Yachting and Boating World forums: Battery drain test.

Impossible to say. It could fail tomorrow or it could soldier on for several more seasons. Any tests you perform only give you a snapshot of its condition at the time of the test.

With regard to the state of charge vs open circuit voltage the figures i use are:

around 12.7 to 12.8 = fully charged
12.2 = half charged
around 11.7 = effectively discharged

All these readings apply after a resting period of 12hours and agree with the majority of published figures. The figures in the second of the two links you quote are vastly different and I would discount them! I cannot comment on a reading taken after standing for only 6 minutes except to say that it would have risen to a higher figure after 12 hours without doubt.

Battery capacities are normally quoted at a 20 hour rate so your discharge test would have been more appropriately done at a current of 3.5 amps with a view to taking 20 hours to discharge 140Ah. Discharging at a higher rate will give you apparently poor results although had you allowed 12 hours recovery time afterwards the open-circuit voltage reading (using my scale) would have given a better indication of the charge actually remaining and therefore enabled a better appraisal of the condition at that time.

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