The care and feeding of a123-based packs...

[oatnet]

Does anyone know where I can buy A123 tabs??

I'm guessing you want tabs to use as solder points, which is great, but how are you going to attach the tabs to the cells in the first place?

Tabs are nickel strips spot welded to the cells at the manufacturer. You can buy nickel sheet or strips anywhere and cut them to be the same size as the ones a123 uses. You won't find nickel strips as an a123 product line.

 

[The Mighty Volt]

Does anyone know where I can buy A123 tabs??

I'm guessing you want tabs to use as solder points, which is great, but how are you going to attach the tabs to the cells in the first place?

Tabs are nickel strips spot welded to the cells at the manufacturer. You can buy nickel sheet or strips anywhere and cut them to be the same size as the ones a123 uses. You won't find nickel strips as an a123 product line.

Hi oatnet and thanks for your reply

I just bought 44 A123 cells.......how do I join them now then??

Cheers!

 

[The Mighty Volt]

I will soon be in possession of around 60 of these cells.

Of all the pack builds and of all the configurations you guys have discussed and mentioned, which one do you think would be best for me, considering

{a} I have limited experience in these matters but am prepared to go it alone

{ b} I have two hubs, an Aotema with a 36v 20A controller and a Crystalyte 5304 with 72v 50A controller {Courtesy of HTB and Maxwell65 respectively}

What else should I know be going and collecting? Balancing leads, silicon wire, series connectors etc?

Personally, I think a 72v pack with A123 is too bulky, and that for 60v+ it is better to build with the 10Ah Headways or Prismatics.

But anyways...lay it on me. Cheers.

 

[MitchJi]

Hi,

I will soon be in possession of around 60 of these cells.

Of all the pack builds and of all the configurations you guys have discussed and mentioned, which one do you think would be best for me, considering

{a} I have limited experience in these matters but am prepared to go it alone

Since you have "limited experience" and your cells don't have the strips (soldering risks damaging the Cells) I'd go with a solderless method. That is discussed at length earlier in this thread.

leamcorp posted a picture with some information here (I think he'd be happy to provide more info or start a thread):
http://endless-sphere.com/forums/viewtopic.php?f=14&t=16341&p=240667#p240667

Postby leamcorp » Sun Feb 21, 2010 1:30 pm
Here's a picture of battery I built last year. This was my 1st attemp, so its not clean but you get the idea. By the way, you remember I was making plastic battery holder last year, this was result of that effort - much simple and extremely adjustable.

As you can see, its in a wooden box (you could use plastic as my later version did). The batteries are not soldered or tied down at all- its just loose cells in a case. The cells are inserted into the box like a battery case - if I want to change anything - just unscrew the box to replace cells, add longer board or copper strip for additional voltage/AH. And if any of the cells are blown like you see so many thread asking what is wrong with their battery, you could unscrew to check each battery without worrying about soldering or where to break the line.

This is a very simple box to build and is amazingly flexible since cost of the copper strip/screw/wood is very cheap. Once you are done, you could use shrink tubing, wood/plastic board, or in my case, couple of round of duct tape for tight seal. So far, I built 24v, 36v, 48v and 72v in multiple shape (not just boxy shape). I'm am in the process of taking everything apart as I got a new bike and I will be building different shape box/pack for this new bike. When you are changing the shape, you do lose some space due to un-usable spot but because these cells are quite small, you minimize those wast.

As mention, I'm building a new case/pack and if you want me to document each proccess, I will but as you could see in the picture, there's nothing difficult about building A123 pack. My next version, I'm using a heat gun to change the shape of plastic board to fit the bike, so it will be custom fitted to my new bike.

By the way, so far only A123 or lipo was able to push my 5304 and BMC 1000w DD motor over 45+mph, no prismatic can do that. Maybe newer ones but not the ones I've tried.

Again, its not difficult to build A123 cylindrical pack - so if anyone have these cylindrical pack... rather than throwing it out because its not "efficient as prismatic", this is one way to use them.

 

[The Mighty Volt]

Hello folks, I got myself around 6 A123 cells which are reading in the range of 2.3v - 2.6v . The rest of the cells are fine and are reading 3.3v- 3.6v.

