In the meantime - -
You do need to charge the battery. You can use jumper cables from a working RV 12 volt system. You can use a portable battery charger, but set it on 12 volts not the 'start' or boost position. Most portable chargers that have a 'start' mode say to only leave in the start mode for a maximum of 30 seconds followed by a 15 minute cooling off time.
Even a 10 amp charger will fully charge the battery overnight, giving that you might be using 4-5 amps each hour to run lights.
http://www.bestconverter.com/Good luck,
Fred.