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12 volt charging at marina

Dec 1, 2020
42
CAL Boats 2-27 Puget Sound (Kitsap)
Based on all the input, I'm thinking this is the type type of battery I should have asked the "yard" to install in my boat. Two of these WEST MARINE Deep Cycle Flooded Marine Battery, 90 Amp Hours, Group 27 | West Marine

After reading their "return policy" I sent an email to see if there is any chance they would facilitate some type of return and purchase of this type of thing. In the unlikely event they offer to make the exchange, is this the battery I should suggest to them?

Then my 50w solar setup would be okay for recharging on the mooring.

Thoughts?
 
Jan 11, 2014
6,826
Sabre 362 113 Fair Haven, NY
This end of the marina is like the wild west. They don't seem to care what you do but dont don't expect them to actually fix anything. They're floating docks that require a dinghy to get to
Hope it is an economical marina.
 
Jan 11, 2014
6,826
Sabre 362 113 Fair Haven, NY
Based on all the input, I'm thinking this is the type type of battery I should have asked the "yard" to install in my boat. Two of these WEST MARINE Deep Cycle Flooded Marine Battery, 90 Amp Hours, Group 27 | West Marine

After reading their "return policy" I sent an email to see if there is any chance they would facilitate some type of return and purchase of this type of thing. In the unlikely event they offer to make the exchange, is this the battery I should suggest to them?

Then my 50w solar setup would be okay for recharging on the mooring.

Thoughts?
My first thought is there are more economical places to buy batteries than West Marine. That was actually the first thought I had when I read the first post. However, that horse is out of the barn.

Sometimes threads like this have 2 branches, the doom and gloom branch and a no shirts, no shoes, no problems branch. Sometimes reason needs to weigh in.

You have batteries which need a specific charging profile to ensure longevity. Longevity in the battery world being somewhere around 7 or 8 years. For the six months you are in a marina and connected to shore power this is not an issue. It is the six months on a mooring that is an issue.

AGM batteries do not tolerate being left in a PSOC for very long. But I don't think this is a dichotomous state, i.e., an all or nothing state. A battery left at 95% SOC won't last as long as one left at 100% SOC but it will last longer than one left at 80% SOC. The solution is to keep the batteries as charged as possible as much as possible.

In a marina with shore power, this can be accomplished by keeping the charger on whenever the boat is at the dock. Simple. On the mooring it gets a little more challenging. There are 2 avenues, try to charge as much as possible, which means a generator or lots of solar or reduce the amount of power being used. Somewhere in this mix is a sweet spot for you, energy use, charging capacity, and battery life. At one extreme, you could use lots of energy, have very little charging, and a short battery life at the other extreme you could have little or no energy use, lots of charging capacity and a long battery life. Somewhere between those extremes is where you want to end up.

In your situation, it is probably best to avoid using refrigeration unless you are on shore power, change all your lights to good quality LEDs (cheap eBay and Amazon LEDs sometimes cause more problems than they solve.), reduce power consumption in other ways, like use a self-contained blue tooth speaker instead of the stereo, make sure all your devices are charged, turn off electronics as soon as you are done, and visit a marina a couple times a summer and fully charge the battery.

I can't tell you how much time you can buy doing these things, however, if you are not an energy miser, the batteries life will be shortened.

Key to understanding what to do is having good data about battery usage. A good digital ammeter will keep you apprised of energy consumption in real time. A Balmar Smart Gauge will let you know the current SOC which will tell you how well your charging system is keeping up with consumption.

Don't despair, all is not lost. Chalk this up to a great learning experience and get out sailing.
 

DArcy

.
Feb 11, 2017
978
Islander Freeport 36 Ottawa
@ricksoth before you get to worried about switching out your batteries consider using what you have. It may not have been the best selection for your use but you are probably better off just sticking with the AGMs and making the most of it. A 50W solar panel will likely be enough to get a good 5 to 7 years out of your AGMs for simple use. AGMs do like a higher charge rate than flooded cells but consider your use. With just VHF, stereo and depth sounder, for a 6 hour sail, you are using about 20 amp-hours. That is around 10% of your total batter capacity (2x 92A-Hr). At that state of discharge a smart charger will be in absorption stage which means you aren't going to be getting any advantage out of a 400 W solar panel or generator.

