How long do I have to keep the fermentation?

I have read that for a regular 5 gallon batch of beer the primary fermentation can go from 7 days up to 14. If I'm fermenting batches of 2.5-3 gallons, should I keep the fermentation the same time or could it be 1/2 or 3/4 of the time since I'm fermenting half the volume of wort? Does this make sense or it's just nonsense?

Fermentation time is pretty independent of batch size, and very dependent on the amount of yeast you pitch. A typical gravity batch (~1.050), pitched with the proper amount of yeast, at the proper temperatures can easily be done fermenting in 5-7 days - no matter the volume.

Once fermentation is complete, then the conditioning phase begins where the yeast clean up some of the byproducts produced during active fermentation (all the sugars are gone at this point so the yeast eat other things). You can do this in the primary, or transfer it to a secondary. Both work great, but produce slightly different tasting beers. It is personal preference

Quick follow up question for this topic...I'm brewing an ale with an estimated abv of above 8%. What is a generous range of time that fermentation should be complete for primary? Looking back at how I worded this question I feel like Yoda...

mac21 said:

Quick follow up question for this topic...I'm brewing an ale with an estimated abv of above 8%. What is a generous range of time that fermentation should be complete for primary? Looking back at how I worded this question I feel like Yoda...

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Yeast doesn't work by calendars, it works at its own pace dependent upon the factors sites above. It will be done when its done. After 7-10 days take a gravity reading. If its at FG then IMO you leave it sit an additional week to clean up and clear

That's what I figured, thanks duboman.

Generally though the higher the OG the longer the fermentation. That amount of time does vary greatly based on yeast amount, temp, etc, just as others mentioned. However, all things being equal, a higher OG beer will take longer to ferment than a lower OG beer. It might also take longer to condition in the bottle.

For example, I have a 1.048 OG stout that I'm drinking now after only spending 2 weeks in the fermenter. But I've got a 1.082 OG Belgian Golden Strong Ale I brewed 3 months ago that I only bottled a few weeks ago. I expect to have another couple weeks at least before its ready to drink.

For an 8% ABV beer I'd expect at least a couple weeks for just normal primary fermentation, plus several more weeks for conditioning. Of course, you can do a shorter tme period with spot on yeast pitching and temp control, but most of us aren't spot on, so we let it go longer. Time is your friend here.

Thanks for the feedback schokie. It's only been a week so far but I'm going to take a gravity reading tomorrow and see how it's coming along. It's an imperial red rye ale that I'm making for a homebrew comp in March. I'm about to start a Belgian strong myself!

What ABV would one want to put yeast energizer into the mix?

I've never had a rye ale before. Sounds interesting.

I'm not sure of an ABV cutoff for an energizer. I don't use anything like that though or any yeast nutrients. You certainly can, and it's probably a good idea, but I don't bother. I made a 1L starter for my BGSA mentioned above and it fermented just fine. However, I didn't put all the sugar in the boil, just the malt. Once primary fermentation slowed, I boiled the sugar and added it to the primary. Fermentation picked back up again as the yeast ate the new sugars. That kept the yeast from getting tired out, or overwhelmed by the higher ABV.

I also added more yeast a few days prior to bottling. Might not have been needed, but I didn't feel like waiting forever for it to carb.