a123 Prisimatics vs HobbyKing Lipo

[neptronix]

C rate does matter. It means that the cells perform better even at lower discharge rates. If i run my cells at 10C constant, they perform horribly even though they are way under spec. They just get warm and turn battery charge into heat.
It adds up if you are using smaller packs, like for example if you wanted to drag race etc.

I have heard of people retiring their lipo packs at 600 cycles if treated well.
In regards to that, i worry about calendar life more than cycle life since i am a fair weather ebiker and not a daily rider. Thus, A123 makes no sense to me, other than for the safety factor.

[EBJ]

Where can you currently buy genuine A123 , 20Ahr pouches ?

x2

[jonathanm]

This thread confirms my current thoughts - as a tinkerer, LiPo is fun and exciting, if I was building anything commercially, or even building something for a not technical friend, it's probably not the way to go......yet.

[EBJ]

This thread confirms my current thoughts - as a tinkerer, LiPo is fun and exciting, if I was building anything commercially, or even building something for a not technical friend, it's probably not the way to go......yet.

I would say it depends on the product being sold. If it's advertised as High-performance and it's dangerous to begin with, then i don't see a problem w/ using lipos.
Example: Extreme electric dirtbike
Some things have an inherent risk, I think it's just that most people don't associate "electric bicycles" as a risky sport. If it was turned into an "extreme" sport, then I'm sure we would see more being sold with Lipos. *and a million warning stickers all over it. haha.

[jonathanm]

I would say it depends on the product being sold. If it's advertised as High-performance and it's dangerous to begin with, then i don't see a problem w/ using lipos.
Example: Extreme electric dirtbike
Some things have an inherent risk, I think it's just that most people don't associate "electric bicycles" as a risky sport. If it was turned into an "extreme" sport, then I'm sure we would see more being sold with Lipos. *and a million warning stickers all over it. haha.

Well that's true enough......I can just imagine selling high powered lipo dirt bikes and my lawyers and investors making customers sign a 10 page disclaimer at time of purchase, lol. A motocross bike or a rice rocket is a pretty dangerous thing and they sell plenty of them......but having said that they are only dangerous through human intervention.....the LiPo can be dangerous through *lack* of human intervention....big difference......

[EBJ]

I would say it depends on the product being sold. If it's advertised as High-performance and it's dangerous to begin with, then i don't see a problem w/ using lipos.
Example: Extreme electric dirtbike
Some things have an inherent risk, I think it's just that most people don't associate "electric bicycles" as a risky sport. If it was turned into an "extreme" sport, then I'm sure we would see more being sold with Lipos. *and a million warning stickers all over it. haha.

Well that's true enough......I can just imagine selling high powered lipo dirt bikes and my lawyers and investors making customers sign a 10 page disclaimer at time of purchase, lol. A motocross bike or a rice rocket is a pretty dangerous thing and they sell plenty of them......but having said that they are only dangerous through human intervention.....the LiPo can be dangerous through *lack* of human intervention....big difference......

With things like Gary's ONE-PLUG charging using the Hyperion charger, LVC's that cut throttle inputs and Alarm out, and fire-proof bags for safety, Lipo's become much harder to "mess-up" and much more simple to use. I imagine in such a situation manufacturer defects could be the only thing to worry about. "just follow the rules and no one gets hurt"

[jimw1960]

Where can you currently buy genuine A123 , 20Ahr pouches ?

x2

If you want pristine cells, a123rc.com was a reliable source for a good price from China, but they seem to have stopped selling the 20AH cells. They do have the 15Ah cells, which might be better for some folks because they are smaller and lighter. Free shipping, too.
http://a123rc.com/goods-473-Excitingly+ ... CELLS.html

If you don't mind B-grade cells with the tabs cut, there is an ebay seller from China who has the 20Ah pouches for like $28 per cell including free shipping. Check out his ebay ads; he shows you how to terminate them without the tabs (good enough for an ebike):
http://shop.ebay.com/xueming0061/m.html ... 4340.l2562

If I may rant, it bugs me that you have to buy these cells from China when we have a perfectly good A123 factory right here in the USA making them.

[Hillhater]

Thanks jimw, its good to know there are sources, even if that are not "pristine" and tab-less .
do you know why they show two distinctly different 20Ahr cells ?..
the APP72161227, and the AHP70165227 ... ??
These are obviously different physical sizes, but why the two versions ?...both genuine A123 ??
Which is the most recent , ...which is "preferred" ?

