Ibuprofen and Tylenol Later...
The combination should work fine. While things are being charged, measure each three cell battery and note their voltage. This says a lot. If you find one battery voltage .3 lower than the others, designate it as the "Weak Sister battery". Time to get out the hydrometer and find out why. One cell weak? two cells? All three? If necessary take images with your camera, remove that particular three cell battery, take it to a battery shop and have them fast charge it. If it continues to be weak, it is a bad battery and will rotten apple in the barrel screw up the others. A strong load tester like the one an Interstate Battery DISTRIBUTOR has (Auto Meter load tester) can successfully test a suspected bad 3-cell battery. Similarly cell gravities that are unequal or flaky* is cause to replace a battery.
*Will equalize with other cells but falls back much too soon. The classic sign of an inferior brand of golf car battery.
