LG Chem Module Build

Cheap 4-life

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I didn’t have time to thoroughly read thru this entire post but I figured I’d mention that I’ve seen a few people have expanding issues with these cells due to not compressing them. They weren’t drawing a lot of amps. My mistake if you already mentioned compression.
 

OffGridInTheCity

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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?
Yes, your numbers / thinking are good here. For wiring, 2AWG (33.6 mm2, chassis a = 181, transmission a = 94) would likely be adequate for short runs. Some like to go thicker - as in 1/0AWG (53.5mm2, chassis a = 245, transmission a = 150). I use this chart for my decisions - https://www.powerstream.com/Wire_Size.htm Chassis a (very short runs) can handle a LOT more than Transmission a (longer runs - say 10, 20ft+)

Excellent pic/wiring-diagram - really help discussion and gives you something to check off when doing wiring!

> I could leave the existing series connections intact.
Yes I agree. Once you're in a position to put a load on the battery (or part of it) you can just pull the amps and touch the existing connections to see if they are warm/hot. As long as they stay warm->cool under max load, then that's all you need in my opinion.

>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
Sure - whatever works with hookup/easy-maintenance for the physical battery. For my inter-pack connections, I buy smaller copper pipe and flatten it, cut it into bars, and drill holes to use bolts to hook packs together. You just need the overall mm-squared (n the chart above) to carry the amps you need.

>wrap the bus bars in heat shrink tubing for safety
Again, great! Some use shrink-wrap. I use electrical tape - have gone thru 10-20 roles of it over 3 years. I really like to make sure + = RED and - = BLACK. So I'll wrap black wires 100% to make them RED if they are positives. In this way, the #1 rule - don't touch RED and BLACK except when hooking in series + to - :)

>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
Again, sure. Me personally - I'm good with non-uniformity to leverage what's there as long as the connections are sound and maintainable.

For the hookup, this is what I'm picturing from the conversation... and if this is correct, then yes sir, you're right in the zone. It sounds like you have a firm handle on things, a good diagram for hookup, and thinking about things very well... :)
1616509719410.png
 

t3kn0f1l3

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I didn’t have time to thoroughly read thru this entire post but I figured I’d mention that I’ve seen a few people have expanding issues with these cells due to not compressing them. They weren’t drawing a lot of amps. My mistake if you already mentioned compression.
Thank you for this tip. I watched D. Poz compress these cells in a video where he makes a module from individual cells, but I had no idea why. I still have one original module that I've not touched, and will measure torque on the bolts before disassembling so when I re-torque the newly-configured modules, I'll at least be in position to avoid this problem. If anyone's interested, I can post the torque specs that I find here. Just let me know. Do you know if the problem was due to not compressing at all, or compressing, but just not enough . . . ?

Thanks again for the tip!
 

t3kn0f1l3

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Yes, your numbers / thinking are good here. For wiring, 2AWG (33.6 mm2, chassis a = 181, transmission a = 94) would likely be adequate for short runs. Some like to go thicker - as in 1/0AWG (53.5mm2, chassis a = 245, transmission a = 150). I use this chart for my decisions - https://www.powerstream.com/Wire_Size.htm Chassis a (very short runs) can handle a LOT more than Transmission a (longer runs - say 10, 20ft+)

Excellent pic/wiring-diagram - really help discussion and gives you something to check off when doing wiring!

> I could leave the existing series connections intact.
Yes I agree. Once you're in a position to put a load on the battery (or part of it) you can just pull the amps and touch the existing connections to see if they are warm/hot. As long as they stay warm->cool under max load, then that's all you need in my opinion.

>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
Sure - whatever works with hookup/easy-maintenance for the physical battery. For my inter-pack connections, I buy smaller copper pipe and flatten it, cut it into bars, and drill holes to use bolts to hook packs together. You just need the overall mm-squared (n the chart above) to carry the amps you need.

>wrap the bus bars in heat shrink tubing for safety
Again, great! Some use shrink-wrap. I use electrical tape - have gone thru 10-20 roles of it over 3 years. I really like to make sure + = RED and - = BLACK. So I'll wrap black wires 100% to make them RED if they are positives. In this way, the #1 rule - don't touch RED and BLACK except when hooking in series + to - :)

>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
Again, sure. Me personally - I'm good with non-uniformity to leverage what's there as long as the connections are sound and maintainable.

For the hookup, this is what I'm picturing from the conversation... and if this is correct, then yes sir, you're right in the zone. It sounds like you have a firm handle on things, a good diagram for hookup, and thinking about things very well... :)
View attachment 24403
Thanks much for this feedback and for the wire-gauge link. I will take your example and use red and black colouring for the shrink wrap on the bus bars. Maybe I'll also print up and post your #1 rule inside the cabinet, once I've got that sorted. I'm constantly aware that I could be doing something that will destroy my equipment and/or worse, so esp. given that I am admittedly a newbie, any safety /damage-prevention advice also much appreciated.

