1p A123 in my buggy... Enough? - RC-Monster Forums

jhautz · 03:38 AM

I have a couple of the Dewalt (A123 M1) battery packs on the way to me and I am planning to build a 6s2p setup for my basher savage, but that will leave me with 8 cells left over. I recently switched the motor in my buggy to a smaller LMT1930/10 I got my hands on for experimentation just to see what a smaller high quality motor could do. I gotta say... In a buggy its still too much power on either 4s or 5s Lipo. At least more than I can control on a track.

Anyway... Back to my question. So I have these A123 cells comming and I was thinking about taking the 8 left over cells and making two 4s1p packs out of them to use in the buggy for racing. I'm thinking that the 2300mah pack would be enough for the 5 minute heat races. Probably even a 7 minute race.(which is all the club mains are going to be according to the owner of the new track). My question is. Do you think the cells will be able to handle the current in a 1p configuration? Will I have isues with battery heat? I know they are rated for 30C constant and 60C burst, but that just seems like it couldnt really be true. I'm actually kinda hoping it will work cuz last time out there I did a few laps with a 3 cell lipo and it was almost perfect as far as power (for me on the track anyway) Speed wise It was as almost fast as the nitros (but still way quicker acceleration), and I was in controll the whole time. Top end on the long straight was hurt by the low voltage, but it was so much easier to drive on the rest of the track, I got much faster lap times. I'm thinking that the 4s A123 will be somewhere in between the 3s and 4s lipos as far as power and thats just about what I'm looking for for now.

Anyone ever try a 1p configuration on the a123 cells? Would I have trouble with them getting hot. Looking for some input from someone who has actually run them in a 1p configuration.

starscream · 04:13 AM

If you want to run A123's in series, I can say from experience that 6S A123's won't quite cut it for racing. 7S is just about enough but 8S should do the trick. If you are planning to run 4S, then you'll have to run them in parrallel in order to keep the voltage at an optimum level.

jhautz · 05.24.2007, 04:58 AM

6s is more voltage than I want. The controller wont handle 7s or 8s and even if I did have a controller and motor suitable for 7 or 8s It would defeat the purpouse of going to a light setup. I might as well just use the motor and controller I already have and run 4s2p. Same weight and cell count. Besides that... 7 or 8s is just way more voltage than needed IMO.

4s lipo should be more than enough voltage for racing, and for me the voltage of the 4s A123 is enough for the track. I'm just wondering if thet can handle the amp draw at 1p.

Maybe I'm misunderstanding what you mean????

bdebde · 05.24.2007, 09:23 AM

jhautz,

Does that 1930/10 run cool in a buggy? I was thinking about trying one of those in mine.

lydiasdad · 05.24.2007, 09:28 AM

I am running 6s1p a123 cells in my hyper 7 and am very happy with it. It uses a 9xl with 12/46 gearing and I get over 10 minutes of runtime. I was worried about the voltage drop when running a 1p setup but these cells have really impressed me. I have a thread about my hyper 7 conversion with pics and more info that may be useful to you.

05.24.2007, 09:30 AM

I tried a 5S1P configuration in my truck with a 9XL. The 1P config was working hard. The batteries got up to 135*F and the punch just wasn't there. I mean, it had punch, but not like my 4S2P 8Ah lipo pack. 4S1P A123, will likely not be enough.

Serum · 05.24.2007, 09:56 AM

their voltage drops too much for impressive results in 1P and in a 1/8th vehicle.

Perhaps when they optimize the chemistry a bit they can hold their voltage better, but on 60A they have a huge drop already.

jhautz · 05.24.2007, 10:13 AM

Ok... Sounds Like that wont work very well then. I'd be interestested in seing graphs if anyone knows where some may be hiding around here. My search was unsucessfull. I may build a 4s1p pack and give it a try just for kicks anyway.

I guess I'll have to get my hands on 4 more cells and build a 2nd set of savage packs then.

The kick in the pants is that a 4 cell devloper pack is $80 plus shipping and the 10 cell dewalt packs are only $100 plus shipping. But then I'll just have 6 spare... :019:

Quote:

Originally Posted by bdebde

jhautz,

Does that 1930/10 run cool in a buggy? I was thinking about trying one of those in mine.

