900mAh will last so much longer, but they may also take longer to charge. I’ve simply bought some AA 2400 MaH batteries for my solar lights. I’ve just observed that the batteries that they’re replacing are 600MaH. Will this make any difference to them working and likewise am I better off fully charging the batteries beforehand such as you talked about above (I think the reply is no to the seconfd question in this case !). Due to the truth that we don’t have all the data in your system we would want you to contact us at so that we will ask the suitable questions, to get you the reply that you may want.