Jeremy Watson wrote in about a common problem:
"I am fanatical about keeping my batteries charged and have always had the habit of charging them regularly. What I don't understand is why, although they appear fully charged, the level seems to fall away incredibly quickly and they don't appear to have been charged to capacity even though they seem to have received the full charge. My alternator is definitely working, so I don't know what the reason might be."
One imagines that, if Jeremy were using a fast charge regulator he would have mentioned it, so let's work on the basis that he is not. Many who charge directly from the alternator only, with no other charging facilities, find they get the same results. It is said that 70% of capacity is the most that can be hoped for when charging in this manner, regardless of the higher level shown by the battery immediately after charging. This figure is misleading as, even if you do not apply any load, the level will drop after a relatively short time - this was just surface charge showing up and if you apply a load immediately after charging you will see the level fall to 70%, or less, immediately.
When batteries are brand new, it is less noticeable that the full charge is non-existent, but as time goes by, the batteries are sulfating with each incomplete charge and their capacity is actually diminishing as time goes by.
It's a good idea to acquire a fast charge device of some sort, preferably a 'smart' one, to avoid 'cooking' the batteries. This improves things considerably, if the alternator is your choice of charging power, giving a fuller charge and saving the engine some wear and tear too!
A 'proper' charge, now and again, will help a lot. If you don't want to invest in a
'proper' battery charger or don't have any means of powering one, it is probably best to cart the batteries ashore and take them to a garage to be over-charged and allow the necessary full plate conversion to take place. This doesn't want doing too frequently but is a good idea from time to time.
This is another good reason for having 6v batteries - they are a lot lighter to lug around! One of our battery banks consists of four Trojan T105 - 6V, 250 AmpHour, flooded lead-acid deep cycle batteries, weighing 62lbs each and measuring 10.38"
x 7.12" x 11.2".
They give excellent service and, having four we can wire them to produce 12 volts or 24 volts depending on what would be most useful at the time.
Before you set off on the big summer cruise, don't forget to pay some attention to the batteries and the alternator, especially if they have been sitting around
for some while.
Give the alternator a going over - check connections and, if you think they look less than brilliant, by all means cut off the last inch or so, crimp on new connectors and re-connect. It's a job much more easily done before you leave than when you're at sea. Make sure you have an interference suppressor installed, too.
Make sure none of your batteries have died of boredom, waiting for their next outing. It's a good idea to test them while you're still in a position to replace them without having to hunt them down in unknown territory, paying whatever the supplier feels like charging a distressed yachtsman... Give all the terminals a good scrub, clean the battery casing, connect the batteries back up, nice and tightly and anoint the terminals and their connectors with a generous dollop of petroleum jelly.
Check the levels in each battery and top them up as necessary. Make sure the batteries are secured properly. Check the battery isolator switches by trying them several times, with the engine off, and making sure they still do their job.
Happy sailing!
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