Let's say you run the fridge for those 6 hours. At a 50% duty cycle that brings your total usage up to around 37 A-Hr which is 20% of your capacity. That is where the smart charger should be switching from bulk to absorption so again you won't be getting anything out of a much more complex setup. If you are day sailing, stick with a small solar panel. If you want to spend a few days at a time on the boat, go for a few hundred Watts of solar.

When it is time to replace your battery, go with deep cycle flooded batteries but read the Marine How To's article on deep cycle batteries first (Main Sail's web site)
 
  • Helpful
Likes: Ward H
Oct 22, 2014
14,238
CAL 35 Cruiser moored EVERETT WA
@DArcy Your numbers are looking at total batter capacity (2x 92A-Hr). It appears you are not considering Depth of Discharge (DoD) of the battery.

The data says to get the longest lifetime out of flood batteries you need to follow the charging parameters for the battery and only discharge the battery to 50% of the battery capacity before returning the battery to full state. With AGM's the same 50% applies. That means the usable capacity of a battery is 50% of the total battery capacity. So the
your total usage up to around 37 A-Hr which is 20% of your capacity
Is really 40% of the total battery capacity.

A consideration, what if I ignore the 50% DoD suggestion and go to say 80%. :yikes:

Testing on flood acid batteries shows that your batteries will die sooner. How much is dependent on the individual battery make up. True Deep Cycle thick plate designs fair better than the car batteries sold as "dual Purpose. Interestingly AGM batteries tend to fair better.

Here is an interesting article that suggest discharging to 80% robs the battery of 6% of it's useful life. Further the author thinks in the grand scheme of things 6% is not much to give up to get more active usage. I think that is an individual call for each owner.
 

DArcy

.
Feb 11, 2017
978
Islander Freeport 36 Ottawa
I must not be good with new math.
2x92 = 184 A-Hr total capacity
37/184 = .201, or 20%

I think your are doubling down on the 50% and only considering 50% of the total then only using 50% of that.
 
Jan 11, 2014
6,826
Sabre 362 113 Fair Haven, NY
Oh, let. me jump in and add to the confusion. Welcome to Batteries and Charging 201.

Keeping the batteries at above 50% yields 92 ah of useable capacity. However, at least in with flooded batteries, when charging back to 100% SOC, the last 20% takes a long time, meaning hours to reach 100%. When cruising or not tied to shore power, this means that there is really only 30% of capacity available, or 184 * .3 = 55 ah available to use.

So, in real life, there is only 55 ah available using 37 ah of that capacity means 67% of the actual available capacity is used. Unless of course the battery is returned to 100% SOC, then the 37 ah is 20% of total capacity or 40% of capacity with a 50% SOC bottom limit.

We'll just skip the issue of declining capacity due to age.
 

DArcy

.
Feb 11, 2017
978
Islander Freeport 36 Ottawa
37 is 20% of 184. 92 is 50% of 184.
So using 37 A-Hr brings you to 80% depth of discharge. This is where the charger switches from bulk to absorption. The point I was making is adding charge capacity won't buy you anything.
 
Jan 11, 2014
6,826
Sabre 362 113 Fair Haven, NY
37 is 20% of 184. 92 is 50% of 184.
So using 37 A-Hr brings you to 80% depth of discharge. This is where the charger switches from bulk to absorption. The point I was making is adding charge capacity won't buy you anything.
My understanding of the constant voltage phase (absorption) is the voltage is held constant and the current gradually declines as the SOC increases until only a very small amount of current can be accepted, about .5% of the ah capacity. The time spent in the constant voltage phase is set by a timer or in a smart charger, the current acceptance reaches a specified level. At least that how my charger works (ProMariner Pro Nautic).

Assuming a 50 watt (4 amp) charging source it would take 9 hours at 100 % efficiency to return those 37 amps back to the battery. However, solar being what it is, it is seldom 100% efficient and charge efficiency declines as SOC increases, time to charge back to 100% also increases.

