Hello, I just have a 12 V/12 Ah motorcycle battery from Varta “for care”. The battery was almost dry and had 0.3V after refilling with distilled water, i.e. brutally deep discharge. First I tried it with a low-priced automatic charger, which showed zero response. The battery is probably recognized as 6V battery. The other charger, from Cartrend with max. 6A charging current, gives at least one feedback in the form of a short ejecting amperemeter. Charging voltage is approx. 13.5 V. My plan would be to fill the battery completely with acid and to hang the “large” charger for 1 – 2 hours. If the battery then accepted the charge, the automatic charger will come back to the battery. Now it would be interesting to know if there is any chance (in whatever form) for success or not.