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diy solar

CATL 271Ah 'Grade A' prismatic cells from Shenzhen Basen - Cell terminals without threading

iirc they're limited to 150W and you can enable 180W if you go through the setup menu. but the heatsink might not be able to shed all the heat
 
Here it is so far. The compression case was inspired by other people's work in this forum. I might put a surface across the diagonal part and put my monitoring display there.

I'd like to add a fuse as a precaution. Is the best place to put it on the negative side between the load and the BMS?

Also, this is going to be part of a solar system powering a shed, but I also want this battery and the inverter to be easily 'detachable' from the solar part so I can bring it into my main house if I want to use it during a power outage. Any thoughts on the best way to make my system modular like this - in terms of wiring, connectors, and housing - would be appreciated.
 

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Thanks, that's good info.

My big concern with helicoils is they are stainless steel being mounted into aluminum, which risks galvanic corrosion over time. I would not use anything in aluminum other than zinc. YMMV of course.

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you might want to look at your chart again... the cross point on the chart between aluminum and zinc is red..which means it will actively corrode. I think you meant aluminum possibly? even though stainless shows as a light green which says "Light Green = Metal Combinations that have no issue."
 
Helicoils have been used in aluminum for 50 years.
It's not a thing to worry about.

So we have : battery terminals are from aluminum , over them we have laser welded STEEL stub with the nut from steel and we connect zinc covered copper bus bars .

The possible poor connection I have seen is between bus bar and very small size of the stub from the battery that is 1mm wide .

can we use a special conductive paste the ensure better conductivity and 10 years of corrosion free for the contact ? I don’t think WD40 is designed for this, it is too liquid and evaporate.

what are your thoughts about this ?
 
So we have : battery terminals are from aluminum , over them we have laser welded STEEL stub with the nut from steel and we connect zinc covered copper bus bars .

The possible poor connection I have seen is between bus bar and very small size of the stub from the battery that is 1mm wide .

can we use a special conductive paste the ensure better conductivity and 10 years of corrosion free for the contact ? I don’t think WD40 is designed for this, it is too liquid and evaporate.

what are your thoughts about this ?
Your concerns are quite legitimate, in my experience.

WD40 is definitely not approprate to improve conductivity. It is good a good lubricant for cutting and tapping aluminum, but not as a coating between conductors.

My cells, at my request, came with the 6mm threaded terminal holes. After much consideration, and minor struggles with two (out of 48) terminal threads being loose, I now affix all of the studs into the threads with epoxy adhesive. I am pleased with the performance of that solution.

Subsequently, over several months, I had minor trouble with “high” resistance connections between terminals and bus bars. In most applications this “high“ resistance would not be discernible, but because we monitor cell voltage to 1 mv of resolution with the BMS, we can easily detect it as "cell" voltage deviation. I eliminated those variations by carefully cleaning contact surfaces with a Scotch-Brite pad, wiping with acetone, and applying a super-thin coating of MG Chemicals “Silver Conductive Paste” to the terminal contact surface. The silver paste looks expensive for a tiny tube, but that tiny tube will last me a LONG time. Only a fly spec amount, spread with a rubber-gloved finger, is needed for each terminal, and it is working great!

Others will suggest here that the silver paste is foolishly expensive, but I doubt if they have tried it. Personally. I do not at all like No-Alox, or other “conductive grease” for this application. One great thing about being a DIY-er is that you can pick your own preferred solution.

BTW, the bus bars are tin plated, rather than zinc plated.
 
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