The solar controller will initially put out as much of the energy it is generating until the voltage level reaches the absorption phase. That phase begins when the voltage is the designated level and then the current will decline as the battery resistance increases. Thus, a larger panel will be putting out more current when it shifts from bulk to absorption than a smaller panel. The key factor is the time it takes to reach the absorption voltage, a larger panel will reach it faster than a smaller panel. With an AC charger, time is not as much of an issue because power is available 24/7. However, there are only 3-4 peak production hours with solar, the faster the controller gets to the Absorbtion phase, the better because charging efficiency declines as SOC increases.

In the article below, there are several examples of this decline. Here's one

TimeCurrentDifference
2 hours11 amps
3 hours4.2 amps6.8 amps
4 hours1.6 amps2.6 amps

The output dropped 10 amps in just 2 hours. Apply that ~90% drop in acceptance to a 50 watt panel and the panel output is now ~.4 amp. In a time limited charging regimen, the higher the initial charge current the faster the battery will charge.

And yes, there is a point of diminishing returns. In the article below, RC demonstrates that the overall time to bring an AGM battery to 100% SOC from 50% is not much different between a .2C charger and a .4 charger. When there is unlimited time, this is not much of an issue, with limited charging time, the quicker the charge source reaches the Absorption phase the better and higher currents from larger panels allow that to happen.


and


A quick note to @ricksoth, Thanks for posting your question. This whole conversation has gone way beyond your initial question, however, it has been helpful to me at least to think more about charging batteries and using solar as a charging source. I'm in the market for new batteries this has been helpful.
 

DArcy

.
Feb 11, 2017
978
Islander Freeport 36 Ottawa
Yes, that's why I was saying in my earlier posts if you aren't using the fridge, using only 20 A-Hr with a few days to recharge, don't over complicate the situation. A 50 Watt panel will keep the batteries charged and you will have many trouble free years out of the batteries.
Running the fridge puts you into a zone where it may have a negative impact on your batteries.
I have 230 A-Hr in my GC2 bank with 250 Watts of solar. My fridge draws about 3 A and the solar keeps up no problem when I'm off the boat. I do plug in the charger when at the dock from time to time, if I think there will be a few cloudy days. I selected wet cells to keep it simple and because I mostly use solar so AGM really are no advantage to me and cost almost twice as much with less capacity. If I had a generator with a large output charger and wanted to charge quickly I can see the advantage but for the majority of us, AGM are not worth the extra cost.
 
Oct 22, 2014
14,238
CAL 35 Cruiser moored EVERETT WA
I must not be good with new math.
2x92 = 184 A-Hr total capacity
37/184 = .201, or 20%
I think you are great with the "new math". And the old math.

Your numbers are correct an I agree. 37 is 20% of 184.

What I stated agrees that 2 batteries with 92 declared amp hours is a total of 184 total amp hours.

When discussing "best" Depth of Discharge (DoD) to maximize useful life of batteries, the generally accepted models recommend a DoD of 50% of battery Amp Hours to give you the useable supply of the batteries..

That would be drawing the each battery down 50% from 92 to 46 amp hours usable DoD.

Using 37 amp hours out of the 46 amp hours of a single battery would be 74% of the useable supply in one battery. But we have 2 batteries available. Two batteries would have 92 amp hours useable supply. The 37 amp hours removed from the 92 amp hours would be 92/37 = 0.402 or 40% of the useable supply. When calculating the replenishment we would need to supply 37 amp hours out of charging systems. @dlochner calculates it would take 9 plus hours to restore the 37 amp hours by the solar 50watt charging system. What is still not considered is the efficiency of the charging system to provide the 4 amps when the conditions are not providing full solar power, such as shading of the panel.
 

