SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Jul 02, 2006, 10:00 AM
Registered User
Joined Jan 2002
6,588 Posts
Thanks, Brad -

Re longevity, I'll have the resuts of 10 Cycles later today, charging @ 10 amps and discharging @ 60.

After I'm done with that (if Austin approves - it's MaxAmps' cell), what would you like me to do to try and blow it up?

- RD
RD Blakeslee is offline Find More Posts by RD Blakeslee
Reply With Quote
Sign up now
to remove ads between posts
Old Jul 02, 2006, 10:26 AM
HammerHead H2o Racing
Deltona, Florida
Joined Jun 2006
19 Posts
Quote:
Originally Posted by bjpaul
Thank you RD for the testing.

- Cycle life.... remaims to be seen at +20C but local RC boat racers here in Florida love the A123's. They usually have to throw away a Nimh pack (GP or IB cells) after around 10 cycles to remain competative. They have yet to see the need to toss a A123 pack.

Brad
Brad,

as you know, we run "SAWS" 1/16th mile straightline FE Time Trials for r/c boat [world speed records] in a number of classes, I.M.P.B.A. and NAMBA...

often our set-ups draw 100-120 amps cont. with spikes i don't want to think about let alone admit on a public forum...

under current I.M.P.B.A. and NAMBA FE rules, we are required to run sub-c's batteries of any chemistry and in T/T [time trials] we do punish them!

after 10 to 15 cycles under these conditions we don't automatically toss them...

if they haven't vented, melted, or shorted, we put them in our [test and sport pack] battery box for future reference...

we are very pleased with the a123 Li-Ion M1 cells in our r/c boat testing so far as compared to the IB and GP sub-c cells we normally run...

in Aug. we'll put them to the real [no-excuses] tests at the I.M.P.B.A. T/T lake in Valdosta, Ga. using I.M.P.B.A. timing equipment running them one to one against [equal voltage sub-c's] thru the lights in three of our current record holding r/c boats...

we'll see what the time slips say...

Ron
waterdog49 is offline Find More Posts by waterdog49
Reply With Quote
Old Jul 02, 2006, 10:44 AM
Suspended Account
USA, FL, Apopka
Joined Dec 2000
4,072 Posts
Ron, thanks for clarifying that, my information was second hand......

Do you guys build your own packs, or did A123 supply pre built packs? I'm asking as it is my understanding that the A123 cells have the vent in the center of the button terminal, so it will be very very difficult to end to end soldier these cells.

Conventional wisdom is that spot welded tabs are not able to handle high amps.... but if you guys are putting +100 amps through the spot welded tabs, I guess that puts that concern to rest.

Brad
bradpaul is offline Find More Posts by bradpaul
Reply With Quote  (Disabled)
Old Jul 02, 2006, 11:05 AM
HammerHead H2o Racing
Deltona, Florida
Joined Jun 2006
19 Posts
tabs

the first test cells we got from a123 came in made up packs [2s, 6s, and 10s] with tabs...

we now get single cells [w/tabs] and make up our own packs using the welded tabs...

as you say, end to end soldering is not an option because of the vent...

the tabs are holding up just fine so far and usually run around 4-6 degrees hotter than the cells after a test run...

the hottest we've managed to get any of our a123 test packs so far has been 131 degrees and that was after a four min. test run in an offshore mono on an "M" course with left and right hand turn bouys...

same boat, same conditions, same course, our sub-c test packs came out at 200-210 degrees...

Ron
waterdog49 is offline Find More Posts by waterdog49
Reply With Quote
Old Jul 02, 2006, 02:04 PM
Registered User
Joined Jan 2002
6,588 Posts
The applications sheet that comes with the A 123 testing kit specifies max. tab amperage as 100 amps continuous.

- RD
RD Blakeslee is offline Find More Posts by RD Blakeslee
Last edited by RD Blakeslee; Jul 03, 2006 at 07:55 AM. Reason: typo
Reply With Quote
Old Jul 02, 2006, 09:01 PM
Registered User
Joined Jan 2002
6,588 Posts
10A charge, 16C discharge, 5 cycles

Manufacturer's recomended maximum temperature is 70C, which is reached @ ~37A continuous discharge (~16C).
Charging was @ 3.8 volts, the recommended maximum.
Charging time was ~ 20 minutes.

The first cycle displayed a larger voltage dip than the others, but capacity was not affected. Apparently the cell was adapting to the 10A charging rate.

The cell heats up about 5 degrees C during charging and has to be allowed to cool to ambient before discharge. That, combined with the cooling needed before recharging and the fact that this cylindrical cell does not cool as fast as a flat LiPo cell, causes overall time per cycle to be about the same as for a LiPo, so the manufacturer's specified absolute maximum charge voltage and temperature cycles will have to wait until tomorrow.

- RD
RD Blakeslee is offline Find More Posts by RD Blakeslee
Reply With Quote
Old Jul 03, 2006, 05:08 AM
Giz
Tony Rogers
Giz's Avatar
Bath, UK
Joined Sep 2003
2,194 Posts
Quote:
Originally Posted by RD Blakeslee
Thanks, Brad -

Re longevity, I'll have the resuts of 10 Cycles later today, charging @ 10 amps and discharging @ 60.

After I'm done with that (if Austin approves - it's MaxAmps' cell), what would you like me to do to try and blow it up?

- RD
I would like you to charge them using a profile similar to that on LiPo/Li/Ion chargers. i.e. up to 4.1 volts (then 4.2 volts if that is okay) to clear up the discussion of whether they are damaged by charging to these voltages.

