Splitting a single pack s-05

So I want to brew two batches in the next couple of days but I only have one pack of s-05 (or is it s-56 now) on hand. I was wondering if I could make a big one gallon starter with the single pack, split it, and have enough viable yeast to pitch for two batches. Just trying to save myself the hour drive to the homebrew shop.

I've often made 1.5 liter starters with 1 1/2 - 2 cups DME and split between 2 batches with no trouble at all. But, in my case the starter is sitting on a stir plate for up to a day and is plenty active before the pitch, so YMMV.

Another option is to brew the first batch and wait until you're ready to transfer it (to secondary/keg) before starting the second. Then, brew the second and siphon onto the yeast cake left behind by the first batch (note - if beer styles differ, lighter/less hoppier beer should be first). I did this for the first time tonight and the fermentation was fully active within about 3 hours.

Yeah pitching onto that yeast cake is the way to go, I generally do that for all my bigger brews with great success. I believe I will just make a one gallon starter and split it between two batches, I really think this will be pitching at a reasonable rate.

No need for a gallon starter. If you want to brew two batches on one day then just do a normal 1 quart starter and put a pint in each batch.