One that has channels that pass sparge water through the grain bed without properly rinsing (one that doesn’t pass over all of the grain surfaces continuously). Batch sparge thoroughly rinses the grains because you pour the warm water in, stir, let it sit a few minutes so the sugars dissolve into solution, and then drain. That’s a very effective process to collect sugars.
Forgot to mention, the mash is fly sparged. I guess that impacts efficiency?
Yes, but it's hard to say whether it would make it higher or lower. When I was using my batch sparge cooler system, my efficiency was often higher than those who fly sparged. There are a number of variables involved.
It is certainly possible to have higher efficiency with batch sparging than with fly sparging if you have a finer crush than the fly sparger. All else being equal, though (e.g. same crush), fly sparging will always extract more sugar than batch sparging.
No, that's not the case. A less than perfect lauter system will reduce fly sparging efficiency. And I know few people who have a perfect lauter system. Batch sparging eliminates that from the equation.
Fair enough. I hadn't thought about that because I have never used or heard of a homebrew lauter "system" that is so imperfect that batch sparging actually becomes the more efficient method. Just curious, what type(s) of lauter system at the homebrew level is this inefficient?
FTR, I use coolers with either the standard round false bottom or a bazooka, depending on batch size, which dictates which cooler I use.
I really don't think channeling at the homebrew level due to lauter tun "design" is a thing. (Although I do know channeling well from my pro experience, where I did deal with a flawed lauter tun.) I think that channeling is one of those "facts" we homebrewers need to worry about that has filtered down (pun intended!) from the pro world because, well, if they worry about it, we must too.
At the homebrew level, channeling has happened to me when there is teig buildup due to the mash schedule. But that has nothing to do with my cooler "design" and is easily managed.
Batch sparging is actually quite inefficient at getting sugars out of the saturated kernel mass, compared to fly sparging. As soon as the sugar-concentration differential is zero, no more sugars are extracted, and this leaves a lot behind. But yeah it's easier and less time-consuming, for sure.