REAL cost comparison between Turnigy and prismatic A123

[wojtek]

before starting, few notes:

1. this thread is NOT a discussion of which chemistry is better. We all know pros and cons of each. There are plenty threads talking about it.
2. I am a lipo fan! I am using polyquest and yuntong, started with zippy and turnigy. I also have a 50v20ah pack made of a123 prismatic cells.
3. My experience and knowledge is limited. 90% of my knowledge is reading this great ES forum. I need your help to make this comparison right.
4. This is only cost orientated comparison. If you want to shit how dangerous lipos are, or how heavy LIFEPO4 is, find another thread or open a new one.

====

To make a fair comparison I believe we should compare nano-tech with similar discharge rate as A123 prismatic cell.
I would suggest to make a comparison based on a popular sized battery pack like 48v20ah or so [there will be a slight difference of V due to different nominal voltage of each chemistry.
Few things to take into consideration in order of importancy
1. Price - both cells and a charger. Also for building a pack out of cells.
2. Life cycle. I do believe that lipos can have longer life cycle than in the specs if taken care properly. But then again, we could say the same about a123. so maybe we should just use the manufacturer's guidelines here?
3. Discharge characteristics: lipo should be used within 80% of the capacity, how about a123? can it be fully charged and discharged without unbalancing / life cycle impact? If so, then we have to make an adjustment - 20ah of a123 vs 16ah of lipo [20*80%] wont be fair. [this is also important when considering real power/ weight ratio in my opinion]
4. Faulty cells. Turnigy estimated % is around 10-15% - is it fair? Not sure about nano-tech though. When calculating the price however we should add 10-15% to the price of the cells.
I am sure original a123 bought from authorised source will have it close to 0%.

Anything that i am missing before calculating? also i cant find detailed specs of a123 cells [im sure i saw it once on the web..]

 

[Hillhater]

...I believe we should compare nano-tech.....
....4. Faulty cells. Turnigy estimated % is around 10-15% - is it fair? Not sure about nano-tech though. When calculating the price however we should add 10-15% to the price of the cells.

I am not sure that is true for the Nano tech Turnigys.
Who has the most experience with those to comment with authority ? ..LFP ?

 

[Xrain]

...I believe we should compare nano-tech.....
....4. Faulty cells. Turnigy estimated % is around 10-15% - is it fair? Not sure about nano-tech though. When calculating the price however we should add 10-15% to the price of the cells.

I am not sure that is true for the Nano tech Turnigys.
Who has the most experience with those to comment with authority ? ..LFP ?

I think 10-15% would be a safe "worst case" scenario.

I ordered around 72 of the 22.2V 20C 5ah Lipo's and we had around 2-3 dead cells and 6 weak total. Keep in mind these packs were abused, not broken in, and experience rather... "extreme" thermal situations.

 

[Hillhater]

That is the figure thrown out by some for the standard Turnigy packs.
As i said ... I am not sure the 10-15% is a fair comparison if using Nano-tech's

 

[Spacey]

Out of the 6 x 8 cell 5.8ah turnighy long packs, 3 of them arrived with seriously low volt cells. The lowest was 0.8v and always cell 8 for some reason.

Wishing I had gone A123 for easy charging. Interested in the outcome of this thread.

 

[theRealFury]

3. Discharge characteristics: lipo should be used within 80% of the capacity, how about a123? can it be fully charged and discharged without unbalancing / life cycle impact? If so, then we have to make an adjustment - 20ah of a123 vs 16ah of lipo [20*80%] wont be fair. [this is also important when considering real power/ weight ratio in my opinion]

Lipo can be charged to 100% (4.2v/cell) and can also be discharged to 100% DOD (~3.5v/cell) and this will not make it spontaniously combust. It just means that if you use the full 100% capacity from the cell then you will be looking at getting manufacturers specifications in terms of cycle life. These lipo cells are made for the RC world where LVC and low C rate discharge are unheard of, hence the low estimated cycle life. In reality in our e-bike / EV world these cells are treated really well and as such rarely get deep cycled and have low discharge rates as 90% of people use a C rate of 2-5C at the most. I have seen several people now with old Lipo battery packs that have undergone >1000 cycles and are still performing well.

