Arkmundi's new A123 26650 battery build

[arkmundi]

Here's a picture of the first major test of the new battery build, with all the soldering and wiring done. Yea, that's my trophy, an aluminium camp plate I use during soldering operations. Haahahaa! Was putting a spot of solder on the bullet connectors as the crimping just wasn't strong enough to pull them apart without stripping the wire out. Made contact and always enjoy the fireworks, after the fact. Didn't even phase the battery one bit, but enough current to melt the aluminium. Hahahhaaa.

Next up, I'll be making a custom box for the battery and attaching it to my ebike, taking the first ride, will be the second major test.

 

[999zip999]

What size battery are you building ? My guess is two 8s 6p for a 48v pack. I think the quailty of A123 is number 1. And being in in the 26650 format will make for a long lasting battery for ebike use and don't see how a bike could over demand from these cell. Your motor will would melt first. Hell with those 1c lifepo4 blue no name cells.

 

[arkmundi]

Its a 12S8P 36V ~20AH pack of 96 A123 26650 cylindrical cells, more a less equivalent to what I'm using now, a 12S1P pack of AMP20 prismatic cells. Yea, I considered a lot of offerings here at ES and elsewhere before 1> deciding to stick with A123's cells, 2> moving from the prismatic to cylindrical format, 3> buying new factory legit guaranteed and warrantied cells (and paying the price), and finally 4> sticking to the homemade mode. Its working well so far, but it has yet to pass that second major test, on the road.

 

[999zip999]

I'm mising something parelle then seriers.

 

[agniusm]

I'm missing something too. Shouldn't your paralleled groups be connected? I mean like this:

Were those discounted 2.3AH or new 2.5AH cells? How much shipping worked out?
So your AMP20 pack is done and gone? I had some more bad cells on mine just from sitting so i hope after year and half all thats left is good

 

[arkmundi]

I'm mising something parelle then seriers.

No, series then parallel. Its made of 8 - 12S bricks. Using Shoe Goo to glue the 12 together, series wired. Then I have an 8P bus to pull the current from those 8 bricks.

I'm missing something too. Shouldn't your paralleled groups be connected? I mean like this [/img]

Not necessarily. It makes no difference whether you build S-then-P or P-then-S or S&P. Its just ultimately current.

Were those discounted 2.3AH or new 2.5AH cells? How much shipping worked out?

I considered, am still considering the older B-grade and discounted cells at A123 AMP20 Cells, new, legit, factory direct!. Erik is offering those for $4 per, with the coupon ANR26650M1A-BGRADE for 100 or more. He's a certified shipper of lithium and will ship anywhere in the USA. Not sure about over-seas, so you might want to check with him - erik@evdmcorp.com. Shipping costs were very reasonable.

So your AMP20 pack is done and gone? I had some more bad cells on mine just from sitting so i hope after year and half all thats left is good

No, still working great! But I popped in my last cell replacement (I had a stash of extras) and wanted to have a new battery pack ready for when that AMP20 ultimately hits the recycle bin. I'm hoping that doesn't happen for a while. Plan is move to the new pack as soon as the box is built. The pBus can handle adding in the old pack, so would have ~40AH for extended trips. So I'll get to take some of the longer rides I've been hoping to enjoy.

A single 12S brick pulled from the pack and displaying bullet connectors to the pBus:

 

[davec]

nice work- do keep us posted with your experience
properly built/managed these should prove years of ev service

 

[Architectonic]

How are you soldering to a123 cells without damaging them?

 

[arkmundi]

How are you soldering to a123 cells without damaging them?

Thanks, probably the most important question in this make. For li-ion cells of any chemistry, heat is probably the worst thing for them and will cause plating of the cathode that over time increases the IR. I was initially reluctant, did research and found a number of good articles including this: Soldering wires to battery terminals. It takes: 1> a digital (temperature controlled) soldering station to hold temperature constant, 2> a flat end tip, 3> abrading the terminals, and 4> technique and practice. I made a purchase of this 60-watt soldering station from CircuitSpecialists and the flat tip. It didn't take long to perfect technique. The cell as a whole did get warm holding the tip on the cathode long enough for the solder to bond, but not so much that I believe it was damaged at all. Certainly the cells all tested the same before and after the solder operation. Used a pneumatic rotor and grindstone to abrade the terminal to improve adhesion.

 

[agniusm]

I'm missing something too. Shouldn't your paralleled groups be connected?

Not necessarily. It makes no difference whether you build S-then-P or P-then-S or S&P. Its just ultimately current.

I think there is a difference and don't take my word for it, look at this:
http://www.elithion.com/pdf/BPC2012Elithion.pdf

 

[granolaboy]

I'm missing something too. Shouldn't your paralleled groups be connected?

