I do not seem to be able to get the battery to 100% charge. I am using the original charger which came with my ancient H3D-39. The original battery is 1850 mAh, and charges to full, as shown in the battery status on the body. While charging the 2900 mAh battery on the same charger, I can only manage to get it to 75% charge. I understand the charger should be able to bring the battery to 100%, though taking longer than the 1850 mAh. Any insights?