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Old 12-09-2008, 11:29 PM   #1
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Shore Power Charging - turn it OFF?

Greetings list.

I posted this on T&T as well.* what do you all think?


The question I have has to do with leaving your shore charger on 24/7 when tied up at the dock.* In theory, the charger is supposed to completely turn itself off when the final charge cycle is completed.

The reality is some(perhaps most)*chargers do not actually shut off, but stay in a 'float' mode, causing possible gassing to occur.*

Also, if continually plugged in, the charger will kick into the regular bulk, absorption, float cycle even if the bank is ever so slightly discharged for lights, bilge pumps etc.

This becomes a problem since you are initiating a charge cycle when the bank is at 99% capacity.* I certainly am no battery expert, but I think everyone agrees that there is a finite number of cycles a battery will provide before death, so one would think limiting the number of cycles would be prudent.

There are charts for batteries that discuss the theoretical number of charge/discharge cycles and the percentage of discharge for the expected number of these same cycles - the idea being to select the optimum number vs. % of drawdown - also factoring in the actual total amount of power for the life cycle of the battery.* This hopefully gives you a 'plan' for how much to deplete the battery before a prudent charge cycle should be initiated.

My practice has been to just leave the shore charger on 24/7 when the boat is in the slip.* If I visit the boat dockside, any loads of lights, pumps. TV etc are picked up by the charger/battery bank.* Watching the Link 10 battery monitor tells me how many amps I may use (which are few) and the shore charger puts back the difference, then returns to 'float' mode.

So, back to the original query.* Is this foolish battery management?*

Some say it is better to shut off the battery charger after a complete recharge, then*let the battery bank deplete to the % that has been selected before beginning a new recharge cycle. The batteries should last longer this way.

Those that like things to be more ''automatic'' can even put a timer on the batt charger circuit to shut it off after a set period of time.

I am pretty sure I have not seen this topic on this forum discussed in the last few years.

Brian Shanafelt
Isobel K 37' Custom Pilothouse

Seattle
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Old 12-10-2008, 04:18 AM   #2
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RE: Shore Power Charging - turn it OFF?

I can give you my experience, I bought Sea Eagle in June 2002 and moved aboard in Dec 2002. I replaced 4 of the 5 8D batteries aboard in the first 3 months. At that time the batteries were charged with a Xantrax 2500 using a Heart 2000 interface. After about 3 years I had an AC power surge at the dock that took out the Xantrax and replaced it with a 3000 watt xantrax inverter/charger. In February of this year I replaced all 5 batteries. None had a problem that I know of. I was planing on full time cruising and did not want to start with batteries that were over 5 year old. In all that time all I did was top off the water every other month and equalized the batteries every 6 months.

Living aboard and now full time cruising gives the batteries a lot of use. Most of my lighting both heads, Lectra scan systems, Nav equipment, radios etc are all 12V. When the engines are running the inverter is running the Refer and Ice Maker. I changed my maintenance schedule to monthly now that I'm cruising.

During all this time my charger has run 24/7 with maybe an hours maintenace a month on the batteries. I also equalize the batteries about every 6 months.
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Old 12-10-2008, 04:51 AM   #3
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Shore Power Charging - turn it OFF?

"but stay in a 'float' mode, causing possible gassing to occur. "

A really fine unit will do just this , and held at 13.0 to 13.2 very little gassing (water loss) will occur.

One problem tho is a short load , say a pump cycling ,which will be seen as a load , resuming charging at 13.8 to 14.4 for a while till float returns.

Another hassle is one batt in the bank dragging down the voltage , resulting in ALL being charged in an attempt to hold up the dead cell.

The RV folks have auto watering setups BUT there mot freeze proof.

The Alt energy folks use Hydro Caps for their very frequent hard charges , and they work fine .

IF you can find a charger that is Voltage adjustable you have the best chance at unattended operation.

Trace BIG BUCK inverters seem the "best" at the task.

RV folks that live aboard solve the problem with a "converter" .

This is similar to a charger BUT only holds the house bank at 12.8 , full charged , with* almost no gassing.
IT will only "charge" a dead batt very wealky as the voltage is Float , not Charge (An extra Volt or more)

They have chargers TOO, but chose to only use it if an actual charge is needed. Most are simple portable Sears 10a , that can charge the car ..

FF


-- Edited by FF at 05:56, 2008-12-10
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Old 12-10-2008, 06:17 AM   #4
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RE: Shore Power Charging - turn it OFF?

On the other side of things......

