A123 Cells
11-24-2006, 02:26 AM
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RE: A123 Cells
Hello,
just I try new battery A123 in own model Leviosa.
weight: 4970 g
accu: A123 10S2P 1530g
motor: Hirotex
prop: APC 22/12
time of flying: 9min.
just I try new battery A123 in own model Leviosa.
weight: 4970 g
accu: A123 10S2P 1530g
motor: Hirotex
prop: APC 22/12
time of flying: 9min.
11-27-2006, 06:09 AM
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RE: A123 Cells
I will step in to respond on Mach's behalf...
He uses the clasic DeWalt pack cells, i.e. 2300 cells in 10s2p
So far testing with 6 T HiRotex outrunner, but propped up (from 20x11 to 22x12)
Data logging to be done soon
So far quite a good impression (better than expected), good for 9 minute flights, Mach says "I would like to have some 5% of power more and it would be perfect".
The available power seems to stay constant or even feels like going slightly up throughout the flight.
Mach is experienced F3A competition pilot of many years, who used to fly all kinds of glow, gas, you name it, and he was the Czech electric F3A pioneer since 2003. He also manufactured the Rhapsody for Jason Shulman to fly at the WC in Poland.
Experiments will follow with a new version of HiRotex, also it would be nice to borrow the Hacker XL 12 for few flights.
Obviously the A123 is missing a bit in the Wh/kg parameter, but has 2 advantages: full charge in exactly 30 minutes, and maybe, just maybe, much longer cycle life compared to Lipo.
We surely hope that the technology may be developed a bit further.
He uses the clasic DeWalt pack cells, i.e. 2300 cells in 10s2p
So far testing with 6 T HiRotex outrunner, but propped up (from 20x11 to 22x12)
Data logging to be done soon
So far quite a good impression (better than expected), good for 9 minute flights, Mach says "I would like to have some 5% of power more and it would be perfect".
The available power seems to stay constant or even feels like going slightly up throughout the flight.
Mach is experienced F3A competition pilot of many years, who used to fly all kinds of glow, gas, you name it, and he was the Czech electric F3A pioneer since 2003. He also manufactured the Rhapsody for Jason Shulman to fly at the WC in Poland.
Experiments will follow with a new version of HiRotex, also it would be nice to borrow the Hacker XL 12 for few flights.
Obviously the A123 is missing a bit in the Wh/kg parameter, but has 2 advantages: full charge in exactly 30 minutes, and maybe, just maybe, much longer cycle life compared to Lipo.
We surely hope that the technology may be developed a bit further.
08-13-2007, 12:12 AM
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RE: A123 Cells
Hi Guys,
This is good info, I was looking for practical application in the A123 support thread elsewhere on this site, you mught take a look.
I figured an 11s2p arrangement would be the best because the cell won't hold 3.6v under load, I figured 3.3v nominal. That may cure the 5% power increase Mach is looking for, but at a weight gain of approx. 140gms.
This pack with wire and packing would weigh approx. 3.5lbs. Heavy, but doable if you can build really light.
I'm building a Black Magic v2.3, if it's light enough A123's may go in, we'll see...
But they sure have a lot of advantages over LiPo's, except for the weight to energy factor.
I'm listening and watching intently!!!
Gene
This is good info, I was looking for practical application in the A123 support thread elsewhere on this site, you mught take a look.
I figured an 11s2p arrangement would be the best because the cell won't hold 3.6v under load, I figured 3.3v nominal. That may cure the 5% power increase Mach is looking for, but at a weight gain of approx. 140gms.
This pack with wire and packing would weigh approx. 3.5lbs. Heavy, but doable if you can build really light.
I'm building a Black Magic v2.3, if it's light enough A123's may go in, we'll see...
But they sure have a lot of advantages over LiPo's, except for the weight to energy factor.
I'm listening and watching intently!!!
Gene
08-19-2007, 05:32 AM
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RE: A123 Cells
After some experimenting, mach has also gone to 11s2p and he reports that the power is very good. His new Leviosa is light enough to stay under 5 kg even with the 11s.
