How much weight can you mount to a wall?
150 lbs is a very heavy set of shelves, unless the bottom sits on the floor and you only need to secure it to the wall so it won't tip forward.  In any case, there is no written limit on weight, but a lot of common sense has to be used in this case. You will want to know what the rating of the "L" brackets are and if strong enough to hold your load. They would have to be securely mounted to studs in the wall with some pretty large screws. There are no anchors for drywall that I would trust for that much weight. Perhaps you might consider some legs from the bottom of your shelf unit to the floor to support the weight.