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Prior to placing batteries into winter
storage make certain the electrolyte level is approximately
1.2" (13mm) above the top of the separators. The electrolyte
level in very cold batteries will be lower than normal, so
let batteries warm to a normal temperature before judging
electrolyte levels.
Once the electrolyte level is
correct ensure that the batteries are fully charged. Ensure
that the battery tops are clean and dry.
See Information
Bulletin 501 & 507.
Now the choice is whether to leave
the batteries aboard your boat or remove and store in a cool
dry area. If the batteries are stored aboard the boat,
disconnect the terminal cables. This will prevent premature
discharge of the batteries due to a ground in the electrical
circuits or failure to turn a piece of electrical equipment
off.
If the batteries become discharged,
the electrolyte can freeze when stored below +20° F (70° C).
Below shows temperatures at which electrolyte, in various
states of charge, starts to freeze.
Specific Gravity
(cor. to 80° F/26° C) |
Freezing Temp |
|
1.280 |
-92° F (-69° C)
|
|
1.265 |
-72.3° F (-57.4° C)
|
|
1.250 |
-62° F (-52.2° C)
|
|
1.200 |
-16° F (-26.7° C)
|
|
1.150 |
+5° F (-15° C)
|
|
1.100 |
+19° F (-7.2° C) |
A 3/4 charged battery is in no
danger of freezing. Therefore, batteries should be kept at
least 3/4 charged, especially during winter weather. The
frequency of checking batteries depends greatly on
temperature. The effect of temperature on self discharge for
the average fully charged, new, conventional battery in good
condition is approximately as follows:
-
At 100° F (37.8°C) .0025 Sp.Gr.
per day
-
At 80° F (26.7°C) .001 Sp.Gr. per
day
-
At 50° F (10°C) .0003 SG per day
A fully charged battery stored at
80° F (26.7°C) will take 30 days before it self discharges
25 percent. At 50°F (10°C) the time period increases to 100
days. This will give you an idea of how often a battery
should be checked.
Some makes of batteries will have a
higher and some a lower rate of self discharge. This depends
on the method of manufacture and purity of materials used. |