Considering the shorter sequences beginning from P09, I believe that the A123s may become a viable solution...
Considering the shorter sequences beginning from P09, I believe that the A123s may become a viable solution...
08-19-2007, 11:16 AM
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RE: A123 Cells
Hi David,
Your English is very good, you must be an American. I heard you were doing some airplane design for Hyperion, the name Helios comes to mind. Looking forward to seeing the parkflyer size.
Can you tell me what Mach is using to charge his giant packs with? Did he break them into smaller packs for easier charging.
Not many chargers here in the US can charge 11s in 1 pack at very high amps. A123's can be charged at 5c, which gives short charge time. 20 minute charge times at the flying field make multiple packs obsolete and cheaper flying.
More pics of his set-up would be nice too, if possible.
Thanks for your info and time David, it is greatly appreciated.
Gene
Your English is very good, you must be an American. I heard you were doing some airplane design for Hyperion, the name Helios comes to mind. Looking forward to seeing the parkflyer size.
Can you tell me what Mach is using to charge his giant packs with? Did he break them into smaller packs for easier charging.
Not many chargers here in the US can charge 11s in 1 pack at very high amps. A123's can be charged at 5c, which gives short charge time. 20 minute charge times at the flying field make multiple packs obsolete and cheaper flying.
More pics of his set-up would be nice too, if possible.
Thanks for your info and time David, it is greatly appreciated.
Gene
08-19-2007, 03:02 PM
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RE: A123 Cells
Hi Gene,
I am native born Czech, thanks for the compliment anyway ... :-)
Did you see the "fullsize" Helios already? If yes, do you have a photo or a link...? I have only made the drawings, but did not see the real thing yet..
We have a very good locally produced charger, the Tema "Power Cube", where you can set all the charging parameters manually... and the charging power is around 300 watts. Great product, never failed me during over 1000 cycles or so. When charging my F3A packs, I can go up to 7A into 10s lipo. Their site is here http://www.volweb.cz/tema_sro/ but no info in English :-(
I will make more pictures when I see Jaroslav Mach, next week I hope.
David
I am native born Czech, thanks for the compliment anyway ... :-)
Did you see the "fullsize" Helios already? If yes, do you have a photo or a link...? I have only made the drawings, but did not see the real thing yet..
We have a very good locally produced charger, the Tema "Power Cube", where you can set all the charging parameters manually... and the charging power is around 300 watts. Great product, never failed me during over 1000 cycles or so. When charging my F3A packs, I can go up to 7A into 10s lipo. Their site is here http://www.volweb.cz/tema_sro/ but no info in English :-(
I will make more pictures when I see Jaroslav Mach, next week I hope.
David
08-19-2007, 04:28 PM
#11
RE: A123 Cells
It surprises me how flyers in the US have dragged their feet concerning the A123 cells -
after trying them in my small electric pattern models -I see no reason why they are not viable for the 5 kilo models .
Some more ex pattern flyers are now trying em - friend Rojo is setting up a small model- and I am now doing a 6 cell one to uses as a kick around . Other local die hards using LiPos are now sticking their toes in the A123 water . The comments have been "I didn't think they worked that well " after seeing the little 4 cell stuff fly.
having done a regulation size model at well under 5K using new ZDZ40 F3A -(which worked very well) I guess I will take a crack at doing a A123 setup on a bigger model
a pack is $110 and If I don't care for the model -I can build other packs from the big ones - so far I set my ESCs for lowest cut off and go fly --when it quits -I recharge it
no harm- no fuss
personally I have no interest in the LiPo setups -- not after using the A123 .
Then again I am not actively flying competition models -just chasing my tail.
Charging is simple n easy - I use a NiCad charger and a Dapter -dual Dapters are also available
10 cells can also be charged directly from 3, 12 V wet cells (36volts)
after trying them in my small electric pattern models -I see no reason why they are not viable for the 5 kilo models .
