The fuel table is used in the following ways:
- Display an estimated state-of-charge for the pack.
- Determining the charge rate in the AUTO charge modes (1c, 2c, 3c)
- Determining the charge rate for storage charge.
The fuel table describes the state of charge based on a given voltage. For instance, 4.2 is fully charged, 3.8v is 50% and 3.7v is 20%. These are rough numbers and the actual value varies based on the C rating of the packs.
Because the fuel table is different between a lower C pack and higher C pack, select the value that most correctly describes the pack you are charging. If you want to use a single present to charge both 18c packs as well as 40c packs you can. But I would not use the AUTO charge modes. Instead use a manually set charge rate. The fuel percentage may not be completely accurate for one type of the pack, but often close enough to use as a general guideline.
However, I find it most useful to have single preset for each charge rate that I use. As 18c packs are going to have a lower allowable charge rate than the 40c packs, it just makes sense to break these out to two different presents. Then adjust the fuel gauge for each.