What is the best bulk and float voltages for kirkland lead acid, starting/deep cycle marine-RV batteries?

Question

the batteries individually are
-12 volt
-115 amp hours
-750 marine cranking amps
-600 cold cranking amps
-750 MCA
-Fitment code: 14
-Group Size: 27DC
-item #: 12852

i know costco doesnt make their own batteries, they just rebrand them from Johnson Controls Inc, but i still cant find much info on them. im pretty sure they are supposed to be maintenance free but they dont say anywhere and there are just 2 square vents on each battery that i dont want to pry on to see if they open just in case i might break them. im using 2 of them in series for a 24volt solar panel system with a xantrex c40 charge controller where you can choose the bulk and float voltages, in the manual of the xantrex c40 for "maintenance-free rv/marine" batteries it suggests 28.8v bulk and 26.8v float (divide by 2 for each individual 12v battery). and for "deep cycle, liquid electrolyte lead antimony battery" batteries it suggests 29.2v bulk and 26.4v float (divide by 2 for each individual 12v battery). but my batteries say they are deep cycle AND marine batteries, should i average the 2 together or what? are these even good bulk and float voltages? i know the batteries go up to around 12.84v or so each when fully charged, can someone help me out? thanks

Answer 1

Marine just means they are more spill resistant than automotive starting batteries as a general rule. They are not deep cycle unless marked as such- as yours are, even so, deep cycle batteries are not much different from automotive starting batteries other than a wider plate spacing, heavier plate frames, a little more lead on the plates and a deeper sediment trap at the bottom. They are in every respect just another lead acid battery. Even so it is best to not discharge them below 80% capacity.



Float voltage just means the voltage applied to the buss when the batteries are at full charge, or at the level of charge they can accept as a maximum. When fully charged, a lead acid cell will measure 2.3 volts in prime condition, which is 13.8 volts in a 6 cell automotive battery, and 27.6 in a 24 volt battery. This the optimum. Over a short period of use and charge/discharge cycling, this maximum drops a little. The 26.8 is high enough to keep a "full" charge on the battery, but not so high as to boil it dry. 26.4 might be high enough in the early usage, but later on it will not be quite enough to overcome the internal resistance of the battery which slowly increases with use over time.



BTW, Johson Controls even rebrands the batteries that bear their name. They contract with the few manufacturers that manufacture batteries these days.



So set it for the 26.8 volt float voltage.



At some point in the future, you will want to open the covers to see where the electrolyte level is, you will be amazed at how fast that level can drop in a solar setup.

Answer 2

Costco Marine Battery

Answer 3

Costco Deep Cycle Battery

Answer 4

This Site Might Help You.



RE:

What is the best bulk and float voltages for kirkland lead acid, starting/deep cycle marine-RV batteries?

the batteries individually are

-12 volt

-115 amp hours

-750 marine cranking amps

-600 cold cranking amps

-750 MCA

-Fitment code: 14

-Group Size: 27DC

-item #: 12852



i know costco doesnt make their own batteries, they just rebrand them from Johnson Controls Inc, but i still cant find...

Answer 5

Marine means that they are more rugged and can take the abuse of a marine environment. I would got with the voltages for the deep cycle batteries.