I wanted to update my this with my researches and where they have taken me. I have been pouring over this for weeks now and have found it really difficult to come to a decision.
After researching the solar forums I came to the conclusion that the AliExpress route is high risk for the following reasons:
-its impossible to know with certainty what you will get, no matter how hard you research the seller, a lot seem to be selling B grade or salvaged units which are likely down to 80% of their capacity and half used up. Those that are A grade are likely to be overstated by at least 10% judging by their basic dimensions and weights.
-free postage is a high risk route to customs impoundment and loss of goods, or high charges.
I looked into Alibaba but came to the conclusion that:
-finding a reputable seller is even harder
-those reputable sellers charge big bucks on carriage. I was quoted $100 and $250 carriage from known reputable brands. This still doesn't cover import tariffs and VAT on arrival. When all costs are tallied then they ultimately come out on a par with reliable European and American sellers.
GWL/POWER LiFePO4 High Power Cell (3.2V/20Ah) - Alu Case - The tiny thing dimensions (178x71x28) and weight only 0.65 Kg makes this cell suitable for EV and lightweight applications as well as for energy storage. Main advantages of the ZG-LFP020AH Supports high speed discharge (3C, 60A) Provides hig
shop.gwl.eu
The European supplier GWL sells these units which when all costs are accounted for are on a par with similar prismatic units from China. Ultimately for the 36V 20Ah battery the cells come out at about €320.00. Capacity is guaranteed, carriage is guaranteed, duties are zero since they are from Europe so no nasty surprises and delays at customs.
However there is a better option which even though they come direct from the USA they are about half the price:
Just $1.90 per cell when you buy a full case! These cells are brand new in the original case. You get 120 of them for just $228. These are genuine K2 3800mah lifepo4 26650 cells. These cells are overstock and this is a liquidation sale. These are not grade B, rejects, or used cells being...
batteryhookup.com
These are army surplus and guaranteed capacity cells with excellent characteristic. The box as sold with all carriage and duties paid so will come out at about the same price as the GWL prismatics. However there are enough cells here to build 2x 36V 19Ah batteries or roughly double the value.
This would allow me to buy a box, build a battery and sell on the 60 surplus cells to recover half my costs. This give a realistic cell cost of about €160 at my door. All from one of the most reliable battery sellers in the world.
Anyone critique my logic ?