DArcy

.
Feb 11, 2017
978
Islander Freeport 36 Ottawa
John, It sounded like you were saying that using 37 amp hours would bring the 2 batteries down 40% depth of discharge which. Using 37 amp hours of a 184 amp hour battery bank brings the bank to 80% of its total capacity. Sure it uses 40% of the theoretical useable charge but that's not what a battery charger will see, it sees (in theory) 80% charge.
I probably should not have confused matters by including the use of the fridge. Without the fridge (as the OP said he sails without usually) would only bring the battery down to 90% total capacity. Adding the complexity of a generator will not gain you anything over a 50 W solar panel in this case since your charger is going to be in absorption stage (unless you plan on running it for 12 hours straight). The 50 W solar panel will recover the battery in a few days even at 4 hours per day and 50% efficiency.
Heck, I used a 10 W panel and got 7 years out of a cheap flooded battery (yes, with fairly good capacity near the end of the 7 years) on my last boat. I know we are talking about an AGM but think about the trade off between the cost of either 300 W of solar or a generator and all the complexity of getting it all up and running on a small boat vs. the cost of killing the batteries in a few years then replacing with flooded cells.
You really need to look at the overall value and level of complexity. For day sailing, the small solar panel is absolutely the way to go. Full time cruising would need more charging capacity or a simpler boat.
 
  • Like
Likes: jssailem
Jan 11, 2014
6,826
Sabre 362 113 Fair Haven, NY
@jssailem and @DArcy The issue with small low power charging sources and AGM batteries is the amount of time the batteries remain at less than 100% SOC. The big advantage of AGM batteries is their ability to accept high initial charge rate which a 50 watt panel will not be able to accomplish. This slow charge will shorten the usable life of the battery. With the boat spending half its life at a dock on a charger will mitigate the damage caused by low charge currents while on the mooring, but not eliminate them.

If the OP keeps the batteries and puts a 50 watt panel with a good Victron or Genusun MMPT controller on the charger he will extend the life of the batteries if he limits their use. Will he get 6 or 7 years out of them? Probably not. Will he get more than a year or two? Probably.

Sometimes the tuition for learning is steep. He might have been better off with FLA batteries, however, if checking them and watering them is really a PITA, then he may be no worse off with the AGMs.
 
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Likes: jssailem
Oct 22, 2014
14,238
CAL 35 Cruiser moored EVERETT WA
Sometimes the tuition for learning is steep. He might have been better off with FLA batteries, however, if checking them and watering them is really a PITA, then he may be no worse off with the AGMs.
I agree.

I know it was hidden at the end of the message just above the article: “Further the author thinks in the grand scheme of things 6% is not much to give up to get more active usage. I think that is an individual call for each owner.”

Having a solar source to keep the batteries receiving a charge is likely the best option. AGM batteries in the boat based on the information provided by Rick May turn out to be the best option. Time will tell. Hope Rick will check back in with updates.

As always it’s your boat and your choice.
 
Feb 6, 1998
11,332
Canadian Sailcraft 36T Casco Bay, ME
#1 If you're on a mooring, and want batteries to last, solar is a must. 50W is pretty much a bare minimum unless you're just "maintaining" a already high SoC.

#2 Not all AGM batteries are created equal and the East Penn AGM (West Marine, NAPA, Sam's Club (Duracell), Batteries Plus, etc.,etc. are all quite poor performers at dealing with sulfation and partial state of charge use (PSoC).

#3 The cycle life to DoD article linked to above is posted by someone who clearly does not understand that these cycle-life charts are mathematically derived, not arrived at through testing, and is why the throughput numbers line up. In the real world taking an AGM (other than a Firefly) to 80% DoD spells murder by owner and why nearly every manufacturer advises 50% DoD as the maximum depth of discharge. Also understand that the data on cycle life is created in a lab and DOES NOT translate to real world use. The batteries in the Practical Sailor PSoC test were taken to 80% DoD and the East Penn AGM battery (West Marine stickers this exact battery) was beyond the BCI defined "end of life" in less than 30 PSoC cycles.

#4 Please take the time to read the May 2015 and August 2015 issues of Practical Sailor if you really want to see why I say "All AGM batteries are not created equally." Here at Compass Marine Inc., (marine electrical) we will not use any East Penn made AGM battery for house use but they do make a great, affordable (unless you buy them from West Marine), start/reserve bank.

