IMO use the charger you have if you can't find the Vector.
You don't need an ammeter since you have wet cell batts that are not sealed. It is nice to see the amps tapering. Just not vital to see that with your batts. You can use a $5.00 hydrometer to see their state of charge. Get the glass tube kind with the bobber that shows red, white, and green.
Keep charging until you are well into the green or as far along as it gets when you want to stop the generator. (Usually not worth the gen gas to keep charging the batts all the way to the top--do that on shore power at home)
I would not trust the percentage charge reading on the charger, only the hydrometer.
