Something seems a bit off with your numbers. If you're losing 5% of your battery "overnight" (at least 8 hours I assume), and you have the larger 86Wh battery, that implies a discharge rate of only 537mW.
900mw - nearly a whole watt - seems very high! Easily enough to cause noticeable warming - a running modern laptop at idle only uses 3-6 watts.
900mw - nearly a whole watt - seems very high! Easily enough to cause noticeable warming - a running modern laptop at idle only uses 3-6 watts.