I used 1" x .185" copper bar stock for my bus bars, and 20 mm stainless studs. 20 mm seemed to be the sweet spot for me for the thickness of the bus bar and the BMS leads. I put some no-ox grease on the terminals before I bolted everything down. Then put heat tape over the terminals and connections. So far so good.Copper bus bar material came in today!
If I go with this, there will be no questions about capacity should I decide to add another 4 cells.
I'll probably need longer bolts!
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McMaster Carr has aluminum threaded rod on their website. They may have aluminum screws, too.It took a few days with only 10A charge capacity to get the cells to full charge for a top balance.
I'm now in a holding pattern waiting for the BMS to arrive.
In the meantime, I have ordered some copper and aluminum bar stock to make some improved bus bars. I bought both because I'm still debating in my head and researching which is the lesser of the two evils. Lower conductivity of the aluminum, or the galvanic reaction between copper and aluminum.
The interesting thing is that the bolts that came with the cells are brass to throw in another galvanic element. I'm leaning towards heavier aluminum bus bars as long as I can find 6mm aluminum screws to hold it all together.
What is the problem with zinc?Whatever I use, I will definitely put connector lubricant on it to reduce the available oxygen to cause corrosion.
I read the contents of Noalox and I'm not a fan because it has zinc suspended in it.
I have a can of SuperCorrA that does an amazing job of protecting connectors.
I think they are worried about electrolysis. I have had lithium batteries in place for over a year now with mixed metals holding them together without any issue at all. This could be a problem 10 years from now but for now it is not. So I use zinc boltsWhat is the problem with zinc?
I'm finding some aluminum hex head bolts and cap screws on eBay...
It is in the specs as a not to exceed number. I am using Nord lock washers.How much torque is needed on these bolts?
From what I understand the early versions of these batteries had M4 terminal holes, but the latest ones are M6. My batch was ordered in early April and they’re M6. The latest spec sheet says M6 too. (Version E). Go with M6 terminals.Are the threads in the terminals M6? I found someone selling these cells on Ebay and the spec sheet he has says they are M4, but that seems tiny for such large cells.
That's the rub isn't it. Its the conductivity between the aluminum terminal and the copper wire that is the most important.How much torque is needed on these bolts? I'd worry about stretching aluminum bolts, especially mystery bolts from ebay, and terminals getting loose as a result. What about using stainless bolts with PTFE shoulder washers to keep the bolts from contacting the terminals or bus bars?
My environment will be low humidity so hopefully the threads last 10 years. I have several fall backs if they don't. Retap the hole to the next size up or insert helicoils. I will also be happy if my cells last 10 years.Your threads are eventually going to corrode away and you have no way to connect to your power source.
@Craig On this forum was selling some Chargery BMSs a while back. Check with him to see if he has any left. I personally use the Chargery BMS8T and have been very satisfied with it.I reached the end of the rope on my BMS. July 1 was the last date they gave me for delivery. The tracking numbers still say "departed original country" after having been "received by airline".
I filed a dispute with AliExpress. I don't know if they will eventually be delivered, but I now need to find another BMS. I just hate that I have been waiting 2 months already and have to start over.
Does anyone have a link to the BMS they bought that delivered quickly?
The BMS I ordered was a 120A. My needs are pretty simple for this project. It's a modern mini camper with all LED lights and a Dometic fridge that doesn't draw a lot of power. It's too small to consider running the air without shore power or generator.What BMS would be good for a 4S pack of these? I assume the max discharge rate would be around 280A, although if I build a pack I would use it to power a 2Kw inverter so I don't see myself pulling more than ~170A continuous out of this pack. Can 3x 60A BMS be used in parallel? Or should I just spring for a 200A BMS?