Battery Experience With Questions and Answers

Arbatax P1010831

Anything learned from battery use on a boat that is not really out there cruising is…well, not very useful. Cruising is different, and much harder on batteries than most other uses. And so much of what you read about sailboat battery life is theory based on…well, not a lot.

So it was great to get an interesting comment from AAC member Rick Salsman, relating his real-world, real-cruising, battery experience.

Over to Rick:


I have just replaced my four old 4D East Pen(EP) AGMs with Lifeline AGMs.

These EPs lasted me from 2006 until the spring of 2013. I was not near a facility to bench test the remaining capacity, but I had noticed a continual decline in the time a reasonable charge could be held. I might have gotten one more year out of them, maybe.

We have lived aboard anywhere from 4-6 months per year since 2007. We use about 200+ amp hours per day while at anchor, running computers, fridge, etc.

Our primary charge source is our 125 amp alternator plus a little from a Superwind wind generator. Cruising in the Mediterranean, with light to no winds in many areas, we do a lot of powering.

We typically charge up to about 85% to 90% battery capacity with the alternator unless a longer passage is underway…

…I have also used a desulfator from Pulsetech, that has run over that whole period.


Do you or your readers have any experience with these desulfators? I wonder how much it contributed to the 7+ year life of the EP batteries.

I was unaware of the ability of AGMs to accept an equalization charge. I am also trying to decide if I should also equalize these Lifeline Batteries when I did not do so with the EPs?

Do you have some thoughts on my battery program, and why I have seemed to get a longer than normal life out of my old batteries and if I should now equalize monthly with the new?

Rick asked some interesting questions. Here are my thoughts.

Longer Than Normal Life?

On the life you got out of the old East Pen AGM batteries, while you say that it was “longer than normal”, and you are probably right (taking into account your use), my thinking is that, given that they only lasted for 3 to 3-1/2 years of actual cruising, this highlights a fundamental problem: real cruising use sulphates lead-acid (all types) batteries and results in a pretty expensive lifecycle.


There are a lot of variables here, but comparing your experience to ours and other reliable second hand evidence, I would guess (and it is just that) that the PulseTech desulfator did make some difference and probably extended the life of your batteries, perhaps as much as 50%.


While monthly equalization is not without its downsides, which I discuss in this chapter of our Battery Installation and Maintenance Online Book, I would suggest that you add monthly equalization to your regime.

I base this recommendation on our own experience with our current set of LifeLine AGM batteries that:

  • Have 2-1/2 full years of out-of-marina cruising on them.
  • Have been equalized once a month, while cruising, with one exception where they went two months.
  • Discharge testing shows they still have over 90% of their capacity left.
  • Our use is even tougher than yours: 250-350 amp hours a day out of just two 8Ds.


If you have real-world, out there cruising, battery life-cycle experience, please share it in a comment. However, please take a page from Rick’s book and make sure you include your usage and charging profile. Comments that say things like “my batteries have lasted 10 years” without that information are simply useless—years mean nothing, it’s cycles, their depth, and how much, and how the batteries were recharged that matter.

We would also be interested in any further real-world experience with desulfators.

If you want to comment on, or ask questions about, subjects such as equalization, please do so on the appropriate chapter in our Battery Installation and Maintenance Online Book. And yes, that will require you to become a member, if you are not one already.

And that brings up another subject. This post, and the last but two, answered questions and brought to the fore (to solicit input in the comments) challenges that two of our members were facing. This is part of our commitment to go the extra mile for those who have contributed to the site.

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Meet the Author


John was born and brought up in Bermuda and started sailing as a child, racing locally and offshore before turning to cruising. He has sailed over 100,000 miles, most of it on his McCurdy & Rhodes 56, Morgan's Cloud, including eight ocean races to Bermuda, culminating in winning his class twice in the Newport Bermuda Race. He has skippered a series of voyages in the North Atlantic, the majority of which have been to the high latitudes. John has been helping others go voyaging by sharing his experience for twenty years, first in yachting magazines and, for the last 12 years, as co-editor/publisher of AAC.

19 comments… add one
  • Chris Nov 16, 2013, 1:16 pm

    We installed 660AH of Lifelines three years ago. We cruise full time between the upper Chesapeake and Exumas. We use 70-150AH a day. We have 405 watts of solar panels, a 3KW charger, and an 85A alternator controlled by a 3 stage VR.

