I'm trying to charge a riding lawn mower battery with a 12 volt, 10 amp/ 2 amp charger. I'm told I should have it on the 2 amp setting for this. Before charging, the battery tested at less than 1 volt. After charging 14 hours, it shows 3.5 v. Checking output of the charger, I get 4.5 volts. The test/charging indicator needle does not move. What's up? Is it operating properly or not, and why? Thanks! I do some household electrical repairs, but I'm not familiar with DC or electronics at all.