Is your security guy saying the fuse strategy isn’t acceptable? If you’re excited about utilizing a 12 V lead-acid battery, these are generally utilized in alarm techniques, and I doubt all of them have to get building permits. If they do accept the fuse or other current/power-limiting device right on the battery, the capability shouldn’t really matter, and you can use a 40 Ah battery to give you 4 A for 10 hours. Lead-acid batteries are in style for bigger tasks since they are usually the lowest-cost possibility and are extensively obtainable. Sealed lead-acid or gel-cell batteries can be found in 6 V and 12 V variations , with the 12 V versions weighing a few pound per amp-hour.