LG Chem Module Build

t3kn0f1l3

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I started this discussion about a battery bank I'm building by posting in W0ss' thread, here, but was given the welcome tip to begin my own thread, so pls. bear with me while I try to summarize the early stages of my build.

I'm working on my first battery build for a ~ 3kw solar array paired with a battery charger/inverter (I've not yet determined which one, but am back and forth between a Schneider and a Radian, 4 kw model either way).

The build I'm working on has (3) li-ion LG chem modules, each of which is wired as: (3p 10s) + (3p 8s). I am still trying to decide exactly how to configure the battery bank, but probably want 48V nominal and want to add BMS protection. One possibility is that I remove a few cells from ea. of the (3) (3p 10s) modules and end up with each of the three modules as (3p 16s) with 18 total cells leftover for another project. Maybe, though, I'll keep all 18 groups in ea. module in series and try to find a charger-inverter with a high cut-off voltage - I'm not sure yet, but I just learned that the Radian inverter I was eyeing cuts off at 64V, so either the original module set up (3p 18s) or the Radian inverter would have to change. Any tips/suggestions on this point v. much welcome.

One other detail:

The cells are the LG chem N2.1 60ah cells:
Max charge full voltage4.2V
Discharge cut-off voltage2.8V


If possible I'd like to disturb the modules as little as possible, so I started by trying to figure out the existing (2) two 8-pin connectors ([1] one of them in the first pic below). By the way, if anyone could tell me the connector part # that fits this, or even how to find the part #, I'd be really thankful. I googled and searched a few forums, but no luck so far.

I started working on the 3p 8s module first, trying to pin out the connector. . . . I guess it makes sense to say first that if anyone has the pin-out for this module or if it has been posted somewhere and I missed it in my forum search, please let me know. I would be very grateful for that info.

For now, I went ahead, using floydR's directions here (thank you), and got as far as what is for me a puzzle with pin2 in the connector on the Left hand side (with the mounting plate on the bottom) of the (2) two 8-pin connectors. The second pic shows my progress so far and also presents my current (sorry, that's got to be an old joke here) puzzle:

each set of (3) parallel cells has ~3.4 V. The trouble I am having with pin 2 is that I am getting only half that voltage when I test pin 2 with several of the the bus bar points, e.g. pin 2 - R side CV1: 1.7V and pin 2 - R sideCV2: 1.8V. It's as if somehow pin 2 cuts one of the cell groups in half, but I am clueless as to how that would work. For me, the mystery deepens when I measure pin 2 - L sideCV1: 3.4V.

Any help appreciated.
 

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t3kn0f1l3

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HI OffGridInTheCity,

The cells I have are like the ones in this video, but (I think?) a bit different than the ones you linked. I'll upload a few pics here of my modules so that it's more clear what I'm working with.

If I go with (3x) (3p 16s), i.e. removing (6) cells from each of the (3p 10s) sections of my modules, I'll probably try assembling a D. Poz-style module with my extra cells. I really like the level of detail he shares in the video.


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OffGridInTheCity

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One more comment - I think these are Lithium-ion (instead of LifePo4) so it would be 14s for a really good 48v nominal battery instead of 16s. Nothing 'wrong' with 16s except that it puts the voltage range higher than mainstream equipment so you'd have to pay special attention to the voltage range.

And yes, @DavidPoz is the 'real thing' / good detail - been following him for a while now :)
 

floydR

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Can you access the voltage sense wire directly? It may be easier to figure out the first ten cells in series then the first 4 cell in series in the 8 cell module. split the 8 cell module in half you could have 24 cells in reserve /use for other projects. There are more choices in 48v inverters than there are in 60v inverters

Later floyd
 

Mart Hale

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I have the same cells, I just bought a 36v inverter and hooked all 3 of min in parallel. I have a thread going about my adventure here ->


I soldered them at first then after those fell off I drilled a tiny hole thru and I used small bolts and terminals to connect my BMS up. Oh yeah, be careful with these some of the terminals are reversed and positive and neg are NOT on the same side on all batteries, I found out the hard way by destroying 2 bms, just verify polarity with these and you will be fine. ( if you have the same modules as mine, they look the same ).
 

