Testing the big 15 and 20Ah LiFePO4 cells is tough! *Pics*

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regmeister said:

I have a few questions I hope someone can help me with.

I am thinking of a pack for 230A continuous. Can anyone suggest the minimum number of cells for 60V operation?

Is there an ideal temperature to run these cells?

LFP, have you worked on soldering these tabs yet? Any thing you can share on that front would be appreciated too.

Cheers, Richard

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19 cells would give you 60.8v nominal, with 70v HVC, and ~51-55v LVC. This would be what I would call the least number of cells to make a 60v pack.

If you just want the least number of cells to make a pack that reaches a peak of 60v hot of the charger, then 17 cells will get you a 62v HVC.

Yes, the tinned copper tab solders as nicely as any material, and the aluminum tab takes LiPo tab solder great. The trouble is just in getting even heat to both sides of the large area of the tab as quickly as possible to avoid the tab transferring much heat into the cell.

Right at the moment, I'm in beautiful Costa Rica, and will be until the first week or so of March, so my focus is on relaxing more then pack building.

You might be able to visit " John in CR " from this forum ! :wink:

you lucky bastard....*looks out window to the 2ft of white snow

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liveforphysics said:

Right at the moment, I'm in beautiful Costa Rica, and will be until the first week or so of March, so my focus is on relaxing more then pack building.

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Luke, enjoy your holiday my friend! Wish my best to John also. It has been snowing here all day, and the temperature is now diving to single digits... I am imagining you enjoying the wavez, the womenz and the ... you know, all the good stuff that if we ol' guys did it, we'd be deadz! :wink:

bigmoose said:

liveforphysics said:

Right at the moment, I'm in beautiful Costa Rica, and will be until the first week or so of March, so my focus is on relaxing more then pack building.

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Luke, enjoy your holiday my friend! Wish my best to John also. It has been snowing here all day, and the temperature is now diving to single digits... I am imagining you enjoying the wavez, the womenz and the ... you know, all the good stuff that if we ol' guys did it, we'd be deadz! :wink:

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You summed it all up well Moose I'm staying with John's beautiful family, and I've got the whole guest house to myself, which is 15ft away from the pool.
His wife is beautiful and a great cook, and I've been loving seeing the sites in CR

We just put a Methy controller, and an extra 1kwhr of precariously mounted lithium taped onto it, and it turned into fantastic pedal-free quick transportation through CR in silence. Can't beat it!

-Luke

VI DE OH or it didn't happen.

Have a good holiday Luke you deserve it I wish I could be somewhere in the sun with a nice pool and no packs to terminate :lol:

pgt400 said:

These cells have fantastic specs...would love a 24S3P pack of 20AH units for my bike. But so pricey right now, hope they get cloned soon

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Pricey??!!! For a technology still in it's infancy, these batteries are immensely underpriced. IMHO

Thanks Etard,

I know I'm not making much on them at these prices and I think any company would struggle to sell them at the price I have them up for. To be honest I set the price too low and it has given me nothing to offer to bigger customers and leaves nothing to cover any problems. There are a few others offering these cells now from what I've seem but their prices range from about 40% more expensive to over double the price. If I had them available in smaller formats like 10Ah I think people would think they are quite cheap but they look at the price of a high voltage high capacity pack and only see a lot of money. There are no cheap, high C rated LiFePO4 cells that come in at bargain prices when you assemble them into a big pack. It's gonna be difficult to compete with a123 26650s that have been taken from used Dewalt packs but even new Dewalt packs work out to very similar per Ah price to what I'm offering.

If I assemble a pack with a high rated BMS like 80A constant with connectors that can take over 100A, mechanically terminated etc, they only compare it to a much lower rated pack that does have all the additional costs associated with a mechanical termination method or the much higher rated parts. I can't do things any cheaper than I already am and if Ping or Headway performance is sufficient, then it's better to stick with the cheaper options IMO. I'm not knocking any of these other options, they do what they do and they do it at a competitive price.

A123 26650s have been around for a few years now and I haven't seen their prices tumbling. The cells I'm offering are actually cheaper than most are selling a123 26650 bare cells in small quantities. I hope I can still get these cells in the future because there is no guarantee and it's looking like most of the cells I have are already assigned to customers. I predict that these cells will not be available at low cost for at least a few years until they are fitted to several production EVs. I cannot see anyone offering them cheaper than I have been anytime soon.

