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Old 11-18-2014, 02:32 PM   #1
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battery load / charge question

OK, I figure I am either going to come out sounding dumb because someone has covered it before, or start a long discussion with lots of technical points.. or both... BUT.. here goes...

We live aboard in the marina and are on shore power most of the time (we work on land). Our shore side 12v load is rather light... LED lights, electric heads, water pump, diesel heater fan, shower sump pump, etc. 6 Golf cart style batteries for the house.

So, is it "better" to leave the charger going all the time or should I shut it off and let the batteries do some "work" then charge them back up? Like every other day or so? I know the charger is *supposed* to maintain a proper charge, it claims to be a 4 stage charger.... but I check water levels the first of every month and about every 2-3 months I have to add to them..4-8 ounces per cell on average.. of course it does not help that the PO let the batteries go almost dry before selling the boat to me. Hygrometer (sp?) shows them to be in the *ok* range, but probably will need replacing within a year or so.

Separate charger for the starter battery.. wondering about doing the same for it.. previous battery died and that seems to be an old fashioned single stage charger. I am guessing it over charged in combination with PO letting it run dry too.

Just hoping to make my batteries last a while before having to dump all that money on new ones.
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Old 11-18-2014, 02:49 PM   #2
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Not sure how to answer your question but will tell you what I experienced. Similar situation with the 6 volt bats needing to be watered a lot and they did not seem to have the capacity they should anymore. Replaced the batteries and the watering went to very minimal and the capacity seemed to be what it should be. I never tried to shut the multi stage charger off to see if it would help with the weak batteries.
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Old 11-18-2014, 03:00 PM   #3
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If you have a 3 or 4 stage battery charger then generally you would leave the charger on all the time you have shore power connected. A modern charger will sense battery voltage and automatically go to a float charge and not over charge your batteries when the batteries are fully charged.

A good marine battery charger is pricey but they will maintain your batteries and not over charge them. Many marine chargers will charge 3 battery banks eliminating the need for a 2nd or 3rd charger.
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Old 11-18-2014, 07:14 PM   #4
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All batteries are good for a certain number of cycles. (and charts are available from most battery manufacturers that show this) How many cycles depends on many things, but one of the determining factors is the depth of discharge. Keeping the batteries topped up (limiting the depth of discharge) will help give the longest possible life. You should leave your battery charger on at all times and let it do it's thing.

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Old 11-18-2014, 07:27 PM   #5
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Out of interest - when manufacturers refer to cycles, how far are they discharging the battery(ies)? Eg - I take it while in the marina on shore power with batteries 'floating' on the charger, thats not cycling. But once out at anchor, if I use, say, only 10% of the a/h cpacity before recharging, is that a 'cycle'. OR do you need to use, over 50% of capacity (or a certain percentage) to count as a cycle?
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Old 11-18-2014, 07:45 PM   #6
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Each discharge/charge is a cycle. WhAt varies of course is the depth. I strongly suggest you check out one of the manufacturers charts on battery life vs charge discharge dep. it's very enlightening.

Here's one. Deep-Cycle AGM | Trojan Battery Company

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Old 11-18-2014, 08:23 PM   #7
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Quote:
Originally Posted by tmiller1116 View Post
OK, I figure I am either going to come out sounding dumb because someone has covered it before, or start a long discussion with lots of technical points.. or both... BUT.. here goes...

We live aboard in the marina and are on shore power most of the time (we work on land). Our shore side 12v load is rather light... LED lights, electric heads, water pump, diesel heater fan, shower sump pump, etc. 6 Golf cart style batteries for the house.

So, is it "better" to leave the charger going all the time or should I shut it off and let the batteries do some "work" then charge them back up? Like every other day or so? I know the charger is *supposed* to maintain a proper charge, it claims to be a 4 stage charger.... but I check water levels the first of every month and about every 2-3 months I have to add to them..4-8 ounces per cell on average.. of course it does not help that the PO let the batteries go almost dry before selling the boat to me. Hygrometer (sp?) shows them to be in the *ok* range, but probably will need replacing within a year or so.

Separate charger for the starter battery.. wondering about doing the same for it.. previous battery died and that seems to be an old fashioned single stage charger. I am guessing it over charged in combination with PO letting it run dry too.

Just hoping to make my batteries last a while before having to dump all that money on new ones.
Sounds like a lot of water to me, which makes me suspect you can tune down the float voltage of the charger. As noted by others, batteries are good for a given number of cycles. The shallower the discharge the more cycles. I doubt that keeping a battery at float voltage by the provision of voltage just above the fully charged voltage would diminish the battery materially.
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Old 11-18-2014, 08:47 PM   #8
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I agree with the others who vote for leaving the smart charger on to do its thing. It's capable of maintaining the battery bank within specs if it's truly a smart charger. If it's a 4 stage charger, the equalization stage will keep them even healthier bu minimizing sulfation.

For the start battery, but a smart charger or a combiner/ACR to provide a smart charge to that battery.

Check our Water Miser caps to minimize water loss.
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Old 11-18-2014, 09:39 PM   #9
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Thanks Ken.
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Old 11-19-2014, 12:45 PM   #10
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Try reducing the float voltage very slightly...by say 0.2-0.4v. That may reduce water consumption without hurting the batteries, Does your current charger sense battery temperature and adjust its charge voltage accordingly?
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Old 11-19-2014, 01:28 PM   #11
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Try reducing the float voltage very slightly...by say 0.2-0.4v. That may reduce water consumption without hurting the batteries, Does your current charger sense battery temperature and adjust its charge voltage accordingly?

guess it is time for me to go look up the manual on it again Before all I researched was if it was 4 stage or not... now I need to look closer.

Thanks! If reducing float charge a tiny bit helps keep them from boiling as much, they might last longer than I hoped.
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