We are replacing our house batteries with AGMs. Are trying to determine which brands are best. Would appreciate experience with different brands.
Our decision to use AGM was not an emotional one but suggested by the top marine professional in the Annapolis area who outfits many of the cruising boats in Annapolis area as well as teaching marine elctronics in seminars at many of the boat shows and for the Annapolis Seamaship school. There are many factors in to deciding to use them and they are not as said a panacea or answer for everyone. I beleive true marine elctronics professionals look at the whole situation, intended usage and make their decisions based on that.I find the differing views on AGMs between typical users and marine professionals to be instructive.
AGM users either swear by them or swear at them. Often, though, they imbue AGMs with almost mystical properties which in the real world don't really exist. They also tend to dismiss older technologies, like flooded lead-acid batteries, and gelled lead-acid batteries as being "dangerous", "messy", or "easy to kill".btrayfors
Advancepowerproducts,comAGM is more efficient.
Based on Peukert's equations, the German scientist who mathematically solved the battery discharge problem, each battery's efficiency can be computed. AGM batteries are generally far more efficient than are flooded lead acid batteries. This is important when determining the cost to charge and discharge the batteries. Generally an AGM battery will give you between 80-90% of the power pushed into the battery, back. On the other hand, flooded lead acid batteries typically have efficiencies in the 40-60% range. The bottom lines here are time and money. Basically you spend more to charge a flooded battery than you do an AGM. This translates to money as generators eat gas, alternators rob horsepower from the engine, and battery chargers eat kilowatts. The real tragedy is that you get less of that power back from the flooded battery than you do with an AGM battery.
AGM self discharge rates are 80% - 99% better.
Batteries, being a chemical equation in flux, are not perfectly stable. A battery will self discharge as it sits. AGM batteries are far more resilient than flooded batteries when it comes to self discharge. The typical AGM battery will discharge 1 to 3% per month, with this rate remaining stable over the life of the battery. Flooded battery models do not fare as well, losing 5-10% per month when new, and up to 20 or 40% per month as they age due to antimony contamination in the negative plates.
Gell batteries from windsun.com - they create solar charging syetmsAbsorbed Glass Mat (AGM) batteries include lead plates packed between silica-glass mats, which hold electrolytes in suspension. They have no input current limitations allowing them to recharge more quickly than Flooded batteries, which typically accept about 35% of their ampere-hour rating, and Gelcells, that accept about 50%. At higher current loads AGMs also maintain usable system voltages for other high current, short duration loads as opposed to their counterparts, which become more inefficient during high current loads. AGMs also boast a longer lifespan than their counterparts, a deep-cycle flooded battery allows for 350 cycles at a 50 percent discharge level and Gelcells allow for 750 cycles whereas an AGM offers up to 1000 cycles at a 50 percent discharge level.
Gelled batteries, or "Gel Cells" contain acid that has been "gelled" by the addition of Silica Gel, turning the acid into a solid mass that looks like gooey Jell-O. The advantage of these batteries is that it is impossible to spill acid even if they are broken. However, there are several disadvantages. One is that they must be charged at a slower rate (C/20) to prevent excess gas from damaging the cells. They cannot be fast charged on a conventional automotive charger or they may be permanently damaged. This is not usually a problem with solar electric systems, but if an auxiliary generator or inverter bulk charger is used, current must be limited to the manufacturers specifications. Most better inverters commonly used in solar electric systems can be set to limit charging current to the batteries.
