Are EV grade battery and solar grade battery manufactured differently?

Hello
I've been looking to buy 32650 size cylindrical LFP cells and the most common attribute I'm being asked is whether I want an EV grade cell 3C discharge rating, or Solar grade cell 1c discharge rating (sometimes 0.5c).

As far as I know, the cell manufacturing process remains the same, and the only difference between the two is the internal resistance values. 3C rated cells are less than 10-12mOhm and 1c/0.5c rated cells are 25-30mOhm atleast.

There is a decent 10-12% cost differential with EV grade being more expensive.

As per my knowledge cells have one common assembly line. My application does not require 3c discharge rating but I feel the so called "Solar Grade" cells are just low quality cells and might not perform as well in the long term.

Am I misinformed? Is there any literature I can look at to increase my knowledge? Do let me know your thoughts.

Thanks
Cheers

There are huge variations in quality of output off any production line.

More so from one run to the next, but even within a given run.

The factory (often one that produces for many client "brands") has a QA binning process, sorting the cells by the various quality indicators.

Chinese military often get the top notch units.

Otherwise best goes to the client to be sold as Grade A genuine to huge OEM buyers like EV manufacturers.

Lower grades of "factory rejects" get offloaded to the various resellers - these are usually those available for purchase in small lots under a full container.

Obviously finer gradations apply.

Counterfeits are common.

Used sold as new, etc.

Someone needing higher power output C-rates will usually pay lots more than low output storage use cases.

But bigger ongoing buyers will always get better deals than small ones only buying occasionally.

veer said:

My application does not require 3c discharge rating but I feel the so called "Solar Grade" cells are just low quality cells and might not perform as well in the long term.

Am I misinformed?

Click to expand...

When you say EV are you speaking of pouch cells? Are you attemting to compare EV pouch cells versus 32650 cylindrical cells for your particular application? The following is just comparing lower discharge 32650 (solar?) cells to higher energy dense 32650 cells.

A Slower discharge 32650 cell with Max Discharge 18A (3C) has just as long or longer life span (cycles) than a 32650 cell with Max Discharge 36A (6C) ... https://www.amazon.com/HAKADI-Lifepo4-6000mah-Rechargeable-Discharge/dp/B09BQXHKNZ/ref=sr_1_3?gclid=Cj0KCQjw-pCVBhCFARIsAGMxhAcvVnHRDWwgL5FrQSSGReiNkXlKkUxOOmqcGyvIAJhBiQX0Cjb01poaAouuEALw_wcB&hvadid=570538696528&hvdev=c&hvlocphy=9019693&hvnetw=g&hvqmt=e&hvrand=299374686366509393&hvtargid=kwd-313605504894&hydadcr=12229_13301612&keywords=32650+lifepo4&qid=1654980748&sr=8-3. It all depends on the intended usage as to which cell to use. Just because a slower discharge 32650cell costs less than a high energy dense cell by no way means it isn't a Grade A cell.

https://www.amazon.com/Solutions-32650-LiFePO4-Rated-Lithium-Phosphate/dp/B09ZBKNB45/ref=sr_1_2?gclid=Cj0KCQjw-pCVBhCFARIsAGMxhAcvVnHRDWwgL5FrQSSGReiNkXlKkUxOOmqcGyvIAJhBiQX0Cjb01poaAouuEALw_wcB&hvadid=570538696528&hvdev=c&hvlocphy=9019693&hvnetw=g&hvqmt=e&hvrand=299374686366509393&hvtargid=kwd-313605504894&hydadcr=12229_13301612&keywords=32650+lifepo4&qid=1654979229&sr=8-2 - $4.00 ea + shipping. Because its MCD of 18A (3C) is less than the MCD 36A (6C) cell it not only likely costs less it also may outlive (more cycles) the more expensive 36A (3C) cell. It all depends on its usage, usage, usage ... toooo many variables to know for sure.

Other 32650 cells (if you haven't checked already) - https://www.amazon.com/s?k=32650+lifepo4&gclid=Cj0KCQjw-pCVBhCFARIsAGMxhAcvVnHRDWwgL5FrQSSGReiNkXlKkUxOOmqcGyvIAJhBiQX0Cjb01poaAouuEALw_wcB&hvadid=570538696528&hvdev=c&hvlocphy=9019693&hvnetw=g&hvqmt=e&hvrand=299374686366509393&hvtargid=kwd-313605504894&hydadcr=12229_13301612&tag=googhydr-20&ref=pd_sl_386jqkq0ch_e

If you explain your application you'll get more specific replies depending on the usage of your specific DIY need(s). Possibly your initial question has been 'adequately' answered for the time being ...

NOTE: Are Grade A 32650 cells even available with only 1C-2C Maximum Discharge (doubt it)? Even if they would likely still cost $4. If that's all you really need then maybe find some used/salvaged 32650 (3C) cells for $2ea. Even so after pre-testing you may find that only half are usable for your application. You may be farther ahead buying those new? $4 18A (3C) MCD 32650 cells. The only thing nowhere does it say they are "Grade A". Like previous post ... Buyer Beware ... don't even know the manufacturing date. Even so for your light duty application (1C to 2C MCD) they may suffice.

In general lifepo4 should be your best bet. If you have enough in parallel for longevity. Quality matters.