You can charge at a higher amperage, but you need to make sure your battery can handle it. Usually 1C is safe, but some older batteries might not be too happy with the rate of charge. Also remember fast charging does kill your battery faster. Do what I do and just keep a large stock of them and get a big charger and parallel charge them. Check out www.bateryuniversity.com if you got any questions on batteries, they have quite the wealth of information there.