for all the hassle of getting the top off, re filling and then sealing it, to gain a possible extra 6 months use out of it I dont think its would be worth it. Get a new one and be confident that you will always be able to start. The little "window' is actually a hydrometer, but it only checks one cell. Gives an indication, but not a truely reliable one of the health of the whole battery.
03 Disco 2a, TD5, Olso blue, 7 seater, Auto, Chipped, EGR'd, 2"lift, SLS, Dual Batteries, Provent, TM-2 engine saver
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