t3kn0f1l3

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Quick update: I think I found the connector as I was searching last night. From what I can tell, the module's boards have this, which pairs to the part I need (I think?): Molex Part 347910080, Mini50 Unsealed Receptacle, Single Row, Non-Bridged, 8 Circuits, Polarization Option A, Black. Two details on this - first there are (3) different polarization options for this part, and I think this module's board has the connector with Polarization option A, but I am going to order and test the part before I know - I will post to confirm either way. 2nd detail: If I am right about this part, then for anyone in the same boat, the above is just the casing - the crimp tins are also required (8 pieces/connector), Molex Part 5600230448‎ - N.B. this particular one is the 22AWG tin; there is a different tin for the 24AWG connector. Now to figure out what wire and what crimper to get . . .

[EDIT: The Molex connector part arrived and I tested it (without the tins). I can confirm it works]
 
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t3kn0f1l3

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One more comment - I think these are Lithium-ion (instead of LifePo4) so it would be 14s for a really good 48v nominal battery instead of 16s. Nothing 'wrong' with 16s except that it puts the voltage range higher than mainstream equipment so you'd have to pay special attention to the voltage range.

And yes, @DavidPoz is the 'real thing' / good detail - been following him for a while now :)
I think I see the wisdom in this - fairly straightforward physical separation of (at least one of) the the 8s 3p module's busbars into (2x) 4s 3p segments using tips by GXMnow, the other one would be a bit more work, but still quite do-able. Voltage range would be between 39.2V Discharge cut-off and 58.8V MAX, so I could run it maybe between 44.4V (3.2/cell) - MAX 57.4V (4.1/cell) or even 56V (4.0V/cell), so as to keep it around for a while. I take yours and floydR's point about this voltage range's compatibility with more mainstream inverters. Hmm . . . I think I am sold :) Thanks much to you both!
 

t3kn0f1l3

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Can you access the voltage sense wire directly? It may be easier to figure out the first ten cells in series then the first 4 cell in series in the 8 cell module. split the 8 cell module in half you could have 24 cells in reserve /use for other projects. There are more choices in 48v inverters than there are in 60v inverters

Later floyd
Thanks for this suggestion - I'll move on to the 10s 3p module and try to map it out next.

In trying to understand what the 'voltage sense wire' is, I followed this forum thread to this site, which explains: "A voltage sensing circuit is a circuit intended to carry minimal to no current so there is minimal voltage drop in this measurement circuit. The voltage sensing circuit should really be considered a voltage correction circuit or a voltage drop compensation circuit. The voltage sensing circuit works by utilizing these smaller sensing wires in order to compensate for the voltage drop in the larger alternator output wires. The larger alternator positive & negative are actually carrying the high current and even if large will suffer from some voltage drop. Voltage sensing is supplied on these high performance alternator regulators so we can achieve the correct regulator set point voltage, at the battery itself, not just at the back of the alternator. These sensing wires measure the actual battery terminal voltage and allow the regulator to drive the voltage at the battery end to the correct point" (Bold Mine).

Makes sense. I have a Q., though: would connecting pins 2 and 5 in the L-side 8-pin connector in my diagram (re-posted in thumbnail here), which gives the full voltage of this 3p 8s module, give me the 'voltage sense wire,' or is that wire distinct from the connection from + terminal to - terminal that I read when connecting the multi-meter to pins 2 and 5? If distinct, how would I find this wire - I mean what would I look for/test for using the multi-meter?

Thanks v. much!
 

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floydR

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Voltage sense and balance lead I use interchangeably probably not right to do so. The voltage of an 8s with each cell at 3.4v would be 27.2vin your diagram the highest voltage i see is 5.57v. the bms uses the balance leads to balance the voltage on a per cell basis.
first find the voltage of the 8s3p pack you go from first negative /main negative of the pack to the last positive of the pack. Then find the pins in the two connector which give you the same voltage.
Later floyd
 

t3kn0f1l3

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I have the same cells, I just bought a 36v inverter and hooked all 3 of min in parallel. I have a thread going about my adventure here ->


