Battery acid if clean (not old acidic water with lead sulfate from a dead battery), can be used to make nitric acid.
It will work if diluted or concentrated.
If dilute 32% sulfuric acid is used you will get diluted nitric which will be about the concentration we need to dissolve base metals (about 32 to 40% HNO3), (which can be used with silver if distilled, after removing the salts by chilling and decanting the solution from the salts).
If you need 68 to 70% HNO3 for aqua regia for example this dilute nitric can be concentrated to 68% by evaporation of water (just by heating, do not boil), if 98% concentrated sulfuric acid is used to make poor mans nitric you will need to add water to dilute the acid, this water can be used to dissolve the nitrate, your goal here is to dilute the acid to get a nitric at about the concentration of the acid needed (or even more dilute that can be concentrated by evaporation).
The evaporation of nitric can be done on the acid before we use it to dissolve metals, or can also be done while we are using the acid to dissolve our metals, this in many ways can be a better process, heat speeds the reaction, the added water dissolves the gases that form during the reaction of metals and the acid, keeping these NOx gases in solution (less NOx gas in the air more of it reforming nitric in solution to attacking more metals, less waste of your acid), the NOx can mix with the water to make more nitric in solution to dissolve more metal and produces less toxic red fumes.
Here adding small increments of H2O2 can be helpful converting NO (which will not dissolve in water) to NO2 which dissolves in the water to reform HNO3.
If you do wish to dilute sulfuric acid.
Never add water to concentrated sulfuric acid. steam explosions will splash acid all over you.
Always dilute the acid by slowly and carefully pouring the acid into the water.