    O. Leadaverage we have recovered our deficit by 1400 each day when anchored. Motoring we are net 0 in three hours The charger is only used when solar or motoring fails to get us back to net zero — Rare. We do not equalize. So far, knock on lead, we have experienced no noticeable reduction in battery performance.

    Sizing the bank to very rarely use more than 25%, going to all LED lights, adding as much solar as tech and aesthetics would allow, and striving for net 0 every day has worked for us.

    • John Nov 16, 2013, 2:33 pm

      Hi Chris,

      Great real-world information. Bottom line, as you say, if you can recharge to full (net zero) after each and every discharge most of your problems go away and equalization is not required—little or no sulphation.

      Even so, I wonder if say a quarterly equalization might not pay dividends for you since some sulphation is inevitable, no matter what? Hum, pretty hard to know or test for.

      Sadley, most of us can’t make your plan work for us, particularly on longer multi-day sailing passages with little motoring.
      The key, as you point out, is a large battery bank and solar capability in relation to usage.


  • Chris Nov 16, 2013, 3:59 pm

    I failed to mention diesel genset. On multi – day, sun deprived runs we use it to run charger. Also gets us to net zero in about 3 hrs at 40% of main engine fuel consumption.

  • Charles Nov 16, 2013, 11:48 pm

    I’m engineer on the brig Lady Washington. We are armed with a house bank of wet-cell batts totalling just over 5000ah, an emergency bank of about 600ah, plus starters for our main and 12kw generators. In addition to the generators, we have a 365amp Balmar aux alternator on the main to charge the house bank. Our house bank was installed eight years ago. I haven’t closely monitored usage rates, but we can typically get about 18 hours out of the house bank following a four hour charge. Accordinding to our Outback Mate-3 and FLEXnet, these numbers are 50% discharge and 95% charge. The Outback system is new, so this profile only represents fairly recent use. My predecessor operated on similar cycles, though.

    The maintenance cycle thus far has consisted only of monthly electrolyte level and SG monitoring. I will add equalization charging. Our inverters manage all our charge controlling. We’ve never desulfated the batteries and have no plan to acquire desulfators.

    For three years, we had AGMs for our main engine starter batteries. A few weeks ago, they turned into puffy marshmallows and were replaced with a pair of 8D wet-cells. I cannot recommend AGMs if you are already in the routine of doing battery maintenance. Maintenance-free batteries provide no symptomology before catastrophic failure (fireball); another reason not to use them.

  • Horatio Marteleira Nov 17, 2013, 8:11 am

    Since many of your readers may use their boats as I do in my current situation – a 1-month or slightly longer cruise per year spent at anchorages – I seriously recommend using normal batteries to get the biggest bang for you buck. When I crossed the Atlantic I purchased 2 expensive deep cycle batteries (about 220 amps total) that lasted about 6 years, powered only by a Rutland wind generator. After that I bought a regular 210 amp wet cell battery in 2007 for 115 euros and it’s still going.
    Note: although my boat is naked – no fridge, no radar, etc. – I use the computer a lot during that short cruise and never run the engine merely to charge the battery.
    Also, I suspect the crossing was hard on the batteries as I also never ran the engine to charge them.
    Bottom line: part-time cruisers may benefit from regular batteries.

    • John Nov 17, 2013, 9:26 am

      Hi Charles and Horatio,

      Thanks for the comments. I think that you are both right that liquid filled batteries are generally more robust and tolerant of abuse than gels or AGMs, although brand makes a big difference to this sweeping statement. Having said that, there are very good reasons for cruisers, dependant on usage profile, to use AGM batteries. More coming on that in a future post.

  • Eric Klem Nov 17, 2013, 10:54 am

    Hi John,

    My only experience with desulfators is with electric cars. One of the cars that I built had a battery pack consisting of 24 Trojan T145’s lead acid batteries in series. These batteries lived a pretty hard life getting cycled below 50% quite regularly (from time to time we would take them low enough that the vehicle would barely move). They were equalized regularly as well, probably at least once a week which is a lot considering there were probably 6 charges a week. After probably 2 years and about 15k miles (I am guessing we averaged 40-50 miles per charge), our charger died and we switched to a high frequency one. At this point, the batteries had lost probably 30% of their capacity and they rebounded to probably 10-15%. The batteries ended up lasting about 30k miles so I would guess they did 600+ charge cycles. I am pulling all of this out of memory so it might be a bit off, I don’t have the logs anymore for it.