1. Price

You probably already thought of this but to save you some time incase you didnt, dont forget to work out the cost of the charging solution as well, pricing up a similar powered charging solution for both chemistries would be good

EDIT: Edited several times for my bad spelling.

 

[wojtek]

thanks for the input - very good point about the charger!
In other question, how much ah can you draw from lets say 20ah of lipo pack and still have good life cycle and keep the packs well balanced - i know that going below certain V will unbalance cells.
Also i hear that there is not much left below 3.5V anyway. But to determine this is quite important from the cost perspective.
As said, i have no experience with HB packs, and with PQ i still had a lot of juice left at 3.5v.

3. Discharge characteristics: lipo should be used within 80% of the capacity, how about a123? can it be fully charged and discharged without unbalancing / life cycle impact? If so, then we have to make an adjustment - 20ah of a123 vs 16ah of lipo [20*80%] wont be fair. [this is also important when considering real power/ weight ratio in my opinion]

Lipo can be charged to 100% (4.2v/cell) and can also be discharged to 100% DOD (~3.5v/cell) and this will not make it spontaniously combust. It just means that if you use the full 100% capacity from the cell then you will be looking at getting manufacturers specifications in terms of cycle life. These lipo cells are made for the RC world where LVC and low C rate discharge are unheard of, hence the low estimated cycle life. In reality in our e-bike / EV world these cells are treated really well and as such rarely get deep cycled and have low discharge rates as 90% of people use a C rate of 2-5C at the most. I have seen several people now with old Lipo battery packs that have undergone >1000 cycles and are still performing well.

1. Price

You probably already thought of this but to save you some time incase you didnt, dont forget to work out the cost of the charging solution as well, pricing up a similar powered charging solution for both chemistries would be good

EDIT: Edited several times for my bad spelling.

 

[theRealFury]

In other question, how much ah can you draw from lets say 20ah of lipo pack and still have good life cycle and keep the packs well balanced - i know that going below certain V will unbalance cells.
Also i hear that there is not much left below 3.5V anyway. But to determine this is quite important from the cost perspective.
As said, i have no experience with HB packs, and with PQ i still had a lot of juice left at 3.5v.

well i have no experience with the big packs but in my limited RC experience with HK lipo at ~3.5v they are all but dead. perhaps 96-98% discharged and that last 2-4% power is the "lipo cliff" where voltage drops real quick.. basically not worth going below that point at all. as for useable AH to have good cycle life, from all my reading on lipo packs here on ES (and i have read almost every lipo thread on here no doubt) to get decent life (esitmated 600-1000 cycles) you would use no more than 17AH, thats with chargng to ~4.17v/cell and discharging to 3.6v/cell. If you wanted to really squeze as many cycles as possible from the packs then you would be looking at 15-16AH max and that would involve charging to ~4.10v/cell and only discharging to ~3.7v/cell (estimated 1000+ cycles, maybe 2000 maybe even 3000 no one really knows)

Very few people have got over 1000 cycles on a set of lipo packs so most of the above is speculation and educated guesses. Actually the only person i can think of that has got over 1000 cycles on a pack is i think liveforphysics. I remembered reading on someone else that was there or there abouts but cant remember who it was... might have been Dogman? Maybe they would be better suited to giving into on this subject if they have the time?

The problem with lipo is that the cell composition and quality had a bid effect on the nominal voltage and voltage over discharge curve so these figures above mey be correct for run of the mill turnigy packs but these figures would not be good for Nano Tech as i beleive that nano tech stays above 3.8v/cell until the bitter end. Not sure i would use nano tech as a comparison though as i beleive A123 are 30c constant and 50c pulse? this would be more in line with the 30c lipo (which i believe are 45c burst?)

 

[wojtek]

great stuff!

can anyone else confirm the following:
LIPO: real usage 17ah out of 20ah
A123: any ideas?

A123 prismatic cell vs Turnigy 30C is fair? Or we say that the higher quality of nano is better comparison to A123?
Not only about C rate but overall...

If so, i will update the initial post...

