Battery Management Systems for Large Lithium-Ion Battery Packs
Section 188.8.131.52.1 Errata
- 6th line from the bottom. "that an support 4 tap points" should be "that an support 5 tap points".
- Figure 6.2.
Graph a. Top 2 rows should be 7 Ah, not 8 Ah.
Graph b. Bottom text should be 4 Ah, not 5 Ah.
- Last sentence of the 2nd paragraph
"so the total pack capacity is only 5 Ah."
so you would think that the total pack capacity is only 5 Ah. Actually, the capacity is only 4 Ah, because the 1 Ah cells are the limiting factor, and there are 4 strings in parallel.
Plots of cell voltage versus time, assuming a 1 A discharge current, will clarify this point (figure 6.3). With cell in parallel, the 1 A current discharges the 7 Ah blocks in 7 hours, at which point their voltage reaches the lower limit and the BMS shuts down the pack (the 8 Ah blocks will still have some charge left). Therefore, the capacity is 7 Ah. With batteries in parallel, the 1 A current is split evenly into the 4 strings: 0.25 A each. That current discharges the 1 Ah cells in 4 hours, at which point their voltage reaches the lower limit and the BMS shuts down the pack (the 2 Ah cells will still have 1/2 of their charge left). Therefore, the capacity is 4 Ah.
Add Figure 6.3 (replacing the removed figure 6.3) to explain with a graph the effect of figure 6.2.
Figure 6.3 1 A discharge plot of multiple, low capacity cells. (a) With cells in parallel, the pack is discharged in 7 hours, meaning that the capacity is 7 Ah. (b) With batteries in parallel, the pack is discharged in 4 hours, meaning that the capacity is 4 Ah.
The point made at the end of page 231 and beginning of page 232 is not valid, and should be removed from the book.
- 2nd paragraph, end of the paragraph. Instead of "each battery that includes a low capacity cell will have a 1 Ah capacity" should be "the 3 batteries that include a low capacity cell have a 1 Ah capacity"
- 3rd and 4th paragraph: delete.
- - Figure 6.3: delete.
- 1st paragraph: delete.