Which Battery Monitor ?

[Mark Johnson]

Originally Posted by SvenG

Gentlemen,





Since we now have complete process agreement I suggest we back off on the emotions and focus on the technical issues. Either agree to disagree or bring some new technical point to the table.

This is a really important topic and I myself am looking into the same question for Senta II so I hope we can keep the thread open and constructive ?

Thanks,



-Sven

Sven, If you set up your system the way I have suggested with a large enough house bank in the first place, and bring the batteries up to "full" either every day or every few days, the Link 10 will serve you well and incredibly accurately. The shallower cycles and frequent "top offs", have all of the advantages I've listed, with the only down side being that re-charge is much less efficient at the top of a batteries charge, taking ridiculously long engine runs. (Thus the solar panel suggestion).

Solar is great for the long slow charge that is preferred to "top off" batteries to 100%, primarily because it is exactly the kind of long slow charge that is best for this. It is also quiet, cheaper, and smell free. The lack of this means of topping of batteries, is why so few boats without them, bring their batteries back to 100%. That last 10% would take such a long engine run for so little gain.

My batteries are determined to be "full" NOT just by the Link 10, but by the 3 stage smart solar charge regulator that has had the batteries full, slightly overcharged, LEDs started to flash, shut down most of the charge, and in 13.6v "float mode", since about noon! The fact that my 3 stage solar charge regulator, and the link 10 both show full at about the same time of day, even though they are in no way connected or interfaced, is confirmation that my Link 10 still defines "full" correctly. There is no running error.

My Link 10 never defines my battery as 80%, or any other % full. It simply tells me how many amps down I am in the morning. (usually 35a) If my battery changed in capacity over time, that -35a would in fact represent a different % down on my now downgraded battery bank, because it would not be as large any more. (This is a moot point). The fact remains that if the Link 10 says -35a, that is how much I need to replace that day to top them off, and when it returns to "0 a/h", and my solar's charge controller has shut down, It is all the information that I need. The batteries are full, I have confirmed it two ways, and the Link 10 starts over.

For me it may be that I cycle my batteries down to as little as 90% full, or as much as 80% full. It doesn't change how accurately the Link 10 tells me how many amps down my battery bank is. If someone wanted to cycle their batteries SO low that they really needed to know what % of charge this - X amps represented, they would need to do regular battery capacity test to stay on top of that. The link 10 does not give % of charge, only the number of a/h that have passed through that wire in either direction. Since I have the longest cycle life batteries, (2@6v L-14 Trojans), float them at "full" most of the time, and otherwise bring them back to 100% every day, small battery capacity changes over time, as well as their tendency to self discharge, are so small as to be trivial and not worth calculating or thinking about.

Only a component failure, like a bad cell, or a lightning strike taking out my system, will cause a power problem or monitor error... the way I use my system!

IF someone only brings their batteries back once a week, the amount of a/h error that could be accumulated in that length of time, is insignificant. Much longer than that without a full charge and re-zero, I really don't know, as I don't personally know anyone who does this.

The arguments against these obvious points that I have made, are so out in left field, that I wouldn't have any idea how to respond, except to say what I have already said: "I wasn't talking to you. I was talking to people who have low to moderate a/h usage, want their system to work for as long and as well as mine does, and are willing to make the effort to do it like I'm suggesting. For these folks, this is how it's done"...

BTW, I never said this would be a solution for everybody. The further out one is on the "consumptive scale", the less likely this system is to be useful, without becoming cost or space prohibitive. Practicality has to be taken into account.

I hope this helps Sven, Mark

[SvenG]

Hi Mark,

Originally Posted by Mark Johnson

Sven, If you set up your system the way I have suggested with a large enough house bank in the first place, and bring the batteries up to "full" either every day or every few days, the Link 10 will serve you well and incredibly accurately. The shallower cycles and frequent "top offs", have all of the advantages I've listed, with the only down side being that re-charge is much less efficient at the top of a batteries charge, taking ridiculously long engine runs. (Thus the solar panel suggestion).

The question I have in that case is why do you need the Link if you have a setup that never runs down by more than a few 10s of percent ?

I'm not arguing that your setup isn't doing what you want it to do and as pointed out in another thread, AGMs topped off almost daily (daysailed) can and have lasted 10 years.

