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Cartridge Style Power Wall
#11
test single cells and then spotweld
mr_hypno likes this post
Building Lifepo4 Powerwall - atm 1400 cells growing

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#12
(12-16-2018, 02:17 PM)emuland-metroman Wrote: test single cells and then spotweld

I hadnt thought of that. .... [long silence] ....

Yes, I suppose if brand new homogeneous cells are being used which test identical capacity/IR when checked individually, that would work -- but I don't think thats what is happening.

cells deteriorate at different rates, and various brands have disparate nominals voltages ... not only is capacity in question but also internal resistance and other stuff which can vary by a significant margin.

once cells are welded together then their discharge rates (mA) are proportional to their RELATIVE capacity.  IE while their C rate of discharge is locked together, their mA discharge rates are all different.  Capacity changes with discharge rate.  therefore once welded together, capacity is unknown/untested.

so like I said, I considered doing this style, but gave up after realising it was beyond the spec of my Opus to measure [capacity > 10000mAH].
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#13
Question - why did you place individual in-line (serial) fuses between each of your modules?
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#14
(12-16-2018, 05:35 PM)DCkiwi Wrote:
(12-16-2018, 02:17 PM)emuland-metroman Wrote: test single cells and then spotweld

I hadnt thought of that. .... [long silence] ....

Yes, I suppose if brand new homogeneous cells are being used which test identical capacity/IR when checked individually, that would work -- but I don't think thats what is happening.

cells deteriorate at different rates, and various brands have disparate nominals voltages ... not only is capacity in question but also internal resistance and other stuff which can vary by a significant margin.

once cells are welded together then their discharge rates (mA) are proportional to their RELATIVE capacity.  IE while their C rate of discharge is locked together, their mA discharge rates are all different.  Capacity changes with discharge rate.  therefore once welded together, capacity is unknown/untested.

so like I said, I considered doing this style, but gave up after realising it was beyond the spec of my Opus to measure [capacity > 10000mAH].

i weld toghether 5 cells from 1000 to 1399 mah (lifepo4 18650).

after doing math on 5 cells, test with opus. variance is around 10% and IR is far low than 1 single cells (parallel resistor rules owns)

so i can say with 0.5/1A discharge capacity will growth and IR lower.

Cartridge system is nice for "hotswap" cells (i mean disconnecting big parallel, check what's wrong, pick faulty cartridge and swap with fully working)
i'm planning/slowly doing 1000+ cartridge... with 8 separated 8S pack only for "hot swappable" advantage
Building Lifepo4 Powerwall - atm 1400 cells growing

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#15
(12-17-2018, 01:14 AM)photon4 Wrote: Question - why did you place individual in-line (serial) fuses between each of your modules?

it looks to me like the fuses go from each 'cartridge' to the busbar.

this provides a similar safety feature that cell-level fusing does.  IE hopefully disconnecting a cell (or group of cells, in this case) that are failing/failed.

(12-18-2018, 08:13 AM)emuland-metroman Wrote: [...]

after doing math on 5 cells, test with opus. variance is around 10% and IR is far low than 1 single cells (parallel resistor rules owns)

so i can say with 0.5/1A discharge capacity will growth and IR lower.

Cartridge system is nice for "hotswap" cells (i mean disconnecting big parallel, check what's wrong, pick faulty cartridge and swap with fully working)
i'm planning/slowly doing 1000+ cartridge... with 8 separated 8S pack only for "hot swappable" advantage

ok, yeah fair enough.  I guess I just got stumped on my own musings and gave up etc.  I do like this method though..

the key, IMHO, is too have a 'big enough' battery.  Read: keeping charge/discharge well below 0.1C ... then it all works out ok.

thats quite a goal you have there (1000+ cartridge).  excellent.   : )  keep us posted for sure.  pictures good.  I got here from finding the images in the 'gallery' feature of this forum ... yours definitly caught my attention, thanks for sharing.
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In The Morning !
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#16
Ive never tested IR on any cell that ive used to date. Properly vetted cells are going to perform everything I need them to. I think adding IR as a cell testing stage adds yet another step that isnt needed if proper steps were already taken. It would make it even harder to mach up a 14s string of cartridges having yet another requirement to consider. FYI I still havent had to do any manual balancing to the wall since my initial balance.

I know I will have to extend my bus bars higher and move my inverter to make room for the next batch of cells that are waiting to be tested. I was thinking crushing the top of the current bus bars flat and torch soldering another length of pipe with an equal flat portion in contact. I know...I should have just made them taller from the get go but I didnt lol! Any better or easier ideas there?
ARLISS likes this post
Cartridge Wall


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#17
(12-12-2018, 07:21 PM)mr_hypno Wrote: Hello all! Finally getting around to my build thread. 

