a123 6.6v questions

[snellemin]

check these out...I used one for a while, before I lost it at the last dragrace.


Towerhobbies sells them. LINK

I solder one up yesterday using 13AWG Dean wires

[ClodMaxx]

nice, snellemin! i'll most likely either make or buy one like in your second shot, since i have my MM batt leads cut pretty short. something like this:

[suicideneil]

Soldering batteries scares me too- I dont want to risk overheating the cells becuase my poopy iron doesnt get hot enough. However, if you have a 60-80watt iron then it is much easier, or so folks say; mine is 50watt so I need to do a test on an old spare cell I have, then I might concider re-doing my 7 cell packs into side by side packs so they lay completely flat. A123 cells are loveliness though, if only they were cheaper in the UK **grumbles**

[brijar]

I got a Dewalt 36v pack and tore it down into two 3s and two 2s packs. Fantastic cells! I didn't even have to solder anything except the wires together. Just had to cut a couple battery bars, which are quite thick compared to the ones used in cheap NiMh packs (radioshack, powerizer, tenergy, etc). They haven't given me any heat problems on my Mamba 5700 Rusty:yipi. Considering I got them for $7.50 per cell makes them a heck of a deal!
The only problems they do give me is lack of tire glue...

Brijar!!!

[VintageMA]

Originally Posted by ClodMaxx

well i called a123 to see if i could change my order (didn't have confirmation that it had shipped yet) to take one of the 2s2p packs out and replace it with 2 of the 3s1p packs, but alas - they were too quick. it was shipped already. so for the time being, i'll be running 4s instead of 5s.

so, i do plan to go up to 5s2p with the a123 cells...which is still only 16.5v. it's going to be on the heavy side...10 cells total, but i'm fine with that.

my question is this: can anyone see a downside to building a deans parallel connector to connect 2 packs that are 3s1p on one side? i would think it would be fine, just wanted to make sure. i could also tear a dewalt pack apart and build a 3s2p single pack, but i hate soldering. i'm ok at it, but i hate it.

Just from my experience (which was very short lived for now) with the A123 cells, they don't hold their rated voltage under load. Granted I was using a 1P setup which didn't hold it's voltage as well as the 2P systems will, but check out the specs on a 2S2P pack here: http://www.a123racing.com/SpecSheets...te_14Aug06.pdf You will be getting about 6 volts on 2S2P @ 23Amps. @ 69Amps you are only talking 5 volts (2.5v per cell)

The packs are very heavy and very bulky. I went with the 2 of the 2S1p packs in hopes of using it in a CRT.5 project @ 13.2v. After running that and comparing it with my 3S 5000mAh Maxamps lipo packs I have to say that I am much happier with the lipo packs. The lipo pack is smaller in size than the 4S1P A123, holds more than 2X the charge and is lighter as well. The A123 cells do have a great punch, but due to the low storage capacity they seemed to dump pretty quickly.

I've never had a problem with lipo when using a decent brand (Maxamps, TP, Kokam/Orion, or TrakPower/FlightPower) so I think I will stick with them until the A123 technology matures over the next few years (which I am sure it will and am definitely looking forward to). IMO the power density (even when compared to NiMH) is too low making for a heavy pack and the cells are too cumbersome for easy placement.

[ClodMaxx]

i could give the list of reasons why i chose the a123 packs instead of lipo, but i'd rather this thread not turn into a lipo vs. a123 debate.

i'll find out about the a123 performance soon enough. i appreciate your input.

[jhautz]

Originally Posted by VintageMA

Just from my experience (which was very short lived for now) with the A123 cells, they don't hold their rated voltage under load. Granted I was using a 1P setup which didn't hold it's voltage as well as the 2P systems will, but check out the specs on a 2S2P pack here: http://www.a123racing.com/SpecSheets...te_14Aug06.pdf You will be getting about 6 volts on 2S2P @ 23Amps. @ 69Amps you are only talking 5 volts (2.5v per cell)

The packs are very heavy and very bulky. I went with the 2 of the 2S1p packs in hopes of using it in a CRT.5 project @ 13.2v. After running that and comparing it with my 3S 5000mAh Maxamps lipo packs I have to say that I am much happier with the lipo packs. The lipo pack is smaller in size than the 4S1P A123, holds more than 2X the charge and is lighter as well. The A123 cells do have a great punch, but due to the low storage capacity they seemed to dump pretty quickly.

I've never had a problem with lipo when using a decent brand (Maxamps, TP, Kokam/Orion, or TrakPower/FlightPower) so I think I will stick with them until the A123 technology matures over the next few years (which I am sure it will and am definitely looking forward to). IMO the power density (even when compared to NiMH) is too low making for a heavy pack and the cells are too cumbersome for easy placement.

