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A123 as receiver pack - no fly voltage? - 2/15/2007 10:54 PM   
ncrego



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Status: offline 		Hello, I'm thinking about replacing some Li-ions and regulators in one of my giant scale gas planes with a pair of the A123 2s packs. What I'm wondering is, what is the safe no fly voltage with these packs? Looking at the discharge graphs, they give little to no warning before they dump, and stay pretty constant through the entire discharge. With regular Li-Ions, my no fly is 7.1v under a 1a load, what would I use for the A123 cells?

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RE: A123 as receiver pack - no fly voltage? - 2/15/2007 11:58 PM   
BocaBen


 

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Status: offline 		I have the same question, but I'm not sure there's an answer yet.
This is in my view the key drawback to those packs when used for Rx.
I think that you have to monitor the number of mA that went in during the charge, and then cross your fingers that at least the same amount will be able to get out.

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RE: A123 as receiver pack - no fly voltage? - 2/16/2007 2:30 AM   
everydayflyer



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Status: offline 		Graph here clearly shows that @1A load and 3V per cell the end is near.

http://www.a123systems.com/html/a123racing/rcdevkitspecs.pdf

It also shows that there is little voltage difference for the complete discharge at this rate.

I would think anyone using these cells in such an aircraft would have a good idea of how long they can fly before using 2000 mAh capacity.
They can be charged / toped off quickly so my advise would be to time usage and top off when approbate.

Charles

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RE: A123 as receiver pack - no fly voltage? - 2/20/2007 4:04 PM   
A123 Racing


 

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Status: offline 		Hello NCR and Ben,

Charles is definitely pointing you in the right direction. The problem is that with such a light load the voltage difference during discharge is very very small. You can try 3.0V, even 3.1V or 3.2V could be helpful.

However my primary advice would be to utilize the fast charge capabilities and simply top it off before you take it out. If you only used 80% the last time you took it out it should only take 2-3 minutes to charge (at 10 amp charge).

Good Luck,

Brian



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RE: A123 as receiver pack - no fly voltage? - 2/22/2007 12:45 AM   
dick Hanson



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Status: offline 		My CellPro 123 recharges extremely quickly - I wired my packs using a 3 wire JR HD male end so I treat the pack exactly as I would any other pack such as a NIMH.
My external JR switch is used as a charge port - I mated a JR HD Female lead to the Cellpro pigtail
Now - I just carry a small 12v battery and the charger in a small plasic tool box -- then plug in charger to batt then charger to model -- in a few minutes -- beep beep beep . full of fuel ready to go
I don't know yet the full charge life for the model but inasmuch as recharge is sooooo simple n quick - it can happen while I refuel the gas tank.
Why pack around 4 hours of battery?
If your battery leads are capable of supplying current needed for YOUR setup - just go with one pack
two sets of leads can be soldered to the pack - then go thru two switches to allow greater amperage transfer.
I think-- one pack is plenty for up to a 40% model but definately two sets of leads and two switches. to keep up the flow .

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RE: A123 as receiver pack - no fly voltage? - 3/2/2007 7:13 PM   
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Status: offline 		Hi everybody, I'm too thinking in adopting these cells as Rx pack.
In this case is a 90 size nitro heli.
My questions are (since I'm not 100% sure about my graphics understanding capabilities)...
If I'm not wrong the above graphic shows that at 1A discharge these cells keep a voltage above 2.5V toi the very end, am I correct there???
Does that mean that they would be safe to use them for the lenght of let's say 75% of the charge without triggering the F/S on the Rx?
I never used 6V pack before (only 4.8V 4300Mah NiMh) what would happen if your 6V pack goes down to 4.9V would the system keep working as it is a 4.8V pack???
I guess that with these cell it would be impossible to get them that far (according to the discharge curve) it seems like they go from being "alive to death" pretty fast.
The other question is do you need any type of reglator to plug this pack to the receiver or would it be ok to plug it straigh in to a PCM futaba Rx?
All my servos are rated for 6V (ecxept the rudder one for which I'll need a step down to 5.3V)
I'll appreciate any help you can give me to understand all this new technology since I'm really reluctanct to experiment with my model.
Thanks again,
Fernando


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RE: A123 as receiver pack - no fly voltage? - 3/3/2007 12:35 AM   
everydayflyer



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Status: offline 		Hi Fernando


Even at a 10A load the voltage stays at or above 3 volts per cell until after 2000 mAhs are consumed. A 5 cell Ni Cd / NiMH would have similiar voltage so there should be no need of a regulator.
Since the A123 do dump all at once I would try not to use more that 1600 or 1800 mAh between charges.