I had a charger that was faulty. It would never reach the float stage and overcharge the batteries if left on. SO obviously this was not healthy. I had to guess when the batteries were topped off. My guesses were never good and 2 brand new 8D's lasted about 18 months....not because of overcharging but because of undercharging. I got new batteries and a new charger and they were going strong at 4 years when I sold the boat. Nothing hurts wet cell batteries more than leaving them off of a charger in a less than fully charged state. If your batteries are gassing when leaving them on a healthy charger, you do not have healthy batteries and they should be changed. Leave the charger on. Even if your fears are real(which they most likely are not), the batteries will still last longer than if you left them in an uncharged state. I will repeat, wet cell batteries HATE to be left off of a charger in a less-than-fully-charged state. Even if they are fully charged when you leave, that charge will fall off over time.
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Old 12-11-2008, 03:44 AM   #5
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RE: Shore Power Charging - turn it OFF?

"Even if they are fully charged when you leave, that charge will fall off over time."{

A good batt in the cold will loose 1/2% a day , at room temp it will loose about 1%a day.

Old batterys that have been discharged too far , or not recharged often enough will loose 3 or 4% a day.

The best season long charger is a solar panel and smart (Trace C 12 is fine) that WILL float the batts at 100% every time the sun shines.

We left our boat with 2 8d start/house batts for 6 months in FL summer.

A slight overfilling of the cells in April , and Nov 15 they were charged AND the water level was still over the plate tops.

Bare the plates and its time for a haul to the battery guy.
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Old 12-11-2008, 08:13 AM   #6
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RE: Shore Power Charging - turn it OFF?

Let me provide a bit of context to my query.

I am considering the benefits of AGM batteries over Flooded lead acid.

When considering an AGM bank, any gassing is a disaster as there is no way to replace lost electrolyte.

In the case of a flooded battery bank, I certainly see the need to keep a very close eye on it as the self discharge issue is significant, but since AGM's will sit for a very long time without self discharging much, then the risk/reward of leaving the shore charger on becomes questionable.

Here in the PNW, we potentially have a 12-month cruising season, but reallistically use the boat the majority of the time from April-September. During the off-season, we may cruise a few times for short duration, but do stay on the boat a couple of times a month.

One site suggests that you fully charge your house bank then disconnect it (for the off-season) and substitute a small, cheap $30 start battery to handle any loads that are produced when visiting the boat - pumps, lights, tv etc, and leave the shore charger running 24/7.

In the above scenario, the cheap battery is sacrificial in that you probably are going to ruin it early by the short cycling, but you will be preserving your more expensive house bank. Also, since this sacrificial battery is a flooded start battery, it will tolerate this type of cycling much better - and you can always add water.

thx
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Old 12-12-2008, 04:01 AM   #7
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RE: Shore Power Charging - turn it OFF?

Since the boat is occasionally visited turning on the charger while your there and OFF when you leave should be fine.

I would install a second bilge switch above the automatic , and have it trip a relay and ring a loud bell.While the charger is off , just in case.

AGM only pay for their pri$e IF you have the need for and ability to really rapidly recharge them , and are willing to PAY! for the silence.

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Old 12-12-2008, 11:30 AM   #8
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RE: Shore Power Charging - turn it OFF?

Quote:
oldfishboat wrote:


Get a good 120 V charger, keep an eye on the bats. Have some fun boating IMO





Couldn't agree more!!!*
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Old 12-12-2008, 04:18 PM   #9
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RE: Shore Power Charging - turn it OFF?

Quote:
Baker wrote:

*
oldfishboat wrote:


Get a good 120 V charger, keep an eye on the bats. Have some fun boating IMO

*

Amen!



Couldn't agree more!!!*


*



*
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Old 12-12-2008, 05:36 PM   #10
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RE: Shore Power Charging - turn it OFF?

I have 3 batteries .. all AGMs, but the start batt is an Optimax high current starting batt and the Lifeline house batts are deep cycle. I have the kind of charger your'e talking about but havn't used it to continually " float " the batteries. Sometimes I charge the batts with the engine running for about an hour but more often I charge the batts with the charger when they get down to about 12.5 volts. This way all 3 batts are sucking up the electrons at about the same rate ( high rate ). I don't think I should should charge batteries with different chacteristics from the same source. When my Lifelines go south I'm going to replace them with Trojan 6v golf cart batts and then I'll have even more different batts .. lead acid and AGM. I don't seem to need the bennifits of AGM. I go doiwn and fuss and play and mess around with my boat every 2 or 3 days so I can stay on top of it.

Eric Henning
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Old 12-13-2008, 03:41 AM   #11
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RE: Shore Power Charging - turn it OFF?

As I said earlier, I charge my batteries all the time. But I am using a temperature compensated charger. I just serviced my batteries yesterday and water was fine. The tops of all the batteries are clean and dry.

