12 volt charging at marina

[ricksoth]

During the first bottom painting when we purchased our Cal in November 2020 we had the yard test the charger and flooded batteries (2 banks) and all items failed their testing. The yard asked what we wanted to replace it with, and not really knowing I selected AGM batteries for the sake of not needing to check water levels in a hard to get to location in the boat. The charger choice was left to the Yard.

We ended up with two "Dual Purpose Group 27 West Marine AGM 92 AH" and a Guest 20amp 2-bank charger, all installed by the Yard and it seems to work when switches are turned on. There are a Bank 1 / 2 volt meter test gauge in the panel and these show 13v.

When the boat is just sitting at the marina, should I leave the charger on in it's trickle charge mode, or should I turn it off after the batteries are showing 13v on the test gauges incorporated in the panel and move the BAT switch to OFF?

Other than turning on the lights when I'm on the boat (maybe weekly for an hour or so), should I do anything else to put a load on the 12v system? I could run the cold-plate icebox system (6 amps), which is the only high load item I have. I don't have an inboard motor, so there is no large starter load.

I have two Goldenrod Dehumidifiers plugged into the AC system on the boat 24/7. This is the only electrical that is in use.

Suggestions?

 

[justsomeguy]

Suggestions?

AGM Batteries - Making The Choice

My observations and experiences over the last 23+ years have led me to some thoughts on AGM's and how the purchasing decisions are made, could be made or things that should be considered other than glossy marketing ads... I see a lot of folks buy them based on misguided advice or just simply...

forums.sailboatowners.com

 

[dlochner]

AGM batteries should not be left at a partial state of charge for very long, so keeping the charger connected and preventing self discharge is probably advisable.

Was the charger hard wired into the AC circuits or is it plugged into a socket?

 

[Terry Cox]

Our boat has two AGM house bank batteries (500 amps) and a Freedom 25 charger/inverter. We've had these for going on ten years and they seem to remain strong. While in the slip, shore power is always on including both 12v reefers. That way the AGMs are kept at full charge. When away, I recharge the house bank every other day to a -20 amps, which is about 90% full. That takes the 8KW Genset an hour and half of run time.

As others have recommended, keeping shore power on to your AGMs would be wise as recommended by the maker. They do not fare well when left in a undercharged state. At least that is what I've learned over the years.

 

[chip veres]

If you are concerned with drying out the batteries by continuous charging (a valid concern), Harbor Fright has a $5 battery maintainer that could never overcharge your batteries in a lifetime. Use one or two of these with the main switch off. As Diochner said, discharge and sulfation seem to be the biggest problem.

 

[dlochner]

If you are concerned with drying out the batteries by continuous charging (a valid concern), Harbor Fright has a $5 battery maintainer that could never overcharge your batteries in a lifetime. Use one or two of these with the main switch off. As Diochner said, discharge and sulfation seem to be the biggest problem.

AGM batteries are sealed and do not need to be watered, drying out is not an issue.

The charger he has is designed for long term charging and maintenance. I would never connect any charging device from HF to any battery I owned, especially very expensive AGM batteries.

 

[Davidasailor26]

AGM batteries are sealed and do not need to be watered, drying out is not an issue.

AGM’s can still lose electrolyte through their vents and dry out (or at least Nigel Calder says they can). But that’s probably limited to more extreme over charging than just leaving batteries floating on a properly designed 3 stage charger.

The charger he has is designed for long term charging and maintenance. I would never connect any charging device from HF to any battery I owned, especially very expensive AGM batteries.

+1. I like a cheap HF tool for the right application as much as anyone, but they’re not the right tool for the job here.

We ended up with two "Dual Purpose Group 27 West Marine AGM 92 AH"

Dual purpose wouldn’t be my first choice. They’re probably not designed for deep discharges and repetitive cycling as much a real deep cycle battery, and the extra starting current is largely unnecessary for small engines. But they are what you have and if they’re doing the job you may as well live with them. When they age out replacing with deep cycle would probably be better.

Other than turning on the lights when I'm on the boat (maybe weekly for an hour or so), should I do anything else to put a load on the 12v system? I could run the cold-plate icebox system (6 amps), which is the only high load item I have. I don't have an inboard motor, so there is no large starter load.

I wouldn’t worry about going out of my way to put extra load on the system. It should work fine on a float voltage without any changes to load.

 

[dlochner]

I like a cheap HF tool for the right application as much as anyone, but they’re not the right tool for the job here.

Yep, for times when there is a high probability of the tool being sacrificed to Neptune.