I Started messing with batteries last year (summer 2017), and my humble beginnings started with whatever I could get my hands on. So free lawnmower and heavy truck batteries was my go to. I built up a 48V bank that eventually had about 5KWHs on the AC side and ran a Reliable brand 1500w inverter (it eventually got killed and I tried anotger 3500w with no luck and they have been replaced with an MPP PIP1648MSX). Eventually adding 2.6KW of solar panels (just leaning up against my garage). After getting the basics down I went on the hunt for 18650s.

 

After many months I tapped out every local source of free or cheap lap top packs. I had just enough good cells to make an initial 4s120p pack (1500-2800mah). I hate soldering with a passion so I decided to do a spot weld build. In the mean time I aquired a sweet gift that a buddy found for me! A Magnum 12v inverter that could handle up to 20v input. So after building the packs I began to play with my lithium ion setup. It worked great and put out about 3.5KWHs. I still use this system to this day. Ive had to tear apart 1 pack because it was slowly getting unbalanced from the others after a year of faithful service.



So after getting used to the basics of running that system I decided to do a little more investing in good quality 18650s through Alarm Hookup and Power2Spare on ebay. I finally aquired enough cells to do something with but wasnt satasfied with making large packs, especially my spot welded ones with no cell protection. In the mean time I dabbled in large format cells and bought some Nissan Leaf modules. These kept me satisfied for a while but the expense of them drove me away from buying more. I sat idle with 1000 tested cells just kind of in limbo what to do with them. Then I caught a glimpse of Glenn Andrew Lockey's cartridge wall. That was my que to get moving on a build. Without dragging you guys down with a bunch of useless build crap, ill get to the point.



The system uses cartridges of 6 18650 spot welded and then placed in a 4 slot holder that is fused at 5 amps per slot to each bus bar. The system works great  and is quick to expand with the only soldering being the joints from the 4 slot holders to the bus bars. Then its just a matter of capacity matching each 6 cell cartridge. So far I have soldered 3 units high and have filled 11 of the 12 slots. Ill have to extend my bus bars to allow for more cell holders to be installed. I haven't done a full capacity test yet but will eventually. Im guessing its about 11-12KWHs on the AC side with my Nissan Leaf stack in parallel. I still have yet to use a BMS on any system I have used and I know I should invest in one! For now im going to use my little volt meters to keep an eye on everything. They have been staying very well balanced.




Im not very good at this whole forum thing so ill be uploading pics from my phone in the next post. This could get messy!

Thanks and happy powerwalling!

'Hello, I really like the cartridges style packs. I am about to get started on my small power wall. I am having a hard time getting enough batteries to build a big wall but need to get started. Is there anything you would do differently from the start that may be of help to someone like me being new to building a power wall? Hopefully when things get better I can get more batteries, as of now I only get what I can free and most of them are from power tool packs that are on the lower side (1000 - 1200) so making the cartridges may be better for me right now. I do have some higher ones (1800-2200) but for the most part they are the lower ones.  I need all the help I can get lol. POWER NO!'
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#18
ARLISS: reply outside of the [ quote][ /quote] section, not inside and preferably 'after' the quoted section. I fixed your previous reply.
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#19
This is awesome! I love the idea of it. The reduction in making the bus bar wiring per one of those 80p (or in my case 60p) packs makes it totally worth it! If I hadn't already done mine the way I did I would switch immediately! I think the battery holders would work just fine, I have a few of them and the tabs on them are so tight that I had to compress them more to make it easier to remove the batteries. Besides, like you said, the larger the pack the less you will pull out of each cartridge. Assuming a large cartridge of 10 batteries with a max amp draw of 1A, you're talking 10A. That's not a lot. In normal usages in a properly sized system you should only be charging and pulling at most .5A (for optimal life and performance). I don't think we have to worry much about IR either.

I just like the fact that you can install a new cartridge so easily! It's like a major production to put together enough to build one set of packs. Just nickel strip a set of them and in less than 30 mins I'd bet you have a new row done! This would just make it so much easier! I can put all the sanyo heaters on set of cartridge and if it's ever a problem I can remove the whole row of them.

The cost is always a factor with those PCB and cell holders type design, but this seems to do away with that notion. The downside is that it's not properly secure, but that can be fixed. In fact, I think it might end up being cheaper than the the usual 80p design too, since it does away with the 4x5 cell holders and the need to make so many bus bar wires, which isn't cheap either.

Thanks for sharing!
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#20
Great project.
Out of interest has anyone got a link to the original project by Glenn that was mentioned? Googling didn't seem to find it...
bogptrsn likes this post
Running off solar, DIY & electronics fan :-)
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