Some more ex pattern flyers are now trying em - friend Rojo is setting up a small model- and I am now doing a 6 cell one to uses as a kick around . Other local die hards using LiPos are now sticking their toes in the A123 water . The comments have been "I didn't think they worked that well " after seeing the little 4 cell stuff fly.
having done a regulation size model at well under 5K using new ZDZ40 F3A -(which worked very well) I guess I will take a crack at doing a A123 setup on a bigger model
a pack is $110 and If I don't care for the model -I can build other packs from the big ones - so far I set my ESCs for lowest cut off and go fly --when it quits -I recharge it
no harm- no fuss
personally I have no interest in the LiPo setups -- not after using the A123 .
Then again I am not actively flying competition models -just chasing my tail.
Charging is simple n easy - I use a NiCad charger and a Dapter -dual Dapters are also available
10 cells can also be charged directly from 3, 12 V wet cells (36volts)
09-30-2007, 09:22 PM
#12
RE: A123 Cells
I'm a little new at this, so I hope the more knowledgeable posters here will cut me some slack, but I've been trying to figure out if electric is they way to go vs glow for pattern flying, and I've come to the following conclusions.
Li-Poly battery technology has inherent disadvantages when it comes to safety, reliability, cost, and charging time. Other than that they work fine. Flying in contests isn't much of a problem because of the time available between rounds to recharge the packs, but anyone who wants to head on out to the flying field and get some practice time in, has to charge as many packs as they expect to need, because charging at the spur of the moment at the field is a time consuming thing to do.
The answer seems to be with the new a123 packs, but they have disadvantages as well. Specifically, if you duplicate the 10s2p Li-Poly pack arrangement, you end up with at least 14 ounces more weight with an a123 pack vs with a Li-Poly pack. This is a big problem, because most 2m electric pattern planes are right at 5 kg, so there's no extra margin available to accomodate the extra weight.
Anyhow, I've done a little figuring and I've come up with the following table:
....................................Li-Poly......A123 #1.....A123 #2.....A123 #3
C-Rating...........................20............30. .............30.............30
Volts/cell..........................3.7...........3.3... ..........3.3............3.3
Cells in Series...................10............10......... .....11..............8
Packs in Parallel.................2..............2......... ......2...............2
Ah per Cell.......................2.5............2.3..... .......2.3.............2.3
Weight per Cell (kg)..........0.05...........0.07.........0.07.... .......0.07
Volts................................37........... .33.............36.3..........26.4
ma.hours.........................5000.........4600 ..........4600.........4600
Watts.............................1850.........227 7..........2505.........1822
Continuous Current......... ..50.............69..............69............69
Pack Weight (kg).............1.00..........1.40...........1.54 .........1.12
The first column shows a typical Li-Poly configuration. Column A123 #1 shows an A123 pack in a 10s2p configuration. Column A123 #2 shows an A123 pack in an 11s2p configuration which should generate voltage about equal to the Li-Poly configuration. This could be used as a direct replacement for a Li-Poly pack. Column A123 #3 shows an A123 pack in an 8s2p configuration. This pack would have lower voltage, but the weight would be almost as light as the Li-Poly pack, and the available wattage would be similar as well.
I'm thinking that this A123 #3 configuration would be absolutely perfect. The only problem is that it needs a new motor that will run at lower voltage, and draw more current. Does anyone know of a motor that work with this pack and output the kind of power needed for f3a pattern flying?
Li-Poly battery technology has inherent disadvantages when it comes to safety, reliability, cost, and charging time. Other than that they work fine. Flying in contests isn't much of a problem because of the time available between rounds to recharge the packs, but anyone who wants to head on out to the flying field and get some practice time in, has to charge as many packs as they expect to need, because charging at the spur of the moment at the field is a time consuming thing to do.
The answer seems to be with the new a123 packs, but they have disadvantages as well. Specifically, if you duplicate the 10s2p Li-Poly pack arrangement, you end up with at least 14 ounces more weight with an a123 pack vs with a Li-Poly pack. This is a big problem, because most 2m electric pattern planes are right at 5 kg, so there's no extra margin available to accomodate the extra weight.
