Battery Charging Techniques

[Stu Jackson]

In a recent post about carbon monoxide detection, we meanered off into battery charging, and Michael MacLeod asked me to repost a particular reply in a new topic.  I've also added Kyle Ewing's question. 

This text comes from page 2 of this link:  http://c34.org/bbs/index.php/topic,4313.15.html

Is it your view that the boat should generally not be plugged into shore power?

Michael, In all of our years with Aquavite and in earlier boats [celebrating our 25th year of sailing on SF Bay this past weekend], we never left our boats plugged in, and none of 'em sank!  The reason is basic:  we just do not know how poorly wired our neighbors' boats may be.  Stray electrical can come from a bad dock wiring design or installation [not in our marina, though] or from poorly wired other boats even to a good marina system.  We intend to have the zincs continue to do their work and not spend money on a new shaft or propeller if we can help it.

That said, I've learned a lot recently from John Nixon, a frequent contributor to this Message Board.  Once I [finally] installed our Link 2000, I learned two very important things:  1) my "energy budget" done in my head for the past ten years was pretty much right spot on (see: http://c34.org/bbs/index.php/topic,3976.0.html); 2) my estimate of input TO the house bank FROM the various charging sources was NOT very good because I hadn't taken into account the acceptance rate of the batteries and the tapering off of the charging amperage even with a smart regulator and a smart three stage Freedom 15 inverter charger.

In discussions by email with John, as a result of what I term "Fridge Follies," wherein I was doing detective work on why our fridge would not restart during the second night at anchor, I learned two things:  1)  equalize your batteries regularly to avoid diminished performance [assuming your batteries are wet cells and your manufacturer says it's OK to do so]; 2)  John provided this: "Leaving lead acid batteries on float charge 24/7 will reduce the useful life of the batteries by as much as 35 to 40% compared to cycle charging, which by definition is to charge them only when they need recharging, then leave them alone. The continuous float charge results in accelerated positive grid corrosion, which has the effect of turning the positive plates in the battery into mush: a soft, expanded material that produces increased internal resistance and decreased deep cycle capacity. I only use cycle charging on my boats now, but I will leave them overnight or maybe for a day or 2 with the charger on just to make sure that they get fully recharged." 

I noted that in order to do so, I'd start a program of plugging into shorepower to top off the batteries once I got back to the slip before I left.  He added: "I doubt that an extra 30 minutes with the charger on when you get back to the dock is going to get your batteries fully recharged: that last 5% or so takes a long time, even with the very low internal resistance of AGM batteries like I have on our boat. If you are adverse to leaving the charger on all the time when you are away from the boat ( which I support completely, but not for the reason you might think...), a good simple way to give the charger time to do its work is to put it on a cheap/inexpensive 24 hr time switch with the ON peg pulled out. Just set it to run for 24 hours when you leave the boat: manually start it with the timer set just after the OFF pin, and it will dutifully turn itself off after a good 24 hour charge. In most cases, that will generally make sure that you have reached that 100% charge that the batteries need to not begin loosing capacity due to sulfation. 

So, for many reasons, it's important to both keep your batteries fully charged, avoid keeping them plugged in 24/7 on float, and take care of them.  I am constantly amazed at the number of plugged in boats that NEVER GET USED.  Whenever the owner comes down to the boat, there are going to be a bunch of things that don't work, most importantly their electrical systems.

The fridge works much better now after the equalization, which I intend to do more regularly now that I know.  The voltage used to drop to 12V whenever the fridge started running.  After the equalization the voltage remains high and only slowly tapers off after fridge run time and during the off cycle of the fridge, the voltage actually rises a bit.

Live and learn.

From Kyle:  Regarding partially discharged batteries and leaving the battery charger on when the boat is unattended, how do people handle leaving the boat after discharging the battery (i.e. after an overnight cruise with little motoring) then closing up the boat for the weekend? 

I dislike leaving partially discharged batteries and dislike more leaving power to the boat, especially if I might be away for a week or two.  I leave the charger on while unloading and closing up but know the batteries need more than an hour of charging.