I think that the inductance is a bigger problem than you think... or may be you have thought about it. Even a few inches of a straight piece of wire will provide enough Inductance for the circuit to ring.. it is the ringing that kills the mega amp MOSFETS.
Very hard to handle.. witness my MOSFET graveyard..!!
Who makes the 20 Ah cells you are testing as they are rated usually for only 3C i.e 60 A max..

cell_man said:

Thanks Etard,

I know I'm not making much on them at these prices and I think any company would struggle to sell them at the price I have them up for. To be honest I set the price too low and it has given me nothing to offer to bigger customers and leaves nothing to cover any problems. There are a few others offering these cells now from what I've seem but their prices range from about 40% more expensive to over double the price. If I had them available in smaller formats like 10Ah I think people would think they are quite cheap but they look at the price of a high voltage high capacity pack and only see a lot of money. There are no cheap, high C rated LiFePO4 cells that come in at bargain prices when you assemble them into a big pack. It's gonna be difficult to compete with a123 26650s that have been taken from used Dewalt packs but even new Dewalt packs work out to very similar per Ah price to what I'm offering.

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I think the 15ah and 20ah a123 prismatics are better quality cells for $2.50 ah: are going to die out very soon.
Even if they are great cells, most newbies and new comers to the forum (and some older ones) cannot afford that kind of a price for batteries, (if you read some posts, only the guys that have been here awhile (and only some) with big motors are buying these batteries (that's not many) because the price is to high for anyone just getting into e-bikes. (even if they are great cells)

The price for those cells will not come down, because the guys on here that have already bought them will be really pissed, but they are just to pricy for an average guy getting into e-bakes.
even if you think you priced them to low, a guy like evcomponents is making more money then you because his bats cost less, and a regular joe doesn't care about your 120amps discharge(or so)

I'm looking for batteries and read this thread and the testing Luke (great work by the way) has done and i think they are great bats, but at 2.50 and amp, i, and most people with average jobs will not buy them. because we can't afford them.
even people that know about these and have bought ping, are going back to ping because their cheaper (even if they have a less discharge rate)

So a question, would you make more money, selling them at $1.90 or even $2 an amp and have 100 sales a week (which you would have a lot more sales at that price) or selling them at $2.50 an amp and having 2 sales a week?

There around ~200 dollars more than a 48v 20ah ping battery and a 100 times better quality...bargain in
my opinion, cant even begin to compare the two bobocop. Want cheap rubbish that will likely
fail get a ping. Want something that will last get the A123s...

KiM

AussieJester said:

There around ~200 dollars more than a 48v 20ah ping battery and a 100 times better quality...bargain in
my opinion, cant even begin to compare the two bobocop. Want cheap rubbish that will likely
fail get a ping. Want something that will last get the A123s...

KiM

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I remember when you were so happy with your SLA's on your trike.

My post is not towards people like you that have $500 to waste on lipo's before they know how to charge them :lol: :wink:
If they are so great (and i see you recommend them to everyone, they are even in your sig, why did you order another $300 worth of lipo and not these ?

As i said, i know they are great cells, but for sales wise, the prize is to high for the average guy.

PS: hey that rymed

Edit: I must say, I don't mean (by what i'm saying) that the price is to high for the quality, What i mean is that it's to high for the average person to afford.

Bobocop said:

If they are so great (and i see you recommend them to everyone, they are even in your sig, why did you order another $300 worth of lipo and not these ?

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I have already explained this in my worklog, the required A123s dont fit my custom enclosure...As to charging lipos i know very well how to charge them if you read my worklog you would know what and why caused them overcharge, need to get your facts .... As to slas no i wasn't happy with them at all they were heavy underperforming overpriced rubbish but at the time the Australian dollar was 59cents to the American dollar making everything else OVER 1000 dollars .. Just because your not able to afford anything but garbage dont assume everyone else cant, there are people here with electric motorcycles and cars that can utilise these batteries there not only for e-bicyle use. What would you recommend to them that are on a par performance wise?

KiM

Well they're not for everyone and no I cannot put them at the price you mentioned. They are what they are and they are already priced very competitively. The higher end cells typically retail at quite a bit higher per Ah than the prismatics I'm offering. If you only need a ping, get a ping, if you want something with higher performance you'll need to pay a bit extra.

