Battery state of charge

[mitiempo]

A small solar panel - say 50 or 60 watts - and a basic controller like the Genusun would solve any undercharging issues.

With your current charging scheme how often do you equalize the batteries?

[Maine Sail]

Originally Posted by Don Lucas

Everything is a comprise. Balance of the reduced battery life compared to the extra wear and tear on the engine and the cost of the fuel plus the hassle of going to get it. I prefer in the long run to buy batteries a year or so earlier because I let their SOC be a little less, than to put the wear on the engine just to charge them all the time (plus the current 2 hour round trip to get fuel).

Now this is just my current equipment and will be different in a few years when time to sail off.

One word...... SOLAR....

Leave the boat, it tops off the batts, and you come back the next weekend to a full bank (if sized correctly)... Less wear and tear on the engine and the bank will thank you...

[sailorboy1]

I know, it's the "everything on a boat can be fixed with the correct application of cash" solution.

[Lake-Effect]

From everything I've read, I take the following course for our flooded-cell battery (which is entering its 6th season of service)

- we charge it whenever convenient. Solar top-up usually, a deep charge after a weekend of use. Over the winter I keep it in the basement and charge it once a month
- we discharge it... as much as we reasonably need to.

Conventional wisdom is that they will last longest if you keep them charged up and avoid discharging them below 50%.

[Maine Sail]

Originally Posted by Don Lucas

I know, it's the "everything on a boat can be fixed with the correct application of cash" solution.

Solar is quite inexpensive now days and a system for your bank can easily be done for $400.00 - $500.00 or less if you shop around. if it adds 1-2 years or more to your banks average service life and less wear and tear on your motor and alt then it's a pretty good deal.. And yes buckets full of $$$$$ solves all boat evils...

[Ex-Calif]

There are a couple of different uses. Weekend warrior and full time cruising.

Weekend warriors with 500 a/h probably got too much battery. Running instruments and radios all day then motoring home usually before dark needs very little power.

Wth 210 ah and 40 w of solar my weekend needs are totally covered. My group 24 AGMs are 6 years old and doing fine.

[sailorboy1]

400+ views and only 11 votes! Does this mean people who have read the thread just don't know what their battery's SOC is to be able to vote?

And to all the people talking about solar and wind that is great. But at some SOC point even with those there must be a point when you decide to run your engine/generator . You aren't just saying "forget it" are you?

[tartansail]

Originally Posted by Maine Sail

One word...... SOLAR....

Leave the boat, it tops off the batts, and you come back the next weekend to a full bank (if sized correctly)... Less wear and tear on the engine and the bank will thank you...

I'm struck that, as far north as you are, you are saying "solar" and not "solar or wind". Locally (about 150 miles South?), advice seems to lean more wind with the comment that the solar uptake isn't as reliable as the wind because of the boat swinging unreliably relative to the best solar charging. Are you in the "Go solar or go home" camp or do you see wind gens as a reasonable alternative? If not, why not? TIA.

[barnakiel]

Originally Posted by Don Lucas

(...) And to all the people talking about solar and wind that is great. But at some SOC point even with those there must be a point when you decide to run your engine/generator . You aren't just saying "forget it" are you?

The reason we start the engine (at least every second day, on the passage) is to keep it oiled and make sure it starts fine. If it delivers some amps at the same time then sure we like the fact but we could just as well go without alternator input.

There are different levels of energy demand on boats and we have already twice reduced our banks: from the original 240 to 160, now planning to use only 120 or so as the house bank. That's cutting our consumption by 50% in about 9 years of sailing, cruising and living aboard.

While on the passages, we do not get mad about how well charged the batteries are. If they get to low then we reduce consumption and start the engine very early morning for about half an hour.

If the passage ends at a dock, we always try to plug in and our shore power charger will fill the banks up in about one night.

And then they die and we change them and that's it.

BTW Banks are split here so the starter battery is nearly always 100% up.

b.