[Michael]

Stu, thank you for starting a new thread with your post.  It seemed too good to bury in our carbon monoxide/propane gas/battery gas/???? discussion.

I am a dunce when it comes to batteries and electricity.  Can you help by answering some questions that arise for me on reading your post. [Later added note: Stu, on searching, I see that you have written elsewhere at this site about batteries and electrical issues. I am following up those posts now so please don't think you should write anything in answer to my questions here that you have written elsewhere. M]

You wrote: In all of our years with Aquavite and in earlier boats [celebrating our 25th year of sailing on SF Bay this past weekend], we never left our boats plugged in, and none of 'em sank!  The reason is basic:  we just do not know how poorly wired our neighbors' boats may be.  Stray electrical can come from a bad dock wiring design or installation [not in our marina, though] or from poorly wired other boats even to a good marina system.  We intend to have the zincs continue to do their work and not spend money on a new shaft or propeller if we can help it.

Question: Will you explain how having your own boat "plugged in" relates negatively (bad pun) to other boats' wiring, bad dock wiring, zincs doing their work.

You wrote: That said, I've learned a lot recently from John Nixon, a frequent contributor to this Message Board.  Once I [finally] installed our Link 2000, I learned two very important things:  1) my "energy budget" done in my head for the past ten years was pretty much right spot on (see: http://c34.org/bbs/index.php/topic,3976.0.html); 2) my estimate of input TO the house bank FROM the various charging sources was NOT very good because I hadn't taken into account the acceptance rate of the batteries and the tapering off of the charging amperage even with a smart regulator and a smart three stage Freedom 15 inverter charger.

Question: are there generally just two charging sources: the [whatever it is - generator?] on the engine and the 110 volt charger?

You wrote: In discussions by email with John, as a result of what I term "Fridge Follies," wherein I was doing detective work on why our fridge would not restart during the second night at anchor, I learned two things:  1)  equalize your batteries regularly to avoid diminished performance [assuming your batteries are wet cells and your manufacturer says it's OK to do so];

Comment: I would ask about equalizing wet cell batteries but will hold off until after searching this website for postings on the subject.  At this point, I have no idea of how to do it.  If there isn't another thread dealing with this topic, I would be interested in knowing from you here how one goes about doing it.

You wrote: 2)  John provided this: "Leaving lead acid batteries on float charge 24/7 will reduce the useful life of the batteries by as much as 35 to 40% compared to cycle charging, which by definition is to charge them only when they need recharging, then leave them alone. The continuous float charge results in accelerated positive grid corrosion, which has the effect of turning the positive plates in the battery into mush: a soft, expanded material that produces increased internal resistance and decreased deep cycle capacity. I only use cycle charging on my boats now, but I will leave them overnight or maybe for a day or 2 with the charger on just to make sure that they get fully recharged."I noted that in order to do so, I'd start a program of plugging into shorepower to top off the batteries once I got back to the slip before I left.  He added: "I doubt that an extra 30 minutes with the charger on when you get back to the dock is going to get your batteries fully recharged: that last 5% or so takes a long time, even with the very low internal resistance of AGM batteries like I have on our boat. If you are adverse to leaving the charger on all the time when you are away from the boat ( which I support completely, but not for the reason you might think...), a good simple way to give the charger time to do its work is to put it on a cheap/inexpensive 24 hr time switch with the ON peg pulled out. Just set it to run for 24 hours when you leave the boat: manually start it with the timer set just after the OFF pin, and it will dutifully turn itself off after a good 24 hour charge. In most cases, that will generally make sure that you have reached that 100% charge that the batteries need to not begin loosing capacity due to sulfation. 

Comment:  On Hali we have four owners.  Different owners use the boat quite a lot...at least for short day cruises.  As a practical matter, we probably are less concerned about a 35-40% reduction in service life of the batteries than we are in knowing that the batteries are charged up whenever anyone comes to the boat and in having dead simple procedures that everyone can follow (like plugging in shore power when we leave the boat).  We will need to think whether there is a dead simple procedure for cycle charging that would avoid our "plug her in" policy which results in continuous float charging.