    Talking to other people who have built electric cars with lead acids, there seems to be a general rule of thumb that a car with a 75 mile maximum range will do 20-30k on a battery pack with a regular charger and up to 40k with a high frequency one. These numbers are not super scientific but there are a lot of these people who had gone through more than 2 identical packs on a single vehicle so they had a decent comparison. Just about everyone I talked to went with a better charger for the second pack if they didn’t already own it.


  • Victor Raymond Nov 18, 2013, 4:52 pm

    Hello John et al,
    We upgraded the battery system and added solar charging to Rajah Laut this past spring. Too early to tell to much except that 8 Lifeline GPL-4CT 6 Volt AGM Batteries at 220 amp hours have not been below 100% charge since installation. Also installed were two Helios 9T6 420 watt solar panels.
    With our 24 volt electrical system the two battery banks each have 220 aHrs each for a total of 440 hHrs. The Tristar MPPT controller shows either Absorb or Float mode and never below 26.4 volts since installation.
    We have been at anchor all this past summer & fall and even at a marina can not use shorepower since we are 220v 50 Hz boat. I have turned the 7Kw Onan generator a few times (just to make sure it works) but after a short time the Trace/Xantrex SW4024 inverter/charger stops charging because the batteries are full.
    The two solar panels also serve as a hard bimini over the entire cockpit area with a slight crown for shedding water. On a day to day basis I doubt we ever get over an average 10% of the total amp hour capacity of the panels. This is partially to do with shading from the mast, the boat swinging on anchor and the fact that the panels do not articulate to maximize gain but so far that has been sufficient for all the refrigeration, electronics, windlass and lighting use we have demanded so far. Next winter in Alaska will be telling with the very short days, heating and lighting requirements. I doubt the panels will do much except keep the snow out of the cockpit. However quite certainly the wind will howl so perhaps the addition of a quiet efficient wind generator will be warranted at that time.
    We also added a Balmar MC-624 smart charger regulator since there is a slight suspicion that the previous regulator might have been the partial cause of the previous Dekka 4D AGM batteries early demise (6 years.)
    To reduce total electrical load we are replacing lights with LED models as they fail. Early spring we replace the anchor/tricolor and spreader lights with LED. We were tempted to do the same with the steaming lights but figured that the engine would be running at that time so plenty of extra electrons for all needs.
    Two years ago we replaced our AC refrigeration with a small 24v system so the need for the AC generator is less but batteries more. Some day would love to leave the generator ashore but time will tell if I have that courage.

    • John Nov 19, 2013, 9:13 am

      Hi Victor,

      Sounds like a great system. The thread I’m seeing here, albeit with a small sample, is that if a cruiser can install a battery bank that is sized at at least four times daily load and install solar panels capable of replenishing daily load, at least every few days, pretty much all battery problems go away. Of course hitting this criteria is not easy because it takes a lot of space for batteries and a way to install a lot of solar in a seamanlike way. The emphasis on the last part is because I’m seeing way too many solar installations that are not strong enough to take the loads of a gale at sea and/or that compromise the seamanlike handling of the rig—sounds like you have that solved too.

      • Marc Dacey Nov 19, 2013, 12:55 pm

        John, this is the way we are going, although I’m not yet done. We had fabricated two cross-braced arches over the aft sailing helm, mounting four 135 W Kyocera panels. This will feed an approximately 1100 Ah battery bank of six 6-volt L16s close to the boat’s CG. Our energy budget (which time and usage will testify as to the accuracy) is perhaps a fifth of total capacity. My benchmark was I wanted to have four to five days of cloudy, windless weather before I approached 50% on the banks and had to consider an engine run to recharge or to break out the Honda 2000s lashed to the deck for a “porta-gen” solution. A multi-pronged approach to generation (solar, wind, genset and alternator) has been key to this design…we grab what we can when we can in order to stay off shore power and to minimize reliance on engine runtime (unless we accept alternator generation as a byproduct of propulsion we’d be doing anyway).

        It is only the rather unusual configuration of our boat and the generous interior volume of a semi-full keeler that permits easy, tightly grouped access to a substantial battery bank, the mass of which will actually stiffen our ride a bit. On more modern designs, it’s more problematic and puzzling.