Anything I can do about these low cells, or are they finito?

Many thanks.

 

[webfootguy]

Hello folks, I got myself around 6 A123 cells which are reading in the range of 2.3v - 2.6v . The rest of the cells are fine and are reading 3.3v- 3.6v.

Anything I can do about these low cells, or are they finito?

Many thanks.

2.3v for a resting voltage is not a problem for M1 cells. I would fully charge it to 3.65 and see how much charge it takes. I would also do a discharge cycle and measure capacity. It is probably ok unless the cell is damaged.

 

[The Mighty Volt]

Hello folks, I got myself around 6 A123 cells which are reading in the range of 2.3v - 2.6v . The rest of the cells are fine and are reading 3.3v- 3.6v.

Anything I can do about these low cells, or are they finito?

Many thanks.

2.3v for a resting voltage is not a problem for M1 cells. I would fully charge it to 3.65 and see how much charge it takes. I would also do a discharge cycle and measure capacity. It is probably ok unless the cell is damaged.

Hey that's great news.....I also have 2 with really low voltage, one is less than 1 volt, around 0.87. The other is 1.86v.....but from what I have gathered, those really are toast.

All in all I got 14 good cells for $120. That's an average of $8.20 per cell, and includes postage. It works out at around $7 per cell with no postage, so it's not too bad, and I avoided customs. Won't go down that route again though, too risky.

Cheers and thanks for the reply!

 

[MitchJi]

Hi,

Hello folks, I got myself around 6 A123 cells which are reading in the range of 2.3v - 2.6v . The rest of the cells are fine and are reading 3.3v- 3.6v.

Anything I can do about these low cells, or are they finito?

Hey that's great news.....I also have 2 with really low voltage, one is less than 1 volt, around 0.87. The other is 1.86v.....but from what I have gathered, those really are toast.

http://endless-sphere.com/forums/viewtopic.php?f=14&t=8469&p=128540

Guys,,, you know all that i have great experience with these dewalt packs 8)

There is something i discovered that impressed me alot about these low cells that we easyly declare: dead ....

I had many of them that i kept for me instead of selling them that i tested again.

I was surprized to see that many cells clos eto zero V was still good with capacity and RI !!

I mean... these famous 1 or 2 "bad"... or even low cells that had 0.9V or 0.2V still gaved me 2150mAh and 10 mohm !! ..

and same results with 5 cycles after that!!

I also had a pack that i kept for me that measured 0.8V with every cells between 0.1 and 0.2V that i successfully charged using individual charger/cell and that gaved me 2100mAh ! with Ri between 10 and 13mohm /cell !!
since the last full charge of that pack i let ist to sit for 2 month on my desk and it still measure 34.75V of SOC !

That's why i say these cells are like buletproof and so incredible!
i'm not saying that everybody should keep these to match with their ebike batt project.. but for something like boostpack they are excellent!

If you try to recharge these lower cells, you will see quickly if they survived or not... the really BAD/DEAD cells will just heat up and will not keep their voltage when you remove the current

The best solution to revive low cells is to begin the charging process at 500mA and when they reach 3.0V you can increase the current.

The DEAD cells will never reach more than 1.5V durin g the 500mA charge process.. the rest should succed.

SO DONT PUT THE LOW "DEAD" CELLS IN THE TRASHCAN IMMEDIATLY !

Doc

All in all I got 14 good cells for $120. That's an average of $8.20 per cell, and includes postage. It works out at around $7 per cell with no postage, so it's not too bad, and I avoided customs. Won't go down that route again though, too risky.

Sounds pretty bad to me. New cells from Toolking 28v packs have been selling for between $5 and $6.25. $7 per cell is a little more than $3 per Ah and new prismatics are $2.50 per Ah. I don't see how paying substantially more for used cells can possibly be construed as a decent deal.

 

[The Mighty Volt]

It's decent because the price I referred to included avoiding customs and included the postage.

The price you are quoting includes neither, as Toolking offer free postage in the USA and there is no customs, as such.

You must compare apples and apples.

 

[The Mighty Volt]

Hi,

I need to wire, somehow, 105 A123 cells into a 72v 12Ah package.

I know that these cells will fit inside the frame of my MTB.