 

[sail sfbay]

...............We ended up with two "Dual Purpose Group 27 West Marine AGM 92 AH" ..........When the boat is just sitting at the marina, should I leave the charger on in it's trickle charge mode, or should I turn it off after the batteries are showing 13v on the test gauges incorporated in the panel and move the BAT switch to OFF?...........

I have AGM house batteries and one flooded starter battery and keep the charger ON its trickle charge mode when the boat is tied up at the marina.

 

[ricksoth]

Thanks to all that shared their knowledge. I will leave the shore power charger energized and working.

Reading the comments brings up a new question. What to do this Spring when the boat is moved to a mooring buoy behind my house? Sounds like I will need to have some type of solar panel charging system for the 6-months the boat will not have AC readily available.

 

[Captain Larry-DH]

Thanks to all that shared their knowledge. I will leave the shore power charger energized and working.

Reading the comments brings up a new question. What to do this Spring when the boat is moved to a mooring buoy behind my house? Sounds like I will need to have some type of solar panel charging system for the 6-months the boat will not have AC readily available.

On the mooring you will need to leave everything powered off, unless you have adequate solar or wind power. If you don’t use refrigeration, a 20w panel (with charge controller to regulate charge) will keep your house bank topped off nicely.
If you want to leave the 6 amp refrigerator running you will need at least 400 or 500w of solar, and add to your battery capacity. That requires a lot of space.
For reference: At 40-degrees north latitude in CT, it requires at least 250 watts of solar to keep my 3amp refrigerator running without discharging the house bank. Of course it varies based on cloud cover. I currently have 320 watts of solar and enjoy a surplus of power on sunny days, reaching 100% charge by noon, but “adequate“ power on overcast days to recharge back to 100% by 5pm. The fridge compressor runs at about 50% duty cycle (more or less).

 

[dlochner]

Thanks to all that shared their knowledge. I will leave the shore power charger energized and working.

Reading the comments brings up a new question. What to do this Spring when the boat is moved to a mooring buoy behind my house? Sounds like I will need to have some type of solar panel charging system for the 6-months the boat will not have AC readily available.

Since you don't have an inboard with alternator, solar is the only way to go. You will need considerably more solar than 20 watts.

Start with determining how much energy you will use while sailing, from there you can begin to calculate the amount of energy you will to recharge your batteries each day. Because battery charging is inefficient, you will need to produce more energy than you use.

There are lots of factors to consider besides just the nominal output of the solar panel, including panel location, panel efficiency, and type of controller.

BTW, you mention not having a starter with a big drain. Starters use very little battery capacity, somewhere around 1 amp hour or less. What starters do use is a lot of electricity for a very short time, somewhere around 200 amps for 10 seconds or less.

 

[Captain Larry-DH]

@dlochner I agree 100% if he uses the boat daily or cruises, sleeping aboard, using lights etc. But if he keeps it on a mooring (with all loads off) and daysails on weekends, 20w is generally enough for the house bank to recharge between uses.

 

[ricksoth]

The cold-plate system will be off on the mooring. I can bring a cooler with me from the house for day sails.

The 20w size panel with basic charge controller seems like what I will want to wire into the system "somehow". This provides the 1.5amp trickle charge when the sun showing.

Do I need to use a relay or something to "disable" this source when the boat is back on the AC dock system if I end up permanently installing the panel someplace (deck or hatch or stern railing) ?

A friend brought along a roll-up "panel" for charging a cell phone. This might be something to go with and just mount it when back on the mooring but remove when sailing and when disconnected it solves the relay question when on AC.

Thanks again to all the comments.

 

[Captain Larry-DH]

The 20w size panel with basic charge controller seems like what I will want to wire into the system "somehow". This provides the 1.5amp trickle charge when the sun showing.

You won't get 1.5A. Real world is always less than rated unless you're at the equator on a clear day at noon.

Do I need to use a relay or something to "disable" this source when the boat is back on the AC dock system if I end up permanently installing the panel someplace (deck or hatch or stern railing) ?

No. If the solar charge controller senses a charging voltage (13v+) it will taper off and restrict its own output.

 

[dlochner]

If you are going to invest in solar, be sure to read this article first. It is one of the best I have read.

Advances in Onboard Solar - Professional BoatBuilder Magazine

Advances in onboard marine solar technology improved efficiency and lowered the cost. But they also introduced more complexity.

www.proboat.com

A 20 watt solar panel will be inadequate for your boat. A 20 watt panel will only provide 1.75 amps, which on average will provide less than 6 amp hours per day. The 2 very expansive AGM batteries on board have 184 ah capacity. A 20 watt panel will be charging at less than 1% of capacity. That may be enough to offset any self-discharge in a fully charged battery, but it will be totally inadequate to recharge a discharged battery.

