I don’t think the C rating is going to matter after the turbine is running. In fact, on one of my planes where I can't fit a larger capacity battery (+3800mAh), I use a 2100mAh, but I have a second 2100mAh to use as a jump-battery. Once the turbine is up and running I unplug the second jump-battery, the single 2100 runs perfectly, even with the larger turbine/pump. With the single 2100 it would fail to start, with a low rpm or volt error.