Anyhow, I've done a little figuring and I've come up with the following table:
....................................Li-Poly......A123 #1.....A123 #2.....A123 #3
C-Rating...........................20............30. .............30.............30
Volts/cell..........................3.7...........3.3... ..........3.3............3.3
Cells in Series...................10............10......... .....11..............8
Packs in Parallel.................2..............2......... ......2...............2
Ah per Cell.......................2.5............2.3..... .......2.3.............2.3
Weight per Cell (kg)..........0.05...........0.07.........0.07.... .......0.07
Volts................................37........... .33.............36.3..........26.4
ma.hours.........................5000.........4600 ..........4600.........4600
Watts.............................1850.........227 7..........2505.........1822
Continuous Current......... ..50.............69..............69............69
Pack Weight (kg).............1.00..........1.40...........1.54 .........1.12
The first column shows a typical Li-Poly configuration. Column A123 #1 shows an A123 pack in a 10s2p configuration. Column A123 #2 shows an A123 pack in an 11s2p configuration which should generate voltage about equal to the Li-Poly configuration. This could be used as a direct replacement for a Li-Poly pack. Column A123 #3 shows an A123 pack in an 8s2p configuration. This pack would have lower voltage, but the weight would be almost as light as the Li-Poly pack, and the available wattage would be similar as well.
I'm thinking that this A123 #3 configuration would be absolutely perfect. The only problem is that it needs a new motor that will run at lower voltage, and draw more current. Does anyone know of a motor that work with this pack and output the kind of power needed for f3a pattern flying?
09-30-2007, 11:23 PM
#13
RE: A123 Cells
ORIGINAL: Brenner
I'm a little new at this, so I hope the more knowledgeable posters here will cut me some slack, but I've been trying to figure out if electric is they way to go vs glow for pattern flying, and I've come to the following conclusions.
Li-Poly battery technology has inherent disadvantages when it comes to safety, reliability, cost, and charging time. Other than that they work fine. Flying in contests isn't much of a problem because of the time available between rounds to recharge the packs, but anyone who wants to head on out to the flying field and get some practice time in, has to charge as many packs as they expect to need, because charging at the spur of the moment at the field is a time consuming thing to do.
The answer seems to be with the new a123 packs, but they have disadvantages as well. Specifically, if you duplicate the 10s2p Li-Poly pack arrangement, you end up with at least 14 ounces more weight with an a123 pack vs with a Li-Poly pack. This is a big problem, because most 2m electric pattern planes are right at 5 kg, so there's no extra margin available to accomodate the extra weight.
Anyhow, I've done a little figuring and I've come up with the following table:
....................................Li-Poly......A123 #1.....A123 #2.....A123 #3
C-Rating...........................20............30. .............30.............30
Volts/cell..........................3.7...........3.3... ..........3.3............3.3
Cells in Series...................10............10......... .....11..............8
Packs in Parallel.................2..............2......... ......2...............2
Ah per Cell.......................2.5............2.3..... .......2.3.............2.3
Weight per Cell (kg)..........0.05...........0.07.........0.07.... .......0.07
Volts................................37........... .33.............36.3..........26.4
ma.hours.........................5000.........4600 ..........4600.........4600
Watts.............................1850.........227 7..........2505.........1822
Continuous Current......... ..50.............69..............69............69
Pack Weight (kg).............1.00..........1.40...........1.54 .........1.12
The first column shows a typical Li-Poly configuration. Column A123 #1 shows an A123 pack in a 10s2p configuration. Column A123 #2 shows an A123 pack in an 11s2p configuration which should generate voltage about equal to the Li-Poly configuration. This could be used as a direct replacement for a Li-Poly pack. Column A123 #3 shows an A123 pack in an 8s2p configuration. This pack would have lower voltage, but the weight would be almost as light as the Li-Poly pack, and the available wattage would be similar as well.
I'm thinking that this A123 #3 configuration would be absolutely perfect. The only problem is that it needs a new motor that will run at lower voltage, and draw more current. Does anyone know of a motor that work with this pack and output the kind of power needed for f3a pattern flying?
