Battery Efficiency

I recently got the newer model 60v angle grinder 4.5in-6in model. This was my introduction to 60v tool and this one can burn through a 6Ah battery in about 15 minutes. I’m wondering if anyone has figured out a charger battery setup than can allow you to cycle them efficiently enough that I can always have a somewhat charged battery. For example if i get two 9Ah plus my 6Ah and a good double charger would that keep me going?