Not necessarily. It makes no difference whether you build S-then-P or P-then-S or S&P. Its just ultimately current.

I think there is a difference and don't take my word for it, look at this:
http://www.elithion.com/pdf/BPC2012Elithion.pdf

I was going to link to that paper dr.bass posted as well. I'm convinced that paralell then series is the way to go...

and A123 is the bomb...I hate being so broke

 

[arkmundi]

I think there is a difference and don't take my word for it, look at this:
http://www.elithion.com/pdf/BPC2012Elithion.pdf

I was going to link to that paper dr.bass posted as well. I'm convinced that paralell then series is the way to go...
and A123 is the bomb...I hate being so broke

Alright, yea, did catch some chatter on a possible issue, but have disregarded (for now) as N/A. Same question on whether to BMS or to not-BMS, an ever disputed issue. I'm still in the latter camp, but I actively monitor my cells. I'm going with a golden rule, to have twice the capacity that I really need, and to stay in the golden zone of 25%-75% charge capacity. If I see an issue, maybe I'll change my mind, but not for now. It was a strategic decision. I like the idea of popping out a 12S brick and balance-charging just that brick, if it looks out of wack. With my AMP20, I'm doing only bulk charging these days, same golden rule and the zone, and those cells are always balanced, within 0.01 volt of each other. I'm expecting the same with the new pack. Its all a grand experiment in any case and I continue to enjoy the journey. Thanks for the post of the article.

 

[999zip999]

The reason I think you can get away with it is because A123 is very strong cell. For S before P. If tried with noname blue cell it would not be strong enough for a ebike at 30amp. Like to know how it works out.

 

[arkmundi]

The reason I think you can get away with it is because A123 is very strong cell. For S before P. If tried with noname blue cell it would be strong enough for a ebike at 30amp. Like to know how it works out.

Thanks, yea, its the hacker mentality, of tinkering until it works well. IR, V & A are all fluxed together. I can see how a cell that's borderline, having developed significant IR compared to th others might mux up the works. But V and A work together, so my pack of 8P should theoretically deliver the 70 amps promised. I need only 30 on throttle and 20 continuous. I'm also not willing to take a cell below 3.0V, though, again, theoretically, should be able to drop it below 1.0V and have it bounce back. So looking for a pack that stays between 36V and 40V, continue to deliver as many amps as the throttle demands, and no more than 15 amp-hours (down to 25% of capacity). In actuality, I rarely do anything more than 10 miles and my rule of thumb is still 1 mile per amp-hour, so no more than a 50% draw-down of the pack.

But its an interesting observation you make, that how you construct a pack may depend a lot on the cell you're using. The A123 26650 cylindrical cells are very long-lived, robust, current delivery packages. I believe my pack will deliver as designed. If not, there's always going back to the drawing board and starting over. Thanks for the post.

 

[999zip999]

I don't take a cell below 2.8 or 2.5v as it is failing on off the cruve so fast is of little use but bad things happing. Never over discharge. As you can't afford to.

 

[agniusm]

Having paid top price for the cells it would be a shame if something goes wrong. Mind that this should last 10 years and proper design is a must. Even A123 papers define what is series and what is parallel connection. BMS falls into the same category. Ignoring all that info is just something I would not do, experts are making those suggestion and I would follow the advise.

 

[dogman dan]

Nice job. I cringe when a noob wants to solder up a battery. But when you research it, then buy the proper tools, then practice first, that's a lot different.

Series first. I cant see why it won't work. You don't have to P first if you aren't using a bms. You have easy to remove sections, and the battery will still work fine at reduced capacity if you remove a section for service.

If you balance the way I do, it will work fine. ( or use a charger that single cell charges all the cells) Find the low cell, then charge or discharge just that cell. Why wait for a bms or charger to discharge a shitload of cells, then charge one low one?

Series first makes it easy to find a low or high cell. I'd attach jst plugs to each section though. So you can run though the whole thing fast with a cellog 8 and check the balancing.

 

[arkmundi]

... You have easy to remove sections, and the battery will still work fine at reduced capacity if you remove a section for service.

If you balance the way I do, it will work fine. ( or use a charger that single cell charges all the cells) Find the low cell, then charge or discharge just that cell. Why wait for a bms or charger to discharge a shitload of cells, then charge one low one?

Series first makes it easy to find a low or high cell. I'd attach jst plugs to each section though. So you can run though the whole thing fast with a cellog 8 and check the balancing.