I soldered them at first then after those fell off I drilled a tiny hole thru and I used small bolts and terminals to connect my BMS up. Oh yeah, be careful with these some of the terminals are reversed and positive and neg are NOT on the same side on all batteries, I found out the hard way by destroying 2 bms, just verify polarity with these and you will be fine. ( if you have the same modules as mine, they look the same ).
Hi Mart,
I read through your thread and learned some important cautions. Thanks for sharing-you saved me from a few inevitable frustrations!
 

t3kn0f1l3

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Voltage sense and balance lead I use interchangeably probably not right to do so. The voltage of an 8s with each cell at 3.4v would be 27.2vin your diagram the highest voltage i see is 5.57v. the bms uses the balance leads to balance the voltage on a per cell basis.
first find the voltage of the 8s3p pack you go from first negative /main negative of the pack to the last positive of the pack. Then find the pins in the two connector which give you the same voltage.
Later floyd
Understood. Thanks.(y)
 

t3kn0f1l3

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Today, I tried to pin-out the 10s3p pack and found most, but not all of the bus bar points that (I think) I need to wire a BMS. (Floyd, you were right that the 10s3p pack was easier to pin-out. Thanks for the suggestion.)

Next step for me is figuring out exactly what voltage sense/balance leads I need for wiring the BMS so I can see what I am missing. Here's my diagram and the bus bar points for each pin that I was able to find.

I'm also posting pics of some terminal tins that I pulled out of an extra connector. I used one of these to check voltages on the module pins this time around rather than touching the module pins directly with the multimeter leads - using the tins was a big time saver in trying to pin-out the module's connectors and might help other newbies trying to do this.

I'm now trying to figure out what type of copper alloy and what size/thickness to use for the high current bus bars that I'm thinking of making to connect the (3x) 14s3p modules in parallel. I'm thinking of copper 110 rather than copper 101 because the copper 110 is significantly cheaper, but I don't know because the 110 is supposed to be hard to machine, so I'm not sure if it would be tough to drill/tap, etc. Insights/advice/knowledge on copper sizing and/or copper alloy type welcome.

Right now my pin-out project has stalled, but if anyone has tips to share, maybe on how to test to see what the pins with no voltage do, I'd be grateful. The proper connectors should arrive next week, making further testing easier.

Happy Friday!
 

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t3kn0f1l3

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CONFIGURATION QUESTION:

I read through this .pdf by the Orion people called Strings, Parallel Cells, and Parallel Strings (att.) that an Orion distributor sent to me. Not sure what BMS I'm going to get yet, but this document cautions strongly against parallel strings for a number of reasons. I've begun to think that rather than trying to parallel my 3 14s3p strings, I am better off parallelling all the cells, so I end up with 14s9p. One advantage this seems to bring is that I could use 1 BMS with the entire battery - they said I'd need 3 BMS's otherwise.

If we leave aside the significant extra labour required to configure (3) 14s3p modules as one 14s9p battery, do you see significant upsides/downsides of going this route? Am I crazy to even think of configuring my 3 modules into 14s9p? Honestly, I will spend the money on 3 separate BMS's (not Orion, though :) ) if that is optimal, but the cautions against this in the Orion document have me rethinking my configuration.

Are there already threads you'd recommend on this q. somewhere on this site? Any of your input appreciated.
 

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OffGridInTheCity

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There is nothing wrong with 9p and would be perfectly fine choice. But its also OK to go the other way. In my opinion, its a matter of your individual situation and what you might think will happen in the future - e.g. expansion, p management, etc.

3 battery(14s3p) vs 1 battery - Some might prefer to have 2 batteries active while they work on or maintain the 3rd battery. If you go 1 battery (14s9p) it will be offline when you work on it - perhaps disabling your system. On the other hand, you might be planning a 2nd 9p...

3 BMS vs 1 BMS - If you have 3 BMSs you have 3 things to track/manage and if 1 fails you want to make sure the other 2 are strong enough so they don't trip due to overcurrent. Each of the 3 BMSs require less balance but 1 BMS maybe able to balance just fine. **A healthy pack does not need strong balance once its balanced** You can do the initial balance by hooking them in parallel before configuring the 14s.