Charles

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RE: A123 as receiver pack - no fly voltage? - 3/5/2007 3:38 PM   
ferincr


 

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Status: offline 		Charles,
Thank you for your reply, that is good news I think it's time to dump the NiMh and move on with technology.
I wouldn't like to abuse of your kindness with somehow silly questions but do you have any estimates (timewise) of for how long can a 2300Mah be used with 5 digital servos, plus a governor (roughly)? I'm not sure if you are familiar with RC helis or just planes.
I understand that I need to think the current draw could be around 3Amps. that would make around 40min. (rough calc.) per pack, would that be the correct way to do this? Or should I estimate more load? I know in an heli the servos are a lot more active than in a plane, but I'm not sure how to calculate the top A draw. Is the specs on the servos info the max draw? Therefore should I add everyone up?
Since you are familiar with electric flight for sure you know better than me.
I'll apreciate any thoughts about this,
Fernando

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RE: A123 as receiver pack - no fly voltage? - 3/13/2007 2:32 PM   
dick Hanson



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Status: offline 		don't try to calculate this !
not enough info to get there
Instead - -get a Cellpro or a very accurate meter and read installed "fresh voltage " aprox 7.2 v
now fly the chopper on the ground for a minute . stop and read again -
likely the 2 cell pack will now read 6.6+volts -that is typically what I see on my packs loaded with rx/servos ON .
I am reading ,using a Whattmeter in series from pack to on/off rx switch
so---get some power on voltage numbers and some "power off" numbers before 1st -second -third flights and write down the exact voltage example: 6.45 - watch this drop each flight - the Cellpro will display 80% --70%-- 60% --etc., as well as voltage per pack and per cell so is very handy method as you can read /charge / test as you go and it is inexpensive .
At about 80% used up -I think mine read 3.2 per cell- (6.4)- so an accurate check is needed !
It isn't risky as it sounds - especially if you wire up for the Cellpro 123 - -I just read after each flight n charge if needed
charge is at 3 amps and full charge occurs when charge rate drops down to about .15 amp -so it is simply a larnin curve.




< Message edited by dick Hanson -- 3/13/2007 2:36 PM >

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RE: A123 as receiver pack - no fly voltage? - 3/18/2007 3:22 PM   
everydayflyer



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Status: offline 		If you know the average amp. load then you can calculate the available safe flying time.

It is safe to use 2000 mAh capacity from the 2300 mAh A123 battery so.

2000 mAh (2Ah) available . Now if th load is 3A average then 2/3=.66 of one hour or 39 min.
Years ago I flew a .50 size Heli with a 1000 mAh 4 cell Sub C Ni Cell battery and only recharged at the field if I flew for more than 40 minutes but I was not a 3D flyer..



Charles

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RE: A123 as receiver pack - no fly voltage? - 3/24/2007 12:16 AM   
Delta Mike


 

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Status: offline 		Dick, would these be safe to run using 2 of the 2300's seperate switches into the batt port and a aux channel,,Like I have always done with me Nicads?

Dennis

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RE: A123 as receiver pack - no fly voltage? - 4/1/2007 4:41 PM   
dick Hanson



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Status: offline 		Safe?
If all is in correct working order - It should be just fine -for even a 40% model

My 33% EDGE model with 8611A servos and a really strong engine can really suck th juice if I flog it
Up to 25 % of full charge on the single 2300 ma pack- so I just top it off when refueling and go fly.
One thing I found -- the "top off" is not always the same the max voltage may be off a little between cells I guess it varies as internal heat varies -I don't fret about it . same thing on Li Po's.
My42% model will get two packs on two switches just as it did on the previous 2700ma POS Expert cells -which had horrible impedance character and voltage went to hell as you cranked hard on all surfaces .
afte doing comparative checks on servos loaded /unloaded on 3 differet size gassers -- the 123 cells show higher voltage holding -under load- than ANY other cells I use . The 4300 Ma low impedance 5 cell packs were closest.
Now, I think I have a feel for how hard I can drive a single or dual pack -as a receiver pack.
Frankly I am now far more comfortable with these- than any of the other setups for RX. especially LiIons and regulators - those have always and remain at the bottom of my list .

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RE: A123 as receiver pack - no fly voltage? - 5/20/2007 3:36 PM   
sergeflavigne


 

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Status: offline 		Hello Dick,

I put A123 cells in all my planes, and I'm using the Cellpro charger. My question to you is: If I fly say my Bling with 7 HS 5645's for 15 Min. using two, 2 cell A123 packs with only using 7% of the charge in each packs, do you think I can safely fly with using one 2 cell pack and topping off after every flight?

