when thinking of the battery bank aboard a cruising yacht, I like to think of a bank account (seems a very convenient analogy)Â
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when your battery bank is FULLY CHARGED, you are comfortable & can use equipment at will ~ not unlike the great feeling of that full bank account
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as you make withdrawals from this bank, you need to start considering how you will make deposits back ~ that same uncomfortable feeling associated with a dropping bank account comes to mind (see how relative this analogy is?)
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* the alternator on the engine is one way to bring the batteries back up
* the shore power charger is another way
* some boats use solar & wind generators
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unlike my cel phone, which seems to still work when the gauge says 2%, the battery bank on the boat shouldn't go below 50%
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conversely, it is very hard to get right to 100%, especially when out at anchor or motoring
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every boat is a little different, but you might come up with a zone between 50 - 90% - meaning you make sure you start recharging as you approach 50% & you keep that charging going until you reach 90% (knowing below 50% will hurt most batteries and above 90% might just be too hard unless you are alongside with great shore power)
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BUT HOW DO YOU KNOW?
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some people talk about measuring voltage, but that's going to throw you bad information if you've just been charging or drawing (making deposits or withdrawals) - so we're working to add BATTERY MONITORS to our fleet - these 'battery fuel gauges' are the only sure fire way to know where in fact the bank isÂ
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don't ROB the BANK ~ related MYSTERIES & MISCONCEPTIONS
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~ some people over the years think that when you plug the boat in, DC appliances magically change over to AC appliances because the boat is plugged in ~Â this is not the case ~ but you may be making withdrawals & deposits at the same rate and holding your bank balance 'even'
~ be aware of multiple chargers when they exist and make sure you have engaged all charging devices you need
~ also be aware that a big invertor/charger may take everything the dock can throw at it - so not the best time to also have hot water tanks & other high load items pulling too
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we're 'generalists' in this arena, if you want more specifics & an ability to dive deeper into this, check out the informative website of PACIFIC YACHT SYSTEMS - presenting at our YACHT EXPO SEMINARS