Building a DIY Lifepo4 charger

[Ampster]

So I am really hoping that the amps will reduce as the cell(s) reach their target voltage. Can anyone confirm?

Typically the charger reduces the Amps to keep the voltage at the Constant Voltage setting. If that is how you have set up your DIY charger that should work.

If that is not how you have set up your charger, don't count on the battery controlling anything. The battery will take all the current and voltage you can give it until it forms dendrites that cause it to short circuit and over heat and swell. Eventually the electrolyte will be forced out of the pressure cap and you will probably notice the smell of ether which is one of the solvents in the electrolyte.

 

[Warpspeed]

Once you get into very serious power,like over a hundred dc amps or so, by far the most efficient and lowest cost solution is to use phase control on the primary of your large transformer. Then all you need is a rectifier, a large choke, and some electrolytics.
By controlling power on the transformer primary, the current there will be far lower than on the low voltage secondary side, and you can do very nicely with much smaller SCRs and heatsinks.

The control system for voltage feedback and current limiting can be as simple or as sophisticated as you wish to make it.