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RE: A123 as receiver pack - no fly voltage? - 5/22/2007 9:34 PM   
sergeflavigne


 

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Status: offline 		Dennis, Are you using regulators, or streight into the receiver?

Serge

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RE: A123 as receiver pack - no fly voltage? - 5/26/2007 1:38 PM   
dick Hanson



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Status: offline 		yes - be sure you understand what the CellPro is sayng - -you don't have to balance each time really but I would watch and find a number of flights which pull voltage down to say 3-1 - the recharge from lower voltage , appears -not positive yet but appears to exercize and allow cells to balance.
again -fer Chrissake forget "calculations" -
it is good to know the usable power output but the variety of servos and the loads from various setups can can change the calculated load by huge factors .
measure the loads and then record typical use . with this profile , you will have the best chance of not over running the batteries.

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RE: A123 as receiver pack - no fly voltage? - 7/26/2007 2:44 AM   
Richard D Bahmann aka/Wrongway



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Status: offline 		I finally found the limit of the monster. As suspected the end came quickly. All in all the batteries are good, it just will take some getting use to the power curves on them.

The plane is a 16 lb 88 inch Extreme Flight Yak with a G-62 on a pipe.

On my two cell 2300 mAh pack with a starting voltage of 6.7 volts I did get 15 flights. Most of the flights were in the 10 minute range and a couple were actually closer to 14. This was over the course of three outings.

I have purposefully not charged to see where the bottom of the well is, and in after though.... I cut it close. I flew the last 5 flights tonight and on the last flight the starting voltage was 6.34 after exactly 10 minutes of flight I landed and checked to find it was down to 5.74 volts. Usually with these batteries you check a voltage and a week later it exactly the same to .01 but after sitting a few minutes it came up to 5.9 volts.

That is were it could prove fatal to the unaware. When I got home I set my Futaba 9C in servo test mode and ran the timer to see if I could get another flight. Out of pure laziness I did not hook up the wing servos so was just running the two elevators, rudder and throttle.

After 8 minutes the noise changed and when I looked over the rudder had stopped and the elevators were not in sync. At this point the battery voltage was at 3.0 v.

So from 5.74 volts to crash without the aileron servos and flight loads was 8 minutes. To me that means a flight begining at this level is a certainty not to complete.

My whole idea was to explore the limits of the battery and I did, thankfully without trouble. If any of you guys have a dewalt power tool and have run the battery out you know how one minute all is well an the next minute it is "Kaput."

So my new no fly voltage, at least for a while is 6.4 volts for a 10 minute flight. It is interesting that many of the flights early on would come back with a .02 voltage loss but the second to last one was .10 voltage loss. (going from 6.44 to 6.34) Then 6.34 to 5.74 or a .60 loss in the same 10 minute flight.

The moral of the story is to keep ahead of the game. Dick Hanson says he just goes ahead and recharges while he is refueling and that will certainly keep him safe. For me, I have a battery in the avionics bay on a quick release and a spare but can't see how I would need to recharge uless I am doing 10-15 hard flights in a day.

I will continue to use these batteries with the education and do really love them.

R

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RE: A123 as receiver pack - no fly voltage? - 7/26/2007 2:25 PM   
dick Hanson



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Status: offline 		Nice write up!
I am now flying 4 cell packs in two, 3.4 lb electrics
I flew a pack till the motor cut - and the Park BEC still provided power to the rx (a 7000 type Dx7) with no reset occurring-pack was at 10.2 after landing.
in the rx's -I never considered trying to fly to the end as my planes can really suck up the power.
Four flights for me is a full day, so the flight times someguys crow about using LiIons and regs mean nothing to me.
having watched how these setups REALLY work ( the LiIons and regs) - -You couldn't give me a set - especially since using th A123 cells.
The new really power hungry servos can do in the resistor regs in short order.

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RE: A123 as receiver pack - no fly voltage? - 7/31/2007 1:04 AM   
psk560



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Great Job man! I have two dewalt packs that I am considering using in my 2.6 comp arf extra. I've been using the Li-ions for about 1.5 years and they aren't holding well anymore.

Questions about receiver packs for anyone to answer...

1. I charged my first pack tonight with a cellpro and it showed about 7.2 volts after charge. Did you use a regulator with these batteries? Seems kind of high to start out with.

2. I have a two receiver system in the comp arf. I run a fused power wire between the receivers so that I have power to both sides is the switches/regs/battery fails... Will I have to disconnect this when I charge a battery?