I have absolutely no idea where to start, even though I have read through this thread.

I dont know if I should just make up lots of small packs, connect them in parallel, and then use an AccuCell to charge them.

Any advice would be much appreciated.

Cheers.

 

[MitchJi]

Hi,

I need to wire, somehow, 105 A123 cells into a 72v 12Ah package.

I don't know if I should just make up lots of small packs, connect them in parallel, and then use an AccuCell to charge them.

First connect 5 or 6 cells in parallel, then connect the parallel groups serially.

 

[The Mighty Volt]

Hi,

I need to wire, somehow, 105 A123 cells into a 72v 12Ah package.

I don't know if I should just make up lots of small packs, connect them in parallel, and then use an AccuCell to charge them.

First connect 5 or 6 cells in parallel, then connect the parallel groups serially.

Okay, let's say I do that...how do I even set them up for charging and discharging...this thread has a lot of technical talk about BMS, but I need really bite-size stuff. Thanks again.

 

[MitchJi]

Hi,

Okay, let's say I do that...how do I even set them up for charging and discharging...this thread has a lot of technical talk about BMS, but I need really bite-size stuff. Thanks again.

Simplest way to charge/balance will be multiple single cell chargers:
http://endless-sphere.com/forums/viewtopic.php?f=3&t=15144&p=226635#p226635

You can use CellLog(s) for monitoring LVC:
http://endless-sphere.com/forums/viewtopic.php?f=3&t=15144&p=226635#p226568

 

[The Mighty Volt]

I finally got around to finishing off my 16s5p a123 pack, which I made using a combination of the existing DeWalt end covers from the 10-cell tool packs, some copper "hanger tape" from Lowes and some nickel-plated battery springs from Mouser. This pack also has a 16-channel LVC board, with Randomly's active cutoff circuit, that mounts on the front of the pack. I posted some early progress pics, a few pages back, but I'll repeat them here:

Each 8s5p sub-pack consists of four 10-cell blocks that are held together via two 6-32 threaded rods.

The two 8s5p sub-packs stack one on top of the other and then the 16-cell LVC board bolts to the front of the completed pack.

Hi there, I am currently attempting a 20s 5p build of A123. Do you have any recommendations for an LVC only module, such as the one you have used here, and how many of them would I need to make my completed pack? Many thanks.

 

[MitchJi]

Hi,

Hi there, I am currently attempting a 20s 5p build of A123. Do you have any recommendations for an LVC only module, such as the one you have used here, and how many of them would I need to make my completed pack? Many thanks.

A similar module is part of this BMS but it sounds like it might be a while for the separate HVC/LVC Module:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=5416&p=253076#p252868

Gary and I are also working on a "split" version of the new BMS that has a small HVC/LVC section that always stays with the pack, and a detachable power stage for the big shunt resistors. The HVC/LVC board does not generate heat and can be wrapped up with the pack. All the sensitive parts stay permanently connected to the cells. The split version is still in prototyping stage, so don't hold your breath.

If you want to use that LVC Module why not just use the whole BMS with a cheap 10a power supply for charging?

 

[jkeny]

My first post here: I'm using 2 of these batteries in an audio project rather than for high power electric vehicle powering.

I wondered if there was a cheap, single cell charger that will trickle charge the batteries when not in use?

I bought one of the Tenergy single cell LiFePO4 chargers. I had to open it up as I'm in Europe with 3 pin power wall sockets & this charger has integrated 2 pin US plug. (It's easy to open up - a screw underneath the Tenergy label holds it together ) It's an SMPS design & I wondered how it might be modified to bring the output voltage down a bit? It's regulated to 3.65V out but I wanted to reduce it to about 3.3V, the reason being 3.3V is the recommended typical voltage for some of the chips it's driving. I'd be happier if the batteries were not at 3.65V driving the chips at their voltage limit & effecting their lifetime or even damaging them.

Would reducing the charging voltage reduce the charge stored in the battery? This is why I'm wondering about a trickle charge as then I guess it wouldn't matter much as the battery would be charged when not in use.

Any help appreciated.

 

[MitchJi]

Hi,

I wondered if there was a cheap, single cell charger that will trickle charge the batteries when not in use?