Your overlarge house bank and solar top-off sounds like one great solution, but maybe not the great solution for everyone, as you mentioned. It the solution we're leaning towards, but it assumes that we can fit enough solar panels and still be mobile

Thanks,



-Sven

[goboatingnow]

Mark can I ask you two questions

(a) how do you know your link 10 is accurate ? How can you claim 1%. What are you comparing it with

(b) you claim all the link 10 does is amp hour counting. What's the function of the " fuel gauge" on the display. Surely that is attempting to display state of charge. ??

As a bonus question can you identify the issue with amp hour counting ? ( hint peukerts law)

A monitor telling you that for example that your boat consumed say 30 Ah is in itself irrelevant . It's relating that to state of charge that's useful. Monitors can of course determine amp hours very accurately, what they can't do is make an accurate SofC determination. This is a point you have over looked

You have an exemplary system. But in fact the monitor is doing nothing really, since by your own admission you don't stress the system.

My boat consumes over 100ah in 24 hours. Underway and can consume more. Replacing that to 100% is practically impossible while underway by sail. I use my own pc based system to monitor battery consumption but I've spent several years as part of a bigger project, designing Smart chargers and monitors.

Dave

[Mark Johnson]

Originally Posted by SvenG

Hi Mark,



The question I have in that case is why do you need the Link if you have a setup that never runs down by more than a few 10s of percent ?

I'm not arguing that your setup isn't doing what you want it to do and as pointed out in another thread, AGMs topped off almost daily (daysailed) can and have lasted 10 years.

Your overlarge house bank and solar top-off sounds like one great solution, but maybe not the great solution for everyone, as you mentioned. It the solution we're leaning towards, but it assumes that we can fit enough solar panels and still be mobile

Thanks,



-Sven

Sven in my case I set up the boat as energy efficiently as possible, with small, efficient versions of things like a watermaker & the inverter, (Which I seldom use). I also went all LED or fluorescent, and omitted a freezer, oven, or microwave. Otherwise I have all of the bells & whistles. While our Searunner is in the most technologically sophisticated 10% of "Searunners", (which were not designed to be), we are probably among the simplest 10% of modern cruising boats. I mean, we even use a black plastic solar heated garden sprayer for showers. By keeping the moisture in the cockpit, rather than down below, it works great!

This level of going small with simplicity, is how we got down to 40 or so A/h of usage per day. I recognize that this is not for everyone, and only used our situation as an example. It is the one I'm most familiar with!

Our batteries are normally only cycled down from 10% to 20% and this shallow a cycle is overkill. I started out with the larger L-16s @ 380 Ah, rather than my current L-14s @ 340Ah. I started out with the larger batteries before I had an electrical system, or knew how efficient I could get the boat.

I switched down to the smaller L-14s when I ruined my first pair by stupidly letting them run dry. By using "Hydro Caps" I only needed water a few times a year, and it made this blunder possible. Now I water on the first day of each season. At over $500, this is an expensive mistake!

If I ever change them again, I will go down yet some more. This has had it's advantages however. It allows us several days of a slight energy deficit, (due to an almost black, "can't even read" level of overcast skies), without cranking the engine. Also... during the 20 to 30 days out of the year that we do overnighters, our daily consumption goes up to almost 100 A/h per day, if we run the radar, ssb, VHF, auto pilot, etc... Now we are cycling down almost a third, and the solar can't replace all of that.

During this 7% to 10% of the year, (passages with overnighters), we are not all solar. Then I crank the engine at an hour before sun up, when the batteries are at their lowest, and can best absorb the alternator's 35 A. I let it run about an hour, and then the sun is up and the solar panels can put in that last 50 A/h over the day.

It is only the 90% of the time spent at anchor that we are "all solar powered".
Some multihulls have SO much solar that they are covered EVEN overnight at sea, but that requires a lot of room, and cash! Our compromise was what worked for us, and made financial sense, while insuring long battery life and system reliability.

A modified version of this was what I was suggesting for you monohullers with much more limited solar panel room and higher consumption.

If you spend the vast majority of your time on the hook like us, set up your system for that. If it is mostly at sea, set up your system for the load at sea.

If you could "energy economize" to limit your daily A/h consumption to say 100 A/h. Then a pair of our original L-16 batteries would be ample. With this bank and a 100 A/h daily draw, you are talking about cycling less than 1/3, even on a high use day, VS 1/2, which is common. This is easier on the batteries, gives a longer life, and a higher line voltage. It also gives a bit of a cushion for error.

Then IF you could mount say, two 110 W panels on a rack over your davits. This is good for from 30 to perhaps 60 A/h per day, depending on the weather.