In other question, how much ah can you draw from lets say 20ah of lipo pack and still have good life cycle and keep the packs well balanced - i know that going below certain V will unbalance cells.
Also i hear that there is not much left below 3.5V anyway. But to determine this is quite important from the cost perspective.
As said, i have no experience with HB packs, and with PQ i still had a lot of juice left at 3.5v.

well i have no experience with the big packs but in my limited RC experience with HK lipo at ~3.5v they are all but dead. perhaps 96-98% discharged and that last 2-4% power is the "lipo cliff" where voltage drops real quick.. basically not worth going below that point at all. as for useable AH to have good cycle life, from all my reading on lipo packs here on ES (and i have read almost every lipo thread on here no doubt) to get decent life (esitmated 600-1000 cycles) you would use no more than 17AH, thats with chargng to ~4.17v/cell and discharging to 3.6v/cell. If you wanted to really squeze as many cycles as possible from the packs then you would be looking at 15-16AH max and that would involve charging to ~4.10v/cell and only discharging to ~3.7v/cell (estimated 1000+ cycles, maybe 2000 maybe even 3000 no one really knows)

Very few people have got over 1000 cycles on a set of lipo packs so most of the above is speculation and educated guesses. Actually the only person i can think of that has got over 1000 cycles on a pack is i think liveforphysics. I remembered reading on someone else that was there or there abouts but cant remember who it was... might have been Dogman? Maybe they would be better suited to giving into on this subject if they have the time?

The problem with lipo is that the cell composition and quality had a bid effect on the nominal voltage and voltage over discharge curve so these figures above mey be correct for run of the mill turnigy packs but these figures would not be good for Nano Tech as i beleive that nano tech stays above 3.8v/cell until the bitter end. Not sure i would use nano tech as a comparison though as i beleive A123 are 30c constant and 50c pulse? this would be more in line with the 30c lipo (which i believe are 45c burst?)

 

[neptronix]

great stuff!

can anyone else confirm the following:
LIPO: real usage 17ah out of 20ah
A123: any ideas?

Eh?

I can get the full rated AH, sometimes just a hair more, out of my lipo packs that are fully charged.
The reason i cycle them at about 90% is to extend their lifespans, that and i don't have a BMS, so i charge to 4.15v/cell currently and discharge to 3.4v/cell average.

If you had a BMS and wanted to use 100% of the lipo pack, you could do it.
It's not like you'd run the A123 without a BMS and expect 100% without providing bit of a buffer.

 

[neptronix]

i beleive that nano tech stays above 3.8v/cell until the bitter end. Not sure i would use nano tech as a comparison though as i beleive A123 are 30c constant and 50c pulse? this would be more in line with the 30c lipo (which i believe are 45c burst?)

I have heard this on the board multiple times, but nobody has produced any discharge graphs.
I have seen a few on rcgroups.com and the discharge curve looks exactly like regular turnigy 20c that i have.
Including the little ridge at the 4 volt mark.

http://www.rcgroups.com/forums/showthread.php?t=1302258

Compare to my graph of the turnigy 20C 5ah pack at ~8.5a discharge.

Just thought i'd point that out since i keep seeing that on here but no claims to back it up.

 

[MitchJi]

Hi,

4. Faulty cells. Turnigy estimated % is around 10-15% - is it fair? Not sure about nano-tech though. When calculating the price however we should add 10-15% to the price of the cells.

Its impossible to say if thats fair or not. Part of the problem is with their lack of quality control its a crap shoot. Its worth quite a bit to be sure the quality is good and that the seller will stand behind the product. So the question should probably be how much are those things worth to a given individual?

 

[wesnewell]

That is the figure thrown out by some for the standard Turnigy packs.
As i said ... I am not sure the 10-15% is a fair comparison if using Nano-tech's

Hmmm... I use 15C 5ah Zippy's. And I've had 0% bad cells. And none have gone bad in the short time I've had them. The charger I use most didn't cost anything. It came with the hub motor kit. So that's $114 total cost for 14s (51.8v nominal). I can balance with the HK-010 Power Analyzer ($19), so I didn't really need the expensive charger I bought. I guess for 20ah that would be about $500. So I don't think you should even consider bad cells unless you consider the fact that a lot of people have to send back lifepo4 packs for bad cells or bad bms's too.