I think the temp compensation is a large reason that my batteries last 5 years or more.
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Old 12-13-2008, 04:06 AM   #12
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RE: Shore Power Charging - turn it OFF?

I think the temp compensation is a large reason that my batteries last 5 years or more.


More likely that you havent smashed them down by 80% to a 20% SOC too often..

Kept them watered , and recharged as soon as realistic after discharge.

You probably dont own the ability to fast charge then (C50%+) , which does harm.
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Old 12-13-2008, 11:09 AM   #13
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RE: Shore Power Charging - turn it OFF?

Concerning shore charging speed.

What would the downside be - if any - to recharging a large house bank - say 1200AH, with a rather puny 3 stage shorecharger - say 30A?

Assuming voltages are set to battery mfg. recommendations, would this very small current (by ratio) recharge cause any harm?

thx
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Old 12-13-2008, 04:00 PM   #14
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RE: Shore Power Charging - turn it OFF?

FF my charger is 140 amp. And you are correct I do not run the batteries to more than 50% discharge.
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Old 12-14-2008, 03:07 AM   #15
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Shore Power Charging - turn it OFF?

We have left our Freedom 25 inverter/charger on 24/7 when the boat is in its home slip ever since we had the unit installed eight or nine years ago. It is charging 2 8D and 1 4D battery. We have had no problems doing this and the batteries have lasted far longer than I thought they would have.

Periodically equalizing the batteries helps a lot to extend their life.

There is never any "water" on top of the batteries with the charger on 24/7.

When our Freedom 25 was installed, the shop hooked up the automatic temperature sensor. In the summer, or when the engine room is warm after a run, the float voltage is 13.5 volts unless it's a very warm day in which case the float voltage will be 13 volts. In the winter when the engine room temperature may be down in the 40s or lower, the float temperature will be as much as 14.5 volts. This is consistent with the voltage/temperature chart in the Freedom 25 manual. If a Freedom 25 installation does not include the optional temperature sensor, the float charge will be 13.5 volts regardless of the ambient temperature.

(I should add that what we are experiencing is with a Heart Freedom 25 from the late 1990s.* I have no idea if the current*equivelent Xantrex unit exhibits the same characteristics.)

(currently in Xiamen, China)

-- Edited by Marin at 04:11, 2008-12-14
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Old 12-14-2008, 03:58 AM   #16
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Shore Power Charging - turn it OFF?

Bshanafelt,

My original inverter charger was a Freedom 25(2500 watt inverter and 120 amp charger) When it died I replaced it with a Xantrex 30 (3000 watt inverter and 140 amp charger). I have a smaller TruCharge 40 amp charger. I tried to use it to charge my five 8D batteries while waiting for the replacement, what I found was that it could not get the voltage over about 13.0 volts when hooked to all 5 batteries. I think the charger has to be sized to the bank to work properly.

-- Edited by Jim Spence at 05:01, 2008-12-14
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Old 12-15-2008, 03:54 AM   #17
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RE: Shore Power Charging - turn it OFF?

I tried to use it to charge my five 8D batteries while waiting for the replacement, what I found was that it could not get the voltage over about 13.0 volts when hooked to all 5 batteries. I think the charger has to be sized to the bank to work properly.

This would be a fine voltage for long term storage .

AS long as no batt in the string dies.

To actually charge a batt the voltage needs to be at least 1 volt over fully charged (12.8)
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Old 12-16-2008, 12:53 PM   #18
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RE: Shore Power Charging - turn it OFF?

I'm not sure if this will help but here are few articles on the topic.

http://www.passagemaker.com/Magazine...4/Default.aspx

http://www.passagemaker.com/Magazine...6/Default.aspx

http://www.passagemaker.com/Magazine...5/Default.aspx

Sincerely,
Dionysios
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Old 04-13-2009, 09:28 AM   #19
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RE: Shore Power Charging - turn it OFF?

Back to batteries again. I want to add a 3rd batt to my setup. My charger (Newmar) is only set up to handle 2 banks. Can I hook 2 batts in parallel, , plus one by itself, thus still charging 2 banks? Or will there be problems with this idea? I also hooked up a timer from shore power that comes on for an hour at 8 hour intervals.
Thanks.
Mike
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Old 04-13-2009, 03:40 PM   #20
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RE: Shore Power Charging - turn it OFF?

Mike, There should be no problem charging the batteries the way you want with the third battery. What is the third battery for? Is this just an addition to your house bank? Why use the timer? With the Newmar charger there should be no need to shut it down and you may not be fully charging your batteries and will cut their usable life considerably. Chuck
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