We are using a bq34z100 to gas gauge a 3 cell Li ion battery. Our circuit is very similar to Figure 8 Multi-Cell and 5-LED Display in the bq34z100 datasheet. The usual current draw for our product is about 750mA and the max current draw is about 2A.
We have noticed some inconsistencies with the remaining capacity measurement when we first connect a battery that get worse as the current draw increases. When I power my product using a DC supply so there is no current draw on the battery, I get the same remaining capacity reading every time I plug in a battery. If I have a normal load of 750mA drawn on the battery, the remaining capacity measurement will be within a 10% spread when I connect a battery. When I draw 2A the reading is quite unreliable.
I am pretty sure this has to do with the IR drop across the battery when the OC voltage reading is taken by the fuel gauge. My question is, is there a mode that I can set in the bq34z100 that will make it work even when current is being drawn from the battery at start up.?
The other option I am exploring is to start the fuel gauge before my power supplies, but I would like to avoid hardware changes if possible.
-Russ