You wrote (or quoted, not sure which on this part): So, for many reasons, it's important to both keep your batteries fully charged, avoid keeping them plugged in 24/7 on float, and take care of them.  I am constantly amazed at the number of plugged in boats that NEVER GET USED.  Whenever the owner comes down to the boat, there are going to be a bunch of things that don't work, most importantly their electrical systems.

Question: Did John have another reason - it is not clear to me that he stated it although he seems to have hinted at it - for avoiding leaving the battery charger plugged in 24/7?

You wrote: The fridge works much better now after the equalization, which I intend to do more regularly now that I know.  The voltage used to drop to 12V whenever the fridge started running.  After the equalization the voltage remains high and only slowly tapers off after fridge run time and during the off cycle of the fridge, the voltage actually rises a bit.

Question: Hali has a selectable battery "tester" for each of the two house batteries, at the panel.  Each gives a voltage read-out only, on an analogue meter.  At what "tested" voltage would you conclude that continued use of a battery is not good for equipment aboard the boat (or that for other reasons the battery should not be used)?"

Many thanks. 

[Stu Jackson]

1. Question: Will you explain how having your own boat "plugged in" relates negatively (bad pun) to other boats' wiring, bad dock wiring, zincs doing their work.

2. Question: are there generally just two charging sources: the [whatever it is - generator?] on the engine and the 110 volt charger?

3. Comment: I would ask about equalizing wet cell batteries but will hold off until after searching this website for postings on the subject.  At this point, I have no idea of how to do it.  If there isn't another thread dealing with this topic, I would be interested in knowing from you here how one goes about doing it.

4. Comment:  On Hali we have four owners.  Different owners use the boat quite a lot...at least for short day cruises.  As a practical matter, we probably are less concerned about a 35-40% reduction in service life of the batteries than we are in knowing that the batteries are charged up whenever anyone comes to the boat and in having dead simple procedures that everyone can follow (like plugging in shore power when we leave the boat).  We will need to think whether there is a dead simple procedure for cycle charging that would avoid our "plug her in" policy which results in continuous float charging.

5. Question: Did John have another reason - it is not clear to me that he stated it although he seems to have hinted at it - for avoiding leaving the battery charger plugged in 24/7?

6. Question: Hali has a selectable battery "tester" for each of the two house batteries, at the panel.  Each gives a voltage read-out only, on an analogue meter.  At what "tested" voltage would you conclude that continued use of a battery is not good for equipment aboard the boat (or that for other reasons the battery should not be used)?"

1.  Boat plugged in affecting others - This is too complicated to get into here.  Suggest you read Nigel Calder's Boatowner's Manual for Mechanical & Electrical Systems, or other fine boating electrical books.  Simplistically, if wiring on boats or the marina is bad, stray electrons can "roam" all over the place and eat your zincs and then your prop and shaft which are protected by said zincs.

2.  Number of charging sources:  Up to you - shorepower charger, alternator from engine, solar panel, wind generator.  Go to www.jackrabbitmarine.com who have a good display or alternate energy systems and equipment.  Read Calder's book.  (10/10/11 - jackrabbit closed.  Ample Power does a good discussion)

3.  Battery Equalization - first thing, do a search on this MB for that word, or Google "battery equalization" and learn about it (again too long to retype) but John explained the WHY of doing it.  Your (crappy, dangerous) charger doesn't have that feature.

