Gigaah

Well my PC Powersupply took a dump on me and blew the breaker in my house. So testing is currently suspended Untill I get a new one. I have a RC10B3 RC buggy on the way I'll try them out in as well. I believe currently the only real RC market for the cells would be cars..if any at all.
I posted trying to find a more suitable charging unit. If not I'll probably just put a timer on it to remind me to manually terminate the charge. The cells seemed to be holding up(20 charges) even CCCV'n to 4.1v but I'm sure it'll shorten the life of the cell. As stated the capacity seems to be going up even.
Hopfully someone else has the ability to test the cells better. I'd even be willing to maybe send a cell out to someone that I could be certain could do the job and would. Maybe a MOD recommended person?

Red Scholefield

My Feedback: (9)

I have been testing the A123 2300 mAh cells, 10C (23 Amps) discharge gets them to 57C (135F) with about 2100 mAh delivered at an average voltage of 2.8 volts. They hold fairly steady at this level for a significant portion of the discharge. I hate to think of how hot they will get at the claimed 70 Amp continuous discharge the are supposed to be capable of. Except for cycle life (unconfirmed) from my first tests I don't see these as the miracle we have been hoping for. They are not compatible with any lithium charges presently on the hobby market. Cut off voltage in flight use could also pose a problem unless you have a programmable ESC. I'm looking at using a 4S pack with about the same capability as a standard 3S LiPo pack.

These cells do have a one shot vent system to prevent them from blowing in an over pressure situation. Actual worse case scenarios have yet to be defined.

Gigaah

Thanks for the info man. Well They say 70A(they actually claimed 80A awhile back). However they only show on thier own dishcarge charts up to 40 holding about 2.6-2.7v. So I'd guess that 40A is safe(17C). I think the site said operating temp of +60C...now is that ambient temp or cell temp?

I'm curious if you plan on cycling the cell at 50-70A(if you are capable) to see the durability and such. As the only real redeeming quality I see on the cells is the flat voltage over capacity and perhaps the Amperage handling. We already know the voltage is flakey. But you can charge them rapidly..I guess thats nice.

If the cells were just 3.6v(cccv 4.1/4.2) they would be a whole lot more usefull.

Red Scholefield

My Feedback: (9)

At this time the I am limited to around 100 watt discharge, which would not allow me to go much over 33 amps on one cell. I'm going to try at 40 Amps just to see if the CBA-II can handle it, knowing the voltage is going to be down a bit below 2.8 volts for most of the discharge.

Stay tuned.

Meanwhile I'm waiting for the 500 watt discharge unit Mountain Models is suppose to be coming out with. With that we can separate the sheep from the goats pretty fast. People making 20C continuous claims better head for cover![>:]

duanes

FINALLY - I got my pack! The condition is identical to the first unit pictured here. I am getting identical results - about 2300 mah initially and moving up after a few cycles. I am using a Graupner Duo 30 charger and it works great on Li-Ion settings - except. When discharging, I set the cutoff at 2.5v. When charging, the Graupner does not like to have the voltage stay below 3v/cell for more than the first three minutes, or it complains. To work around, I did the manual charging at 5amps for a few minutes and the voltage builds back to about 3v in 3-4 minutes. Then I switched to the Li-Ion auto charging. The cutoff is 3.6 v/cell and matches that found on the a123systems.com spec sheet.

I did notice that the solder tab between cells 5 and 6 is significantly lighter than the others - looks like a fuse type function. I am putting together a high amp sink assembly (light bulbs) to test 40C and higher drain.

I did think of a good use.... Since they can peak at very high drain, I am going to try putting them on my starter (4S).

duanes

I tried it out - and this works pretty good!

I have a Sullivan UltraTork Starter (The big 24v job). It works well with 4S, but much better on 6S. The pack us pretty ugly right now, as it is just taped to the back end of the starter. The added weight is a lot less than the big Nicad packs that are normally used. The 4S is slightly lower powered than using a lawn mower battery that is normally powering my field box.

I am also going to try a 5S2P to run the entire field box. This is MUCH lighter than the lead acid battery that is normally there. I'm interested to see how this holds up on a day of flying. As an interesting side - I wired a 12v and a 6v lead acid in series and used it to directly charge the a123. The pack charged very quickly as the initial amp draw was around 50-60 amps for about 3 minutes and dropped down quickly as the voltage built up. After a 5 minute charge, I tested the pack and got > 4000 mah out of the 5S2P. The pack did warm, but was still easily held in the hand.