[EBJ]

Where can you currently buy genuine A123 , 20Ahr pouches ?

x2

If you don't mind B-grade cells with the tabs cut, there is an ebay seller from China who has the 20Ah pouches for like $28 per cell including free shipping. Check out his ebay ads; he shows you how to terminate them without the tabs (good enough for an ebike):
http://shop.ebay.com/xueming0061/m.html ... 4340.l2562

If I may rant, it bugs me that you have to buy these cells from China when we have a perfectly good A123 factory right here in the USA making them.

I also wonder why the seller states only a 3C discharge 10C burst ? I was under the impression a123 had awesome 30C discharge ratings?
The ratings he is giving for these seem closer to the Headway LifePo4 cells. Perhaps a safety spec to save his ass from people demanding performance from "neutered" cells ??

[jimw1960]

I also wonder why the seller states only a 3C discharge 10C burst ? I was under the impression a123 had awesome 30C discharge ratings?
The ratings he is giving for these seem closer to the Headway LifePo4 cells. Perhaps a safety spec to save his ass from people demanding performance from "neutered" cells ??

I think they are downplaying the C-rate on these because of the tabs. The connectors he is using to terminate them are only good for limited amps. If you tried to put 30 C through those ring terminals, it would probably cook the terminal in short order.

[jimw1960]

the APP72161227, and the AHP70165227 ... ??
These are obviously different physical sizes, but why the two versions ?...both genuine A123 ??
Which is the most recent , ...which is "preferred" ?

Are you talking about the ebay seller? I think it is just different batch numbers. They look the same size to me. The pictures in his listing are the same stock photos that he uses in all his listings, so maybe there are different types of batteries shown just as examples of how to terminate them. I know at least one person on the forum that bought from this seller and was satisfied with the transaction.

If you don't mind the extra work of making the terminations, just spend another $150 or so on a BMS and charger and you have a really decent A123 battery for less than a ping battery.

[auraslip]

I think another thing people forget in doing a energy density anaylisis is that lifepo4 is much more tolerant to deep discharges. Where a123 shows a decrease in cycle life when taken to 100% or 90% DOD, lipo shows a HUGE decrease in cycle life when taken to the same state. Not sure about the differences in cycle life between the two when we're talking about charging voltages, but the common thought here is to charge to 90% SOC for lipo. In any case, you'd be hard pressed to actually use 1500-2000 cycles that LIFe is actually capable of, so you could go from 0% to 100% DOD every cycle and it'd still last years.

If that's the case, and you care about cycle life, then you'll be cutting 20% - 15% of the capacity out of your lipo pack. I feel this mostly negates the weight and volume advantage that it has.


BTW, how do you terminate the a123 prisimatics? Curious to see how feasible it is for someone like me to build a pack out of them!

[whatever]

that ebay link above is interesting, if u go to his taobao site, he sells same cells for half the price, so assuming his taobao price is double his cost price, that makes 400% mark up on the ebay price........not bad

[lesdit]

I think those are different. Last time I checked, there were also 15ah ones, for $4 . It clearly stated that they were not prime and maybe only good for a headlight or something.
Also, the taoboa site is multiple,different sellers, like alibaba, it seemed to me?

that ebay link above is interesting, if u go to his taobao site, he sells same cells for half the price, so assuming his taobao price is double his cost price, that makes 400% mark up on the ebay price........not bad

[Hillhater]

the APP72161227, and the AHP70165227 ... ??
These are obviously different physical sizes, but why the two versions ?...both genuine A123 ??
Which is the most recent , ...which is "preferred" ?

Are you talking about the ebay seller? I think it is just different batch numbers. They look the same size to me. .

Yes the Eby seller with the A123 , 20Ahr cells.
If you look at the pictures , it shows cells with 2 different "model" numbers....APP72161227, and the AHP70165227 .
Those are A123 type designations ( not batch numbers) and denote the cell dimentions in mm's with a 3 letter prefix.
IE, .. the APP72161227, is 7.2mm thick, 161 mm wide and 227mm long..
Similar for the AHP70165227 , which would seem to be slightly thinner, wider, but the same length.
Probably of more significance is the 3 letter type codes "APP" and "AHP" ...but no idea what those mean.
The two types are similar , but not the same, both made in Korea, but obviously made to some different specifications, ..but what and why ?
Its just a little worrying that we dont fully understand what these cells /differences are.

