I have build a rechargeable battery with 10 Ah and 13,5 volts with LiFePO4 cells.
The numbers of this battery are impressive. The discharging current is up to 100 A and the charging current is up to 50 A.
The voltage is very stable until the of discharging so you can get the whole capacity out of this battery. This is what I did in the IOTA Contest in 2013 on Fanø Island (EU-125). I ran about 4 hours of the contest with my Kenwood TS-50S with 100 watts.
The battery is made of Headway 38120 SE cells. I have ordered them at Modellbaufuchs Onlien Shop in Germany.
The cells have screws on both ends so you can easily put them together to a package. The enclosure is just carton.
Here you can see how the wiring of the cells and the wiring from the cell connectors to the balancer connector. The exact wiring of the balancer connector depends on your battery charger and what balancer system you are using.
The battery is as small as a FT-817 and the weight is about 1,5 kg.
This picture shows the charger that I am using. A blancer id intergrated and the maximum charging current is 3,5 A.
This little device is a volt meter and an alarm. You can select the voltage for the alarm. The device shows the voltage for every single cell and the overall voltage of the battery. It is importand to have this kind of alarm because the battery will be damaged if the voltage of a cell goes below 2,5 volt.