I had similar results as you with did running my lightning staduim 10 on 4s1p a123. I actually found that running 3s2p gave me better acceleration and better top end witha little gearing adjustment. I'm carrying 2 extra cells around now, but they perform much better.

BTW someone mentioned a 1940/7 drawing to many amps for the a123 eariler, but I actuially think that it would be fine. I run a 1940/7 in my savage with 5s2p a123 and it rubns great. Because I didnt need a LVC with the a123 I was able to use an older style BK controller I had around. If you run a123 the 9920 and 12020 become very atractive options again.

[zeropointbug]

http://picasaweb.google.com/SethHulsebosch/RCPhotos

Check out the Eagletree graphs at the top of the page there.

[zeropointbug]

Originally Posted by jhautz

BTW someone mentioned a 1940/7 drawing to many amps for the a123 eariler, but I actuially think that it would be fine. I run a 1940/7 in my savage with 5s2p a123 and it rubns great. Because I didnt need a LVC with the a123 I was able to use an older style BK controller I had around. If you run a123 the 9920 and 12020 become very atractive options again.

I agree, when I ran 5s2p on a 7XL, it had awesome power, able to flip over the truck at any speed with WOT. I had it geared for 45+mph, and I think it could actually hit 50mph because of the tire ballooning on the badlands.

[VintageMA]

Originally Posted by ClodMaxx

i could give the list of reasons why i chose the a123 packs instead of lipo, but i'd rather this thread not turn into a lipo vs. a123 debate.

i'll find out about the a123 performance soon enough. i appreciate your input.

I have no intent in aiming on starting a debate on A123 vs lipo - cause that could be never ending.

Simply - I tried them and they are not for me right now.

I think in the 2P configuration in which you are going they will be much better than the 1P config I used - that will put them closer to that 5000mAh mark whichgives a nice blend of power to the motor and a decent amount of runtime.

If you are able to fit the batteries comfortably into your setup and they work for you - then I see no reason to bash them. They really do have their positive sides - the fast charge time, the safety factor, and the 1000+ rated cycles vs. about 200 or so cycles for a lipo.

It is definitely a battery technology that I will monitor closely and see how it progresses over the next few years. Once it matures to the next level - I could see it easily take the place of lipos in the car/buggy arena.

[kenkamm]

I run a E-Revo with an Align 600XL and Align 75A ESC and 8S1P A123s, and the thing is nuts. I put the long wheelbase rear suspension arms on it and lowered the ride height to the lowest setting on the arms, and this thing lights up all four road rage tires from a stop, and hits 45 MPH at top end. The A123 cell seems like the ideal application for this kind of thing. It's tough, safe, and no timers or low voltage issues. Sure, the voltage drops under load... but my answer to that is, add another cell. They can discharge at 70A continuous and 120A peak (for up to 10 seconds.) I buy the dewalt packs on ebay (about $100 for 10 cells), and make whatever I need from them. Each cell has tabs on it, which are plenty robust enough for soldering to, and you don't risk heating the cell (certain cell death.) I use a TP-1010C and 210V balancer, to keep tabs on cell health. I charge them as fast as I can and they don't complain. At that voltage the 1010 maxes out at 6A charge rate, so the charge is quick enough to keep me happy.

[zeropointbug]

Word, I run 7s2p pack on a 1512/3D for 38,000rpm and the truck has moe nuts! I then made a 7s pack and geared it for slightly slower, at 40mph it still has lot's of power (~1250 watts), and the truck was little over 9 lbs, it was so nice and agile.

There is a new battery tech i just found today that looks VERY promising. It can discharge 50C continuous and only reach 34*C (93F) in the lab tests. They compared it to an A123 (or at least I think), the A123 cell at 13C (30A) continuous and it reached 66*C (150F).... that has got to tell you something about these cells.

LINK

[ClodMaxx]

dang guys. that's a lotta watts!

got both 2s2p packs today, and the charger. first impressions are that the packs are heavier than i thought they'd be, and that charger sure is small for what it can do!

i can't make a test run until this weekend. i have my power supply, but the charger uses alligator-clip style connections to the charger. i have my power attachment unit that the charger clips to at my parents, which is 1.5 hours away.

glad i paid to have the packs rushed to me so i can wait to run them this weekend, lol.

[kenkamm]

Hmm, I'd like to see more about that cell, like more specifics on size, weight, and voltage.

[kenkamm]

zeropointbug, any pics of your setup?