when thinking of the battery bank aboard a cruising yacht, I like to think of a bank account (seems a very convenient analogy) 

 

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

 

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?)

 

* 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

 

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%

 

conversely, it is very hard to get right to 100%, especially when out at anchor or motoring

 

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)

 

BUT HOW DO YOU KNOW?

 

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 is 

 

don't ROB the BANK ~ related MYSTERIES & MISCONCEPTIONS

 

~ 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 ~  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

 

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

when charging batteries, remember how we fill a jerry can and understanding is easy

we just returned from a series of YACHT EXPO SEMINARS and our good friend JEFF COTE with PACIFIC YACHT SYSTEMS shocked the groups with little known facts about batteries and marine electrical

one participant said it was hard to start asking questions because his brain was completely full and the quality and quantity of great information at the event was LIKE DRINKING FROM A FIREHOSE

to take a quick note from JEFF'S ELECTRICAL 101 session, think of topping up the batteries as you would filling a JERRY CAN



when filling one of these, you can initially open the nozzle right up and fill quickly - think of this as BULK CHARGING

as you get past 85%, one needs to slow down or it will spill everywhere - this is ABSORPTION CHARGING and trickier to do when you are out cruising, so some cruisers will bring the batteries up to around 85% and then start using them again

topping off a near full battery - replacing the gas that evaporates so to speak, is called FLOAT CHARGING and newer battery chargers are able to do this without damaging the batteries - what JEFF called not killing the batteries with "DEATH BY 1000 PAPER CUTS"

for more helpful tips - check back or check out the PACIFIC YACHT SYSTEMS BLOG