YES Deligreen does make batteries .. they have a large R&D, warehousing, and manufacturing facility outside of Hunan China. Not sure why they have other products from other vendors also on their webpage - perhaps they are sister companies -- but ALL we purchase from them are the BLUE ALUMINUM batteries and then we ourselves package them for our internal needs ...
Look - to be clear - I have nothing against Battleborn -- and for the last several years everywhere I looked there were Battleborn batteries -- but now with tarriffs at rock bottom and shipping cheaper and a MASS amount of Chinese companies now offering the same grade of battery and BMS as one could get with Battleborn - its OK for people to decide that they want to get twice the battery for half the price if they do it themselves. The Battleborn discussion has turned into a FORD vs CHEVY, COKE vs PEPSI .. You have to get the one that best for you ...
You interchange the terms cells and batteries, but the difference is the key to this subject, which makes it difficult to talk about it if people don't use correct terms.
I am now 99% certain Deligreen does not make cells. They sell cells of different OEMs and make their own batteries. You buy cells from them, but they are not made by them. As far as cells go, Deligreen is a VAR, probably a good one as you can vouch for them. Their site claims a warehouse in Europe, so I wonder if US is or isn't an important market for them.
There are many important differences between Battleborn batteries and other re-branded Chinese batteries. BMS quality is one of several factors. Other factors are where employees are located and how much they are paid for their skills, how strong US based customer service is, who is financing the business and how much profit the owners are demanding. All the items
@FilterGuy listed cost money, and they cost more if business is heavier on US side than on China side, especially engineering and support.
I work for a company that does everything
@FilterGuy listed in the US, only cells come from China, from the best source we can find and we always look for the best ones. This also costs money. This makes our product expensive, but we have a wait-list of customers who are willing to pay a premium for highest quality product.
On the other side you have importers where 100% of product is done in China and only a couple of guys are in US selling them. Support is limited, engineering is non-existent, but profit is high because sales guys are full of BS and business is financed by a bank or a loan shark. All these 10 years warranties are pure BS, but people believe them.
Battleborn is somewhere in the middle of this equation, that's why they are popular, but competition is coming and the market will be red hot soon enough.
As for DIY forum like this one, of course many people would make their own batteries, they just need a source of good cells and a decent BMS.