I bought one of the Tenergy single cell LiFePO4 chargers. I had to open it up as I'm in Europe with 3 pin power wall sockets & this charger has integrated 2 pin US plug. (It's easy to open up - a screw underneath the Tenergy label holds it together ) It's an SMPS design & I wondered how it might be modified to bring the output voltage down a bit? It's regulated to 3.65V out but I wanted to reduce it to about 3.3V, the reason being 3.3V is the recommended typical voltage for some of the chips it's driving. I'd be happier if the batteries were not at 3.65V driving the chips at their voltage limit & effecting their lifetime or even damaging them.

You could use a DC convertor set to 3.3v but I'd (see below) charge them to 3.65 and put a tiny, brief load on the cells before use.

Would reducing the charging voltage reduce the charge stored in the battery? This is why I'm wondering about a trickle charge as then I guess it wouldn't matter much as the battery would be charged when not in use.

Any help appreciated.

Yes it will substantially reduce the energy storage if you charge them to 3.3v. No need to keep them on a trickle charger. They maintain their charge for a long time.

If you charge them to 3.65 they will drop down to 3.3v almost immediately if you put a small load on them (a small bulb should do it). If you do it that way the energy loss will be nil.

 

[jkeny]

Hi,
You could use a DC convertor set to 3.3v but I'd (see below) charge them to 3.65 and put a tiny, brief load on the cells before use.

Yes it will substantially reduce the energy storage if you charge them to 3.3v. No need to keep them on a trickle charger. They maintain their charge for a long time.

Trickle charging was the wrong term to use - I simply wanted the batteries (there are 2) to be topped up when they are not in use so I wanted to leave a charger permanently attached. There's a switch which when ON connects the batteries to the audio circuit & when OFF connects the batteries to the charger circuit.

If you charge them to 3.65 they will drop down to 3.3v almost immediately if you put a small load on them (a small bulb should do it). If you do it that way the energy loss will be nil.

Ok, I wonder could a charger be programmed to do this - charge up fully & then apply a load for a short while to bring the voltage down to 3.3V or do you know any circuit or schematic to do this?

Thanks for your help

 

[The Mighty Volt]

Is there any difference in levels of performance between the A123 M1 cell and the 18650 variant?

I was quoted a price of $1.89 per 2000 of the A123 cells, 18650 variety. Is that a reasonable price, in the estimation of the forum members? Thanks.

TMV

 

[amberwolf]

I'd think if you are going 18650 size, you might as well go with Konions instead. They should be lighter *and* higher watthours (because of higher voltage, if no other reason). Also that higher per-cell voltage means you could go with less cells for the same voltage pack. I'd also expect the Konions to be cheaper.

Based on what I have read, I'd guess Konions are about as safe as A123 with an equivalent BMS to keep them balanced and warn of low/high cells.

 

[The Mighty Volt]

I'd think if you are going 18650 size, you might as well go with Konions instead. They should be lighter *and* higher watthours (because of higher voltage, if no other reason). Also that higher per-cell voltage means you could go with less cells for the same voltage pack. I'd also expect the Konions to be cheaper.

Based on what I have read, I'd guess Konions are about as safe as A123 with an equivalent BMS to keep them balanced and warn of low/high cells.

Hi Wolf, thanks for the reply. What is your experience of Konions in terms of their C rating, or discharge capability?

 

[amberwolf]

Experience--so far none, just reading about them on the web for various uses, like DoctorBass's stuff.

I'd say they have high enough C-rates for what we do, if you're already paralleling a bunch of cells anyway.

The question really is "what discharge rate are you looking for?". Then: "how much space do you have for the pack?" and "what voltage does the pack need to be at?". With those answered, then it's possible to find the right cells to do that.

Most of the time, even a heavy ebike (like CrazyBike2) doesn't need more than 10-15A constant, with excursions into 30-50A for a few seconds here and there. Doing that with Konions vs A123 probably nets you less cells with Konions, given that the A123 will need more series cells, but you probably don't need to parallel as many more Konion cells.

http://www.endless-sphere.com/forums/viewtopic.php?p=241434#p241434

Consider a single 18650 A123 than can discharge 30C or a single Sony/Konion 18650 that will happily chirp out 17C. Etc. I suspect another aspect is that they're allowing for some cells/strings to go bad without effecting performance too much.