Responded to a post that now seems to have gone :?

bobocop said:

I think the 15ah and 20ah a123 prismatics are better quality cells for $2.50 ah: are going to die out very soon.
Even if they are great cells, most newbies and new comers to the forum (and some older ones) cannot afford that kind of a price for batteries, (if you read some posts, only the guys that have been here awhile (and only some) with big motors are buying these batteries (that's not many) because the price is to high for anyone just getting into e-bikes. (even if they are great cells)

The price for those cells will not come down, because the guys on here that have already bought them will be really pissed, but they are just to pricy for an average guy getting into e-bakes.
even if you think you priced them to low, a guy like evcomponents is making more money then you because his bats cost less, and a regular joe doesn't care about your 120amps discharge(or so)

I'm looking for batteries and read this thread and the testing Luke (great work by the way) has done and i think they are great bats, but at 2.50 and amp, i, and most people with average jobs will not buy them. because we can't afford them.
even people that know about these and have bought ping, are going back to ping because their cheaper (even if they have a less discharge rate)

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Bobo, you don't have background or experience to evaluate LiFe pricing. a123 m1 cells have been selling for far more than $2.50/ah to RC an EV crowds for YEARS, and demand has been high. These cells are cheaper and easier to work with, and cell_man is doing us a huge service by bringing them to us.

I think the major barrier to entry is the development of pack- building techniques - I have seen this with every new cell format. Other folks said the very same things about the Headway cells you are now touting.

While I agree that high discharge is Not relevant criteria for most EV applications - what is the
point of 20c when you discharge a full pack in 3 minutes - it's corallary is a high c CHARGE rate, I can do a full charge in 1/2 hour.

Your definition of "the average guy" is very subjective - the average guy in my area wouldn't blink twice at these prices, your area may vary. All I hear is sour grapes because you don't have the scratch to play - too bad, but don't waste your breath trying to talk the rest of is out of it, we know better.

that's kinda silly, it's like saying a Porsche sucks because you can't afford it. Oh wait, they suck even more because
EVERYONE can't drive one, eh?

uh, OK.

all I have to say on this matter is this, some things in life are worth eating ramen for.

/certified ramen chef templar of the realm

Thanks guys and Oatnet I've actually now got a termination method I'm pretty happy with and will be having the parts machined locally soon. I'm still looking at ways to slim the weight of the termination method down a bit (about 350g for 16S pack) but the basic idea is there. Should have some prices soon and they will make the termination pretty straightforward IMO.

will_newton said:

that's kinda silly, it's like saying a Porsche sucks because you can't afford it. Oh wait, they suck even more because
EVERYONE can't drive one, eh?

uh, OK.

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Your so out of it

I don't mean (by what i'm saying) that the price is to high for the quality, What i mean is that it's to high for the average person to afford.

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You must be one of those rich little kids that your parents work hard to support your habits.
Try working for it, and then you'll understand mypost.

If you can afford $1000 worth of batteries, that's fine, YOU ARE THE MAN, all i was saying was that it's a bit to high for us THAT ARE NOT MEN LIKE YOU,
YOU ROCK,

Wow this has been a busy week for me, I found 2 people to put on my ignore list.

Anyhow, cell_man lmk when you have a kit ready...

So before I build my pack, I am trying to charge all the cells in parallel first. Several folks I respect claim that this will permanently balance it. I figure that theory would be worth testing on these quality cells. I'm using a dc-dc converter tuned to 3.65v/20a and I am charging them 8 at a time. My killawatt says I have put some .74kwh into those cells, so am guessing they arrived discharged. I also notice they all have ah ratings on the tabs - were they all discharged to 100% DOD. What was the low voltage cutoff?



-JD

bobo . wtf man ?

If they seem outta reach for ya then just go with what you like an save us the negativity.

I dont know much about the whole battery thing but i can see that these cells and the next generation of cells to come (wich im sure will also be pricey) are precisely what EV's need. wich imo is a pack that can be abused , charged in minutes rather than hours and weighs bout the same or less than a motorcycles full fuel tank.

weather or not you like/can afford them is not even on the radar.

as lfp is showing they can be abused. they are safer than lipo . they can be charged fast . their dimension and weight per ah is top drawer and as far as im concerned its like a snowball rolling down hill, the bargain price has been set by cell-man and hes getting action . matter of time before someone else with access to these cells sees the potential for $ and markets them the same way he has and that = competition and the price comes down. or the next generation comes along driving the price of these down. its how it works.

Or even better . get the hell outta toronto that place sucks and costs to much for what you get. better jobs, climate and women in bc and alberta. put more coin in your pocket and the women might help you with the anger problem.

Well said enoob, and oatnet!
There is no need for the negative angle on cell_mans work.
Cell_man keep up the excellent innovation and I wish you success with all your ventures.
Cheers,
Matt.P.