Some other disadvantages of gel cells is that they must be charged at a lower voltage (2/10th's less) than flooded or AGM batteries. If overcharged, voids can develop in the gel which will never heal, causing a loss in battery capacity. In hot climates, water loss can be enough over 2-4 years to cause premature battery death. It is for this and other reasons that we no longer sell any of the gelled cells except for replacement use. The newer AGM (absorbed glass mat) batteries have all the advantages (and then some) of gelled, with none of the disadvantages
with the proper care this is not really true. Ask how many sailors actually equalize their lead acid batteries monthly properly- flooded batteries will outlast AGMs every time in terms of charge-discharge cycles
This is simply not the case. The technology of th AGM makes them much more resisitant to vibration. In addition with AGM you do not have ANY acid problem. With AGM you have No spilling acid on your clothes when filling them or testing them, No discoloration or repair in your battery comopartment as there is no gas or sulfuric acid mist emitted during charging like with wet cells. This gas smells like rotten eggs---ever wonder why and what it is ( it is sulfur)- flooded batteries will take a lot more abuse than AGMs
I agree that AGM systems must be matched more carefully, however there is no limnited rate for charging as their is for wet cells- flooded batteries do not require expensive upgrades of online charging capability
This has been discussed. Initially this is true, but when you add in the maintainence costs as well as the amount of the cost of energy ( wet cells take longer to charge to 100%, and must be charged at a higher point of discharge than AGM, and are less efficient in obtaining and making energy), ther longer the AGM lasts ( that is owners responsibility) the cost curve becomes a non issue. In other words a AGM which lasts 8 years will pay for the initial higher costs through the lower charging and energy efficiency costs. Plus NO Maintenence- flooded batteries are a lot cheaper than AGMs
Obvious turth as they have been around much longer. As time advances this will not remain the truth. If you are cruising to Vanatu or the Solomons Islands this may be an issue. If you are cruising on the Chessie, United States or Canada this is a non issue.- flooded batteries are available everywhere in the world
Dave,Our decision to use AGM was not an emotional one but suggested by the top marine professional in the Annapolis area who outfits many of the cruising boats in Annapolis area as well as teaching marine elctronics in seminars at many of the boat shows and for the Annapolis Seamaship school. There are many factors in to deciding to use them and they are not as said a panacea or answer for everyone. I beleive true marine elctronics professionals look at the whole situation, intended usage and make their decisions based on that.
One of the most widely used arguments against AGM/ Gell is that they are more expensive. But are they really? The initial cost of the AGM is not just the only factor here. The cost of charging them must also be brought into the equation. This includes the charger, the cost of the energy to run the charge ( be it engine or genset), also the rate of discharge. The following is qouted from an article:
Advancepowerproducts,com
Gell batteries from windsun.com - they create solar charging syetms
with the proper care this is not really true. Ask how many sailors actually equalize their lead acid batteries monthly properly
This is simply not the case. The technology of th AGM makes them much more resisitant to vibration. In addition with AGM you do not have ANY acid problem. With AGM you have No spilling acid on your clothes when filling them or testing them, No discoloration or repair in your battery comopartment as there is no gas or sulfuric acid mist emitted during charging like with wet cells. This gas smells like rotten eggs---ever wonder why and what it is ( it is sulfur)
I agree that AGM systems must be matched more carefully, however there is no limnited rate for charging as their is for wet cells
This has been discussed. Initially this is true, but when you add in the maintainence costs as well as the amount of the cost of energy ( wet cells take longer to charge to 100%, and must be charged at a higher point of discharge than AGM, and are less efficient in obtaining and making energy), ther longer the AGM lasts ( that is owners responsibility) the cost curve becomes a non issue. In other words a AGM which lasts 8 years will pay for the initial higher costs through the lower charging and energy efficiency costs. Plus NO Maintenence
Obvious turth as they have been around much longer. As time advances this will not remain the truth. If you are cruising to Vanatu or the Solomons Islands this may be an issue. If you are cruising on the Chessie, United States or Canada this is a non issue.
Lastly in this, I have on a number of times helped fellow sailors who have been involved in a knockdown or a rough passage to clean out their battery comparments where there was acid spill and incidents caused by the wet cells movement during the rough seas. For safety is is so very important to do a good job of tying down and isolating your batteries so they dont move. With AGM this is a non isuue
With all respect to Bill ( whose posts a have huge respect for and have followed his advice many times) I think the main point here is whether you want to have a maintainace free system. Yes it is more high tech, sort of. As Bill and Mainsail have pointed out AGM are not for everyone. The proponents of it however are not just highly energized users or purchasers of the batteries, but professional marine electronics technicians also. In some of the sailors on here it may be quite and advantage to utilize them, and in many not so much to justify the added expense. You will need to do the maintenance though.
Batteries purchase is right up their as a topic on here with correct anchor, sail material and firearms in its many dimensions and ability to energize ( I like this word as you see especially when discussing batteries) the posters on here. Is there an always right answer to this. NO I think not. It depends on you usage and abilities and dedication to electrical maintenance. To long distance cruisers who that's all they do is maintain their boats...no brainer. To the average weekend user, maybe a different story. All sides can find factoids to support their own conclusions, just as I have. My recommendations are to consult a local to you marine electronics professional to go over your specific usage and needs to help you make the most educated decision.
Dave