plasticman

My Feedback: (97)

I found one of the tabs to fall off rather easy; this was out of three packs that I was building. I think what I will do is cover the tabs with electrical grade silicon. That should hopefully secure the tab and provide a little protection from vibration as my appliation is for a gas plane. I am using twin receiver packs with a Smart-Fly battshare for redundancy.

David

AmateurE

I have to concur with others regarding the tabs falling off. Out of the 4 VPX packs, 3 cells had the tabs fall off in my hand. The other cell was firmly welded.

Bob

thaus

My Feedback: (2)

With tab failure this frequent, how can anyone chose these cells to power their receivers?

coro_sk

When using BEC, it seems to be a problem. I plan using the cells in miniEllipse which I love, the risk of crash is strongly not welcome..
I will backup receiver power, probably, even if I have no tabs to fall off my M1A cells.

Anyway, You can solder to those cells, there is no problem EXCEPT A RISK OF DAMAGE to cell..
You have to be really as quick as possible, I mean half of a second. Then cool the cell terminal by wet sponge, immediately.
If not succesfull, let it cool down and try again later, never try to repeat immediately..

everydayflyer

I have read post of $4000 plus aerial video Helies being crashed due to poor welds on LiPoly tabs so what else is new?

My record:

A123 Racing /DeWalt 2300 mAh cells.
4 cell from A123 Racing and one had one dab weld. All of the Dewalt cells ahve been fine.
I have built
5-- 4S packs
4- 4S packs
1 -6S pack
2-3S packs
Total of 48 DeWalt cells in packs plus I have on hand a 10 cell brick , a 4S group and a 2S group , all welds checked for a grand total 64 Dewalt / A123 Racing cells. I also have one DeWalt that is unopended so welds unknown.

Each cell has 4 welds one each end so 8X64=512 welds with one bad one.

I have built 4- 4S packs from the B&D VPX packs and all welds have been fine.

Charles

coro_sk

Right now I am curious whether the single post appeared yet, about A123 M1A cell failing with open circuit, was the function of internal fuse going to open circuit, or perhaps failed tab, hopefully? I would be glad if it would be just the tab falling off..

Anyway, I will backup receiver power in my full mould electric powered glider. But I will let it be in small foamies.

And in addition, few small diodes hooked to balance port, may help bridging the open cell. Motor must cutoff immediately, but receiver and servo power may run thru balance port, bypassing open circuited cell thru diode, and use power of remaining cells. Diodes will be added to Cellshield-like DIY device. It just have to be avoided to reverse connection (it would burn diodes immediately).
And I dont expect troubles with powering just the receiver by 2s pack, as the currents are small compared to what electric motor consumes - but with tabs secured, or wires soldered to cells.

rmh

For the truly faint of heart and naysayers
(oddly enough ,those who never use anything till it's obsolete )
We offer the attached help

Lormuhl

Amen to that Dick. After following these 123 threads I had to build one pack and test them for myself. After much testing, to see it for myself I decided to convert. I have already converted my H9 Ultimate biplane, GP Ultimate, Aerowrks 90-120 Yak and soon will be converting my Aeroworks 100cc Yak to A123's. I have done away with my regs. Theses cells are fantastic. With all of the cells I have built so far, VPX packs and 2300's I have not experienced any bad welds to date.

rmh

Yeh - I beat the shi- out of my 2300s and the 1100 by using the 1100's in a big foamie -and ran em flat time after time after time and watched the voltage shifts balancing as recharge occurred on EACH cell (using CellPro 4 charger).
Funny thing --according to the charger and then the othe NON balancing charger - I did absolutely zero harm to the cells .
When I see comments about "excssive tab failure" - I can bet money - the writer has no experience whatsoever with these -or likely-- any cells.
Some hints for the totally uninitiated :
1. If you are going to build a pack - enlist the assistance of someone who has some experience in soldering wires to cells - these are all very easy to do but there are basics in doing ANY cell soldering
2 get a charger which does balance and displays each cell during charge and balance.
Tho this is not mandatory - it is awfully helpful in seeing what the heck actually occurs.
3. At the very least, get a inexpensive VOM (That's a Volt Ohm Meter) and read cell voltages
4. make a simple discharge device -from tail light bulbbs of'n an old Chev is fine (#1157) and wath voltage during discharge
good info - compare it with ANY/ALL other cells you use .
The A123 cells have a very flat discharge -read charts (If you understand what they represent ) and then see how your own setup compares . After all this is accomplished and absorbed --- Then publish comments about how well other cells compare to these, used for power and servo power.

Mr.Pibb

My tab failure was NOT due to anything I did. It was broken straight out of the package. I've not had any fail after the fact.
I've soldered directly to the cells a few times with no problems (including the one that the tab had fallen off of).

rmh

good show!
I bet the cell also works as well as the others
Y/N?
These are tough little buggers .

cyclops2

I switched from NIMH to DEWALT & B&D PVX. I never felt like I was risking anything just to fly. LIFE is good. Hey. Lithium Iron does mean LIFE.

I sold the 4 fire extingushers.

Rich

AmateurE

Just wanted to say I think these cells are excellent in my planes. I have been making 3S2P packs out of old laptop batteries for a long time so a 4S A123 1100 is a lot lighter and offers huge power benefits. What's not to like. The tabs falling off is just something you're going to have to check when you build your packs. While in their original VPX holder, I doubt one would see any failures when used in its intended tool as there is no opportunity for the tabs to move. The 3 out of 4 VPX packs that lost the tab came off with barely a touch of a finger. If the weld is going to fail, I'm sure you'll see it when you repace the original wiring. No big deal as soldering is quite easy.

