Im currently using a 12V Lead-Acid battery to power a speaker amp but when the voltage gets to 11.5 volts, it no longer has enough power for the amp. Im wondering if there is a easy circuit i can build that will take 11-12V in and put 12.5-13V out 11.5 volts for a longer time. A good battery should have about 13.7 volts present when fully charged,
i use amaron battery my solar panel 65amp amaron battery
  We must think safety when we are working around and with batteries. Remove all jewelry. After all you don't want to melt your watchband while you are wearing the watch. The hydrogen gas that batteries make when charging is very explosive. We have seen several instances of batteries blowing up and drenching everything in sulfuric acid. That is no fun, and would have been a good time to use those safety goggles that are hanging on the wall. Heck, just break out your disco outfit. Polyester is not affected by Sulfuric Acid, but anything with cotton will be eaten up. If you do not feel the need to make a fashion statement just wear junk clothes, after all Polyester is still out of style. When doing electrical work on vehicles it is best to disconnect the ground cable. Just remember you are messing with corrosive acid, explosive gases and 100's amps of electrical current.
Basically there are two types of lead acid batteries (along with 3 sub categories); The two main types are Starting (cranking), and Deep Cycle (marine/golf cart). The starting battery (SLI starting lights ignition) is designed to deliver quick bursts of energy (such as starting engines) and therefore has a greater plate count. The plates are thinner and have somewhat different material composition. The deep cycle battery has less instant energy, but greater long-term energy delivery. Deep cycle batteries have thicker plates and can survive a number of discharge cycles. Starting batteries should not be used for deep cycle applications because the thinner plates are more prone to warping and pitting when discharged. The so-called Dual Purpose Battery is a compromise between the two types of batteries, though it is better to be more specific if possible
  Battery Don'ts

• Don't forget safety first.
• Don't add new electrolyte (acid).
• Don't use unregulated high output battery chargers to charge batteries.
• Don't place your equipment and toys into storage without some type of device to keep the battery charged.
• Don't disconnect battery cables while the engine is running (your battery acts as a filter).
• Don't put off recharging batteries.
• Don't add tap water as it may contain minerals that will contaminate the electrolyte.
• Don't discharge a battery any deeper than you possibly have to.
• Don't let a battery get hot to the touch and boil violently when charging.
• Don't mix size and types of batteries.

State of Charge	Specific Gravity	Voltage
		12V	6V
100%	1.265	12.7	6.3
75%	1.225	12.4	6.2
50%	1.190	12.2	6.1
25%	1.155	12.0	6.0
Discharged	1.120	11.9	6.0