Originally Posted by noelex 77
I would advise the opposite. AGM and gelled batteries have a longer life, but at a greater cost. If you are are crusing developed areas flooded batteries are usually the cheapest option, but if you need to replace the batteries in underdeveloped areas the cost is much higher. Transport costs are a significant part, batteries are very heavy and flooded (but not AGM and Gel) batteries are classified as hazardous goods. The longer life of AGM or gel can make them cheaper than replacing them in underdeveloped countries.
Having your house battery bank set up so it is possible to separate them into 2 banks ( giving 3 banks including the start batteries) is helpful when crusing any areas where deep cycle batteries are difficult to get. If batteries fail you can pick the best old batteries to form one bank. In underdeloped countries it is very difficult to get deep cycle batteries at short notice, but car start batteries can be got anywhere. This can form a cheap
second bank. This combination will last untill you can get somewhere where deep cycle batteries are cheap
, or at east available.
Even better if when leaving on your voyage if you replace half the batteries with new ones, the two house banks will be different ages, which makes sudden complete house battery failure unlikely.
I think a completely separate start battery that is used only for starting ( or possibly the anchor winch
as well) is good insurance
I just did a Google
search for "agm vs flooded battery life". On the first 5 pages these are the sites I found that were not trying to sell batteries.
FLA AGM Battery Life Span - Moderated Discussion Areas
AGM Absorbent Glass Mat (AGM) Battery Information - Battery University
FLA About RV Batteries
AGM AGM battery takes primary role for idle stop-start in microhybrids - Vehicle Electrification - SAE
No direct statement- Frequently Asked Questions - Batterytender.com
This site indicates that flooded gets better cycle life than gel or AGM at the cost of regular maintenance
. However although the site is an alternative energy emag, the actual answers were from an interview with Trojan battery employees:Alternative Energy eMagazine - Batteries for Alternative Energy Systems | AltEnergyMag
This site was a reference for the Wikipedia article that appeared in the first 5 pages:
FLA Sterling Power Products: What is the best battery to use for an auxiliary charging system?
This site indicates that Gel gets more cycle life than AGM when cycled deeply (>80%DOD): Battery Tutorial | ChargingChargers.com
The count was about 6 to 2 that FLA gives more life cycles.
The technician's comments from the first site listed are consistent with my experience as an engineer
, just because something is advertised as maintenance-free and manufactured that way doesn't make it so.
Total life cycles is not the only part of the story, there is also the maintenance
required, the charging regime and the use conditions.
Use on a sailboat is not particularly rough except perhaps in regards to temperature. Sailboats are relatively low in vibration and if they turn upside down the batteries will be among the least of your worries. Consequently AGM has little or no advantage here.
FLA's require monthly maintenance to get the better cycle-life. AGM are maintenance-"free". Advantage AGM. As a world-class procrastinator this is the primary reason I would chose AGM.
If the boat is going to be unattended and not have any charging source for long periods (months) then the AGM with the much lower self-discharge rate has a big advantage. If the boat has solar panels
then the FLA's will survive just as well or better provided you can check densities and water
levels every 2-4mo.
If running the engine is your primary charging source, then the AGM has the advantage, charge acceptance rates are 50-75% faster meaning the engine can be run for about 2/3 the amount of time as FLA batteries saving engine wear and fuel
If you are going to spend a lot of time away from any civilization and worry that the whole battery bank will die all at once and you will have to have batteries shipped out on short notice to an out of the way place, then the AGM's have the advantage.
For run of the mill cruising and living aboard
panels in the US, Caribbean
, FLA's have the advantage in price
and longevity IF you can do the maintenance regularly.