Just seen these Tenergy LiFePO4 SLA Style Battery 12.8V 20Ah at parts express by my house and wondering if they would be any good for car audio. Iv been seeing people using the juicebox lithium batteries and the 40 ah one is $1500 . So just trying to see if 2 of these would be the same. Really trying to cut down on weight and my van build and this would help out alot rather than having 500 plus pounds just for batteries

Even found some 20ah lithiums for under 200. . What is there to look for in then that the juicebox ones have?

Anyone know?

Unless you are planning on running something at relatively low current draw AH is a pretty useless spec for us in car audio. You should really look at cranking amps, which shows you how much current can be drawn over a 30 second period reaching 9-10 volts (IIRC). You could pick up 4 of the prismatic cells from EvWest and wire them in series for a total of 14.4v nominal and around 1000a for 10 second maximum. If you were to look at a similarly spec'd AGM they are capable of much more current. The main benefit of Lithium is charge time and weight, they are significantly down on output current as they are very temperamental.