I agree. I hooked 3 to a 1.5 amp tender charger and it had a hard time and never got to full charge even after 2 days. Shumacher makes a nice charger that is 2 amp/15amp/Start that is a float charge in the 2 amp setting BUT will pull more amps if the battery needs it. Some float chargers will not bring a very low battery back to full charge such as ones that are "Maintainer" chargers.