Solar Power Solution

How do I charge/jump start the 18 volt battery of an antique car?

It’s a 1947 Cadillac, I was supposed to be starting it up periodically for the owner, but there’s not enough juice. Can I just use a regular 12 volt starting pack, or just jump it off of my truck like a 12 volt battery, or are my options more limited?

First, a 47 Caddy has a 6-volt system not 18 volts. And, no, you cannot jump it with a 12 volt battery without risking serious damage to hard to find parts. Purchase a battery charger with a 6/12 switching system and use it to keep the battery charged.

Diesel 10 9-Volt battery