      • Chris Nov 19, 2013, 2:53 pm

        While strength is preeminent, windage is a big deal, both as it affects strength requirements and as it affect boat handling/performance. We have had folks tell us that there was a noticeable adverse impact on boat handling by having panels high and/or astern of the rudder. Weather helm, reduced pointing angle upwind and boat speed have all been been cited. A solar panel on a pitching boat in a breeze is a remarkable turbulence and drag creator.

        For these and other reasons, we chose to place our 59 in x 79 in array 3 in above the bimini. This meets panel cooling requirements and makes the panels and bimini top a single aerodyamic unit* ahead of the rudder. As a consequence, we have seen no adverse impact from the installation. When hit by 69kt winds followed by a few hours in the 50-40kt range, we didn’t even notice the panel’s presence other than the rain and hail didn’t make as much noise hitting the bimini.

        * The Reynolds number for the bimini connected to the dodger plus panel is in the same order of magnitude as the bimini connected to the dodger alone.

        • Victor Raymond Nov 19, 2013, 5:50 pm

          John and Chris,
          Windage is the key for sure. We have a 40mm aluminum tube frame that was constructed originally for the bimini. We installed the two panels on top of the frame forming a perfect hard roof to the bimini. In two gales so far, at anchor, the effect was negligible. With a large ocean swell, the jury is still out but, Chris, I am encouraged by your reports that high and aft of the rudder produces the most deleterious results. Perhaps center cockpits designs are ideal for this type of set up.
          John, if I could have installed four 8D batteries in the current battery box space I would have done so. Not sure what Peter Smith was thinking! Just another inch here and there would have done it. Hopefully the next iteration will present us with a proven lithium ion solution with less weight and many more amp hours. In the meantime conservation is key.

        • John Nov 20, 2013, 9:03 am

          Hi Chris,

          That’s a very good point on windage. Some of the contraptions I see on the sterns of boats with all kinds of junk on them must have a very real effect on performance.

          • Marc Dacey Nov 20, 2013, 10:21 am

            John, an unfortunate davit failure underway plus the appalling windage and weight issues were among our reasons for rejecting davits at the stern. Windage here can be substantial, but a 3.10 m Zodiac is not often counted as the main offender.

  • Fuss Nov 20, 2013, 7:55 am

    On the subject of strong secure mounting of panels. This is not always easy to achieve however to be safe, they must be mounted reasonably securely. I have seen some pretty flimsy installations in the past that would not stand up to any even mild storm.
    I too had the thoughts about how to mount them, how will this spoil the lines etc.
    I have three 135 W Kyocera panels.
    They can all be tilted to any position and clamped securely.
    One is mounted on the double backstay.
    One port and one starboard on the pushpit top rails. These two can either hang inboard or outboard vertically, depending on circumstances.
    All three are on quick release NOAA brackets and the two pushpit ones could be ditched overboard in about 30 seconds each with no tools.

    Solar panels are something that I think every voyaging boat should have in these modern electricity generating times. I now never need to run my generator. Well, almost never.
    It seems a shame to have no solar panels at all just for the fear of occasional conditions or the look once installed. Design the installation so that if/ when they could cause a problem you can just ditch them.

    Whats the worse that can happen…. you have to buy two new panels.

    • John Nov 20, 2013, 9:10 am

      Hi Fuss,

      Each to their own, but I would never add solar panels in a way that could result in them becoming a problem in heavy weather. I find heavy weather at sea enough of a problem without having to deal with solar panels, or anything else, that must be re-secured or dumped. Keep in mind that what takes 5 minutes and is easy in smooth water can easily take an hour and be highly dangerous in a gale. For example a panel that got loose when its blowing 40 knots could easily take my head off.

      Also, I won’t have panels on the top of the hard dodger or bimini on our boat, because that’s where I stand or sit to tie in a reef or work on anything that needs doing on the boom.

      To me, the ability to withstand a gale and handle the rig properly trumps all other concerns.

  • Matt Boney Feb 19, 2014, 10:04 am

    Our experience is worth adding here after 7 years fulltime liveaboard on a 42ft Hunter Legend.

