Not necessarily time for new batteries. Here are a couple of things to check.
1. By all means measure and record
the specific gravity in each cell. You may find one that's bad.
2. Assuming that the batteries are really only a couple of years old, and that they were not run dry (with electrolyte level below the top of the plates), and that you don't have a bad cell, it's most likely that they are sulphated due to improper charging. A battery starts sulphating at the factory, from the moment the sulfuric acid is added. Proper charging to 100% capacity and occasional "equalization" with voltage above about 2.6VDC per cell is needed to keep the plates free of lead sulphate crystals, so that they can accept and deliver their full energy as designed. Letting batteries sit for extended periods at less than full charge will cause them to sulphate badly over time.
What to do? You have a couple of choices.
1. Give the batteries a full charge, then try equalizing them. Then, cycle them a few times (full charge, deep discharge, full charge) and see if they recover.
2. There are a number of desulphation devices on the market, with more appearing all the time. I'm in the process right now of testing some of these on a variety of batteries. It will be a couple of months before we'll be able say anything with confidence about whether or not these devices do anything good, but there's a growing body of anecdotal and semi-scientific evidence to suggest that they well might. Since they're pretty cheap
, I think in your situation I'd give one a try and see if it doesn't help over the next few months. If not, well, you can always use it on the new batteries where it will likely help extend their lives.
Anecdotal, preliminary evidence from the tests: at the start of our testing we had two "bad" batteries, one golf-cart sized gell 10 years old and one T-105 Trojan flooded battery 4 years old which had been badly mistreated. Both failed the internal resistance checks, and their calculated CA was very low. Both of these "bad" batteries, in two separate banks, seem to be doing considerably better after several cycles of charging-discharging-charging followed by just two cycles of charging/pulsing-discharging-charging/pulsing. THIS IS ONLY INDICATIVE, NOT DEFINITIVE, in the absence of further testing and analysis of the data.
BTW, I've got two old and very mistreated 8-D AGM
batteries on charge right now to add to our testing. They came to me in a sorry state, with voltages under 2VDC! One had even been dropped several feet onto it's corner, as the lifting strap broke. We'll see what happens when the pulsator is attached!
S/V Born Free