Here is, FYI, some details on the Delphi batteries:
Batterie FREEDOM marine servitude et dÃ©marrage, BATTERIES MARINES, ElectricitÃ© -
They are the same batteries than the Vetus ones (although Vetus give you a 108 A/20 when Delphi is a 105 A/20, they are exactly the same...only the sticker is different).
If you want to have a lifetime significantely over 4 years, these Delphi will not garantee you to have it.
My last set (4 x 105 and 4 x 75) didi not last more than 4 years as well.
I guess they were not "off work" when I bought them and poorly stored (on the ground, no frequent or permanent charging
...) by the seller, which is reducing the life expectancy of course.
life is very difficult to assess from one boat to another one, one area to another one...apparently our areas are very similar (we are in Cherbourg...) so we can compare.
If you are looking for a long life expextancy, you should look for other battery's type, the "best" ones being the 2 volts elements like ones from Mastervolt, but you need 6 of them to make 12 volts, they are bulky, heavy and, of course pricey.
If it is not a problem to use the 2 volts elements, according the manufacturer and users, life expectancy can goes up to...10 years!
Which is kind of balancing the price
way higher than for "usual" batteries.
Here are some infos:
Batteries & Terminals | Mastervolt. The world‘s leading brand in maritime, mobile and solar energy solutions.
The website can be in French as well and is full of information and tutorial.
Another very usefull website (in French, if you are from Morlaix, should not be a problem...) is this one:
Voilelec __ Voile et Electronique : Christian Couderc
Generally, the life expectation of batteries depends on the environment
(temperature) and the way they are managed.
The Delphi / Vetus type is having a 400 cycle (charge - discharge) life expectancy in theory, for example.
But if they are not properly manage, this will be reduce and you can have a battery
failure after 2 years or may be less.
One good way to not damage your battery is to never discharge them more than 30% to 50% (30% is better and safer anyway, 50% a great maximum, never to go further).
this, you need to have a good and sensitive battery monitor
device with proper alarm
settings.nd cycle counting.
Keeping them charged 100% as much as possible is another way to save the batteries.
I hope that in the next future, battery technologie will improve (the car industry could give a good boost for that with all the development in electrical
vehicles that need significant capacity and deep discharge characteristics...as we do for our boats).