Many Christians have a tendency to read passages like this, and conclude:
"I need to love others, so that my sins will be covered."
The word "charity" tends to throw off modern readers, as though we should go out and give our things away to the poor. In this passage, "charity" is the translation for "agape" or God's unconditional love.
And it is God's love for us, not our love for anyone.
Let us respect this passage in the light of all Scriptures, for no scripture is of private, i.e. isolated interpretation (2 Peter 1: 20)
Under the New Covenant, we love because God so loved us first:
"For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life." (John 3: 16)
"But God commendeth his love toward us, in that, while we were yet sinners, Christ died for us." (Romans 5: 8)
Notice that God "commends" -- present tense -- his love for us.
"In this was manifested the love of God toward us, because that God sent his only begotten Son into the world, that we might live through him." (1 John 4:9)
"In this was manifested the love of God toward us, because that God sent his only begotten Son into the world, that we might live through him." (1 John 4: 10)
"Herein is love, not that we loved God, but that he loved us, and sent his Son to be the propitiation for our sins." (1 John 4: 17)
So, what is Peter talking about, when he says that we should "love one another deeply"?
When we understand how deeply our sins have been put away from us, loving others will not be hard, In fact, when we recognize how deeply forgiven we are ,we can in turn love one another deeply.
And that is the essence of love under the New Covenant:
"Let all bitterness, and wrath, and anger, and clamour, and evil speaking, be put away from you, with all malice: 32And be ye kind one to another, tenderhearted, forgiving one another, even as God for Christ's sake hath forgiven you." (Ephesians 4: 31-32)