rick88ss

Hi there. I'm new to flying RC airplanes but decided to start with electric RC airplanes. The Hobbico Electristar looks like a pretty good beginner plane so I ordered one and should be getting it next week.

http://www2.towerhobbies.com/cgi-bin...I=LXNVC0**&P=0

Besides using the 2 7S NiMH and 2 2S LiPo battery packs has anybody used the newer A123 Dewalt batteries in this plane? How many would be needed to run the motor safely? I wanna look into this option so I can get the right battery/charger combo once.

I think running 2- 5S A123 packs run in parallel is my best option. It will still be lighter than the recommended 2- 7S NiMH packs and a little heavier than the recommended 2- 2S LiPo packs.

If I buy a Dewalt 36V pack what are the other specific items I will need to make two 5S A123 packs. I also want to be able to balance charge both packs on the same charger. I need two 5 cell packs instead of one 10 cell pack because of COG concerns.

List of needed parts ??

- Dewalt 36V pack
- Heatshrink for 2 packs (what size?)
- 2 female Deans plugs with 12 gauge pigtails
- ?? (balance harness for batteries and charger?)
- Charger??

Which balance plugs(harness)?
What charger to charge both packs at the same time?

Thanks for the help and sorry for the long post

rmh

apparantly not many on this forum have even heard of the 123 cells --
I fly with 4 cells in a 3.3 pound Diamante and I am also doing a thing called the jesky 300 with same power (ELite 32 and a 75 amp Align ESC and an external parkfly bec .
I think you are going overkill for that little plane
compare --powerwise - a single 123, 4 cell pack to a LiPo 4 cell pack
Iknow the guys with the autocalcs will say no way - but go ahead - these things beat lipos in actual use - plus being faaaar less expensive and easy to use --and safe. and you have to go out of your way to screw em up -as for balance forget it - just run em down to mid 2 v per cell and recharge -they will rebalance themselves.
charger ?
If yo have a good NiMh type -- buy a DAPTER and use it --39 bucks works like a champ.
if you are just crusin - the pack runs a long time but I get 6 min banging the Diamante around- I stop flying at 3 vols and swap packs then stuff the other pack right into the charger and keep on going.

mrasmm

for a balancing diagram check out http://www.commonsenserc.com/page.ph...po_wiring.html

I dunno what charger can charge a 10s lipo at the same time, but if you made your charging harness into a 5s2p adaptor, just about any charger out there that charges 5s lipo's could do it.

I do agree with the above though, you're only gona need a 2s whatever p pack. I dunno how many mAh the a123 packs are, but you need 3200mAh that can discharge 20C If you post back the mAh rating and the C rating of the a123 packs I can sure help you with it =)

here is the info from that link you sent.
REQUIRES: Batteries: Two 7-cell 8.4V 3000mAh NiMH battery packs, GPMP0355
OR two 7.4V 3200mAh 20C discharge batteries with balance,
GPMP0622
Charger for NiMH (HCAP0255) or LiPo packs
Building and field equipment

The lipo is a 2s, and the NiMH is the 7s, hopefully that makes sense.

rick88ss

I believe all A123 cells are 2300mAh and are rated at over 20C. I think a 5 pack should work right? But 1 5S pack is still only 2300mAh so I think I'll need 2 5S apcks run in parallel for 4600 mAh. What do you think?

rmh

go ahead -- but the 4 cell pack I have will pull over 30 amps with ease -

you are using other cells as referrence - mistake- these suckers are all by themselves
the ampere hour does NOT need to be as high as a Lipo as you can run the 123 into 2 volt range with no harm.
double the pack if you must -
but talk with guys using them first..

mrasmm

unless I am really off on something, a 5s pack would fry these things. Nominal is 3.3v, so to match you've really only going to need a 3s, and maybe a 2p if you want longer flight times. I agree though on the amp draw, there is no way that you'll need a 2p setup just for the amp draw alone =)

check this link for more info
http://www.a123systems.com/newsite/i...ts/cells26650/


wow, off of a123's site
"A123 cells can be continuously discharged to 100% depth of discharge at 35C rate"

rmh

I get performance equiv to 4 cell LARGE LIPo packs -and tho time wise it is not capable of long flights - -there is now critical shut of time to avoid battery problems
also recharge is fast n quick
I can do more flying over a 8 hour period (to make a point) than if I was using LiPo ,simply because I can recharge instantly-no wait to cool down etc - also I can charge in the plane -no fire danger .

captinjohn

Dick Hanson: where is a good place to buy the 123 cells? Will they work on a 30 inch span Edge? thanks Capt,n

matt13

Hello, I will be trying EP for the first time and will be using a E-Flight 60 motor in a trainer to learn more about this form of power. For me the price of batteries was been the big stumbling block when it comes to leaving my trusted glow motors at home. One needs at least two if not three packs to have the same freedom to fly for as long as one wants. Having said that, I would like to try the A123 batteries for the e-flight 60, how many cells and in what config do people suggest? Matt

captinjohn

Dick Hansen: Where is the best prices on the Dewalt battery packs? Thanks Capt,n

Red Scholefield

My Feedback: (9)

There are 70 offered on e-Bay right now. $100 including shipping. I doubt if you will find a better deal at this time.

cwharper

Alright you have given me the A123 bug again. I ordered a bunch of dewalt packs for use in a bigger project and had some left over so I thought I would put them in my electristar which by the way is an excellent little plane. So here are my thoughts and opinions on pack size and arrangement as well as charging.