[Maine Sail]

Originally Posted by tartansail

I'm struck that, as far north as you are, you are saying "solar" and not "solar or wind". Locally (about 150 miles South?), advice seems to lean more wind with the comment that the solar uptake isn't as reliable as the wind because of the boat swinging unreliably relative to the best solar charging. Are you in the "Go solar or go home" camp or do you see wind gens as a reasonable alternative? If not, why not? TIA.

Actually solar does quite well in Maine, if installed well. If you base it on solar insolation maps our average is Portland is 4.51. NY City is 4.08... Our winds in the summer are also light and solar very often beats wind on daily performance. I have nothing against wind but find solar, more reliable, longer lasting, less expensive, and quiet...

Wind gens are fine but do require more maintenance. I just this winter re-built a 7 year old wind gen. It has had two sets of blades in 7 years and required all new bearings, a bead blast and re-powder coat. The solar panels on this customers boat are 13 years old and show no signs of age and have required zero maintenance since installed (other than wiping bird crap off them). They still have not yet re-installed the wind gen and with their Kyocera panels they are finding they really don't need it. They can run their boat for multiple weeks in Maine on just the solar and this includes running a Frigoboat that stays cold enough to have ice cream.

Properly installed and sized solar works well here in Maine.. For taking batteries from 80% state of charge to 100% SOC, for mooring sailed boats, it is tough to beat solar...

[Lake-Effect]

Originally Posted by Don Lucas

400+ views and only 11 votes! Does this mean people who have read the thread just don't know what their battery's SOC is to be able to vote?

No, it means that it does not boil down to an easy number: first because the state of charge as a percentage is often hard to determine, second because this is the real world - we use our batteries as necessary. Also, the battery performance will depend on battery chemistry and format (flooded, AGM, gel), age of batteries, load as a percentage of bank capacity, performance of the chargers...

But there IS a number in the thread, and in most expert advice about battery sizing: for longer battery life, try to not discharge below 50% of capacity.

Here's a link on sizing.

Originally Posted by Don Lucas

And to all the people talking about solar and wind that is great. But at some SOC point even with those there must be a point when you decide to run your engine/generator . You aren't just saying "forget it" are you?

Of course not. But that decision comes from knowing your boat, and being able to estimate remaining charge based on time and measured voltage.

Selecting a percentage in your poll would be tantamount to saying that there is a failsafe, universal way of establishing the SOC, and that the measurement would be repeatable for any boat, and neither are true.

[Dockhead]

Originally Posted by Don Lucas

Everything is a comprise. Balance of the reduced battery life compared to the extra wear and tear on the engine and the cost of the fuel plus the hassle of going to get it. I prefer in the long run to buy batteries a year or so earlier because I let their SOC be a little less, than to put the wear on the engine just to charge them all the time (plus the current 2 hour round trip to get fuel).

Now this is just my current equipment and will be different in a few years when time to sail off.

+1 !

I save $16,000 a year being on a mooring rather than in a marina on shore power. The mooring without shore power is much harder on batteries -- will reduce their life by half, maybe more, even with me working hard to treat them right. But $2,000 for a set of batteries is small change compared to the savings -- would buy me only a little over a month of berthing. So I willingly go for the same kind of compromise as Don does. And like Don, I am also not willing to run up dozens of hours of genset use or engine use just to get the last nth degree of charge on them.

Batteries are consumables like fuel; how you consume them is a balancing act like anything else on board.

I am, however, hoping that my present set of Trojans will last me until Lithium Ion are ready for prime time!

[Dockhead]

Originally Posted by Lake-Effect

No, it means that it does not boil down to an easy number: first because the state of charge as a percentage is often hard to determine, second because this is the real world - we use our batteries as necessary. Also, the battery performance will depend on battery chemistry and format (flooded, AGM, gel), age of batteries, load as a percentage of bank capacity, performance of the chargers...