Now, crank your engine for its normal daily run, (early in the morning, so you use the BIG amps when the batteries are lowest and can absorb them best). Run only long enough to bring your batteries up from 100 A/h down, to only 50 A/h down.

From here the solar takes over, and your batteries are topped off with the optimal three stage charge, by the end of the day.

At this point, both your solar charge controller, and the Link 10, confirm that you are topped off, the Monitor re-zeros, and as the sun goes down, it accurately counts the A/h going out until the next morning.

If you underestimate the length of your engine run one morning, or it becomes exceptionally overcast, causing your batteries to get no higher than -10A/h by sundown, it won't hurt a thing. You just make a slightly longer engine run the next morning, and since the Link 10 only counts A/h in or out, not % of charge, there is absolutely no accumulated error created by not ALWAYS bringing the batteries ALL the way up to "0". Even several days without getting to 100% charged and re-zeroing the monitor, will cause no problem at all.

The more often you do achieve 100% charged the better, but it is not etched in stone, and even every couple or three days is INFINITELY better than intentionally NEVER even approaching fully charged batteries, like so many cruisers do, because it takes so long to do it with an alternator alone.

IF you can fit within these "moderate parameters", the benefits are all that I have pointed out, and will definitely save money in the long run. On the other hand, if your daily consumption is closer to 200 A/h, it becomes much more problematic to find enough room for more than a token amount of solar.

I ONLY pass this on as a benefit to those that like the idea, and to explain how to do it for them. I have no personal "ax to grind" and don't want to push "my way" of doing things on anyone.

Mark

[Jeff Millar]

Mark, Your comments make very good logic to me, regarding specifically
the last 15 % of the recharge being best done by solar array.
Assuming the 80% charge by the engine driven alternator.
This is true and acceptable.
My idea in the interest of trying to keep recharging with the engine to a
minimum time peroid would be to split my large house bank into 2 house
banks. One would be fully charged on stand-by and yes the last 15% of
its recharge via the solar array.
The bank in operation would be monitored and discharged down to no less
than 50%.
The standby battery would be selected at that time and the other partially
discharged bank immediately recharged to 80% from the engine alternator
and then the solar array would charge it up to full charge.

What is wrong with this concept. Please I also am here to learn from those
willing to share their hands on experience.

[goboatingnow]

for proper bbattery charging, the internal. "car" regulator in your alternator is a terrible choice. Any decent alternator should have an external marine suitable regulator, many of which are 3 stage chargers as well.

Dave

[Jeff Millar]

Stupid comment to make here.
Where we are in a detailed technical concern.

Guess it takes all sorts.

[Pete7]

Jeff, I think it's unnecessarily complicated, requiring manual monitoring and switching the charge across the two banks. Also you are drawing one bank down a lot further than having all the batteries together.

If the bank is 400AH and you use 100 AH a day, splitting the batteries into two x 200AH will mean one half the bank going down to 50% before you change over. Whilst if the batteries are all together in one bank then they are only drawn down to a 75% level so a much gentler discharge level.

Pete

Originally Posted by Jeff Millar

My idea in the interest of trying to keep recharging with the engine to a minimum time peroid would be to split my large house bank into 2 house banks. One would be fully charged on stand-by and yes the last 15% of its recharge via the solar array.
The bank in operation would be monitored and discharged down to no less
than 50%. The standby battery would be selected at that time and the other partially discharged bank immediately recharged to 80% from the engine alternator and then the solar array would charge it up to full charge.
What is wrong with this concept. Please I also am here to learn from those willing to share their hands on experience.

[Maine Sail]

Originally Posted by goboatingnow

for proper bbattery charging, the internal. "car" regulator in your alternator is a terrible choice. Any decent alternator should have an external marine suitable regulator, many of which are 3 stage chargers as well.

Dave

Dumb regs can work just fine if the absorption voltage is correct. Many older dumb regs have the voltage set far to low but most current alts are most often at 14.2-14.6 volts with 14.4 being the most common I see. The idea that all boaters who don't have a "smart" regulator is a "terrible choice" is not applicable to all situations and may not be as "terrible a choice" as you make it out to be in the real world.

If you have GEL Cell, TPPL or AGM or are in a hot climate then temp compensation is a great "smart" feature. I install lots of external regs but also talk many of my customers out of them when they are not necessary for the use/application. No sense in selling my customers something they don't need, as many installers do, when they don't really need it.