I didn't see what voltage you were charging to so you may already be doing this. If cycle life is not affected by a normal li/ion or lipo charge, that would make life considerably easier for many with ordinary chargers.
Giz is online now Find More Posts by Giz
Reply With Quote
Old Jul 03, 2006, 07:44 AM
Registered User
Joined Jan 2002
6,588 Posts
Giz,

Charging yesterday was at the manufacturer's recommended voltage for fast charging (3.8 volts. Post #21).

The maufacturer's specified absolute maximum charging voltage is 4.2, which I'm doing @ 10 amps today. I'll hold the discharge down to 16C, so the temperature won't exceed the recommended maximum and we can separate adverse charging effects (if any) from adverse high temperature effects. I hope I can get 10 cycles done - the cell heats up during fast charging, unlike a LiPo, and cooling time has to be taken after charging as well as after discharging in each cycle.

Later, ten discharges @ 26C will be done to see how much the cell's capacity degrades when discharged to the manufacturer's specified absolute maximum temperature limit.

Apparently charging or discharging in excess of the absolute limits would be required to destroy the cell.

- RD
RD Blakeslee is offline Find More Posts by RD Blakeslee
Reply With Quote
Old Jul 03, 2006, 08:49 AM
Giz
Tony Rogers
Giz's Avatar
Bath, UK
Joined Sep 2003
2,194 Posts
Great. I'll look forward to your results.
Giz is online now Find More Posts by Giz
Reply With Quote
Old Jul 03, 2006, 12:30 PM
Vic and Quinn Walton
rc2xs's Avatar
Santa Barbara CA
Joined Jan 2006
590 Posts
wow this is veyr interesting I can deffinatly see the possibilities of these cells in larger planes. I look forward to seeing more discharge information form you RD
rc2xs is offline Find More Posts by rc2xs
Reply With Quote
Old Jul 03, 2006, 01:58 PM
Suspended Account
USA, FL, Apopka
Joined Dec 2000
4,072 Posts
In the old days of Nicads, I used a cooling tube while charging. With sub C Nimh it became clear that they that worked best hot. And Lipos are in the battery bunker while charging. So for me the cooling tube became obsolete. Looks like with the A123's I may need to find where I stored the cooling tube.

It might be interesting to see after you have completed your cycle runs to see what effect running hot off the charger has on holding discharge voltage.

Brad
bradpaul is offline Find More Posts by bradpaul
Reply With Quote  (Disabled)
Old Jul 03, 2006, 07:41 PM
Registered User
Joined Jan 2002
6,588 Posts
The manufacturerís specified maximum allowable charge routine is CC/CV 4.2V @ 10A for 15 minutes; 100% charge is said to be obtained.

Running this routine produced charger shift from amp to voltage control @ 12 minutes. The amperage had dropped to .9 @ 15 minutes, when the cell was disconnected from the charger. The cellís voltage @ disconnect was ~4.1, dropping to 3.82 in 15 minutes, 3.75 in one hour. The voltages varied somewhat, due to variations in the cellís voltage at the 15-minute mark and variations in time to cool after charging and before graphing. Note the relatively large voltage drop in the first discharge, where the cell was allowed to rest for an hour after charging. Charging temperature delta was about +9C.

This routine can be done on a standard LiPo charger, provided the CV phase is terminated @ 15 minutes from start of charging.

- RD
RD Blakeslee is offline Find More Posts by RD Blakeslee
Reply With Quote
Old Jul 03, 2006, 08:09 PM
Boffin
rpage53's Avatar
Victoria, BC, Canada
Joined Apr 2001
3,400 Posts
Is there anyway you can post a charge graph with temperature? The boaters have reported that cells vent when charged to 4.2V, but I suspect they must keep them on the charger too long. Of course, having to manually terminate the charge is a recipe for disaster too.

Thanks,
Rick.
rpage53 is offline Find More Posts by rpage53
Reply With Quote
Old Jul 03, 2006, 08:22 PM
Registered User
Huntington Beach, CA
Joined Dec 2004
481 Posts
Wow, the cell did its best on the 10th discharge! Does that mean that the cell has a "break-in" period, or does it need to adjust to the demands being put on it?
TMetalMan is offline Find More Posts by TMetalMan
Reply With Quote
Old Jul 03, 2006, 09:07 PM
Suspended Account
USA, FL, Apopka
Joined Dec 2000
4,072 Posts
Great work RD! You answered my question in that warm off the charger they seem to hold voltage across the complete discharge. About 2000 mah of useable capacity at 2.65v pulling 37 amps .......... with a 15 minute recharge!

Now if A123 could develop a 3500mah cell that would deliver 16C continuous and keep the weight around 100 g almost any nitro/gas plane or helicopter could be converted to electric without taking out a second mortgage for Lipo's.

Brad
bradpaul is offline Find More Posts by bradpaul
Reply With Quote  (Disabled)
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion A123 is introducing li-ion battery packs for R/C cart213 Batteries and Chargers 82 Aug 02, 2006 11:17 PM
Discussion Apex 2100 15C, CBA/10X Amp. Graph RD Blakeslee Batteries and Chargers 12 Jul 27, 2006 12:01 AM
Discussion Enerland 2100 20C CBA/10X Amp Graph RD Blakeslee Batteries and Chargers 0 Jun 19, 2006 11:29 PM
Discussion DN Power 2100 20C, CBA/10X Amp Graph RD Blakeslee Batteries and Chargers 0 Jun 18, 2006 09:35 PM
FS: Li-ion 1350mah pack & Batt. Amer. QN-012DC Charger sgil2001 Aircraft - Electric - Airplanes (FS/W) 0 Dec 27, 2003 08:41 PM