Thanks for posting the pic. It's almost what I'm going to end up with, but I've gone in and adjusted the configuration in your image and updated it to what I have. Please correct me on this if I am wrong, but I do not believe that this really changes the wire gauge/amp specs and recommendations from your representation, but just so anyone reading the thread (especially anyone with the same module) does not get confused:

Newly_configured_total battery.png


Thanks again!
 

Cheap 4-life

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Thank you for this tip. I watched D. Poz compress these cells in a video where he makes a module from individual cells, but I had no idea why. I still have one original module that I've not touched, and will measure torque on the bolts before disassembling so when I re-torque the newly-configured modules, I'll at least be in position to avoid this problem. If anyone's interested, I can post the torque specs that I find here. Just let me know. Do you know if the problem was due to not compressing at all, or compressing, but just not enough . . . ?

Thanks again for the tip!
No I don’t know how much they were compressed, but they cells-packs I seen expand did not have any compression
 

t3kn0f1l3

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No I don’t know how much they were compressed, but they cells-packs I seen expand did not have any compression
OK, thanks. I'll post torque spec after I have the chance to measure it from my one untouched pack - for anyone with the same module.

[Edit: torque for the threaded rods is somewhere around 60 in. lbs. I am guessing the exact spec will be in the chevy mechanic's manual. Does anyone know if the mechanics manuals for the different EV's are posted somewhere on this site?]
 
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400bird

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Cool build, I am trying to get my hands on a full Bolt pack. But they are scarce right now, I blame GM for buying them and burning them down in testing their software update

Anyways, I can't tell exactly what you have going on in that pinnout. But, my guess is that the unknown pins are temperature sensors.
 

t3kn0f1l3

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Thanks 400bird.

Had to go back to paying work recently, so slowed down on the build, but am still chipping away.

Seems like there's a shortage of a bunch of things these days. Didn't know about the full Bolt pack shortage. I'm guessing you are checking salvage yards through https://www.car-part.com/ ? Are you planning to use the full pack for solar backup?

About the unknown pins, I've got the Molex connectors now and, once I'm finished with my battery surgeries, probably end of the coming week, I'll go back to this part of the project. In this video, starting ~5:15-6:20, D. Poz figures out that one of his pins has no reading because of a blown glass fuse on his board. I'm guessing that either you're right about the temp. sensors, or I have one/some blown fuses. Will know better in about a week.
 

400bird

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Yes, I just found a pack (4 miles on the odometer) on car-part and now the national search is back to 0 results for a Bolt battery.

I am not planning to use the entire pack. My permit is written for 2* 14s strings. I may add 1 or two more once I am through permitting.

I'll have to sell off the remainder. Or maybe BIG battery? I could do 60kwh of battery!

Right now, the pack hasn't even shipped yet, so I am far from that point.
 

Cheap 4-life

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Thanks 400bird.

Had to go back to paying work recently, so slowed down on the build, but am still chipping away.

Seems like there's a shortage of a bunch of things these days. Didn't know about the full Bolt pack shortage. I'm guessing you are checking salvage yards through https://www.car-part.com/ ? Are you planning to use the full pack for solar backup?

About the unknown pins, I've got the Molex connectors now and, once I'm finished with my battery surgeries, probably end of the coming week, I'll go back to this part of the project. In this video, starting ~5:15-6:20, D. Poz figures out that one of his pins has no reading because of a blown glass fuse on his board. I'm guessing that either you're right about the temp. sensors, or I have one/some blown fuses. Will know better in about a week.
That fuse was on a Chevy Volt. I don’t think the Chevy Bolt comes with a fuse for each cell on the battery
 

t3kn0f1l3

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Yes, I just found a pack (4 miles on the odometer) on car-part and now the national search is back to 0 results for a Bolt battery.

I am not planning to use the entire pack. My permit is written for 2* 14s strings. I may add 1 or two more once I am through permitting.

I'll have to sell off the remainder. Or maybe BIG battery? I could do 60kwh of battery!

Right now, the pack hasn't even shipped yet, so I am far from that point.
Excellent! Sounds like an ideal pack. In terms of permitting, I'm also planning to pull a permit, but have no idea what kind of regulation my inspector will be following to check the battery. All he told me is that all components have to be certified, but I'm not sure what that means when it comes to the battery, and don't want to push it. I'm not sure, for example, what he'll say about a BMS. What's your situation for permitting on the battery part of your system?
 

