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Old 31-05-2012, 10:48   #1
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Battery Charging While on Shore Power

When at the dock on shore power, is it best to keep a smart charger on the batteries full time or deep cycle them and charge one or two times a day? Which will help extend the life of the battery bank?

I have 8 Optima Spiral Gel Cell marine batteries in the bank. They are charged by the following means: an engine driven 60 amp alternator, Victron Skylla 80 amp fully automatic battery charger or a Mastervolt Charge Master fully automatic charger.
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Old 02-06-2012, 12:46   #2
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Re: Battery Charging While on Shore Power

Any help and advice appreciated
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Old 02-06-2012, 12:50   #3
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Re: Battery Charging While on Shore Power

Good question. I always kept my Heart invertor/charger on when on shore power..... didnt seem to hurt anything, but I was living aboard...
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Old 02-06-2012, 12:58   #4
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Re: Battery Charging While on Shore Power

I gave this answer on another forum, but I think it answers your question.

With a good battery charger that goes into float mode it is better for the batteries if they are left permantly connected.
Make sure the float voltage is appropriate for your batteries. If there is little load on the batteries slightly lowering the float voltage is beneficial.

Most marine battery chargers are sized so that will completely keep up with house loads. If this is the case it is probably helpful for most batteries to periodically, say once a month, to do a slight discharge and recharge cycle. This tends to stir up the electrolyte. Switch the battery charger off and allow the batteries to drop down to a SOC around 85%. Restart the battery charger and it should go into bulk mode before dropping down to float. Some battery manufacturers also recommend equalisation when used in this manner.

Check the start battery is getting some charge and not not slowly running down from self discharge.

Don't ignore the issue of galvanic corrosion when permantly connected to shore power and don't do the above if the voltage is not appropriate. Be particularly careful if you are using a car battery charger, these often have just a single charge voltage which is too high for perminant connection.
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Old 02-06-2012, 14:31   #5
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Re: Battery Charging While on Shore Power

Thank you. This was very helpful.



I gave this answer on another forum, but I think it answers your question.

With a good battery charger that goes into float mode it is better for the batteries if they are left permantly connected.
Make sure the float voltage is appropriate for your batteries. If there is little load on the batteries slightly lowering the float voltage is beneficial.

Most marine battery chargers are sized so that will completely keep up with house loads. If this is the case it is probably helpful for most batteries to periodically, say once a month, to do a slight discharge and recharge cycle. This tends to stir up the electrolyte. Switch the battery charger off and allow the batteries to drop down to a SOC around 85%. Restart the battery charger and it should go into bulk mode before dropping down to float. Some battery manufacturers also recommend equalisation when used in this manner.

Check the start battery is getting some charge and not not slowly running down from self discharge.

Don't ignore the issue of galvanic corrosion when permantly connected to shore power and don't do the above if the voltage is not appropriate. Be particularly careful if you are using a car battery charger, these often have just a single charge voltage which is too high for perminant connection.
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Old 02-06-2012, 15:48   #6
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Re: Battery Charging While on Shore Power

Not an expert here, but the OP stated that he had gel cells - I don't think occasional light discharge followed by short bulk charging is going to "stir up the electrolyte." Also, gels don't self-discharge nearly as much as flooded cells.
I would contact the battery manufacturer and ask their opinion on this one. Too much advice that has been good for many years, is no longer quite so applicable to the "new" battery technologies.
I am guessing that any good "smart" charger left connected for a trickle charge, will do no harm, but as I said, I am no expert.
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Old 02-06-2012, 19:20   #7
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Re: Battery Charging While on Shore Power

The issue is really "cycles." Don't discharge them and you reduce the cycles. Cycles determine aging.