4.  Different Owners - I discussed that philosophy in the earlier long discussion about your boat.  You can chose to keep it as simple as possible, and run the boat like a rental car operation.  Or you can chose to educate the owners so they understand more for their safety.  I would consider learning far superior.  If YOU and your shipmates do NOT think that a 40% decrease in battery life is worth $$$, then, continue to pursue your way of doing things.  I would definitely care about that kind of unnecessary outlay that could EASILY be completely avoided with a mere tad of judicious operational understanding.  I asked before: do you have a Link or other battery monitor?  If your goals are simplicity and making sure the batteries are charged, then you NEED a monitor, because up til now you've been simply guessing about the overall condition of your batteries, which is a completely different thing that assuming they're charged BECAUSE YOU SIMPLY LEFT THE YELLOW CORD PLUGGED IN ALL WEEK.  Please, Michael, think about the different concepts.  If they don't worry you, then - your boat, your choice.

5.  Other reasons for NOT leaving plugged in - don't know, perhaps John will join the party here, could be as simple as people stealing shorepower cords for the copper these days, but given what you have to address, I would think it's small potatoes at this stage.

6.  Battery "tester" - 11.8 V is a dead battery, 10.5 V everything will stop working.  Analog meters are horribly poor when compared to digital.  See above discussion about battery monitors.  Relying on voltage alone is poor battery management.  Download and read the Ample Power Primer, previously recommended in almost all of my charger thread discussions (www.amplepower.com).  Also read West Marine Advisors in their catalogs' electrical section, 'specially about batteries and chargers.

[Ken Juul]

A few random reasons not to stay plugged in 24/7.

I know Thunderstorms aren't the norm in B.C., but they happen.  Lightning strike causing a voltage surge through the marina wiring frying the electrics on your boat.

Joe Power Boater up the dock keeps the refer, ice maker, battery charger, and heater on so his boat is dry and ready to go for the next weekend.  Power overload pops the breaker, not found for several days.  If you (or co-owner) left anything on your batteries are probably dead also.

Mr Murphy decides it's time for that unseen 120V power line between the shore power plug and the electrical panel to chafe through and short, the resulting fire destroys your unattended boat and those around yours.

Your neighboring dockmate or repairman or marina personnel accidentally bumps the dock cart into your dock power box/cable.  The momentary disruption causes arcking inside the plug.  May cause fire, eventually will result in replacement.

It's all doom and gloom.  That said hundreds or thousands of boat owners do it and have no problems.  It's your boat, your choice.  Personally I'm in the unplug when you leave camp.

[Stu Jackson]

Ken, very good input.  There have been many discussions about battery operation, and one in particular, "batteries and the fridge," years ago, raised many valid issues about why people keep the fridges going - I want cold beer (vs. bring a cold six pack when you drive to the boat, the fridge will cool down in short order); a want to leave my ketchup and mayonnaise and mustard onboard just alike a cabin-in-the-woods (vs. it's not that hard to get small bottles and take em with you each time); I want ice (v.s buying a small pack on the way).  The list is endless.

Reason for this is twofold:  one to address the "leaving it plugged in controversy," and second, to begin to address Kyle's question:  

You've been out all weekend, don't want to leave your boat plugged in, KNOW that your house bank has NOT been fully charged.  What do you do?

I think the answer is what John Nixon suggested to me.  Saying that, we have a Freedom 15 inverter/charger combo wired directly into the incoming A.C. wiring.  Using a simple timer would require cutting the incoming wires and wiring a timer in the A.C. wiring.  Could be done.  I'm fortunate because we live close to the boat and I can get down and unplug if I choose to leave it on one night.

I added a small solar panel.  By the time I return the next week the batteries are full again.

What are others' experiences?

[Michael]

Stu:

Many thanks.  I appreciate the time you've spent on this topic here and elsewhere.

1.  I do have Calder's book...and think I have even read it once right through...but, in my brain, the study of batteries and electricity seems to fit into the same category as the study of weather: I can read about it but don't get it...and what I do learn doesn't stick.  The problem may be inadequate practical experience...but that can be remedied.

2.  Probably only shorepower charger and alternator from engine make sense for us with Hali.

3.  Battery Equalization - I'll read about this...and, yes, I unplugged that charger this morning.  Lionel and I have agreed today that we will get a better charger...which will give us something extra to investigate.