400bird

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I am excited to get the pack and tear it down. But, it hasn't even left the junk yard yet.

My city the (AHJ) is under and following CEC 2016. Which I believe comes from the NEC 2014. This older electric code does not require the battery to be UL listed at all or even for the application. Newer code does call for all components to be UL listed. I would double check with the permit office to see what version or year of electrical code they are using.

If my area had adopted the newer code I could not use the Bolt battery.

My code does require the inverter and some other components to be UL listed, so no knock off inverter for me. I am also limited on max DC voltage, so I can't run one of the HV DC inverters.
 

t3kn0f1l3

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That fuse was on a Chevy Volt. I don’t think the Chevy Bolt comes with a fuse for each cell on the battery
Yes, good point. I'm not sure either, but there are white globs of some type of rubber insulator on the board. I'll pull them off when I get a chance and take a closer look. Here's another pic.
 

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t3kn0f1l3

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I am excited to get the pack and tear it down. But, it hasn't even left the junk yard yet.

My city the (AHJ) is under and following CEC 2016. Which I believe comes from the NEC 2014. This older electric code does not require the battery to be UL listed at all or even for the application. Newer code does call for all components to be UL listed. I would double check with the permit office to see what version or year of electrical code they are using.

If my area had adopted the newer code I could not use the Bolt battery.

My code does require the inverter and some other components to be UL listed, so no knock off inverter for me. I am also limited on max DC voltage, so I can't run one of the HV DC inverters.
OK, thanks. I'll find this out. For framing inspections, my AHJ tends to use older codes rather than newer, but it seems important that I get clear on the version of the electrical code and then get everthing installed and inspected before they upgrade :). Appreciate the tip.
 

400bird

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Talk about failed inspection. My permit expires soon. I'm going to have to call for an inspection and fail (because the work is not complete) to extend my time.
 

t3kn0f1l3

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I've started to balance one of my 14s3p modules by 1. recording the voltages of all 14 cell groups and then 2. using a Battgo charger to bring the slightly lower cell groups up. Once I've got all cell groups to within 10mV (.01V), I'm planning to hook up a REC BMS that's on its way now. I've read through a few threads and also this document (v. good) on top balancing for LiFpo4 cells, but are different from the NMC LG cells I've got. For anyone working with these modules, GXMnow has a detailed protocol that makes good sense to me and that I'm using.

My q. now is how to charge the 14s3p module for bench testing while I'm still without the solar Inverter/Charger - the Battgo charger goes up to max ~30V, but I need something that goes to ~60V. Here's what I'm thinking, but please weigh in, 'cause I don't know if this is viable: I have (3x) old laptop power supplies, each one 19.5V, 3.34amp, (giving me 58.5V, 3.34 amp). Can I just wire these three in series and use them to charge my 14s3p module once I've got the BMS connected to it? Other than the ridiculously long time (~1week) to charge, would I be doing damage?

Any feedback appreciated.
 

OffGridInTheCity

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Don't know if you can series these or not. If the battery is at 48v I don't think you want to charge at 58v... you want something more gentle - e.g. a charger typically is a few volts higher and adjusts as the charge happens. Maybe I'm wrong - others will surely comment :)

But, you might be better off just buying a charger that can pump in enough power to do it in reasonable time - something like this 4a - 200w range for $60 - https://www.amazon.com/58-8V-Charge...14s+lithium-ion+charger&qid=1617399838&sr=8-5 or beefier
10a - 500w range - https://www.amazon.com/Charger-Lith...=1&keywords=14s+charger&qid=1617399420&sr=8-3

A 14s charger is one of those generally useful tool when you have 14s batteries :)
 
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400bird

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I would guess that you cannot use the laptop power bricks.

From my research the DC- is connected to the AC neutral. So trying to series the chargers actually creates a short.
You can easily test this with a meter to verify.

Second, most of that type of charger is unregulated. So, it's just going to pump out full blast until it overheats or fails in some other way.

A bench power supply, adjustable DCDC converter, or (preferably) an actual 14s charger would work.
 

t3kn0f1l3

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OK, thanks OGITC and 400bird. I'll look into these two options. Was trying to work with what I have until I get the inverter/charger, but no sense in cheaping out over this and wrecking something. Feedback appreciated.

[Edit: just ordered the unit on the second of OGITC's 2 links, Model: YL600, i.e. 58.8V 10A, 14s Charger. Says it's suitable for 51.8V batteries, but also says it's good for 14s li-ion, so charges up to 58.8V (4.2vx14s). I'll post again after receiving to let you know if/how it works (~2 week shipping). If anyone's got tips, especially common errors that I should avoid in charging full modules, pls. let me know/post a forum link. Thanks!]
 
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