First pack size is discussed. Four cells is the recommended lithium polymer size and that is a nominal voltage of 14.8v. So to get equal performance with A123 cells you need to know the operating voltage of these cells which is about 3.1v under load and 3.3v resting. Then five a123 cells in series should do it at about 16.5v nominal and 15.5v under load. This is pretty close to the nominal and loaded voltage of the stock nimh packs as well. Since I have cells already I am going to then make two 5s packs and parallel them together for the extra capacity and also to distribute the amperage draw between the two packs for less wear and tear on them.

Next let's discuss pack arrangement. Just this afternoon I test fitted some cells in the battery compartment. It looks like I can't stack two cells on top of one another without them either hitting the door or not going into the compartment well. So, I arranged five cells in two rows of two with one on the end and will do the same for the other pack. If I take out the metal battery brace under the receiver then one pack will slide toward the tail and the other toward the nose very nicely and can then be positioned for correct CG and secured with velcro straps. To make the packs I am planning to use deans wet noodle wire and strip the insulation off then soldering it between the cells and just fold the cells end to end and tape together.

Finally charging. I have charged A123 cells with the Triton2. However, the task required a lot of baby sitting toward the end of the charge. I used nimh mode and monitored the voltage so as not go over 3.6 volts per cell. Essentially what I was doing could be called a manual constant current/constant voltage charge because toward the end of the charge I manually reduced the amps to maintain 3.6v per cell (18v) until I was at 0.5 amps then manually ended the charge. Part of the reason for going to A123 cells is the very quick recharge capability and right now there aren't many automatic chargers that can take advantage of this feature. My solution is a Mastech HY5020e cc/cv power supply capable of 50v and 20 amps for a total of 1000 watts and fully adjustable. With this I can charge at 18v and 20 amps (10 amps per pack) for a 15 minute recharge.

Hope this helps,

rick88ss

Cool. Let us know how the Electristar performs with the A123 batteries (runtime,amp draw,etc) I'm waiting for a new fuselage for my Electristar and I also need new batteries since both of my Lipo packs got messed up in the crash. If it goes well with the batteries I might get 2 packs.

I have a Bantam BC-6 charger and you can charge A123 packs with it. The max amps is only 6 though.

Red Scholefield

My Feedback: (9)

Yes, the BC-6 is set up so you can set the correct termination voltage of A123 packs, and balance them as well.

cwharper

Report on power usage with 5-cell A123 in Electristar. Mind you I have altered my setup a bit. I am still running the C-42 stock motor but my controller is now a CC-80. I have also changed the prop to a 13x6.5E APC.

Amp draw was 35 contant amps at about 16 volts. So that means I have 560 watts. This is lots better than even with two freshly charged nimh packs and either just as good or better than with the 4-cell lipo battery.

I believe for most people sticking with the 11x7 prop that came with the plane and changing to A123 cells would be a good combination. However, my earlier prop experiments showed that a 12x6E APC drew less amps and had more static thrust than the 11x7. But unless you have a beefier controller I would stay away from the 13x6.5 prop unless you accept the risk of overheating your controller.

By the way the A123 cells got just warm enough to tell they were warm. Can't wait to see the reaction at the field when I fly then come into pit and leave again in 15 to 30 minutes all day long. It might take two or three charges but someone might notice how quickly my turnaround time is.

I expect runtime with a 5s2p pack to be about 25 minutes of half throttle flying or 15 minutes of WOT.

rick88ss

Where did you get the cells to make the packs? Dewalt 36V packs?

cwharper

Ebay, about $10.50 per cell and made the packs myself. Look for "moyer" selling them in quantity lots. Be patient.

rmh

Inow use 4 cells -a 13x8 prop --a EFlight 32 motor and an ALIGN ESC plus a Parkbec BEC- on two complete setups
this way I have very good feedback as to what really works.
1 - 40 amps on 4 cells is fine they get warm but about 100F -really cool by their battery standards.
2 flight times 8-10 mins depending on how aggresive I fly either aerobat.
I have run it flat -in th air - no problem when lande I had 10 volts and simply recharged .
3 -I can use more prop load yet - the 40 amps still yields 11 v

captinjohn

How many cells are in a 36 volt DeWalt power pack? Thanks Capt,n

rick88ss

10 cells at 3.6V each