Homebrewers Association  AHA Forum
General Category => All Grain Brewing => Topic started by: thehorse on April 04, 2011, 01:10:18 PM

So first of all, I'm not concerned with increasing my efficiency as I don't really care. I just want to be as consistent as possible and predict what it would be based on the grain bills of new recipes. I downloaded and started playing with Kai's Batch Sparging spreadsheet, which is really great. I just don't get some of the results I'm getting.
Rough Recipe
21.2 lbs of grain
Kai's Spreadsheet Settings
80% extract potential (I know this is rough)
100% conversion efficiency
.12 gal/lb absorption
Results = Says I should get 87% efficiency with an OG (After 15% boil off) of 1.046
Brewing Software  Brew Target and iBrewMaster  Same results
Same grain bill at 80% efficiency it tells my my OG will be 1.052
How can I have a a higher predicted efficiency and a lower OG with the same post boil volume.
Does anyone else use this spreadsheet?

A missing piece of info (that's necessary calculating efficiencies) are your volumes

Sorry
11.5 gallon batch
1.3 gal/hr boil off = 13.45 preboil
8 gallons Mash
8 gallons Sparge

Quickest way to sanity check the calcs is to use the concept of "gravity points". That is, since we don't know the details of the grist, we'll just assume 36ppg (points per pound per gallon). Some grains might be different than that but it's a pretty good average value to use. So, 21.2 lbs of grain at 36 ppg yields 763.2 "gravity points". If you divide that by your final volume (11.5 G), you could theoretically end up with a OG of 1.06637 if you had 100% efficiency.
Since you ended up with 1.046, it looks like your efficiency would be 46 / 66.37 = 69.3 %
80% would give you 66.37 * 0.80 = 53 (OG = 1.053) so the softwares look to be pretty close.

Thanks for the reply, your calculations are exactly what I keep coming up with. I really like the idea of using Kai's spreadsheet to predict efficiency and also gravity based on that efficiency, but I keep coming up with a higher efficiency and lower gravity than what I would expect?
Maybe I'm plugging in the wrong values into the spreadsheet, but I don't know how?
Has anyone else out there used this spreadsheet?

I have used it. The boil off numbers seemed off.

So I actually figured it out. There is a miscalculation in the 1st plus 2nd runoff section. The wort gravity is not correct. However, even if you don't have a 3rd runoff that section appears to be correct.

I've been looking all over his site and can't find the spreadsheet. Anyone have the link to Kai's Batch Sparging spreadsheet?

The link is on this page: http://braukaiser.com/wiki/index.php/Batch_Sparge_and_Party_Gyle_Simulator