[witzgall]

Maretron has a sensor that is NMEA 2000 compliant. To see the data, however, you need to both have the N2K network up and running 24x7, and have a display product (such as their PC software) running 24x7 as well. That would use way too much power, except for some big power boat that has stuff like this running all the time anyways.

Chris

Originally Posted by Maren

Are any of these NMEA 2000 compliant? I've tried looking this up on the web but no real luck there.

[S/V Antares]

"Dumb regs can work just fine if the absorption voltage is correct."

Maine Sail

This is very encouraging to hear. I repowered with a Beta 38 and 100 amp Iskra Alt. that is internally regulated and not easy to change to external. I did not have time to concider alternatives.

I have a link 10 (simple solutions for simple minds) which changed our life (for the positive) as we are on the hook 6 months a year and use the engine for charging about 150 -200 amp hours a day.

Also thaks for the great work you have posted on your "How to site" the SOC info was very enlightening

[Mark Johnson]

Originally Posted by Jeff Millar

Mark, Your comments make very good logic to me, regarding specifically
the last 15 % of the recharge being best done by solar array.
Assuming the 80% charge by the engine driven alternator.
This is true and acceptable.
My idea in the interest of trying to keep recharging with the engine to a
minimum time peroid would be to split my large house bank into 2 house
banks. One would be fully charged on stand-by and yes the last 15% of
its recharge via the solar array.
The bank in operation would be monitored and discharged down to no less
than 50%.
The standby battery would be selected at that time and the other partially
discharged bank immediately recharged to 80% from the engine alternator
and then the solar array would charge it up to full charge.

What is wrong with this concept. Please I also am here to learn from those
willing to share their hands on experience.

I see the logic in what you're saying, and yes, that's one way to go. The down sides are... that it is more "complicated" to have two house banks, and simple is always best. Also, if you have the same amount of batteries, but they make just one larger bank, you will be cycling the house bank to a much shallower % of discharge. This doubles the lifespan of the house batteries, and if monitored carefully, a LARGE reserve in one house bank, (in my view), is safer than a more complicated system with half the house bank's "reserve", always being discharged to the point of not being available. Remember, if you have an engine cranking battery as a back up, the risk of a disaster due to low house batteries, is less. You already have a redundant energy system.

Now, this shallower % of discharge comes with a downside. It exacerbates the issue of batteries only accepting a small portion of the alternators BIG amps, near the top of the batteries' charge.

A good compromise would be to take your one large house bank down to only... 65% charged, bring them up to about 85% with the alternator, early in the morning, and then let the solar panels top off the last 15% over the day, when usage of the batteries is at a minimum.

It can't be over stressed... Money spent converting anchor, running, and reading lights to LEDs, and cabin lights to fluorescents, as well as super insulating a small refrigerator, will save BIG bucks compared to the attempt to generate twice as much power. Microwave ovens and inverters are quite unnecessary "most of the time", and I'd suggest that you only use them when there is no problem topping off the batteries that day.

We run as many things as possible, (like TV, lap top computer, etc.), that take low V DC, on 12V to 19V DC "car adaptors", rather than the AC to DC black box, that they came with, for home use. This makes it where we only need to use the inverter infrequently, to charge nicad batteries and the like.

Most boats can cut their energy consumption in half, and that is a good first move. Then access your boat's energy needs and decide what compromise works for you.

Mark

[goboatingnow]

Originally Posted by Maine Sail

Dumb regs can work just fine if the absorption voltage is correct. Many older dumb regs have the voltage set far to low but most current alts are most often at 14.2-14.6 volts with 14.4 being the most common I see. The idea that all boaters who don't have a "smart" regulator is a "terrible choice" is not applicable to all situations and may not be as "terrible a choice" as you make it out to be in the real world.

If you have GEL Cell, TPPL or AGM or are in a hot climate then temp compensation is a great "smart" feature. I install lots of external regs but also talk many of my customers out of them when they are not necessary for the use/application. No sense in selling my customers something they don't need, as many installers do, when they don't really need it.

I disagree in fact most car alternators are now designed to top up maintenance free batteries and set the max charging voltage at around 14 v especially as they are not temperature compensated. I've never seen standard alternators generate 14.6 volts as this is above the gassing voltage.

It's important to point out that the standard car alternator and it's associated regulator is not designed to charge batteries. Modern alternators provide power to run the cars electrical system. Since cranking an engine takes a very small amount out of a battery. The alternator never really has to do much charging and isn't optimised to do so .

This is why the last 20% of the charge cycle , ie the absorption cycle takes so long with a standard regulator.

