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a123 6.6v questions
so i just took the plunge and ordered a pair of a123's 6.6v 4600mah battery packs and their hypersonic charger. my question is this to anyone that bought similar packs from a123: is there anything special i need to know? i guess i'll find out how they fit in my battery trays (they'll currently hold 8 sxs ni-mh cells) and i ordered some velcro straps to hold them down.
will it really charge in under 15 minutes? do they stay in balance as well as everything i've read? i don't plan to run a LVC - they should drop, and drop quick, at the very end. a good visual cue to stop running. :rofl: any insight on my new purchase would be appreciated. :great: |
If you bought A123 racing packs, you are covered for balancing and what not. And yes, they stay balanced very well; I have custom made packs and they only go 'so far' out of balance, then thats it, nothing more it seems.
Yes, they will charge your pack in 15 mins if they are at 0% charge. What are you using these packs in exactly? |
yep - i bought the whole kit from a123. i've thought about tearing a dewalt pack down to build r/c packs, but it just seems soooo.... scary, lol.
they're going in a 10 lb. 8 oz. e-maxx - i have a thread on the build in the t/e maxx parts section. thanks zpb. |
anytime! :yes:
May I ask what motor you are using? It should be over 2400kv if you want good power from your truck with 13.2 volts. |
i have a Lehner 1940/7 hi amp, which is about 161kv short of 2400.
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Oh, well then that should work for sure then, just gear it up to get your speed, and you should have lot's of power.
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:yipi:
here's hoping! i just inadvertently fried a matched 7 cell pack today... i'm through with ni-mh. hopefully i'll have much, much better luck (and power) with these a123 packs. thanks again! |
Well, as far as luck goes with A123's... LUCK IS TIER ONE!!! They are very robust/durable cells, both physically and electrically.
Power is very high, theoretically (in actual power they can deliver), but as far as running a motor type load, that's where the lower voltage holding capability is limiting you, compared to lipo. But, overall, they deliver much power for their mah rating, that's for sure, and they can handle the power too. They are very safe cells. |
The only thing that gives me concern with the setup that you are proposing is the current draw. That 1940/7 is going to draw a good bit of current as it is. Running that hot of a motor in a 10+ lb truck on what will be essentially be 3.5S lipo is going to draw a lot of current.
What controller are you going to be running? If you're going with the MM, just watch the temps. On the upside, those packs are very nice. I experimented with a couple of them when my LHS first got them in. They have punch right up until they dump and they do indeed charge in 15 minutes, although that 15 minutes is for each pack. It will take you around 30 minutes to charge both packs. A ThunderPower 1010C should be able to charge both packs in series in 15 minutes. |
well, i asked on here what controller to use with the LMT on 14 cells and i got a lot of votes for the MM. so that's what i chose... and on some trial runs w/14 cells this past w/e, it did get warm - as did the batts. the motor was cool, as i suspected it would be.
i'm also concerned as i'll have to gear up to about 51/20 to get the 40 mph speeds i'm looking for. i may run 5s with the a123 packs someday, and i'll most likely have to get a higher quality controller. right now i'm leaning towards a MGM, but i may be able to hold off long enough until the tekin comes out (not even holding my breath for the MMM). |
The MM does do well on 4S or the equivalent nimh voltage, but that's my point. If you are just changing the power source, with all other things being equal, and running a lower voltage, it's going to draw more current if you are expecting the same performance as you had before.
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i gotcha. that's why i'm planning to gear up to a 20t pinion (i was planning to use about a 17t on the 14 ni-mh cells) to get around the same speed. but if i go with 5s instead of 4s, i should be able to gear back down... or is my thinking flawed?
edit: going up to 5s a123 cells will require a new controller. i may 'experiment' with the MM, however. since i have two 2s2p packs, i'll have to make a 3s2p pack from the dewalt packs...darnit. but...if i bought a dewalt pack and built a 3s2p, i could use the remaining cells to make a 4s1p pack for my crawler. ding ding! we have a winner! |
When you gear up, it will draw more current. Going to 5S A123 with the MM shouldn't be a problem. I can't remember if I did it or not. I ran 5S A123 in my 8ight T, but can't remember if I used a MM or Monster Pro.
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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. :whistle: |
Deans parallel connectors are fine, I use my homemade one alot and it does not get hot, so I figure that it is ok. From what I have read the deans are only good for a 60 amp draw, but that must be continous, not sure what a 60 amp continuous sytem would look like, but it would be powerful!
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check these out...I used one for a while, before I lost it at the last dragrace.
http://www2.gpmd.com/image/g/gpmm3142.jpg Towerhobbies sells them. LINK I solder one up yesterday using 13AWG Dean wires http://i189.photobucket.com/albums/z...r/DSCF1089.jpg |
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:
http://home.comcast.net/~truerc/Charge/DEANSPAR.jpg |
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**
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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:oh:... Brijar!!! |
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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 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. |
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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. |
http://picasaweb.google.com/SethHulsebosch/RCPhotos
Check out the Eagletree graphs at the top of the page there. |
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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. |
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.
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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. :yes: LINK |
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. :grrrrrr: 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. |
Hmm, I'd like to see more about that cell, like more specifics on size, weight, and voltage.
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zeropointbug, any pics of your setup?
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Awesome trucks. Much nicer than my hack approach. :)
Also, now I see the link in your sig (duh on my part...) |
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that is a pretty great shot! :yes:
question: for my 2s2p a123 pack, there's only 1 balance wire coming out to the balance tab. how does only 1 wire balance 4 cells? or is that tiny wire split 4 times and somehow the balancer can see them separately? |
Okay, that one wire is a tap to the connection between the 2 cells series connection. Then it uses the main connectors + and 'balance tap'(-), then for cell # 2, it uses 'balance tap'(+) and main battery -.
Understand? |
i think so. i at least understand how they're all joined physically. but the charger/balancer only sees 2 cells (series) instead of 4, right? seems to be the case, as the charger will only charge up to 3 cells.
thanks...i'm a balance noob. this is my first set of batts that aren't ni-mh. :sarcastic: i guess i don't understand how each of the 2 sets of cells in parallel balance independently of each other... it seems they don't, which doesn't make sense. hey, as long as they make my truck go fast, what do i care, right? :neutral: :mdr: thanks zpb. |
Holy Balloon wheel, Batman!! Or should I say, zeropointbug!
Great shot(s)! http://picasaweb.google.com/SethHuls...41171742933938 Great camera work by whoever was running it. |
Thanks, lol!
IIRC, that was me starting a donut-fest, trying to get it to spin in a tight circle. The camera man was my uncle from Netherlands (Holland) with some wicked camera skills, yes. :mdr: |
Hi Folks,
Well I made an attempt at some video of my E-Revo with the Align brushless hardware. After making the video I realized it doesn't showcase the power all that well because the resolution of the video isn't all that great and the road rage tires don't grip that well on the grassy hill, and the steepness of the hill isn't obvious on the video. Also since I had to film it while my fiance drove, it was a bit tough since she has a total of 10 minutes of R/C driving experience. Still, I tried to show how the truck can crawl along pretty well and then smoke all four tires at will, even on pavement. I just wish there wasn't so much gear noise. The whirring from the Align motor sounds pretty cool though. I just swapped in a Neu 1515/2.5D and the gear noise is even more evident. It doesn't seem to have that much more power than it did with the align motor, but I need to experiment with the gearing a bit more. But it's a testament to the Align motor. They are powerful and inexpensive, especially on the used market. Next I plan to build a E-Maxx and put the Align motor in that and keep the Neu in the Revo. Man, this thing is fun. :yipi: Video: Please right click and do a Save-As |
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