You cannot update the BIOS without a battery that's at least partially charged -- on some systems, you can bypass the check, but on others you cannot. In any case, plan on replacing the battery before you try -- doing otherwise is a very bad idea.  If you do decide to force the update, finding a location that has a UPS (uninterruptible external power supply) would be a very good idea.  
I'm planned update BIOS A04 to A09 but my battery is broken and can't use again, my house have chance get outage so I don't want motherboard get bricked. I found 1 post Dell BIOS Guard if I failed at midway, old codes will still there, more is my model not supported BIOS Recovery. Model: Inspiron 14 3458
How do I know if BIOS Guard in my laptop?