3. What load did you use when testing the voltage on the batteries in your flights?

Thanks again R for the hard work! That is a bunch of flights on one battery.

Craig



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RE: A123 as receiver pack - no fly voltage? - 7/31/2007 2:07 AM   
Richard D Bahmann aka/Wrongway



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I only charged mine to 6.7 volts. I was nervous about unregulated on 7.2 volts because they don't come off the voltage like my Nimh's did. (the nimh's were down to under 6.5 volts in the first flight the A123's took two flights to go from 6.7 to 6.66)

For your question #2 I do'n't know the answer.

I tested with a 250 mAh load and typically got a .10 volt drop.

I hope this helps.

Richard

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RE: A123 as receiver pack - no fly voltage? - 7/31/2007 2:10 AM   
psk560



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Status: offline 		Thank you for your quick response. Keep the info coming as you test further.

Craig

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RE: A123 as receiver pack - no fly voltage? - 7/31/2007 8:07 PM   
psk560



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Status: offline 		I ran a little experiment with my new receiver pack....

---I used two taillights to discharge the batteries. Measured current was approximately 3.35 Amps (As measured by my DMM).
---Each minute I measured the voltage at the battery connection.
--- I used the battery for 10 minutes, then let it sit for 20 minutes. The spikes in the graph show where the ten minute intervals occured. The fourth test only ran for 3 minutes before the voltage got below 6 volts.
--- I calculated approximately 1.843 AH used by the batteries.
---When connected to the Cellpro charger the batteries read 3.07 volts per cell. Each stayed balanced through charge. The charger put 2.072 AH into the battery in 35 minutes. The charge was 100% complete at 29 minutes but it took another 6 minutes to balance the batteries??? (Really weird here as the cells showed the same voltage on the cellpro. I believe the balance sectionof the charge has something to do with how the charger goes from a 4 amp charge to 0 amps. It takes time...)
--- The cells stayed at room temperature through discharge and charge.

Very cool cells! I'm still trying to determine the best stop fly voltage and load to put on my checker. More testing is going to be needed. On the graph I would say anything above 6.3 volts should be pretty safe. It took another 10 minutes to bring the battery under 6 volts with a 3.35 Ampere load. Hummmm.....


Craig


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RE: A123 as receiver pack - no fly voltage? - 12/25/2007 7:50 PM   
atvracer



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Status: offline 		any more info or testing ?

there some very good info here i'm building a 88" yak and want to keep light and safe i've been using lipos with a reg for years in all of my planes and helis with good luck but allways hated getting a reg and have more stuff to go wrong or fail

so i can run A123 to the RX without a reg cool but isnt 6.7+volts a little high for the servos also i read some wear some guy's are using the RX pack to power the ignition also using 2.4gig RX is this safe and doable ?

now i'm thinking about a switch to A123

thanks
ATV

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RE: A123 as receiver pack - no fly voltage? - 12/25/2007 8:16 PM   
Richard D Bahmann aka/Wrongway



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quote:

ORIGINAL: atvracer

any more info or testing ?

there some very good info here i'm building a 88" yak and want to keep light and safe i've been using lipos with a reg for years in all of my planes and helis with good luck but allways hated getting a reg and have more stuff to go wrong or fail

so i can run A123 to the RX without a reg cool but isnt 6.7+volts a little high for the servos also i read some wear some guy's are using the RX pack to power the ignition also using 2.4gig RX is this safe and doable ?

now i'm thinking about a switch to A123

thanks
ATV


I have been running thetwo cell 2300 A123 on my EF yak for well over 100 flights now. In reality the power comes down to 6.6 by the second flight. No problems with the Hitec 5945's and 5955's at this voltage.

Check with Bob Pastorelli on the A123 and ignintion thread. He has sucessfully run the single 2300 two cell on flight and ignition and 2.4

http://www.rcuniverse.com/forum/m_6166262/anchors_6790487/mpage_8/key_/anchor/tm.htm#6790487

They are great batteries!!

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RE: A123 as receiver pack - no fly voltage? - 12/25/2007 8:38 PM   
atvracer



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RE: A123 as receiver pack - no fly voltage? - 12/26/2007 12:37 AM   
SinCityJets


 

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Just an FYI, Desert Aircraft has approved using a 2 cell A123 pack direct to their ignition. As far as running them straight to the receiver, everyone I know who runs A123's does NOT use a regulator. The voltage of an A123 pcks is the same as a freshly charger 5 cell Nimh. So, the choice to run a receiver is yours, but most do not.

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