marinetrader
Senior Member
- Joined
- Oct 6, 2007
- Messages
- 301
The most popular kind of battery in marine use today is the standard lead acid battery. Using an electrolyte consisting of sulphuric acid, these cells can store large amounts of electrical energy in a relatively small space. The energy is stored in lead grids that are inside the battery. The lead explains the massive weight of lead-acid batteries.
The battery selection is further spread along the lines of battery construction. Presently, there are three common battery technologies: Wet-cell, Gel, and AGM.
Wet Cells are the most common lead-acid battery-type in use today. They provide the most size and design options and are developed for many different uses. Wet-celled batteies have a grid of lead plates that is used with the acid. Since the grid is not supported except at the edges, flooded lead-acid batteries are mechanically the weakest batteries. Since the container is not sealed, great care has to be taken to ensure that the electrolyte does not come into contact with you (burns!) or seawater (chlorine gas!), or an explosion from the hydrogen produced. Batteries should always be stored in a spill-proof box.
Gel cell batteries use a thickened electrolyte . So if the container is broken, the cell will continue to perform as normal. Furthermore, the thickening agent prevents stratification by forestalling the movement of electrolyte. As gel cells are sealed and cannot be re-filled with electrolyte, controlling the rate of charge is very important or the battery will be finished in short order.
AGM or Absorbed Glass Mat batteries are the latest generation of batteries.* Instead of a gel, fiberglass mats hold the cells and electrolyte in place. The bond between the fiberglass mats, the lead plates and the battery housing makes them spill impervious and the most impact resistant batteries on the market today. They were originally designed to be used in aircraft.* I have 4 of them on my personal trawler.
An AGM battery can do anything a gell-cell can do, but only better. However, since they are also sealed, charging has to be controlled cautiously or they too can be ruined in short order.
Absorbed Glass Mat batteries are relatively new but are rapidly winning acceptance. There are some good reasons to use them:
1 - Absorbed Glass Mat (AGM) batteries can dispense a charge at a higher rate than flooded cells.
2 - No gassing under normal conditions: AGM batteries are sealed under pressure to recombine oxygen and hydrogen into water during the charging process. You find AGM batteries on high-end new yachts such as Hinckley and Broward.
The ability to put AGMs in the bilges (they can even function under water) also lengthens their lives; Remember that for every 15 degrees over 77F, a battery's life will be cut in half*
AGM batteries will even operate upside down and even if a container is crushed, it will not leak. This should be of particular importance to blue-water cruisers that could find themselves tossed around; you would not want sulfuric acid in your boat. And as always, appropriate tie-downs are always recommended.
AGMs require no maintenance once the charging system has been properly set up.
There is one issue that must be considered however and that is the price of an AGM battery:
Let's review prices
-*** Wet cell 8-D - $150.00
-*** Gel - 8-D - $250.00
-*** AGM - 8-D $365.00 (Marine centers have them for $501.00)
So choose the battery you feel is best for you and have fun with your trawler.
The battery selection is further spread along the lines of battery construction. Presently, there are three common battery technologies: Wet-cell, Gel, and AGM.
Wet Cells are the most common lead-acid battery-type in use today. They provide the most size and design options and are developed for many different uses. Wet-celled batteies have a grid of lead plates that is used with the acid. Since the grid is not supported except at the edges, flooded lead-acid batteries are mechanically the weakest batteries. Since the container is not sealed, great care has to be taken to ensure that the electrolyte does not come into contact with you (burns!) or seawater (chlorine gas!), or an explosion from the hydrogen produced. Batteries should always be stored in a spill-proof box.
Gel cell batteries use a thickened electrolyte . So if the container is broken, the cell will continue to perform as normal. Furthermore, the thickening agent prevents stratification by forestalling the movement of electrolyte. As gel cells are sealed and cannot be re-filled with electrolyte, controlling the rate of charge is very important or the battery will be finished in short order.
AGM or Absorbed Glass Mat batteries are the latest generation of batteries.* Instead of a gel, fiberglass mats hold the cells and electrolyte in place. The bond between the fiberglass mats, the lead plates and the battery housing makes them spill impervious and the most impact resistant batteries on the market today. They were originally designed to be used in aircraft.* I have 4 of them on my personal trawler.
An AGM battery can do anything a gell-cell can do, but only better. However, since they are also sealed, charging has to be controlled cautiously or they too can be ruined in short order.
Absorbed Glass Mat batteries are relatively new but are rapidly winning acceptance. There are some good reasons to use them:
1 - Absorbed Glass Mat (AGM) batteries can dispense a charge at a higher rate than flooded cells.
2 - No gassing under normal conditions: AGM batteries are sealed under pressure to recombine oxygen and hydrogen into water during the charging process. You find AGM batteries on high-end new yachts such as Hinckley and Broward.
The ability to put AGMs in the bilges (they can even function under water) also lengthens their lives; Remember that for every 15 degrees over 77F, a battery's life will be cut in half*
AGM batteries will even operate upside down and even if a container is crushed, it will not leak. This should be of particular importance to blue-water cruisers that could find themselves tossed around; you would not want sulfuric acid in your boat. And as always, appropriate tie-downs are always recommended.
AGMs require no maintenance once the charging system has been properly set up.
There is one issue that must be considered however and that is the price of an AGM battery:
Let's review prices
-*** Wet cell 8-D - $150.00
-*** Gel - 8-D - $250.00
-*** AGM - 8-D $365.00 (Marine centers have them for $501.00)
So choose the battery you feel is best for you and have fun with your trawler.