But there IS a number in the thread, and in most expert advice about battery sizing: for longer battery life, try to not discharge below 50% of capacity.

Here's a link on sizing.



Of course not. But that decision comes from knowing your boat, and being able to estimate remaining charge based on time and measured voltage.

Selecting a percentage in your poll would be tantamount to saying that there is a failsafe, universal way of establishing the SOC, and that the measurement would be repeatable for any boat, and neither are true.

+1

I measure SOC of my batteries by measuring the voltage with a precise Victron battery monitor at a time when the batts have not been charged or strongly discharged for a few hours. I don't disconnect them so it's not a true open circuit voltage test, but I figure that the results will be close if the rate of discharge has been no more than 4 or 5 amps for a 420 amp/hour (at 24v) battery bank.

I track the amp/hours consumed per the Victron battery monitor versus my quasi-open circuit voltage, and keep an informal log. That gives me another data point and helps me be acutely aware of the SOC.

I follow the same 50% rule as everyone, and like others didn't vote in Don's poll, since I charge not at some particular SOC, but when I can. I group AC power tasks so that I have efficient generator runs, usually once a day, sometimes twice. I will not start up the generator specially to charge batteries unless the SOC falls to 50%, but I usually don't have to make a special generator run just for battery charging. I have a massive 110 amp schoolbus alternator on my main engine (regulated by an Adverc), so a relatively brief bit of motoring puts a lot of charge into the batteries. So unless I'm sitting on the mooring or at anchor somewhere without moving, my batteries get charged from even brief use of the main engine anyway. (The Adverc has an unusual program which seems to help get the batteries over the hump from 80% to 100% -- it will apply the full 28.8v absorption voltage all the way to 100%. It avoids gassing by switching this high voltage on and off at a rate which changes as the batts approach a full charge -- that is, as they accept less and less current. It seems to work well and seems to be much more efficient for that last 80% than what my regular Victron charger does.)

What concerns the generator -- I usually will not charge beyond 80% or so unless I'm using AC power for some other task. That's because the batts are already accepting so little power that it's simply an inefficient use of generator time. So if I'm at anchor or on the mooring for a long period of time, I use the batts between 80% -- and 50%, then back up to 80%, repeat. Any even short passage under motor will usually get the batts up to 100%, so they rarely go more than a few days without a full charge, even if I'm never in a marina. Seems to me like a perfectly decent regime (if I could only stop forgetting to turn stuff off and killing them ).

[Stu Jackson]

Originally Posted by Dockhead

+1 !

I save $16,000 a year being on a mooring rather than in a marina on shore power. The mooring without shore power is much harder on batteries -- will reduce their life by half, maybe more, even with me working hard to treat them right. But $2,000 for a set of batteries is small change compared to the savings -- would buy me only a little over a month of berthing. So I willingly go for the same kind of compromise as Don does. And like Don, I am also not willing to run up dozens of hours of genset use or engine use just to get the last nth degree of charge on them.

Batteries are consumables like fuel; how you consume them is a balancing act like anything else on board.

I am, however, hoping that my present set of Trojans will last me until Lithium Ion are ready for prime time!

If you follow the logic of solar, you can extend the life of yoru batteries by a year. An investment of $500 is a pretty quick payback, isn't it?

[sailorboy1]

Originally Posted by Stu Jackson

If you follow the logic of solar, you can extend the life of yoru batteries by a year. An investment of $500 is a pretty quick payback, isn't it?

Not really. A complete house bank of 460AH cost me $440 last year. If solar extended my battery life from say 4 years to 5 years it only goes from $110/yr to $88/yr. So that $22/yr savings will need over 20 years to pay back.

The pay back really is if you need to run your engine to recharge. If so on my mooring with full time use I figure I would need to run my engine every 2 days for abot 1.5-2 hours (maintaining a SOC between 50-80%). Not counting engine wear I figure this would cost around $400/yr.