Author Topic: A123 Packs - wiring etc (Read 1046 times)

Wynn Robins · « **on:** November 22, 2010, 04:32:50 PM »

Cna anyone give information and or diagrams on how to wire A123 packs together so they are usable to replace say A 4S 4000mAh pack

i am thinking about going to A123 - but not sure how to go about it all.

TIA

Dan Bregar · « **Reply #1 on:** November 22, 2010, 06:05:05 PM »

Wynn

The 4S lipo pack gives 14.8 volts, and a 4 cell A123 will give you 14.4 volts wired in series like the lipo pack.

William DeMauro · « **Reply #2 on:** November 22, 2010, 06:05:45 PM »

There is allot written over on RC Groups battery and charger section on A123. Just go here http://www.rcgroups.com/batteries-and-chargers-129/ and then search A123. A guy who goes by the name Everyday Flyer has done a tremendous amount of work and research with A123. I do know that there will probably be a weight penalty but you can discharge them further.

Wynn Robins · « **Reply #3 on:** November 22, 2010, 06:20:02 PM »

I understand I can wire them is series to get the required Voltage - but you need to wire them parrallel to get the capacity up.....the A123 cells come in 1100 or 2400 mAh only - pretty sure this is not enough to get through the pattern....

how do I wire them to get the required Voltage AND capacity?

cells weigh 70g each - 5 cell pack -350grams plus wire - maybe 380grams - still lighter than ZIppy Flightmax 400grams

Igor Burger · « **Reply #4 on:** November 23, 2010, 02:56:01 AM »

Hi Wynn,

the trick of using A123 is, that
1/ you can discharge them to almost 100%. I know guys flying without timer, just with servo tester and flight time is limited by capacity of the battery. Means they go 100% capacity every flight. It is not good idea, but it makes it clear that it does not kill those cells like lipos. So the weight pennalty is not so hot problem as you do not need to carry dead weight.

2/ Cells have only 2.3Ah, while really usefull capacity at high discharge rate is 2.1 - 2.2 at max. 4s1p pack is too small and 4s2p is too heavy. That is why I use 6s1p packs. It is just enough for 5minutes flight time with 12x6 ACP prop. But I note it need motor with lower kv at about 700rpm/v which will limit the current. AXI2826/12 is ok, but AXI 2826/13 (specially done for this aplication) is better, because it has one turn more of the same wire thickness, so it has better copper filling and thus better efficiency. Axi 2826/10 has already too high curren with 6s battery (~10% higher). If you have really light model, then also scorpion II 3020/710 will work well, but it runs hot and it will probably need to replace bearings early.

Dennis Toth · « **Reply #5 on:** November 23, 2010, 08:59:33 AM »

Igor,
What other motors will work with the A123 besides the AXI and Scorpion? Would the Plettenberg Orbit 30-12 @ 650K/v work or the Orbit 25-14 @ 670K/v work? I think we need to keep our amp draw down to about 27 amps to get the 5m 20sec needed for the pattern. What rpm and prop are you using on the AXI 2826-13?

Best, DennisT

Igor Burger · « **Reply #6 on:** November 23, 2010, 09:50:12 AM »

Sorry, I have many producers here few kilometers far, so I use local products, but I can tell that for example MVVS 8 works also well, and also Scorpion 3026/710 ... but they are too large for 6sA123 .. you must remember, that you have limited capacity in that battery, and prop 12x6 at ~9000 rpm does not load it too much, so bigger motor is also a kind of dead weight. larger motor is not always more effective since you have iron loses and it depends on mass of the motror.

I would try to select from motors with weigth from 150g to 200g, kv somewhere up to 700, Ri max. 45mohm, I0 max 1.5A

I would say that scorpion 3020 is smalles acceptable, scrorpion 3026 largest .. AXI is somewhere in between golden middle way :- )))))))))

I have very bad experience with chip copies of those motors while flying indoors, so I never tried such motor on large model, so I cannot tell.

Regarding those smaller A123 cells with capacity 1.1Ah, I think it is not anything for us, they are heavy and expensive (for the capacity).

John Hammonds · « **Reply #7 on:** November 23, 2010, 05:25:42 PM »

I used A123 cells while I was learning to fly again and their robustness certainly proved it's worth. I think I only managed to destroy 1 cell and that was due to a figure 9 where nothing disconnected and the motor went into a shaft run, the pack was wedged up against the spinning can and it wore through the cells outer casing.

The weight penalty although it exists, is somewhat offset by the fact as has already been said you can use 90% or more of the capacity with no apparent ill effects. For me the biggest problem was matching the whole package. If you find you are short of power to complete the schedule you have to add an extra cell which in turn throws your motor (KV) off the chart so you need another motor and effectively have to start again. Lipos are available in such a wide range of capacities it's fairly easy to just keep the voltage and adjust the capacity. With A123's the only alternative to another cell is to go parallel (Bit of a bummer when say 3.2ah will do the job to have to go to 4.6ah).

So..... Question if I may?
I have seen the 1.1ah A123 cells and although they appear to have quite a weight penalty is there anything inherently bad in mixing cells in say a 3s2p pack where one "stick" is 2.3ah and the other 1.1ah? My kindergarten electrical knowledge tells me that as long as I don't mix capacities in series I should be fine. Would doing this effectively give me a 3.4ah pack? Despite the weight penalty I would think it would be considerably lighter than 2 sticks of 2.3ah cells and lighter is lighter regardless of the efficiency if it does the job.

Also for Wiring info have a look on here... http://scriptasylum.com/rc_speed/index.html aimed at electric cars but there is a good page on Lipo Wiring (Applies to A123's as well). Check under the "Electrical" heading.

TTFN
John.

Dean Pappas · « **Reply #8 on:** November 23, 2010, 07:10:22 PM »

It looks like a 6S 2300 mAh A123 will fly a 55 ounce ship with a nice margin of capacity. At 60 ounces you are cutting it close, and some diligence will be required. 55 ounces with a set of A123s is no trivial building task: the pack will weigh 420 grams or 15 ounces. Motor, prop, spinner and ESc will probably add another 10 or 11 ounces so you are looking at a 29 ounce airframe. Igor's 60 ounce example proves that you won't be out in the cold if you miss by a few ounces, but don't expect to fly a 65 ounce ship on that battery.

later friends,
Dean P.

Igor Burger · « **Reply #9 on:** November 24, 2010, 04:08:58 AM »

John, The weight of the 1.1Ah cell is 40g what makes total 640g for 6 cells. I think it is much better to add only one extra cell 2.3Ah what will pust voltage to acceptable value of 6Lipo cells with weight difference only 70g. Motors with kv~700 will need only ~1.7 Ah instead of 2Ah (6cell). It will be able to supply also 13x4.5 prop. at little higher rpm.

Author Topic: A123 Packs - wiring etc (Read 1046 times)

Wynn Robins

A123 Packs - wiring etc

Dan Bregar

Re: A123 Packs - wiring etc

William DeMauro

Re: A123 Packs - wiring etc

Wynn Robins

Re: A123 Packs - wiring etc

Igor Burger

Re: A123 Packs - wiring etc

Dennis Toth

Re: A123 Packs - wiring etc

Igor Burger

Re: A123 Packs - wiring etc

John Hammonds

Re: A123 Packs - wiring etc

Dean Pappas

Re: A123 Packs - wiring etc

Igor Burger

Re: A123 Packs - wiring etc