What distinguishes a "Batch" style devise?

I know that J tubes are known for needing a lot of fire tending while in use, and there are folks building "batch box" style heaters that are loaded and then burn untended for sometimes several hours. My question is what defines a batch style from a non-batch style heater/stove? Is it a matter of how long it runs unattended; How much fuel it can be loaded with at a time: Some other criteria?

Any thoughts are appreciated.

The reason I'm asking is, I've built a rocket heater that much resembles a J tube but it can be run for 45 minutes without tending and can go through 4 to 5 loadings ( approx 4 hours total run time ). It can take split wood up to 4"x4" and 14" inches long or 2 pieces 3"x3" once it is up to running temp.

Well, there are heater/stoves and then there are rocket stoves and rocket mass heaters. Batch Box Rocket was the designation coined during development of the core when there needed to be a name for the thing. There's extensive information, drawings, designs, and etc. available on Peter van den Berg's site: https://batchrocket.eu/en

My 6" (system size) batch box rocket mass heater can take up to 6 to 8 inch diameter logs. But like the J-tube, batch boxes are designed to run full tilt, same quick fast hot fire, to charge the thermal mass. The fire burns to coals within 45 to 50 minutes when fueled with large diameter 16" long hardwood logs, and about 30 to 45 minutes on 2 to 3 inch diameter sticks.

One advantage of the batch box is that it can support a fire viewing firebox door. And there's zero fire tending, simply load it, shut the door, sit back and watch'er roar.

My J-tube (7 1/2" system size, 7" x 7" feed) can take good sized logs and run for 40-45 minutes before reloading, and generally does not need tending either. It runs hot and furious until coaling phase. I use a mix of wood sizes to fill the feed, sometimes only three or four logs. Somehow the idea took hold that small sticks are essential for RMH operation, though Ernie Wisner has said that he uses large logs frequently.

Duane Hylton wrote:I know that J tubes are known for needing a lot of fire tending while in use, and there are folks building "batch box" style heaters that are loaded and then burn untended for sometimes several hours. My question is what defines a batch style from a non-batch style heater/stove? Is it a matter of how long it runs unattended; How much fuel it can be loaded with at a time: Some other criteria?

The most basic difference is that J tube style receives fuel vertically into an open feed tube. Batch box style loads the fuel horizontally, usually into a box enclosed with a door that lets in a certain amount of air. Batch box also follows more specific design criteria than J-tube to be super efficient. J-tubes are still much better than conventional wood burning stoves, but Batch Box takes that into the next level of consistent efficiency.