Sourcing a LOT of custom 18650 battery packs with BMS

I'm looking to source large quantities (500-2000) of custom 18650 battery packs and I wanted a real person's opinion on which supplier to use. I've already contacted the following suppliers:
• Batterybro/Voltaplex
• AceOn
• Liionwholesale
• DNKpower
• Orbtronix

I'm pretty sure Orbtronix doesn't do custom packs but I reached out anyway. Does anyone have experience with sourcing large quantities of 18650 packs with a custom BMS? Any input/experience is appreciated!

You need your own person actually on the ground in china to do this correctly. All else will be a gamble, or much more expensive than necessary.

Thanks for the advice. Any idea how I'd go about finding a reliable contact in China?

Contact a trading company and go from there. Or if it's a long term thing you can ask universities, focusing on engineers who speak english.

There are 2 main important reasons to have your own guy there: QC and ensure problems are fixed before an entire run gets frocked up. Also you will get better pricing and generally less bullshit (although still plenty) if the factory think it's selling to another chinese dude.

Long as your dude isn't a crook.

Or I should say, a short-term scammer as opposed to one more reasonable looking for the long con.

If the cost to fly there spending a few weeks initially then a few days per year ongoing is less than 10% of the budget, that would likely be a good investment.

A personal level of trust is worth more than technical expertise, QAing batteries is not rocket science.

Im planning to start a custom battery company based in Croatia, just for jobs like this one.
If you could give me some specs, I could maybe give you an offer
The cells would be sourced from nkon or other reliable supplier and you could drop by to do QC anytime