4. Different Owners - knowledge for safety.  Yes.  And on further thought (spurred by your concern on this point), it has struck me that we must be able to do something simple that will result in the batteries being charged in the best way without requiring that everyone understand why.  Generally, I write up a "standard operating procedure", once I think I understand something, and the owners are pretty good about reading the procedures but, perhaps like me with batteries, it doesn't always stick.  In the case of charging the batteries, several of us go to the boat often enough that, once we have an adequate battery monitor/charge controller, we could leave shore power disconnected (or just the battery charger off if we can live with Ken Juul's thousand natural shocks that shore power is heir to), then I - or anyone else who has read the "battery charging procedure" and wants to follow it - could run the battery charger when needed.

4a.  Other than the analogue voltmeters, we have no fixed battery monitor.

5.  Battery "tester" - If our analogue voltmeters were reading accurately, we were pressing the "dead battery" level occasionally with our old 4D's.  I may have run the windlass with one or both batteries into that zone.  I could kick myself for doing that if I did.  I don't suppose its too good for the windlass motor.

Thanks again, Stu.

[Stu Jackson]

Michael, re battery chargers, there's NOT anything to investigate.  As John Nixon mentioned in one of the referenced links on chargers, "...I cannot recommend anything BUT the Truecharge 20 or 40..."  John's a professional battery-person.  Isn't that enough?  With your OEM (I assume) alternator and your relatively larger house bank of (2) 4Ds, I'd recommend the 40 to reduce your charging time when plugged in.  You could even get a good input when plugged in for the time you spend at a fuel dock.   Many stories of how and where to mount it on this board.

One other question not asked is how your four folks use the boat:  marina hopping or anchor out, and if so, for extended periods of more than one or two nights?  Would be helpful to know to continue to assist.

[Michael]

Stu, one of my buddies (obviously not yet consulted by yours truly) is an inverter/power controller designer. Every once in a while, I have heard him muttering about various of the Xantrex devices, sometimes favourably, sometimes not so favourably, so I thought I would consult him on the choice though I saw favourable references on our c34 site to the Truepower charger.  Of course, I am not sure that my buddy will be approaching the question from a sailor's point of view.

You asked how our four owners use Hali.  It is probably too early to say.  We only acquired the boat in March, 2007.  Last summer we cruised her little.  Our use hasn't settled down yet.  Having said that, my predilection when cruising is never to overnight at a dock, to anchor out always, and to conserve power fanatically.  Typical Scottish behavior, I would say.  On the other hand, most of the other owners are not power-conservationists and, I suspect, are more willing -- or even keen -- to tie up overnight when they can.  There has been some expressed disbelief when I have doubted (without the benefit of a power analysis) that we can cruise for long and use the fridge full-time!

[Jon Schneider]

I'm probably the only one who supports the idea of leaving the boat plugged in for the sake of the charger, but here goes.  A 2000 gph bilge pump consumes over 8 amps.  If you had a leak that kept that pump going, a 400 AH bank would only last one day.  I've got two pumps; they'd run the bank down considerably faster.  I also have spoken to a tech rep at Xantrex (I have a Xantrex XC3012 charger) who claims that the charger is not always charging, and that if it does not sense a current drain, it will not cycle on for 20 days.  Your charger may vary in this regard, and, of course, this is only the charger manufacturer's side of the story (which reminds me of Michael's post in the CO thread about the painter and the lion....)  I have a call into a tech rep at Trojan Battery, but haven't heard back yet. 

Regarding this supposed 40% reduction in battery life due to float charging (i.e., on/off charging cycle), I'm not convinced.  Where's the data to support this.  Sounds to me like a number pulled from a dark place.  Is John's assumption that "float" is synonymous with "constant trickle"?  If so, we're talking apples and sirloin.  What I do believe -because every source I read confirms it- is that continued undercharging is very bad for lead acid batteries (unclear to me about Gels and AGMs). Continually operating the battery in a partial state of charge or storing the battery in a discharged state will result in a condition known as sulfation. Sulfation reduces the battery's performance and may cause premature battery failure (source: Apex Battery).  I just don't know how a weekend sailor who lives 100 miles away from his boat, such as I do, can not leave the charger plugged in (and therefore the boat) after the weekend sail. 