My reasoning exactly! What I'm doing with my 12S1P AMP20 is monitoring cells after my ride with 2 celllogs and leaving them on when charging. There are always a few cells that seem to go higher on charge than the others and my alarm sounds when any hits 3.6 and I'll stop the charge process. The cells then all come to rest within 0.01V of one another.

So the logic of my design was that I wanted to continue a practice that is working well for me. But the idea of wiring up all those JST's and having 16 celllogs monitoring just seemed much. So I'm setting up a charging station with the Celllog contacts mechanically applied and I'll periodically monitor & charge each 12S string independently. My Smart Charger from Batteryspace does a great job bulk charging and has that nifty bank of 6 LED lights indicating roughly when the pack is 20%, 40%, 60%, 80% and 100% charged, when it automatically shuts off. I'm shutting the charger off at 80%

 

[arkmundi]

Having paid top price for the cells it would be a shame if something goes wrong. Mind that this should last 10 years and proper design is a must. Even A123 papers define what is series and what is parallel connection. BMS falls into the same category. Ignoring all that info is just something I would not do, experts are making those suggestion and I would follow the advise.

Agniusm, I can't argue your points. Yea, I read the Cylindrical Cell Battery Pack Design Guide, so its not a matter of not knowing what A123 is recommending. I'm taking a sparse approach and reason I can add in elements, like a BMS, should my experience dictate. I appreciate expressed opinion, but need to form my own independent opinion, as should all makers in their make. Sure longevity is a factor. I'd like to see a full lifetime. But based on extensive research here and elsewhere, I'm of the firm opinion that cell failure is most often from charge > 3.6V and discharge < (1.0 to 2.0)V, which I'll be avoiding through practice, not device. Heat as well, but that is due to over-amping the cells and I won't be coming anywhere close to that.

 

[agniusm]

All is good as long as you are confident and happy. Not criticising just my view as why errors occur lurking on ES and I think its human error factor. No matter how long you drive your car and how good of a driver you are, accident will happen big or small in a lifetime. Anyway I wish all the best experience with fresh battery build.

 

[arkmundi]

. Anyway I wish all the best experience with fresh battery build.

Many thanks and much respect!

 

[arkmundi]

Finished the new battery build today and took 'er for a spin. Performing as expected and no hickups. Will post more after I get a sense of how well it charges and keeps the charge.

 

[tomtom123]

Here's a picture of the first major test of the new battery build, with all the soldering and wiring done. Yea, that's my trophy, an aluminium camp plate I use during soldering operations. Haahahaa! Was putting a spot of solder on the bullet connectors as the crimping just wasn't strong enough to pull them apart without stripping the wire out. Made contact and always enjoy the fireworks, after the fact. Didn't even phase the battery one bit, but enough current to melt the aluminium. Hahahhaaa.

Next up, I'll be making a custom box for the battery and attaching it to my ebike, taking the first ride, will be the second major test.

Where you get these batteries? and price ? how reliable are these? lifespan 2 years at least?
thanks

 

[wineboyrider]

FWIW I do the exactly the same thing (series then parallel) with my 12s lipo packs ( a high C rate cell) and it's been working fine. I pull out a pack of of 12s 5ah lipo and balance charge each and every individual cell and I mark and watch the IR of each of the cells. This is all without a BMS of course.

 

[arkmundi]

Where you get these batteries? and price ? how reliable are these? lifespan 2 years at least?
thanks

These are new, warrantied genuine A123 2660 cells from http://www.buya123batteries.com/ANR26650_Lithium_Ion_Cylindrical_Cell_p/300475-306.htm. Full carton of 100 cells, so for a $1.00 discount per or $8.75 a cell. Very reliable - you're unlikely to find a more reliable cell. See the http://assets.buya123batteries.com/images/a123/26650_data_sheet.pdf. I'm expecting 2,000 charge/discharge cycles at ~1 per day, or about 5 years, but that's 80%<SOC<20%. You're welcome.

FWIW I do the exactly the same thing (series then parallel) with my 12s lipo packs ( a high C rate cell) and it's been working fine. I pull out a pack of of 12s 5ah lipo and balance charge each and every individual cell and I mark and watch the IR of each of the cells. This is all without a BMS of course.

How are you doing that - and I mark and watch the IR of each of the cells? Thanks.

I was riding and thinking about the S then P, P then S, or S&P connection methodologies and the analogy that came to mind was a viscous fluid, that the electrical charge of a battery moves around according to the internal physics of the cells. In other words its not static. The relative difference of charge between cells will remain low. In other words, my expectation is that the cells will self-balancing. The assumption is that the cells are identical or close thereto. No differential IR. Its a safe assumption when all the cells are from the same manufacturing run and have the same use. But over time, it won't be a mere assumption - I'll be monitoring the SOC of the individual cells.