When lead acid batteries discharge, the lead plates inside dissolve and get thinner. Deep cycle batteries have thicker plates than say a standard Walmart battery so you can take them deeper without damage. However if you take them deep, but charge back up too slow, the lead does not reform over the plates evenly, only close to the terminals. This can lead to the next heavy discharge making the plate away from the terminal even more thin, possibly even damaging. Do this several times... bad battery.
To mitigate some of this effect, buffer materials are added to the dielectric (acid) in order to prevent the plates from dissolving unevenly and to help plate up evenly. This normally works great, however after let to sit for a while, these materials can leave a coating on the lead that prevents reaction. This can be resolved by administering a heavy load on the battery for a few minutes, then a normal recommended charge cycle of at least several amps. Do this a few times and the battery should increase capacity significantly. Some very good battery managers will perform this cycle for you, administering an AC like cycle if the battery is detected to have low capacity.
A very good series of deep cycle batteries is called Sunwise. I have pounded the ever-living snot out of one at work developing an advanced solar charging system for remote devices. Mostly single battery systems, but need 10 year serviceability. It performs many restoration functions, and is really careful about the last 10 percent of capacity which is considered severe emergency reserve. Tap into that and battery life suffers.
Last edited by liquidsquid; 07/04/13 06:45 AM.