[lesdit]

Here is how I see it: many a123 cells are in test phase at various large companies. A123 makes changes to the cells driven by the potential buyer. Some of these cells are being sold to recycler companies when they are done with a batch. Mine are definitely used cells.
I think of them like greyhound dogs, retired after they served their duty as race hounds. The cells I got will serve out their life powering an electric mountain bike, only asked to make a fraction of their design amperage.
My first batch, from a person on this forum, should be closer to design spec. , to make 100 amps in my Prius Phev.

[oatnet]

C rate does matter. It means that the cells perform better even at lower discharge rates. If i run my cells at 10C constant, they perform horribly even though they are way under spec. They just get warm and turn battery charge into heat.

Heat is not always your enemy. Did you know that many EV's have pack heaters that draw additional current to heat the cells so they will perform better? Lithium and Lead Acid actually deliver a higher voltage under load, and more WH, when heated up. If you want to extend the cycle life of your cells, making the pack bigger to reduce your depth of discharge has a big impact - buying higher c-rate cells to reduce heat at low-c discharge, not so much.

Anyhow, first I have to ask why you would be running at 10c continous in the real world, which would discharge your ebike pack in 6 minutes? That is a very short commute. It is my opinion that to be useful as a commuter, an ebike needs to have at least 1/2 hour of runtime, YMMV. That 1/2 hour run time translates to a 2c continious discharge.

I think what you are saying is that your 20c lipo, when discharged at 10c, has a high voltage drop and generates a corresponding heat load. What you are asserting, based on that, is that higher C batteries have a lower internal resistance, which generates less heat during discharge. However, this is NOT always the case, some cells may be better able to dissipate heat and hence have a higher C rating - assuming the manufacturer is not just making up the specs anyhow. Given the range of IR available in current chemistries commonly available to this hobby, yes the effects of IR will be significant at a 10c continious discharge, but that is (5) times typical demand.

At lower C ratings on quality cells, the impact is so small as to be insignficant. It would be interesting to see the differences in voltage drop/heat generated, say between 20c and 30c lipo discharged at 2c. I would expect differences to be very very small, despite a 50% increase in C rating - and this would debunk your assumption. A higher C-rate gives great bragging rights, but it does not make a significant difference at real-world discharge rates.

Of course, there are always crappy cells out there that will heat up like a toaster oven. I figure the cheap cells of both chemistries don't fit into this discussion. I only run midrange LiFe (>=5c) and above, I don't buy the 1c/2c/3c lowrange LiFe because it is heavy and the cost savings over Headways or a123s is not enough to make lowrange worthwhile to me. Most people run "safer" HobbyKing LiPo, and don't run cheap no-name 1c/2c/3c LiPo because it is more likely to burn.

like for example if you wanted to drag race etc.

We might be arguing different points. Note that my post said. "My personal belief is that c-rating is largely irrelevant in EV's - unless you are building an exhibition bike that only runs for 2 minutes." Drag racing would fit into the exhibition category.

However, if you build an exhibition bike that needs to discharge at 10c cont, then you anticipate how the cells perform at that rate when designing the pack:

1) Determine the target voltage you want on that system, and build to that voltage at the discharge rate you require. If you want a pack to run at exactly 48v, and the cell runs at 2c=4v/10c=3v, then build 10c pack with 16 serial, and a 2c pack with 13 serial. Both packs will deliver 48v for most of the discharge cycle, because you have sized the voltage drop to the load.

2) Ventilate the pack accordingly. Heat is expected in drag racing, one of the billion things one has to accomodate when running hardware close to its limits.

...i worry about calendar life more than cycle life since i am a fair weather ebiker and not a daily rider.

Then, even if c-rate had the level of impact you assert, it does not matter to you either, right? Since you expect your cells to die of age not cycles, does it even matter if your cells get warm at 2c?

-JD

[whatever]

i've ordered some of the ebay cells to see how second hand they really are,
if they are genuine a123 that might well be ok for some time.
I can confirm though that the cells are used/second hand.
There is a nifty device in a picture on the taobao site of a meter that measures capacity of cells. Would like to get my hands on one of those

[neptronix]

As for measuring, any mid-high price RC charger will do what you are asking for.
You can also use an amp/watt metering device, although you will get more of an approximation of the AH left.

There are fancy units out there like the west mountain radio CBA-2 too.

Anyway, good luck with the cells.

[magudaman]

Resurrection!!! whatever Did you ever get your cells and see how they worked out for you? I am looking at purchasing some cell on ebay or from a123RC soon but am thrown off by the different cell Prefix letters. That worries me! I am really afraid they will not be up to the same discharge rates as the AMP prefixes verses APP AHP ones. I know Mavizen says they sell the AMP ones and claim that they handle 15C continuous and 30C intermittent.