can those who have done this project give me an idea of what the time involved and costs would be for this job ? I won't factor in battery cost , since th home batterie are done. So i have to replace my house bank with two 8Ds at 220 aH each, or my 2 31 XT Lifelines at 135 aH each, or 4 6v golf cart batteries which will require a re wire. (our primary issue is whether to replace the original 440 a H 8 D bank with another set of 8 Ds, to get enough aH to use the inverter which needs a 'recommended' 400 aH minimum bank. But we never use the inverter; all it runs is galley outlets and the microwave. ) So 4 years ago , we replaced the 8 Ds with 2 lifeline XT 135 Ah batteries . now we're contemplating the switch to 6 volts . thanks for all words of wisdom...
Forget using 4D or 8D batteries. The only reason boat builders install them is because they
look impressive at boat shows and require less labor & material cost to install. They are doing no one any favors by installing these batteries.
Beyond that, due to the square shape of the cells, there is
no way to
properly orient an 8D flooded battery on a sailboat so as to not
expose the plates when heeled. Any manufacturer that installs
flooded 8D batteries on a sailboat is simply not doing their job well.
This is the first part of ABYC E-10 under "Installation". The FIRST THING YOU SEE!
"
10.7
INSTALLATION
NOTE: When installing flooded batteries on a sailing vessel, consideration should be given so
that the orientation of the battery minimizes the uncovering of battery plates while heeling."
This
fail, on top of the fact that they are not true deep-cycle batteries, leads to short life.
Even the trucking and agricultural industry are rapidly moving away from using 4D or 8D batteries. Some battery manufacturers have even stopped producing flooded 4D and 8D's altogether. This includes deep-cycle manufacturers such as US Battery Corp and Trojan.. Only in AGM or GEL will you
regularly find a 4D or 8D battery that is
actually a deep cycle battery. Both Dyno and Rolls
do produce a deep-cycle version, in a flooded battery, but the rest are simply "starting" or "dual-purpose" batteries with a
deep cycle sticker slapped onto them.
The Lifeline GPL-31XT is a 125 Ah battery not 135Ah so you actually have 20 Ah's leas than you think. Whether this matters or not would depend upon you actual daily -Ah consumption and ability to recharge. If you are looking at replacing Lifeline AGM's at year 4, your charging system and/or use are likely not working as they should. Flooded golf cart batteries are
much less costly to chew through in short order than AGM's...
Sizing your bank should ideally be inclusive of your inverter, whether you use it much or not. When sizing a lead acid bank for cruising use, it should be sized based on 30-35% of its face value Ah rating as your
usable capacity. With AGM's 35% is usually fine, they charge a bit faster, but with flooded deep cycle batteries sizing for 30% as
usable capacity is safer.
When cruising you will usually cycle from 50% SOC to about 80-85% SOC, hence the 30-35%
usable capacity figure. Once you're more than a day away from the dock, or a full charge, your usable capacity shrinks due to the
rapidly declining charge acceptance above 80-85% SOC
. If you continue this
partial state of charge use (PSOC), each day, between full recharges, the
usable capacity shrinks even further due to what is called
PSOC walk-down..
In reality your 400Ah bank really only has a usable capacity when out cruising of about 120Ah's. A 250Ah bank only has about 75
usable Ah's. Also keep in mind that this sizing does not include for any aging, capacity loss due to age or PSOC walk-down. In short, a bigger bank, discharged shallower wins over the long haul....
Installing 6V batteries is a minimal cost difference so long as you have the available height in your battery box. A few series & parallel jumpers, battery box, some hold downs and re-programing your charge sources for
optimal voltages are really the only differences.. If you really want to do it right some Water Miser caps or an automatic watering system can be installed too.
If you are in the market for deep cycle batteries this article can help shed some light on the buying process.
What is a Deep Cycle Battery?
.