Well, I've gotta apologize for the age mistake: I looked up the date of purchase
of the 8 T-105's on my boat, and found it was June 2006. So they're just over two years old. They test better than 80% of capacity, even without equalizing recently.
Six of these make up my house battery bank (675AH total). I can tell you that during my recent 8-day cruise
they performed perfectly. And, as usual, after a few deep discharges and recharges they "regained" some capacity. This is evident from the very noticeable difference in voltage-under-load for a few hours after charging.
Batteries that haven't been exercised for awhile, or "equalized", will often show an alarmingly low voltage soon after a load is applied. For example, mine drop quickly from 12.6 to 12.4 within a few minutes when the batteries have only been kept on charge at dockside for a few months. However, once you exercise them, i.e., give them a few deep discharges and full recharges when cruising, the voltage-under-load stays up there much longer.
These are the batteries maintained by the Victron. They have only been equalized once in their 2-year life. The float voltage is set for 13.2, and absorbtion voltage at 14.4. I'm gonna up this soon...maybe to 13.6 or 13.8 and 14.8, respectively....and see what happens. The batteries, BTW, are fitted with WaterMiser caps, reducing water loss and making inspection
and top-off very easy.
I have two -- actually three -- other battery banks of interest. One, also on my boat, consists of two T-105s which are dedicated to the windlass
. They are maintained by an Iota
DLS-55/IQ4 (PWM pulse charger) which is left on most of the time when at dockside, and which is used periodically away from the dock
, powered by an onboard AC generator
. These batteries are the same age as the house batteries, and test better than 80% of original capacity. Test instrument was a Midtronics 500/XL conductance/resistance tester ($600).
Similarly, I have a T-105 battery bank used at home to power all my radios: ham, marine
, military, commercial
. It is maintained by an Iota DLS-45/IQ4 charger, on all the time. I draw anywhere from a few amps to 90amps with the linear amplifier when transmitting. This bank is over four years old and tests better than 80% of capacity.
I have two other banks of interest. These are Gelled golf cart batteries which are almost 12 years old. At age 10, they were removed from a friend's sailboat and I used them for battery testing in a longitudinal study of pulsers for almost two years. Believe it or not, these four 12-year old batteries test 70-80% of capacity. And, being gells, they hold a charge for a long time without charging. Simply amaazing!
I hear you
re: stresses on batteries. However, I would point out that few batteries are stressed any more than your average car battery in terms of vibration, shock loading, heat, cold, etc. Typically, even cheap
car batteries subjected to extreme heat and extreme cold last 5 years or so.
So, I've gotta agree to disagree with you. IMO, there's simply no way
a 5-6 amp periodic load on a healthy house bank is gonna stress a deep cycle battery bank, providing it is connected to a good charger and kept fully charged most of the time.
In fact, given the smart circuitry used in many battery chargers today, the batteries won't even "see" the load of a Danfoss compressor -- or even two or three of them -- the chargers compensate instantly for loads applied to the 12V system, with virtually no change in float voltage.