Do not solder high current
crimp connectors such as battery
lead terminals . It's very difficult not to have partial dry joints and the resulting higher impedance can generate local heating
. Invest in a proper high capacity crimp tool or have the terminals professionally crimped on.
I have elucidated my views on tinned wire elsewhere. I don't beleive it's needed except in areas subject to excessive moisture or damp. European boats don't use it in general and I've never seen any significant corrosion
. My own is 22 years old and uses untinned wire , no problems.
But to each his own.