I ran into a battery drain situation on the 299. Doing a little googling, it seems to be extremely common on all the DD series but of course no one ever returns to say if they resolved it. Basically I was going to see if anyone here has sourced and fixed their issue? This is certainly down my experience lane, but sometimes getting clues from others is helpful. I do know the alternator is not the issue. Diodes won't do this. The drain seems to cycle between 200mA and 0A at about 1X per 2-3sec. Consistent with a module waking up or similar logic circuit, or maybe even the ECM. I realize some have "fixed" their issue with a master switch, but I'd like to spend a few trying to actually source the problem first.
See this thread. Despite the fact that they are different models your machine will be wired pretty much the same as regards the main bus bars/relays/fuses from batt+. 249D Parasitic drain I have a 249D. Recently, I’ve noticed the battery dead every time I go out to use the machine. When i check for continuity through the kill switch, it proves positive. So, I initially thought it was a bad Kill switch, which this machine is equipped with. I installed a new switch, same problem... HeavyEquipmentForums
299D serial-JST. Battery draining over 2-3 days. Parasitic drain amp was .26 and higher. Went through schematic following process of elimination, which most stated in above comments. Found only component to drop amps was the main power2 relay behind cab(outer most). Replaced, amps now 0.012. Time will tell.
Your not the first guy to have problems at this location behind the cab where the power relays and some fuses are. Process of elimination is always the best way, better than firing the parts cannon. Simon C