My only comment is that with open cells you can use a hydrometer to check the state of charge of each cell, so in a day or two, once the acid and topping up water have mixed, if the cell readings differ by more than 0.030 across the cells then you have a faulty cell (Lucas said 0.025). If you get sealed cells then you can't use a hydrometer and boater testing involves fully charging, letting it sit overnight, then noting voltage, disconnecting, letting stand for a day or so and then comparing the voltages. Both should be almost the same.
Some here have been bitten by an earlier vendor of lead carbon batteries, so are likely to be somewhat biased. Carbon can't alter the chemical processes in lead acid batteries like sulphation, but it may well mask it. especially with sub optimum charging.