I'm a little new at this, so I hope the more knowledgeable posters here will cut me some slack, but I've been trying to figure out if electric is they way to go vs glow for pattern flying, and I've come to the following conclusions.
Li-Poly battery technology has inherent disadvantages when it comes to safety, reliability, cost, and charging time. Other than that they work fine. Flying in contests isn't much of a problem because of the time available between rounds to recharge the packs, but anyone who wants to head on out to the flying field and get some practice time in, has to charge as many packs as they expect to need, because charging at the spur of the moment at the field is a time consuming thing to do.
The answer seems to be with the new a123 packs, but they have disadvantages as well. Specifically, if you duplicate the 10s2p Li-Poly pack arrangement, you end up with at least 14 ounces more weight with an a123 pack vs with a Li-Poly pack. This is a big problem, because most 2m electric pattern planes are right at 5 kg, so there's no extra margin available to accomodate the extra weight.
Anyhow, I've done a little figuring and I've come up with the following table:
....................................Li-Poly......A123 #1.....A123 #2.....A123 #3
C-Rating...........................20............30. .............30.............30
Volts/cell..........................3.7...........3.3... ..........3.3............3.3
Cells in Series...................10............10......... .....11..............8
Packs in Parallel.................2..............2......... ......2...............2
Ah per Cell.......................2.5............2.3..... .......2.3.............2.3
Weight per Cell (kg)..........0.05...........0.07.........0.07.... .......0.07
Volts................................37........... .33.............36.3..........26.4
ma.hours.........................5000.........4600 ..........4600.........4600
Watts.............................1850.........227 7..........2505.........1822
Continuous Current......... ..50.............69..............69............69
Pack Weight (kg).............1.00..........1.40...........1.54 .........1.12
The first column shows a typical Li-Poly configuration. Column A123 #1 shows an A123 pack in a 10s2p configuration. Column A123 #2 shows an A123 pack in an 11s2p configuration which should generate voltage about equal to the Li-Poly configuration. This could be used as a direct replacement for a Li-Poly pack. Column A123 #3 shows an A123 pack in an 8s2p configuration. This pack would have lower voltage, but the weight would be almost as light as the Li-Poly pack, and the available wattage would be similar as well.
I'm thinking that this A123 #3 configuration would be absolutely perfect. The only problem is that it needs a new motor that will run at lower voltage, and draw more current. Does anyone know of a motor that work with this pack and output the kind of power needed for f3a pattern flying?
Woodie
10-01-2007, 06:35 PM
#16
RE: A123 Cells
I'm looking at the 6350 Dualsky motor right now, and the only concern I have is the rated wattage capacity. The Dualsky website says that this motor can handle 2000W for no more than 15 seconds, whereas we'd need to be able to output at least 1825W continuously. This makes me concerned that this motor mght not swing a big enough prop at the needed speed to give the kind of thrust that's needed.
The Hacker motor looks interesting though. The C50 8XL has a gearbox with a 6.7:1 gear ratio, so the corrected kV rating is 2030/6.7 = 303. Also, this motor has a lower resistance so it would draw more current at the lower pack voltage, and the fact that this motor is still in the XL family implies that it's capable of delivering the same kind of power as the XL Hacker motors that f3a flyers usually use.
The Hacker motor looks interesting though. The C50 8XL has a gearbox with a 6.7:1 gear ratio, so the corrected kV rating is 2030/6.7 = 303. Also, this motor has a lower resistance so it would draw more current at the lower pack voltage, and the fact that this motor is still in the XL family implies that it's capable of delivering the same kind of power as the XL Hacker motors that f3a flyers usually use.
10-02-2007, 09:20 AM
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RE: A123 Cells
Hello.
A couple of comments:
1. A typical F3A 10s li-po pack weighs more than 1.0 kg. for 5Ah capacity. The TP Extreme 5000 weighs approx. 1200 grams, others may be even more.
2. Even if you use a faster spinning motor in combination with 8s 123's, you are carrying significantly less "fuel" than you do with 10s or 11s, so the flight times would have to be shorter. (Assuming that you are using the same power (i.e. watts). The amp. draw would be higher, and you would empty the packs quicker.)
