I am in the process of mounting a Cruise 4.0 on a Lure 13.5 kayak, so thought I would share the experience I have from buying Lithium batteries from China.
First of all I havent tested the batteries yet, so I can only comment on the experience dealing with this particular seller and that the batteries did charge to full in the expected time and holds 29,1v after 1½ week of rest.
I ordered: 2x25,8v80Ah battery packs + 14S 140A BMS and a 14,7v30Ah pack to run my gps, lights and bilge.
The nice thing was that the seller allows one to tailor make the pack you want and in my case I wanted 14 series of 3,7v Samsung cells, as this is what Torqeedo is using in their 106Ah packs.
And they are only 13kg each + waterproof
So this is what I got for 1600 bucks, including shipping to Thailand
And here is the sellers store on Aliexpress. I have no connections to him whatsoever, but he is swift to answer questions (many from my side) and did make the batteries exactly as I requested. Time will tell if they hold up...
http://www.aliexpress.com/store/1898584 ... 5.4.HuGPvB