Bob

dirtybird

My Feedback: (5)

I made up a 4 cell VPX pack for an electric I am flying. I had been charging it with a lab power supply with 3A max output. I set it to max to get a quick charge and went inside to check the NFL scores. I came back 20 minutes later to discover all 4 cells had been distroyed. Apparently one cell reached its maximum and shorted. The rest then went sort of like dominoes.
The good news is they did not explode and burn my house down. The cells were warm but not hot.
From now on I will set the power supply voltage for 3.6 volts/cell.
I had made the 4c pack to replace a 3cell LIPO. It was way too much. I would have yanked the wings off that little airplane. I will replace it with a 3c unit.
Has anyone tried to charge a 3c pack from a 12v lead acid battery directly? It seems the voltage ought to be about right.

everydayflyer

Been doing that with 3S 2300 mAh pack for some time now. Wire resistence would need to be higher ( longer length) IMO for these smaller cells as I do not really think 20 plus amps would be to good for them.

http://www.rcuniverse.com/forum/m_6477096/tm.htm

Charles

flipflop

Here's a shot of my Hacker A20 powered Mini-Tiburon bipe with the VPX cells. Ten minutes of assorted aerobatics, hovering, and a lot of just flying around about 2 feet high used only 580mah. All up weight is 9.9oz. No more waiting 2.5 hours to charge a lipo for me. The A123 batteries have definitely put the fun back in flying electrics.

pcpacker

I am excited to find this new thread, but also a little disappointed. I just purchased two lipos from united hobbies and they haven't come yet. I would like to get into these 123s for the safety
and because the power seems to not "drop off" like it does with lipos.

I need to know a couple of things if you all don't mind sharing. Where can I buy the balancing leads and do you crimp those on? Also, I need to purchase the shrink wrap for the pack. Where can I find that?

Lastly, if I build a 3 cell 1100, how does this compare to a lipo in the following ways. Charge rate is 1C or 2C? Discharge rate is 20C? What shut off voltage should I select on my ESC?

Thanks for your help!

everydayflyer

Balancing leads depends on charger/balancer being used. A123 Racing sells their's.
I use Poly Quest / Hyperion ones mostly. Cheap Battery packs.Com sells, balancing leads, high grade super flex wire,heat shrink(e-mail them for size you need),and connectors.

Charge at 5A (approx 5C) .20A. cont. burst to 30A plus no problem. I use 2V per cell or auto Ni setting.
Note: When they show signs of the power droping they are empty. Setting the LVC higher does not really work / help.

Two points, They are heavier than similar capacity LiPolys and the have lower voltage.

They make up for this with ability to be discharged 100% without damage,deliver very high discharge without damage,fast charge without damage and great life expectancy and they are tuff as nails.

I have used a 4S 1100 B&D pack to replace 3S Thunder Power Pro Lite 1320 in some of my Foamies. 3S TP PL 3.2 oz. / 4S B&D (VPX ) 6.4oz. . VPX more volts under load equals more power ,more amps. . Flight times same with both.

Charles

dirtybird

My Feedback: (5)

I am thinking of quick charging my 3c 1000 pack from a 12V lead acid battery with two silicon diodes in series with the battery. That should drop the voltage to about 10.6V and keep from ruining the pack. That is if I can find suitable diodes.
Has anyone tried that?

everydayflyer

First of two diodes will drop approx. 0.7V each (1.4V) which is the 12V Pb has a good charge will be closer to 12.6 so 12.6-1.4=11.2 which would be fine but when the 12V drops to 12.2 or less then the charged to (pack) voltage will be lower and it will take much longer per charge.

There is a very good reason I use the Zip line. It is cheap,readably and works extremely well.
Charles

rmh

With your background in electricity/electronics --
why not build yerself a lashup of some 1157 bulbs -(your choice as to how many ) and use em to charge /discharge the A123 packs and monitor the amperage /voltage changes as yo go -
they waste power -but any resistor charger setup wastes power.
Obviously the setup shown is a discharge setup - but IF--you used 3 cells and then hit the whole mess with a 12 jolt acid battery - the bulbs could reduce power to the A123 pack
the bulbs were designed to handle 12 volts -- just add some switches to add/subtract bulbs from the circuit as desired. Thenice thing?
yo can SEE what is going on.

dirtybird

My Feedback: (5)

It is my understanding the charge voltage should be held to 3.6V/cell. Are you saying they can handle more than that?

dirtybird

My Feedback: (5)

If I can dredge up the ambition somewhere I might give it a try. It sounds like a good idea.

everydayflyer

3.6 per cell is the recomended charge to voltage for maximum life. They can be charged to 4.2 per cell. They hold no real capacity past 3.6 per cell. If you fast charge to 3.6 per cell and stop thre charge they are not really full as there was no CV stage. Charging in the tapering qusia CC stage to a higher voltage makes up for the lack of a CV stage.


Post from my Zip charging Thread

http://www.rcuniverse.com/forum/fb.asp?m=6477096

See second attachment . Note Max voltage in legend on left hand side which is 12.42 volts.
This is a 3S 2300 mAh pack which has been to that level many times and now has 266 flights on it and it has lost only 6% capacity.

Note : 1100 mAh cells should not be charged at thishigh of an amp. rate.


Charles

Max1965

Just wondering something.
Could these 1100mah cells be used as "splits" along with the 2300mah cells? I am thinking along the line of running a 4s1p 2300mah pack with a 2s 1100mah pack in parallel..... Any idea if this would work and what would be the gain in flying time? Right now I am flying about 5 minutes full out on a 2300mah 4s1p pack but I have enough room in the plane for an additional 2s 1100mah pack and any extra flight time would be nice.

Inquiring minds?