The recommended method of charging lead acid is. IU charging , that is constant max current during bulk mode then entering absorption mode with the terminal voltage kept high to generate the shortest absorption cycle consistent with specs. And gassing

All your charging sources be they solar wind , alternator , unless there are of trivial power , should be capable of IU or even IUU charging.

This requires smarter regulators on alternators whose primary design feature is to charge batteries. That's why standard regulators are terrible.

It always surprises me to see people spend large amounts of money or smart AC battery chargers, solar MPPT controllers and then leave one of the most efficient systems saddled with a poor controller.

I think this is because there isn't a simple way to add external regulation to standard alternators and partially it's because the existing regulator " will do" attitude

I would recommend you ensure your existing charging systems are optimised before adding new ones.

Therefor I regard advice that solar should finish off the charge cycle as misplaced. High powered alternators coupled to proper regulators can easily do 100% charges and can even do so quite aggressively if you are prepared to monitor battery water levels ( or even fit an auto watering system).

It's amazing how archaic and poorly instrumented most boats charging systems are.


As to solar my experiences are that short of very large arrays. Most of the time whatever power I generated was mostly consumed by the consumers in the boat. This was especially true under sail. Very rarely did the solar system successfully take the batteries upto 100%, until we shut down the everyday consumers ( like when we left the boat locked down and electrically off them the solar worked great at topping the batteries off.

I have a custom written PC data collection system that allows me to Log the currents and voltages of all my charging sources and my discharge currents etc. It provides a multi day trace of activity and that's what's I base my observations on. I previously in my career did a lot of research and design into battery charging.


Dave

[goboatingnow]

It can't be over stressed... Money spent converting anchor, running, and reading lights to LEDs, and cabin lights to fluorescents, as well as super insulating a small refrigerator, will save BIG bucks compared to the attempt to generate twice as much power. Microwave ovens and inverters are quite unnecessary "most of the time", and I'd suggest that you only use them when there is no problem topping off the batteries that day.

This debate seems to be orientated towards boats that are static. I don't know about you but I developed my energy model based on the case of the boat moving under sail.

I wanted a system that allowed me to run my autopilot , instrumentation , radios, chartplotters underway. ( night time bringing the most energy consumption).

Few people in thoses circumstances get anywhere near 40 ah per day. At anchor I have electric fridge cooling, entertainment systems etc as well as my radio running. Invertors are used as required.

I applaud thoses that can electrically minimalist lifestyles. But they are the minority. We need to focus on the middle ground of users not the outliers

Dave

[Mark Johnson]

Dave, the only reason I suggested that "solar is better for topping off your batteries" is this: If you are 60 Ah down and have a smart powerful alternator, the first 30 Ah will charge quickly, and the last 30 Ah will take several times as long. No matter how powerful or smart the alternator, batteries will only accept a slow, steady, low A charge, near their top 15% or so. It is just a waste to run a 50 HP engine, opperateing a 150 A alternator, to put 20 A into a battery bank for two hours. It is just incredibly inefficient. This is why most folks who charge only with their alternator, seldom top off the batteries every day like we do. They have lower line V, things run less efficiently, and the batteries last half as long.

I also had a bad experience with solar on both of my last two boats, (going back to the early 70s). It is a different world now technology wise, I know more about what I'm doing, and we now get 100% of our energy from 285W of solar panels, 95% of the year. (Our boat consumes about 40 Ah / day).

For 100% solar... One needs to have an energy efficient boat, enough battery size to run the boat for a couple days if necessary, (staying above 50%), and have "twice" the solar power than you need to replace your daily consumption. This is why we STILL get to 100%, EVEN on cloudy days.

For more consumptive boats that haven't the room for enough solar, the compromise I suggested makes sense. You can be 100 Ah down, and put back the first 80 Ah with a big "smart" alternator in the morning. It might only take 45 minutes???
Then, with a single 110W panel on your davits, you should get about 30+ more Ah over the day. IF your boat continued to consume 10 Ah over the sunny hours of the day, then the solar's extra 20 Ah will have topped off the batteries, in the long slow way that they require at the top of their charge.

If after crunching the numbers it doesn't work out, you just add another panel, or a longer morning alternator run. What ever floats your boat...

The point remains the same. Topping off your batteries daily pays many dividends, and solar is a more practical way to do it than an alternator. Like almost everything, it works well if you set it up appropriately, and not so well if you ignore the rules I've pointed out and still expect a good result.

It really makes sense for a lot of folks...

Mark