I havent run it too much yet, but it seems good so far. Smaller and lighter, but still has plenty of torque. I couldnt tell a difference between the 1930 and the 1512 that I had in there. I ran a couple packs thought it on 5s while bashing in some rather tall grass and had some heat issues in the esc, not the motor. (Too be expected in grass taller than the wing:032: ) Then I also ran a couple 3s packs though it on the not quite finished yet track and it ran perfectly. Like I said, I started out trying to run 5s, then 4s and then 3s was almost what I was looking for power wise. I needed just a tick more speed and it would have been great.

So yes I think the 1930 is plenty of motor if your set it up right. I know that back in the day Mike used to run and e-maxx on a 1930 with pretty nice results. The 1930 sure is powerfull for its size. Much more powerfull than the old L can feigao I have around here.

Serum · 05.24.2007, 10:26 AM

zeropoint has got some graphs on his gmail picasaweb thingy..

jhautz · 05.24.2007, 12:13 PM

Quote:

Originally Posted by lydiasdad

I am running 6s1p a123 cells in my hyper 7 and am very happy with it. It uses a 9xl with 12/46 gearing and I get over 10 minutes of runtime. I was worried about the voltage drop when running a 1p setup but these cells have really impressed me. I have a thread about my hyper 7 conversion with pics and more info that may be useful to you.

Have you had any issues with heat in the cells? Just curious what ESC you are running also. With 6s the voltage would be higher so the currrent will be less than with the 4s I'm considering, but it sounds like you have had some decent results here. You are encouraging me to try it and at least see what I get.

lydiasdad · 05.25.2007, 12:01 PM

Heat is not an issue at all with the batteries. They have only been warm to the touch after each session. I am using a bk 7020 esc. I disagree with serum about them not performing well in a 1/8 vehicle. The vehicle the cells are used in is irrelevant. As long as the amp draw from the batteries is not excessive, they can work very well in a 1p configuration. That is why I used a low kv motor an 6s with conservative gearing, to keep the amp draw down. If I had a video camera I would post a vid of it, I think many people would be surprised at how much punch my buggy has. I would link to my hyper 7 thread if I knew how:005:

zeropointbug · 12:52 PM

I have plenty of experience with A123 cells, I was probably one of the first persons to have acquired some (release day, developer kits). 1p in a buggy is not enough, the voltage drop will be quite substantial. You will have to keep the amp draw below 70 amps to keep good voltage sustained. They can deliver lot's of power for their mAh rating indeed, but you have to design your pack to take into account voltage drop. You should design your battery pack first, then choose your motor.

I have a 5s2p A123 pack, under 100 amp 'spike' draw, the voltage is roughly 14volts.

Do you know what the expected amp draw will be?

01:15 PM

I can see how that Hyper 7 running the 1P setup with the 9XL might seem like it's doing ok. A 9XL running 12/46 in a buggy is kind of undergeared and probably isn't demanding much from the batteries. If you bumped that gearing up to around 16/46 (which is where I would run it), then I think the batts will start to sweat a bit in a 1P configuration. As I said, I ran the 5S1P setup in my 8ight T with the 9XL geared 16/46 and the batts got up to around 130* in about 5 minutes, which was how much runtime I got. Well, a bit more, but the batts heated up pretty quick.

I suppose it's all a matter of how you want to run. Knowing jhautz (having seen videos of his stuff and how he runs), I think I can safely say that the 1P config isn't going to work very well for him.

lydiasdad · 05.25.2007, 01:55 PM

Quote:

Originally Posted by AAngel

I can see how that Hyper 7 running the 1P setup with the 9XL might seem like it's doing ok. A 9XL running 12/46 in a buggy is kind of undergeared and probably isn't demanding much from the batteries. If you bumped that gearing up to around 16/46 (which is where I would run it), then I think the batts will start to sweat a bit in a 1P configuration. As I said, I ran the 5S1P setup in my 8ight T with the 9XL geared 16/46 and the batts got up to around 130* in about 5 minutes, which was how much runtime I got. Well, a bit more, but the batts heated up pretty quick.

I suppose it's all a matter of how you want to run. Knowing jhautz (having seen videos of his stuff and how he runs), I think I can safely say that the 1P config isn't going to work very well for him.

Might seem like it's doing ok? HA! I got to get a video camera.

bdebde · 05.25.2007, 03:23 PM

Quote:

Originally Posted by lydiasdad

Might seem like it's doing ok? HA! I got to get a video camera.

Then try a higher output lipo pack and SEE the difference!