Battery charging is inefficient, if the panels generate 6 ah per day, much less than that will actually end up in the battery. What you will be doing is murdering your batteries because once on the mooring the batteries will not be fully charged. AGM Batteries can not tolerate long periods at less than 100% SOC.

To keep your batteries healthy, you'll need to have a charging capacity of at least 10% of capacity (.1 C) and closer to .2C would be better. To reach this capacity the panels need to produce 20 to 40 amps per hour, 240 to 480 watt panels would be needed. Being in the PWN, where sun is an anomaly, bigger would be better. Panels with greater efficiency (see the Calder article) will let you get away with smaller panels, but not without a hefty price tag.

So, before wasting money on a small solar charger, better to do some research. Ocean Planet Energy, Coastal Climate Control, and Alt-E are retailers with good information. Also check out MarineHowTo.com and the Musings with MaineSail forum here on SBO.

 

[DArcy]

Going with .1C as your selection for solar in this case may be overkill. On my previous boat I had a 10W solar panel to keep one of my batteries topped up and I would get about 6 or 7 years out of them. They were FLA, not AGM, but if you read through MainSail's post linked in post #2 above FLA are susceptible to sulfation, not just AGM. That is a good read, well worth the time.
It really comes down to how you use the boat. If you are just day sailing without the fridge on then you are not going to bring the SOC down very far on the batteries and can get away with a small solar panel. If you are living aboard for weekends or longer then you will need 250 or more watts of wind and/or solar since your outboard won't have a big enough alternator.

 

[Benny17441]

That must be a power boat Marina. Dual purpose batteries are not the best option for a sailboat as small auxiliary engines and outboards are easily started by full deep cycle batteries which provide a longer life and capacity. When you ask if you should leave the charger on it depends on the length of time that you will be away from the boat. If it is one week, you can leave it off but if it is 2 months or more leave it on. The reason is batteries will self discharge over time and a less than fully charged battery will start sulfating which reduces their useful life. Batteries also need exercise so it would be good for at least once a month to run the refrigerator for a couple of hours and then recharge. The Golden Rule with batteries is to recharge to 100% immediately after use. There is some evidence that leaving a charger on maintenance function 24/7 is a little detrimental and that at least the charger should be disconnected after two weeks and the batteries exercised. Many of us prefer convenience over an strict regime of maintenance. I leave my charger on 24/7 and will mostly run my refrigerator continuously and have not noticed a significant adverse effect over my expectations of battery life. Last thing check if your bilge pump is hardwired to the batteries or through the switch. Depending on your needs to clear the bilge you may want it to be active 24/7. Warning, check the float switch if so equipped as many batteries have died as a result of these switches which are prone to failure. I personally have leak proofed my boat and switch the bilge pump off when away from the boat for more than a day.

 

[ricksoth]

Now I'm thoroughly confused.

I don't need to run the cold-plate system. I don't need to run anything. The boat will have a float switch added to the bilge pump before it moves to the mooring, but since the bilge water level has not changed more than 1" in 2 months I'm not very worried about sinking on the mooring.

There is no way for me to charge at anywhere near 0.1C ( 10% of 184ah or 18.4 amps) with any size solar panel that I would be willing to put on the boat. I have some limited charging from the Honda 9.9 but it's 6 amps at WOT.

If the batteries are 100% charged when I move to the mooring, is the 1-2 amp (25 or 50w) panel with the regulator enough to meet the trickle charge and keep them at 100%? Something like this image?

It seems like my uneducated assumptions that the AGM was a better choice, was a fool's decision. Sounds like some basic flooded (cheap) batteries might have been a better choice given how the boat and it's batteries will be used.

No one likes to waste money, but $600 is a a small amount really compared to the other costs of ownership. The AC charger will take care of them for 6 months of the year, and maybe a basic solar system will not "kill them to fast" during the other 6 months.

We have a blue-top AGM in a 20' Whaler that is going on 4 years old and we have taken pretty poor care of it based on what I have read here. At the marina it's had a AC trickle charger, but during the winter the battery was fully charged before storing it in my garage and then pulled out 6 months later - charged up and installed in the boat. Seems like it should be on the smart-charger all winter in the garage.

Is spending $200 more for a solar system worth doing or should we just treat the 2 banks badly like the Whaler and hope we get 4+ years of use out of them by only charging when the Honda is running for the summer ?

 

[Project_Mayhem]

Yep, for times when there is a high probability of the tool being sacrificed to Neptune.

Such as when a cheap charger frys your batteries?