How does weight figure in the quality of a lifePO4?

[Pinzmann]

So I’m in the market for a 50ah battery. Have a Nermak one I got year ago or so. Did a capacity test, came out ok. Ended up using it for a diy power station. Looking for another one to use as a supplemental power source. Looking at different makes and noticed a large variation in weight. The one I have is 10.6 lbs, another is 13 lbs, yet another is 18 lbs. any significance to the weight?
Just noticed that the 18 lb advertised 768wh compared to the others at 640wh. Is that the difference?

 

[sunshine_eggo]

Weight should have no correlation to Wh if Ah and cell count is the same.

A 50Ah 4S LFP battery has 640Wh of energy (50Ah * 3.2V * 4).

A 768Wh 4S LFP battery is 60Ah (768Wh/3.2V/4), not 50Ah.