I use Batrium because its 1 BMS (my personal bias :) ), is uniquely designed so it doesn't care about 3p or 9p - WM4 can manage up to 200+ individual p(s) - and has strong balance current for easier management (such as adding in a new battery) but its $$
 

t3kn0f1l3

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Thanks OGITC,

That's v. helpful. I understand the limitation of having 14s9p will be that the whole battery is down for any servicing. In my case, I think I am willing to take that risk in order to be able to have the benefit of only one BMS. I'm going to take a look at the Batrium BMS this week - a quick review showed many different components with this manufacturer, so I'll probably give them a call to get up to speed quickly and to get a quick sense of cost for my application. I don't mind spending some $ for extra reliability/safety.

If I do go with 14s9p, I'm wondering how the wiring will work. I've done up a diagram here, and am wondering . . .
Wiring Modules as 16s9p.png


1. Would I leave the existing series connections intact, or would I have to disconnect each of the existing series connections, i.e. between cell groups 1, 2, 3, etc. in ea. module?

2. After connecting the 14 cell groups in each module in parallel, how would I connect the 9p cells in series? Would it be via a separate bus bar? Or, if in my q. 1, I can leave the individual modules' series connections intact, would I simply connect the terminals of ea. module to a 'master' bus-bar terminal - as depicted by my yellow connectors here?

I should also ask - is there anything wrong with my diagram not treated in answering my other q.'s?

Thanks v. much for the help!
 

OffGridInTheCity

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I get nervous about doing my own wiring, much less reading someone else's diagram :) I take these to be the main parallel power for 9p (rather than paralleling for BMS sense leads). Given that, the diagram appears to me 'power connection wise' to be perfectly correct.

I don't think we've discussed the max power (amps) you plan to draw from this 14s9p battery - do you have an idea? For example, if its 80a then you'll want the red wires in the diagram need to be on the order of 4AWG.

If you do 14s9p, and the red wires are power wires, then all the red wires in the diagram above need to carry the max amps of the entire battery. Its not just bus-bars at each end. Bus bar (thinking) would be more appropriate if you did 3 separate 14s3p because each separate 14s3p would only need t carry 1/3 of the max amps from the battery into a common busbar that needed to carry the max amps.

>1. Would I leave the existing series connections intact....
You can. Me, I would do a quick thin wire test - e.g. just touch the endpoints of where the red wire will be bolted/hooked on to make sure there's no short before affixing the red wire. A quick sizzle/melt of a very thin wire is controllable compared to a main amp carrying wire. :)

>2. After connecting the 14 cell groups in each module in parallel, how would I connect the 9p cells in series?
This would be the same as how to I connect the 3 groups of parallel cells to get 9 parallel cells. You either need to physically arrange them that way and use the native mechanics or and connect them using custom wire.

I may not of answered your questions - due my lack of detailed vision of what you're physically planning. The electrical diagram was great - maybe some pics of the units would help if you don't get enough info from this response (or others may chime in).
 
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prepared1

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While you are trying to decide which direction to go, perhaps OGITC would comment if pouch cells in larger format blocks stay fairly balanced if they are new, or in very good condition? Would they be better, or worse than cylindrical, or prismatic in this regard?
 

OffGridInTheCity

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While you are trying to decide which direction to go, perhaps OGITC would comment if pouch cells in larger format blocks stay fairly balanced if they are new, or in very good condition? Would they be better, or worse than cylindrical, or prismatic in this regard?
As in any 2nd hand battery situation - the best approach would be to test each individual unit/cell for ah and IR. BatteryHookup says 'around' 66% of capacity (e.g. 40ah out of 60ah) so these are significantly used. If there's any significant difference (say 5% or greater) then arrange into groups by 36ah, 38ah, 40ah, 42ah, 44ah... (type of thing), eliminate any self-discharge, and distribute evenly to make up groups of 9 parallel (if he goes that way) so that each group of 9 has similar total ah per group.

Same process as 18650 (test and evenly distribute) to get best results.

If that's just all to difficult... then take a chance and perhaps have a 'equalization backup plan' if the shelf has room etc. Its better to build good packs in the first place! and I can't recommend this - but what I did.....

