- Know what kind of cells they are using and buy a couple cells to do life cycle tests on them.(Mainly now with lith-ion)
Half of the lithium ion cells I've used for cell phone and laptop replacements suck. There is a good chance this is the case with large packs made from cells that suck they want to sell you in a Chinese scooter they slapped together in 5 days.
Don't let the urge to be cutting edge lead you into bankrupting yourself. Wait for reliable data guys. People selling this stuff don't know anything about it other than how much they make off of it. It's true. Salesmen know nothing about these things.