I think its better if you say: I`m sorry Sarah, but the battery of my home phone is going to be discharged. If it`s possible, could you please try to call back later?

I am a native English speaker and have never heard the word 'discharged' used in a sentence before (whether it is a word or not?). You would use 'disconnected' if the call stopped unexpectedly, or 'ran out of battery / ran out of charge / the battery died' if you want to say your battery life ended.

No, the "if" part is a little wrong. "I'm sorry Sarah, my home phone just discharged. If it is possible, can you call me later?" Btw, in the "I'm" you used a grave accent `. You have to use an apostrophe '

What do you mean "discharged"? This doesn't make sense.

ok ok