In some of my earlier 1s100p 18650 packs that were built willy-nilly (before I joined this forum and listened to @Wolf :) ), once I saw them in operation via Batrium I 'adjusted' sagging packs (about 10% of them) by tacking on 3, 6, 9 cells to the 100cells. I did this by using 18650 4 x cell holders sitting on top of the pack w/alligator clip wires. Not pretty - but then, when I did maintenance I soldered them in permanently to the pack. This had the desired affect of evening out those few packs.
1616440206545.png
 
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t3kn0f1l3

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I get nervous about doing my own wiring, much less reading someone else's diagram :) I take these to be the main parallel power for 9p (rather than paralleling for BMS sense leads). Given that, the diagram appears to me 'power connection wise' to be perfectly correct.

I don't think we've discussed the max power (amps) you plan to draw from this 14s9p battery - do you have an idea? For example, if its 80a then you'll want the red wires in the diagram need to be on the order of 4AWG.

If you do 14s9p, and the red wires are power wires, then all the red wires in the diagram above need to carry the max amps of the entire battery. Its not just bus-bars at each end. Bus bar (thinking) would be more appropriate if you did 3 separate 14s3p because each separate 14s3p would only need t carry 1/3 of the max amps from the battery into a common busbar that needed to carry the max amps.

>1. Would I leave the existing series connections intact....
You can. Me, I would do a quick thin wire test - e.g. just touch the endpoints of where the red wire will be bolted/hooked on to make sure there's no short before affixing the red wire. A quick sizzle/melt of a very thin wire is controllable compared to a main amp carrying wire. :)

>2. After connecting the 14 cell groups in each module in parallel, how would I connect the 9p cells in series?
This would be the same as how to I connect the 3 groups of parallel cells to get 9 parallel cells. You either need to physically arrange them that way and use the native mechanics or and connect them using custom wire.

I may not of answered your questions - due my lack of detailed vision of what you're physically planning. The electrical diagram was great - maybe some pics of the units would help if you don't get enough info from this response (or others may chime in).
Thanks for this. The thin wire test is a great idea and I will use it - makes me wonder how many other important safety procedures there are as I slowly assemble the system . . . but that for another day.

I am now half way through the module 'surgery' to produce the (3x) 14s3p modules from my original (3x) 10s3p + 8s3p. If I connect these (3) modules into 14s9p, I am thinking that I'll stack them on top of one another inside a welded rack. Since the terminals on the modules should line up vertically, I'm wondering if I can then use vertical bus bars to connect each of the cell groups - so bus bars for the red lines in my diagram (I'll attach that again here. I'm thinking I'd wrap the bus bars in heat shrink tubing for safety - if that method of insulating them will work (?).

Here's a pic of one of the almost finished, newly-configured modules to clarify what I mean in my q. #1 above about whether I could leave the existing series connections intact. I mean - would I be able to leave the existing copper busses that connect each 3-cell group to the next and use the existing module terminals, just connecting them via the appropriate gauge to a common bus bar (the yellow lines in my diagram). Or, do I have to cut these busses, separating each 3p (and so, in turn, each 9p group) and connect them using one single 'meta' series bus bar? My question comes from not knowing whether having 3 separate and distinct series connections would somehow create a problem. I believe your above answer is that I can use the existing series connections and use my 3-yellow line conductors, connecting the existing 3 + terminals to one common +ive bus bar, and the existing 3 - module terminals to one common -ive bus bar. With the pic to clarify, though, is this correct?

Reconfigured Module into 14s3p.jpg
Wiring Modules as 16s9p.png


As for max current draw, I plan to use as much as I can produce by solar. My household use is ~33KwH/day after having reduced and changed out a number of appliances, etc. over the past few years. My plan for this summer is to put in ~3Kw of panels, then in a year or so another ~3Kw. For the inverter, I think I am going with the Schneider XW Pro 6800 W model so I don't have to get another inverter in a year or so for the second panel array. In this case, I would eventually want to run 6000W of power at 48V. Using I=P/V (just showing my math, so it can be corrected, if wrong), I'm getting 125A. If this math is correct, I should be fine with a single 150A BMS? What should my busses (red wires) be, i.e. should they be sized for 150A, or maybe 200A? Please bear with my newbie-level calculation questions here.

I appreciate your help!
 
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