3. If you by "continuous current" mean average current, then this will be significantly lower than 50A. 24-25A is more likely. (But max A may still be 75-80A)
Regards,
Magne
A couple of comments:
1. A typical F3A 10s li-po pack weighs more than 1.0 kg. for 5Ah capacity. The TP Extreme 5000 weighs approx. 1200 grams, others may be even more.
2. Even if you use a faster spinning motor in combination with 8s 123's, you are carrying significantly less "fuel" than you do with 10s or 11s, so the flight times would have to be shorter. (Assuming that you are using the same power (i.e. watts). The amp. draw would be higher, and you would empty the packs quicker.)
3. If you by "continuous current" mean average current, then this will be significantly lower than 50A. 24-25A is more likely. (But max A may still be 75-80A)
Regards,
Magne
10-02-2007, 10:31 AM
#19
RE: A123 Cells
Magne,
You are quite correct re the "fuel" quantity. Taking Brenner's figures the Lipos store around 18.5 WHrs and the A123s around 15.2 WHrs so about 80% of the lipos. BUT we normally have to leave 20% capacity in the lipos so as not to damage them whereas the A123s can tolerate full discharge so maybe not too dissimilar useable performance.
I think the move to shorter Preliminary schedules will also help those who want to experiment with alternative power supplies.
Malcoolm
You are quite correct re the "fuel" quantity. Taking Brenner's figures the Lipos store around 18.5 WHrs and the A123s around 15.2 WHrs so about 80% of the lipos. BUT we normally have to leave 20% capacity in the lipos so as not to damage them whereas the A123s can tolerate full discharge so maybe not too dissimilar useable performance.
I think the move to shorter Preliminary schedules will also help those who want to experiment with alternative power supplies.
Malcoolm
10-02-2007, 08:33 PM
#20
RE: A123 Cells
Malcom is right.
My thinking was that we could take more total energy percentage out of the A123s because they are are much more tolerant to abuse, and if you add this 20% margin to the energy available in the A123 pack, you start to get back to parity. One thing I hadn't considered though is the %discharge available as flights acumulate. I've heard that f3a flyers are replacing their Li-poly packs after 200 flights, and after this same number of flights the A123 packs are going to be down to about 85% capacity. The problem here is that Li-poly packs just lose performance, but you can still get an 8:30 minute flight in, but since we are now draining the A123 packs almost empty to make up for the capacity deficit our flights will start to get short as the packs age, and we will no longer be able to squeeze in full flights.
On another note, someone told me today that next year FAI is going to increase the max weight limit for 2 meter pattern planes from 11 to 12 lbs to accomodate the electrics. If this is true then we are back in business with the 11s2p replacement A123 pack. This would be an ideal situation for flyers that currently fly Li-poly packs because they can just substitute A123 packs for their Li-Poly packs, and go flying. Has anyone heard about this?
My thinking was that we could take more total energy percentage out of the A123s because they are are much more tolerant to abuse, and if you add this 20% margin to the energy available in the A123 pack, you start to get back to parity. One thing I hadn't considered though is the %discharge available as flights acumulate. I've heard that f3a flyers are replacing their Li-poly packs after 200 flights, and after this same number of flights the A123 packs are going to be down to about 85% capacity. The problem here is that Li-poly packs just lose performance, but you can still get an 8:30 minute flight in, but since we are now draining the A123 packs almost empty to make up for the capacity deficit our flights will start to get short as the packs age, and we will no longer be able to squeeze in full flights.
On another note, someone told me today that next year FAI is going to increase the max weight limit for 2 meter pattern planes from 11 to 12 lbs to accomodate the electrics. If this is true then we are back in business with the 11s2p replacement A123 pack. This would be an ideal situation for flyers that currently fly Li-poly packs because they can just substitute A123 packs for their Li-Poly packs, and go flying. Has anyone heard about this?
10-02-2007, 09:12 PM
#21
RE: A123 Cells
ORIGINAL: Brenner
On another note, someone told me today that next year FAI is going to increase the max weight limit for 2 meter pattern planes from 11 to 12 lbs to accomodate the electrics.