Regarding electrolysis, I check my zincs; not a problem.  Regarding all of Ken's mishaps, I'm betting against Murphy (and looking for wood to knock on as I write this); they all seem like pretty far-fetched instances and outcomes, with the exception of someone tripping the dock power supply line (though it's never happened in the 12 years I've been on one particular dock, nor to me anyplace else).  Even if the main power did get tripped, the 10 other stinkpot owners on my dock would re-set it in a heartbeat.  They couldn't be without their big screen TVs and air conditioners for more than 10 minutes.  But in this instance, what Ken is really arguing against is simply not leaving any 12v appliance on (other than the bilge pump, I assume).  Good idea, but irrelevant to the issue of whether or not to remain plugged in to charge. 

Okay, all you unplugged types, take aim ;)

[Stu Jackson]

Michael, if you did a search on "energy budget" you'd find this:  http://c34.org/bbs/index.php/topic,3976.0.html  See the first post and click on the PDFs file.  It answers your question, and is included in Calder's very valuable book.

Jon's position is well founded and has merits, your boat, your choice.  BTW, Jon, John Nixon has been a member of the C34 IA for many many years and actually is now the owner of his second C34, after a dalliance with a Stamas 44 for a while.  He does know his stuff, and if he shows up here, as he often does, he may be able to answer your questions.  I am sure it's not something pulled out of a hat or any other dark place.  As noted in either this or an earlier thread from Michael that got moved over here (the co monitor that brought all of this up), John's position from a battery longevity point of view is that charge and disconnect (not his phrase, but go look it up in that post) is better for battery life.  Battery life is among MANY of the issues facing us as skippers, and fear of sinking at the dock is certainly up there among the top ten on the list.

[Michael]

Speaking of lions, Ken. [No, I mean Jon! Thanks for the correction, Jon.] Or maybe Christians.  You may have no limbs left when the "unpluggers" are finished with you.  Having been a "plugger" for the past year, there is part of me that is heartened by your stand...it plugs for you.  Officially?  I am on the fence.  Your vindication would only be confirmation that I was dumb lucky.  All the same...good luck.

Added later: Thanks, Stu. I've looked at your power budget .pdf.  I've dimly thought of doing such a power analysis for Hali.  You know, the trouble with this site is it keeps suggesting really good things to do that there will never be time enough to do.  On another point, for a leading "unplugger", your response to Ken was decidely temperate!  Are you by any chances thinking of hopping on the fence?

[Jon Schneider]

On another point, for a leading "unplugger", your response to Ken was decidely temperate!  Are you by any chances thinking of hopping on the fence?

I think you meant me, not Ken (Ken's a member of the unplugged club).  BTW, Stu is the consummate diplomat.  He's always the one adding reason and the voice of sanity to idiots like me as we spout off.  I wish he were running for office in November! 

[Ron Hill]

Guys : I do not and never have recommended staying "plugged in" especially if you are not on board.  All of the reasons listed above and in my 10 to 20 previous posts on this very topic. 
I believe that Lead acid batteries will tend to sulfate out when sitting at a 100% charge and never discharged. 
In addition there's the threat form thunderstorms/voltage surgesfrom lighting/wear and tear on your charger etc.  The constant charging ON/sensing/turn OFF of the charger wears it out for 24/7 for what ?? - a cold beer that you could have picked up at 7/11 ??
Your boat do what you want ! 

[Ted Pounds]

Jon,
I'm with you.     Or at least I was until I sold my boat...

[Rick Johnson]

Jon, there are at least two pluggers here.  I just like my beer cold and I'm at the boat every day.  It's nice to be only 3 miles from the marina...  The water was 75 degrees today and air was 95 degrees...  Gotta love Texas....

Cheers,

Rick