Since the A123 is 1.1Ah, 30C is 33A. The Konion is 1.3Ah, so 17C is 22A. I'm sure that for what we do that's plenty. If you're looking into motorcycles, well, that's another story. But if you're after super-high-performance, you may have other issues to deal with, anyway. If they're for mobility use, you probably won't even see a few amps at a time out of them normally, (other than startup currents) so it doesn't matter.

 

[The Mighty Volt]

I have 120 A123 cells.

I want to divide the 120 cells into 5 packs of 72v each, thats 24 cells per pack, all joined in series.

Thats a 72v pack, 24s, @2.3Ah

I then want to join each 72v pack in parallel to the next to bring out a total of 72v 11.5Ah.

The idea is that when the cells are dead, that each pack can be disconnected and then put on charge, on its own.

Question: Is this feasible, and, if so, what BMS should be used?

The idea here is that not each 72v pack will be the same shape, as they are being fitted internally into a frame. But every pack will have 72v, and 24 cells in series to bring out that 72v.

Thanks.

 

[amberwolf]

I have 120 A123 cells.
I want to divide the 120 cells into 5 packs of 72v each, thats 24 cells per pack, all joined in series.
Thats a 72v pack, 24s, @2.3Ah

Are those 18650 A123, or the larger ones? If the former, they are 1.1Ah not 2.3.

I then want to join each 72v pack in parallel to the next to bring out a total of 72v 11.5Ah.
Question: Is this feasible, and, if so, what BMS should be used?

Feasible, sure. I keep reading that it is better to parallel the cells first, then put the parallel sets in series, though. That way any weak cell isn't going to either die or be overly stressed, as it's directly-paralled brethren will take up the slack.

You can still make differently-shaped and placed packs, and series them instead of paralling them. It will actually take less wiring, too, as you only need to run one wire from one end of each pack to the next, instead of two.

For BMS, any LiFePO4 BMS could be used. Do you just want LVC warning on the vehicle? If so, just get Celllogs or similar, and you can monitor per-cell voltages. Or use the hobbycity LVC boards that are even cheaper; they have a beeper built in and I think an output line you can use to trigger ebrake to cut off your controller at LVC. You can parallel all those lines easily enough if you put optocouplers on the LVC boards, so any low cell/string can turn off the controller.

If you use the Celllogs you also can use them during charging for HVC and per-cell/string voltage monitoring.

If you want full balancing BMS, you could go with the new v4 or the old v2.6 F/G BMS from TPPacks or RechargeableLithiumPower. I guess you could also use a signalab (ping) one, if they make one for that many cells. HC has other stuff you could use, too, but you'd have to string a few together since most are maybe 6s. I'm sure there are lots of others out there, too; I read good and bad about various ones here every week or two.

 

[The Mighty Volt]

Hey AmberWolf, thanks a lot for that.

The cells are the M1 Dewalt Cells, with the white paper, some from Dewalt packs, others brand new.

My understanding hitherto is that if I make up the packs in parallel, that I will be forced to make up smaller packs, each at 11.5Ah, and then join them all into a 72v block via series connections.

Conceivably, this means I would have 5 batteries in parallel a pack, @11.5Ah {5 by 2.3Ah parallel} and 3v per pack.

120 batteries at 5 batteries per pack results in 24 small packs, each at 3V 11.5Ah as suggested above.

Then the 24 packs are connected in series, bringing the voltage to 72V and the Ah remaining at 11.5Ah.

Whilst this offers up the advantage of allowing me to make lots of small packs which I can now wedge into tight spaces, allowing me to make the most of my frame, it also presents, as I see it, the problem of how to manage the cells.

The way I am visualizing it is that what I have, if I follow the above format, is 24 PACKS in series, each containing 5 CELLS in parallel.

The common method of using a BMS involves considering how many cells are in series.

Here, I would be dealing with PACKS in series instead.

How does one go about approaching that issue?

Thanks.

PS I am now just waiting for Docs 4 Dewalt 36v babies to get here, and this particular built goes active. It will be documented so once it gets done other people can use it as a template.