The 1st check is to put a good fully charged and off the charger for 2 hours battery on, that battery needs to be close to 80/800 ish and see what happens, I make the following obs : Means nothing, 20 miles per day every day means about 15 to 20 minutes of charge rate, not nearly sufficient to replace the start amps cost I tried a Maplins 13W charger in the window all year and it gives a quoted 743mA, don't believe it - I made it closer to 200mA on the brightest stonking summer day. Convert your 150W into amps then divide it by four over a whole years facing the sun then you might have some idea of the real value - it - the solar is however a good idea for those who can not connect a 5 or 7 stage conditioner changer for an 80Ah need. When the world was proclaiming the new Jesus battery, I was already warning people off them. Nevertheless it is a straight swap size for those who don't want to make a mod on the battery tray / FCM / shroud and cables. This is not complicated they are totally different animals, they are all AGM but the red is the one you want and is for a high enough for long enough belt to start an engine, blue is marine multi and yellow is just the size of the stud as in the blue has a 5/16ths and the yellow a 3/8ths stud. The marine is designed for slow release - running lights radio converters etc and the red is for CCA giving it all now to start a car.