Here is the best advantage I have found of these cells - rapid recharging!

duanes

BTW: I used 30" of 14 guage speaker wire for connect the a123's to the lead acid batteries. I suspect that the resistance prevented a HUGE initial current. The 14 Gauge wire did get hot where the alligator clips were attached, but the temp cooled pretty quickly after the first 45 seconds or so. At the end of the charge they were definately hot to the touch but not hot enough to burn

TRY THIS AT YOUR OWN RISK ! I don't want to get flamed if someone ends up with a Radio Shack logo burned into their finger tips.

iamscottym

I work for a tool company, and have had the chance to do a lot of testing with the new liion tools out- bosch, milwaukee, and dewalt. I dont have the test specs on dewalt, nor can I give out my company's cells' specs..but I can tell you this. If you start discharging any of these cells above about 10C, you're going to kill cycle life. I currently use 3.6 1000mah, 1100mah, and 1300mah cells(1300 not out yet in tools- testing phase) from our tools in rc cars, and have been looking into putting liions in a magister(see my thread under trainers). I've crunched the numbers, and quite frankly, if you dont get liions free, they're not worth it. Sure in cars they're sweet- but finding room for all the cells is a pain. However, in planes its just not worth it. While they are lighter per watt hour than nimh(about 50% lighter), lipo are 200% lighter, and have much better power(P=iV)/weight ratios.

Red Scholefield

My Feedback: (9)

" However, in planes its just not worth it."

My, what a shock! Here are a couple that seem to be enjoying A123 packs 4S2P.

iamscottym

I didnt say it would work. However, since several people are claiming high current draws are possible..I'm gonna test a bunch of cells. If indeed these cells can put out 10-15C, then they're right up there with lipos. However, since the rest of you have to buy tool batteries or whatever to get the good cells- since companies are buying up the supply just for their products..they're not THAT great a deal:for instance, bosch litheon tools use a 1.0Ah cell..the best way to get them is their new liteon 36V..around 180 for the pack, 20 cells. so 9 bucks a cell. A 3s4p pack, ie: 10.8V (liion are 3.6V/cell) 4Ah..aka 12 cells, will set you back 108 bucks. However, it will weigh in at 18.4 ounces. Compare that with 9.14 ounces for a 3s2p 4Ah thunder power pack(which however is 150 bucks). Nimh however, say a 9s1p pack of 4300's..10.8V, 4.3Ah...comes in at 20 ounces, but its only 50 bucks. Plus, it can crank 30+A and still maintain 1.2V/cell. To me, that doesnt make liion seem like a hell of a deal.

However, I have some 1.1Ah's from dremel stylus's, and new 1.3 Ah's that will be going into the dremel 10.8V(not out yet- not till around january), and bosch will also offer the 1.3Ah's in an upgraded pack(similar to the current nicd's, where they sell 2.0Ah and 2.4Ah)..for a little more money. Since the cells weigh the same as the 1 Ah's..they start to catch up on lipo some. Now a 3s3p pack is still 3.9Ah..but weights 4.6 ounces less than a 4Ah pack of 1Ah's.- coming in at 13.8 ounces. Granted, for super high performance lipos still have the upper hand- but for those who want more than nimh, but dont want the expense(and danger) of lipos, liions are alright. That is of course, assuming liions can put out more than the rated 8C.


Red- can you tell me whose's tools those cells are from? Also, how many Ah's, and weight please.

Scott

Holger

Hello Scott,

You will find the manufacturer and the specs, if You use the two links of the first post of this thread!

Red wrote (6/22/2006 1:00:09 AM): Holger

engleswing

Just go to A123systms website. They give you all the tech. info. they are 3.3v cell that don't incinerate or explode.

PlaneKrazee

My Feedback: (14)

Are these batteries any better than lipo cells or should we just stick to lipo now that they are up to 20 tro 25C discharge?

Red Scholefield

My Feedback: (9)

LiPos discharged at the 20C rate will not even come close to A123 cells discharged at that rate.

PlaneKrazee

My Feedback: (14)

Hello Red,

Would you recommend these cellls over nicad or nimh cells? WHat charger would you use?