Also, don't leave the boat plugged in when you're not there.
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Old 02-06-2012, 21:10   #8
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Re: Battery Charging While on Shore Power

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Originally Posted by Stu Jackson View Post
... Also, don't leave the boat plugged in when you're not there.
But if you're gone a long time you need to be aware of battery self-discharge, and any always-connected loads (bilge pump that occasionally cycles, battery monitor, FM radio "remember the pre-sets" connection, and other stuff like that). You don't want your battery to drain too low, since that's a great way to kill it.

I use solar panels to keep the batteries topped off without requiring any shore-power connections. Disconnecting the shore power definitely improved the lifespan of my zincs. If you're in fresh water the zinc erosion and electrolysis is less of an issue than it is for us salt water folks.

As long as you keep an eye on the electrolysis issues and electrical safety, with the appropriate always-on charger you should be able to keep your batteries in good shape. By disconnecting the shore power you do reduce the chance of corrosion and fire. With care, either choice can be reasonable.
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Old 02-06-2012, 21:26   #9
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Re: Battery Charging While on Shore Power

I lived from 1999 to 2005 with a battery bank of 10, and have heard so conflicting advice.
But one piece of advice I can offer is to change the order in which your batteries sit in the bank, so that they get roughly equal use. I have learnt the end battery becomes a 'slave' and overworked thus reducing it's life.
I used solar panels to keep the batteries topped.

Cheers Geoff
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Old 02-06-2012, 21:53   #10
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Re: Battery Charging While on Shore Power

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I lived from 1999 to 2005 with a battery bank of 10, and have heard so conflicting advice.
But one piece of advice I can offer is to change the order in which your batteries sit in the bank, so that they get roughly equal use. I have learnt the end battery becomes a 'slave' and overworked thus reducing it's life.
I used solar panels to keep the batteries topped.

Cheers Geoff
There will be less of this issue if you wire the bank so you connect the positive cable to one end of the paralleled bank, and the negative cable to the other end. This way all batteries see very close to the same cable resistance and the load is well-balanced. If you connect the positive and negative cables to the same battery, this is the one that will provide most of the current, and will get most of the charge.
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Old 02-06-2012, 21:56   #11
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Re: Battery Charging While on Shore Power

I have a good smart charger and leave it plugged in all year. I even did this before I went to a 12 volt refrigerator. I don't want my batteries to die when my bildge pump is doing what it was intended to do, save my boat when I am not there to do it for myself.
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Old 02-06-2012, 22:05   #12
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Re: Battery Charging While on Shore Power

Yes good advice Paul, it surprises me how many get that wrong !

Geoff
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Old 02-06-2012, 22:45   #13
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Re: Battery Charging While on Shore Power

With the prices of solar panels coming down drastically, it makes sense to buy a small 50-100 watt panel with a small MPPT regulator for the job.
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Old 02-06-2012, 23:37   #14
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Re: Battery Charging While on Shore Power

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With the prices of solar panels coming down drastically, it makes sense to buy a small 50-100 watt panel with a small MPPT regulator for the job.
I think MPPT regulators are a great idea (although I've killed two BlueSky units with a few tiny drops of salt water), but if you are just trying to keep up with self-discharge and other small loads you can save some money by using a simple regulator instead. The PV7D (below) is good enough for a 50W panel:

http://www.westmarine.com/webapp/wcs...classNum=50530

This won't squeeze the maximum power from your panel, and it won't rapidly charge your battery, but it will keep it fairly well topped off while your boat is waiting in the slip.

If you are actually considering a more powerful system then you should definitely look at MPPT controllers.
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Old 02-06-2012, 23:50   #15
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Re: Battery Charging While on Shore Power

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I think MPPT regulators are a great idea (although I've killed two BlueSky units with a few tiny drops of salt water),.

That's disturbing,..I just bought the Blue Sky 2512. After receiving it, I noticed they sent a cheesy house-hold electrical box. I used a sealed stainless steel one instead. I emailed them with a recommendation that if they advertise the unit to also be used for marine, they should provide a marine enclosure. I never received any word back...bad sign!
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