On another note, someone told me today that next year FAI is going to increase the max weight limit for 2 meter pattern planes from 11 to 12 lbs to accomodate the electrics.
This is not true, there is no weight change for 2008. Unless there is some emergency proposal, you wont see any further changes to F3A until 2012 believe....so we are stuck with 5kg until then.
10-03-2007, 01:27 AM
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RE: A123 Cells
after this same number of flights the A123 packs are going to be down to about 85% capacity. The problem here is that Li-poly packs just lose performance, but you can still get an 8:30 minute flight in, but since we are now draining the A123 packs almost empty to make up for the capacity deficit our flights will start to get short as the packs age, and we will no longer be able to squeeze in full flights.
I have never used A123 cells, so I can't comment on how they perform when they get old. (Don't know if anybody have experience with this yet, for our application.)
However, I often hear that people say that li-pos will loose capacity when they get old, and after such and such number of flights will be down to 85% capacity. My experience (after 4 year of electric 2m pattern flying) is that:
1. None of my packs have ever reached 200 flights
2. The real, usable capacity is not reduced. However, as you state, the packs just loose performance (voltage, which again results in reduced current). In reality, this performance/voltage reduction actually INCREASES available flight time, as I am not able to draw full power out of them. Typically I will discharge 4-4.2 Ah for a P07 flight from new batteries, while this may be down to 3,5 Ah or less for older packs, and the available power is noticably down, particularly when it is cold. (Which it is here, most of the time.)
Regards,
Magne
10-03-2007, 02:55 AM
#23
RE: A123 Cells
I'm afraid I posted in haste yesterday and did not calculate the theoretical energy storage in the packs correctly. I should have multiplied the figures by the number of cells so that the capacities become: Lipo 185 WHr and A123 121.6 WHr.
The premise that it isn't good to completely discharge the Lipos still holds and 20% reserve capacity for decent life seems to be the figure (have you been leaving this in Magne?) so the useable difference between Lipos and A123 is 185 x 0.8 = 148 WHr and 121.6 WHr which is less than 20% difference.
I still think this might be an option for the shorter schedules, I hope somebody tries it.
Malcolm
The premise that it isn't good to completely discharge the Lipos still holds and 20% reserve capacity for decent life seems to be the figure (have you been leaving this in Magne?) so the useable difference between Lipos and A123 is 185 x 0.8 = 148 WHr and 121.6 WHr which is less than 20% difference.
I still think this might be an option for the shorter schedules, I hope somebody tries it.
Malcolm
10-03-2007, 08:33 PM
#24
RE: A123 Cells
Ok, I've updated my table based on the information that you guys have given me, and it definitely looks like the 8s2p pack isn't going to be the cure-all answer. However, I've added two extra columns with two more options. The A123 #4 column shows a 9s2p pack which also doesn't seem to cut it because It still can't make an 8:00 minute flight before the pack goes dead. The A123 #5 column is the same 9s2p pack, but I've reduced the total energy consumed by 10%, and this seems to look like it might just make it, because I have more than 8 minutes of flight time. (not by much I'll admit..) and the weight of the pack is only 2 oz more than the Li-Poly pack.
With the right motor I'm speculating that this might work. The only way it could work though is if it's possible to limit the maximum motor current draw so that the total energy is reduced by say, 10-15%. If this is done by electronically limiting the motor current by programming the ESC, then the net effect would be to even out the performance of the pack from when it's new to when it's old, and if an old pack that's down by 15% in performance still works, then this pack should still work as well, at least up to the 15% degradation point.
What do you guys think? [img][/img]
With the right motor I'm speculating that this might work. The only way it could work though is if it's possible to limit the maximum motor current draw so that the total energy is reduced by say, 10-15%. If this is done by electronically limiting the motor current by programming the ESC, then the net effect would be to even out the performance of the pack from when it's new to when it's old, and if an old pack that's down by 15% in performance still works, then this pack should still work as well, at least up to the 15% degradation point.
What do you guys think? [img][/img]