I go to start my car and starter cranks and turns very slooowly. I take it out and charge it at 12-amp for two hours and it works fine. How long should I charge the battery to make sure it gets its full capacity. A repair manual gave me two options. Load test the battery or use a hydrofomer. I'd just charge it overnight at 2-amp. Which of the three or any other ideas is a practical option to determine charged?
-TIA-
How old is the battery? If It's new or nearly new, a hygrometer tells the tale, but an old battery can have lost a large part of the active element from its plates and show a perfectly normal reading on a hygrometer. Such batteries will usually work fine in warm weather, but as winter temperatures come into play their lack of stamina shows up. Sure they'll charge right back up in no time, after all you're only charging an effective plate area the size of a quarter! But if your engine doesn't start on the first turn you're dead in the water.
So for such batteries a load test is the proper diagnostic. And if the battery is more than 5 years old I'd buy a new one anyway.
I've heard it said that the common auto battery loses about 20% of its capacity each year. So if you had 500 CCA tha first year you would have 400 CCA the second, 320 CCA the third and so on. Throw in the cold weather reduction and soon you are in a no start condition. This is why it pays to buy a large amp battery and change it often.
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