Practical Sailor May 2015

Practical Sailor August 2015

P.S. West Marine 105Ah AGM $339.99. The same exact 105Ah battery, with a Duracell sticker at Sam's Club, is $179.74. That's a $160.25 premium for a sticker......

 
Dec 1, 2020
42
CAL Boats 2-27 Puget Sound (Kitsap)
Hello all --

I have collected some more information noted below.
  • I have "wiggled" into the space where the batteries are stored to access some wiring and it was a challenge.
    • Accessing this space to check Flooded battery water levels would not be fun
    • How often do I need to do this checking?
  • I found some info on batteries and solar at (www.chargingchargers.com) and explained my dilemma to their tech guys and their opinion was:
    • AGM or Flooded - no difference in sulfation. Since you already own AGM - keep them.
    • Sulfation issues will be minimal if you restore the draw-down load within 7 days
    • Plan on 3 hrs per day of usable sun for good solar in your math
      • Thus 3 x 7 = 21 charge hrs in one week to restore what was used
      • 30-50w panel will restore 37-60 amps of drawn load
    • Keep it simple - maybe start with one panel and a basic charge controller.
      • Add another panel if you find you need it and get comfortable with solar
    • Don't recharge both batteries using a single solar input if the battery starting voltages are different, it will undercharge one and over-charge the other. Recharge individually if their starting voltages are different. Keep the battery switch in BOTH most of the time to keep it simple.
  • West Marine will exchange the AGM's if I want to do that.
37-50 amps is way more than a day sail would use. A 2-3 day weekend on the hook which is mostly periodic cold-plate running at 6ah draw is probably okay. The longer trip in Puget Sound requires some overnights at a marina with AC during or after the trip to quickly recharge using the AC 20 amp charger.

Based on this info and reading most of the shared comments on the thread, I plan on keeping the AGM's and buying 30-50w panel and controller which will be stowed when sailing.

Additional thoughts by the learned group of posters here is appreciated.
 
Jan 11, 2014
6,826
Sabre 362 113 Fair Haven, NY
The tech guys are a bit optimistic. At higher levels of SOC charging efficiency drops due to internal resistance in the battery.

Doing the math, (50 watts * 3 hours * 7 days)/12 = 87.5 ah At best when the battery is at 80%SOC and with 80 % efficiency you'll only get 70 ah a week. Throw in a rainy day or two or a day sailing and the available power drops quickly. As the the SOC increases charging efficiency will decline even more until it approaches 0%.

The refrigerator cold plate only draws 6 amps, however it will run about 50% of the time unless the box is exceptionally well insulated and seldom if ever opened. The daily draw with be about 72 ah, about 40% of your total battery capacity. With only a 50 watt panel, you will never be able to keep up.

At this point, keeping the batteries and adding at least 50 watts of solar is probably your best option. Just bear in the mind the limitations and set your expectations accordingly. The batteries may have a shorter life with the charging regime you have, however, it might be a worthwhile trade-off given how difficult it is to check and water less expensive FLA batteries. In a few years you may make the same decision, just remember that West Marine is not your best source for batteries or anything else for that matter.

While researching battery choices for my boat, I came across this document, it is a bit technical and will likely take a couple of reads to understand, but it was informative. I found it on the OceanPlanetEnergy.com website (This is the company owned by Bruce Schwab and Nigel Calder).

 
  • Helpful
Likes: jssailem
Jan 11, 2014
6,826
Sabre 362 113 Fair Haven, NY
An oxymoron?
I think it depends on where you are located. My marina is quite reasonable, there are other nearby marinas that are half again as much or more.

Sailing on the southeast shore of Lake Ontario is very affordable. :)
 

DArcy

.
Feb 11, 2017
978
Islander Freeport 36 Ottawa
I think it depends on where you are located. My marina is quite reasonable, there are other nearby marinas that are half again as much or more.

Sailing on the southeast shore of Lake Ontario is very affordable. :)
Dave, just don't calculate the $/days in the water and compare to our southern neighbours ;)