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Battery Charging Routine Basics


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#121 lockgategirl

lockgategirl

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  • Location:continuous cruising
  • Boat Name:Mona Lisa

Posted 29 February 2012 - 07:50 PM

Short version:
How long will I have to run the engine to fully replenish a nearly depleted 600ah bank whilst also running the fridge, water pump and lights?

Long version
I'm not sure how long it should take to re-charge a almost completely depleted battery bank. I've read back through a bunch of alternator/charing/battery threads but they're all a bit over my head tbh.

My setup is barus shire 45 with domestic alternator (not sure of size right now - guess it's the 'default' one), starter altenator and travel power. I've got a 600ah battery bank (I think) that's about 2 years old but has only been used attached to shore power until I bought it a month ago. It's got a powermaster 1500 inverter charger that manages charging from the shore power (which I don't have)

It all seemed fine when I was cruising down from reading. Doing 8 hours a day left my batteries fully charged at 12.8 or so. Last week I left the boat and they were reading 12.2v according to the powermaster. I left the fridge on and a week later they were 11.8 but amazingly still powering the fridge.

So on saturday I moved it for three hours or so and left the engine idling for another two. Yesterday I moved it for another hour and left it idling for at least 6 (albeit with the travel power on and powering my stereo). I made it all the way back up to the heady heights of 12.2 again last night only to find it drained to 11.8 again before bed. All I'd been running was the 12v fridge, 12v lights and the laptop for an hour. Is this normal? Have I damaged my batteries by letting them get so low? Do I need to stick water in the top of them or something? Should my inverter measure the voltage as > 13 when the alternator is on (it's not) and the actual voltage when off?

How long should I expect to charge my bank given 12v fridge, 12v lights, pump and 1 hour laptop per day. I was guessing a couple hours a day max but I may be wrong here. How do I measure my usage?

Your fridge, if it is anything like ours, will decimate your batteries if you leave them without charging for days at a time. Also we have found that the lap top can take a lot of power if you are, for instance, playing on line games. In addition to all this I think that 12.2 volts is not a fully charged battery bank to begin with.
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