Ltd., H50AA-2000HD High-drain Type Cell with an internal impedance of 18 mOhm. See the attached pdf file

The danish dealer writes 10A as a max discharge current: http://www.avionic.dk/product_info.php?cPath=131_130&products_id=4900&osCsid=3065473ded6bf53cd72ecb33c4f126d6

Edit: The dealer has just informed me that the datasheet has an error. The internal resistance is 12-13 mOhms so that is twice as good as Sanyo.