Laying up batteries

[Miker]

I shall be taking my boat out of the water next month. Do I need to remove the batteries and store them in a frost proof place such as my garage? I have done this in previous years but it is a job I would rather avoid if not necessary. If left in the boat I shall be able to charge the batteries occasionally.

Advice appreciated.

 

[Guest]

I've never had any problems doing what you mention. All I've read on the subject suggests providing batteries are kept fully charged they'll be OK.

 

[Guest]

My batteries stay on the boat all year. I just make sure that they are charged on a regular basis

 

[steve_cronin]

Your batteries will be OK so long as they are kept FULLY charged. That means not at 13.8 volts as supplied by most marine chargers but at 14.4 volts which will give full capacity. The freezing point of sulphuric acid is quite low and unlikely to be reached even in chilly Britain. Keep an eye on levels though by topping up with distilled water at regular intervals.

To keep your batteries in top condition an "intelligent" charger like the Sterling is essential. This starts with a plate cleaning boost at 16.8 volts and then starts charging each battery in phases up to its maximum capacity, then it keeps the batteries at full level by a sequential trickle charge until you put a load on them again or the mains supply is interrupted when the whole cycle re-starts. Conventional chargers (13.8vdc) only reach 85% of the rated Ah capacity and are intended for the road vehicle environment where just getting the vehicle started again after a period of charging is the priority.

In boat (domestic) batteries we require an electrical storage system which we can run down, leave for long periods of depletion and then re-charge, expecting that they will be unaffected. Sadly this is not the case and the longest lasting batteries are those which never have a load put upon them and certainly never run down to say 60% capacity but of course this is impractical

Steve Cronin

 

[robp]

In their regular place on the boat is reasonably free from extreme temperatures. The normal arrangements for keeping the boat frost free should suffice. They do need to be kept charged though.

 

[davidphillips]

How regular is regular?

 

[Jcorstorphine]

We always ran our batteries down with a 24 watt lamp and then charged them up and left for a month, then repeated so as to cycle them. Seemed to work as they lasted for years (about 6 to 8 ish)

 

[J_Priedkalns]

Our Canadian winters are a "little" cooler than U.K's and our method of storing ship's bateries is to leave them in the boat fully charged ie the batteries have had an equalizing charge to ensure all cells are fully charged. DO NOT add any distilled water to the battery during the storage period UNLESS you have means of charging the battery immediatley otherwise the batteries will freeze. This method has worked for our deep cycle batteries which lasted for over 13 years! As a matter of interest our winter temperatures can drop to -40C on a regular basis.

 

[J_Priedkalns]

PS.....

The following is info I obtained from a reputable battery manufacturer in Canada regarding freezing of battery electrolyte:

Specific Gravity of electrolyte.........................Freezing Temperature
corrected to 80deg F (26.7deg C)

1.280..................................................-92deg F (-69deg C)
1.265..................................................-71.3deg F (-57.4 deg C)
1.250..................................................-62deg F (-52.2deg C)
1.200..................................................-16deg F (-26.7deg C)
1.150..................................................+5deg F (-15deg C)
1.100..................................................+19deg F (-7.2deg C)

Prior to placing batteries into winter storage make certain the electrolyte level is approx 1/2 inch (13mm) above the top of 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.
A 3/4 charged battery is in no danger of freezing!

The self discharge for the average fully charged conventional battery in good condition is approx as follows:

At 100deg F (37.8deg C) the self discharge is 0.0025 Sp. Gr. per day
At 80deg F (26.7deg C) 0.001 Sp. Gr. per day
At 50deg F (10deg C) 0.0003 Sp. Gr. per day

A fully charged battery stored at 80deg F will take approx 30 days before it self discharges 25%. At 50deg F the time period increases to approx 100 days. This will give you an idea of how often a battery should be checked. These numbers will vary as some makes of batteries will have a higher and some lower rate of self discharge depending on the method of manufacture and purity of materials used.