    5 x 210 Ah Lifeline AGM Service batteries
    37 Ah Red Flash AGM Starter Battery – on its side under the floor
    2.5 KVA Victron Inverter/Charger – 120 Amps
    100 Amp Balmar Alternator and Balmars ARS-5 smart regulator
    4 HP Fischer Panda DC Generator – 280 amps
    5 watt solar panel for Starter Battery – no other split charging
    140 watts flexible Solara solar panels – on foredeck
    400 watt DuoGen Wind/Towing generator
    BEP Battery Monitor and a SmartGauge

    My AGMs are now 10 years old and were probably not looked after very well for the first 4 years, but knowledge gained from the Net has kept them going.

    We don’t have enough solar, but with the wind genny we can usually replace our daily usage so it is only night time hours that drain our batteries. Spend nearly all our time at anchor in the summer but here in the Med we can get to shorepower once a month on a quay or restaurant. We must get fully charged overnight so that’s why we have a 120 amp shorepower. If we are getting too low I will sometimes run the 280 amp DC genny for a few hours to get us up to about 85% before we finish with the shorepower.

    Our batteries have now started showing signs of lost Ah so we equalize them 2-3 times a year and that brings them back. Our BEP battery monitor can’t cope with the old batteries as all the parameters that it needs change as they age. I spent 18 months trying different Peukert’s Exponents, up from 1.12 to 1.17. – I changed the Charge efficiency from 98% down to 90% – and I have tried all Ah capacities down to 600 Ah and still the Battery monitor can’t keep track – and I have disabled the Auto-Sync feature and ONLY reset to 100% when I know the batteries are full.

    Battery monitors are essential on a boat but when the batteries age they can be a nightmare and be highly inaccurate. Most boats I have seen have installations problems, or extra kit has been added and bypassed the shunt, and nearly ALL of them are programmed wrong. I have now bought a SmartGauge that doesn’t use a shunt but only uses voltage to give you a very, very accurate State of Charge. It has proved a very good investment.

    This is a very sophisticated monitor that uses clever mathematical algorithms to work out the % depth of discharge of the batteries just by measuring the voltage, and it does this over one thousand times a second. It learns the battery status and becomes more accurate the more it “learns”, whereas a shunt based Battery Monitor becomes more and more inaccurate over time. The SmartGauge doesn’t have a shunt so shows no Ah readings in and out, it only shows the % State of Charge of the battery and the voltages of two banks.

    Because it doesn’t use a shunt, it is cheaper than most Battery Monitors and is very much easier to install as only two wires need to be connected. The only information it needs is the type of battery being monitored. It does have a huge range of alarms and a very long and detailed user manual for those who want to get the most out of it. A second battery can also be connected to monitor the starter battery voltage only. It has been proved by Enersys, who make Odyssey batteries, to be much more accurate than any shunt based Battery Monitor.

    The one and only disadvantage of this device is it doesn’t measure current, so a cheap digital current meter can be sourced from another supplier fairly cheaply

    This British invention is widely used by US and UK military vehicles, and can now be bought from Balmar.

  • leo elwell Sep 22, 2015, 11:37 pm

    In a former career, I worked on airplanes. Airplanes are “28 VDC” and many use NiCad or lead acid batteries, with high charging currents can be used. When we were “reconditioning” a battery (desulphating) in addition to watching the battery temperature, it was also important to check the condition of the cables. This is even more important with 12 VDC systems, as due to the lower voltage, the charging currents can be quite a bit higher. If the cable or connectors are somewhat resistive due to corrosion or age, you can have a substantial voltage drop. Then your battery “sees” a lower input voltage. If the cable has a long run, then the voltage drop can become quite substantial if the cable is old. Visually, you will not be able to tell unless the insulation is bubbling or burnt. If the insulation is showing signs of overheating, you are late in the game. You will have to tell if the cable or connector is resistive by getting out a good voltage meter and checking by hand for temperature around the cable while the batteries are being charged. If the cable is warm, that means it is resistive. Think of it as an electrical burner (hob) on a range. Resistance at 12 VDC and substantial amps of current is bad. If the cable is warm, measure on a low voltage DC setting with the VOM meter from one end to the other end. The higher the change in voltage between the two points, the more resistance in the cable/connector.You should aim for voltage drops that are as low as possible, like 0.5 VDC or less. In fact, it is just not batteries that can catch on fire, cables can too! I wonder if some of the people out there with problems with charging and keeping batteries happy might not have resistive cables?

    • John Sep 23, 2015, 8:20 am

      Hi Leo,

      Great tips that I totally agree with, thanks.

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