It will probably take an overnight charge to bring them back fully. It really depends on your converter/charger. If it kicks it to fast charge mode then it will have them back 90% in 4 or 5 hours but then it usually takes several more hours at a slow charge to get the last 10%. You can check if you have a volt meter by measuring the voltage at one of the house 12v outlets. If the voltage goes to 14.2 or higher then its probably in fast charge mode, if its only 13.6 its in normal charge mode and it will take twice as long.