New Energy 20Ah Cells

[Hawkeye]

Does anyone have any experience with the New Energy 20Ah cells from electric car parts? They seem decent to me, but I'm no expert... 4000 cycles at 80% DOD, $313/kW.  https://www.electriccarpartscompany.com/New-Energy-20Ah-Aluminum-Encased-Battery

I'm looking at building a ~8kW battery bank for my home, to be paired with a ~4kW solar array (PV is relatively small due to space constraints). Is it ridiculous to build a 125-cell battery bank?

[Hawkeye]

Weird, I keep getting email responses but they aren't showing up here. First timer... am I doing something wrong?

[Dacian Todea]

Maybe people are replying directly by email and they need to post on the forum if they want the post to be public.

As for those cells they are fairly expensive and typical for small cells.

But since you want a very large pack then those are very expensive. Check the large 280Ah cells available on alibaba at around 80 to $100 those are way better value and being larger capacity cells it will be easier to build a 8kW battery. And 4kW array is to large for just an 8kW battery unless you want to use the dual PV array setup see SBMS0 manual for details on that.  If not a 4kW array will require at least a 12kWh battery and better a 16 to 20kWh one so max charge rate is in the 0.2C to 0.25C range.

[Hawkeye]

Thanks for the reply Dacian, that makes sense. I hadn't thought about the charge rate, I will work on budgeting a larger battery bank.

I'm a little wary of spending that much money on Alibaba, but it seems like the folks on this forum generally have pretty good success. I've also been looking at Winston; they quoted $360 per 300ah cell (WB-LYP300AHA) direct from manufacturer. Plus $1850 shipping (for 4 cells!). Sure is a big price delta... are Winston batteries really that much better?

Thank you for sharing your wisdom, this forum has been super helpful. A friend of mine used your BMS in his school bus and had nothing but good things to say. I have a lot of respect for what you've got going here :)

[Dacian Todea]

Winston cells are good but not at those sort of prices.  $360 for a 300Ah battery vs $80 in some cases for a 280Ah CATL battery (CATL is one of the world largest battery manufacturers where winston is not even on that list).

[Hawkeye]

Gotcha. Is there a higher Ah CATL battery (~600Ah+) that you recommend? I'm feeling better about Alibaba with a CC, but it sounds like paralleling the 3.2V batteries isn't the best for balancing. (https://diysolarforum.com/threads/ordering-16x-280ah-cells-from-shenzhen-luyuan.13862/) Or am I misunderstanding? 

[Dacian Todea]

Any number of parallel cells will be no different in any way than a single higher capacity cell. The parallel cells have no choice other than to be at exact same voltage so perfectly balanced.

What is not allowed is to parallel batteries made of multiple cells in series.

So if you buy 16 cells to build a 24V battery the only allowed option is to parallel groups of two cells so it will be the same as having a single 560Ah cell then 8 of those groups will be connected in series.

[Hawkeye]

Excellent, that makes sense. Thanks Dacian.

[Kohala Jim]

I'd be watching intently if you proceed here...
my first battery attempt will be a 4s20p build