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View Poll Results: What Battery Monitor system do you run?
Basic Amp and Volt gauges 41 20.00%
Link 10 29 14.15%
Link 20 22 10.73%
Link 1000 11 5.37%
Link 2000 29 14.15%
Trimetric 2020 8 3.90%
DOC Wattson model R102 0 0%
Victron BMV 602 21 10.24%
CruzPro VAH-35 4 1.95%
Clipper Battery Monitor BM-1 11 5.37%
Other - please add info to thread! 29 14.15%
Voters: 205. You may not vote on this poll

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Old 05-04-2011, 17:25   #181
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Re: Which Battery Monitor ?

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Originally Posted by goboatingnow View Post
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

Agreed, that the days at sea are at least twice as consumptive. This is when our solar self sufficiency is a "hybrid compromise". During the 20 days a year or so that we do overnighters, we crank the engine at 6:00 AM and in an hour have the first 40 of the 80 Ah that we're down. Our panels then "both" run the boat, (with a watermaker, computer, autopilot, VHF, GPS, SSB, refrigeration, stereo, as well as fans), AND put back the last 40 Ah of power needed to top off the batteries before sun down. This is how I know that the "combination approach" works so well.

Even if you spend a third or the year at sea, you can do what you're already doing, (but with less engine time), and the other two thirds of the year, the solar tops off your batteries as I suggested.

Very few people spend as much time at sea as on the hook. This is why it makes sense to be as energy efficient & energy self sufficient during the majority of the time makes sense. Then, do what ever is necessary during the minority of the time spent at sea, with the knowledge that even an engine failure will not leave you with NO power, just less... You may have to hand steer some, but your GPS, lights & radios at least will have power.
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Old 05-04-2011, 17:38   #182
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I don't disagree but I find I have close to 100 ah/24 hours at anchor I then find that my panels are mostly just servicing the ongoing consumers. Little or nothing is going to top up the batteries. I have found that once I am prepared to top up with water I can aggressively push the absorption phase with the alternator ( while still staying inside manufacturers specs). I have good spiral wound traction batteries that can take the punishment. I am considering building a diesel DC generator to remove the need to start the main engine and to eliminate the light loading problem. ( and perhaps fitting a auto watering system)

I love solar , but it never quite delivers what you need.

Ps I also have some thundersky lithiums that I'm designing a BMS for. No need to ever charge to 100% and no absorption phase anyway And a peukerts exponent of effectively 1.
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Old 15-04-2011, 15:30   #183
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Re: Which Battery Monitor ?

well, what nexst ?
the best of these brands, are Mastervolt and Victron.

the rest is trying to get there.

say no more.
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Old 15-04-2011, 19:39   #184
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Re: Which Battery Monitor ?

I never really felt I need anything aside than the Volt meter.

Our boat is all basics - only two energy sources (the alternator and the solars) so if the lamps are dim ... I know it is time to do something. But somehow the lights here hardly ever get dim.

Amp meter is fine to, if you have one but ours has been broken.

I have the Trimetric onboard still in its box. I think I will get it a small shunt one day now and install it - will be so nice to worry about all those Amps going in and out.

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Old 13-06-2016, 15:57   #185
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Re: Which Battery Monitor ?

I have just stumbled upon this thread. As an EE with extensive experience designing, installing and maintaining sailboat DC systems, I can tell you that there is a lot of detail in this thread, some of which is close – and a lot that is not.

For what it is worth (and that mayn’t be much) in our boat we run a Cruising Equipment Company AH-2+ (and have for the last 20+ years), and it is as good a monitoring system as they get. The AH series was the successor to the Quad Cycle (also a Cruising Equipment product, but primarily intended for use with flooded cells), and the original Link systems (sold by Xantrex) were essentially a repackaged AH system (after Cruising Equipment and Heart Interface were sold to Xantrex).

There is only one way to determine with any precision and accuracy the “state of charge” of a deep cycle lead-acid battery: measuring the specific gravity of the electrolyte. This is not possible (at least outside of a laboratory) with gels or AGMs, and not feasible in a sailboat with any battery type.

So what we do – and in the real world all we can do – is approximate when it is time to start charging by monitoring the amount of energy removed from the battery since it was last “full,” in units of amp-hours. In theory, if we know the nominal capacity of a battery (say 96 AH @ 20 hours for a G31 Sonnenschein-pattern gel), and if we know we have taken 29 AH out of it since fully charge at a rate not materially different from 5A, then the battery has been discharged about 30% (i.e., has about 70% remaining). I stress: “about.”

Any halfway decent AH meter will be perfectly accurate – at measuring and displaying integrated AH flowing through the shunts over time. What isn’t accurate or precise is what this means about state of charge, which is affected by factors the meter cannot evaluate. The dominant of these collateral factors is rate of discharge: your 96AH battery is only nominally capable of 96 AH at the 5A discharge rate: it is actually a smaller capacity battery at a higher rate and a (slightly) higher capacity battery at a lower rate. Other collaterals include temperature, plate warpage (caused by excessive current discharge) and sulfation (caused by allowing a partially discharged lead acid battery to sit for a long time with being fully recharged).

What is a fully charged battery? There is one easy way to tell – and, apart from specific gravity readings, only one way: put the battery on a competent three-stage shore-powered charger for an extended period of time. When at float voltage, the battery acceptance goes to 0A (which may indicate on the meter as much as 0.1A input, on account of noise), the battery is fully charged. Your battery monitor may indicate a positive number of AH, but that is meaningless; the “extra” AH “into” the battery was actually spent as heat. A good monitor will begin counting “down” from a full battery as soon as load is put on it. (That is to say, it will not take credit for the positive AH number.)

When to recharge? At least by the time the battery has been discharged to the 50% point, and in real life the life of the battery will be far longer if you recharge sooner. So if you figure you’ll need about 100 AH between charging sessions, you need at least a 200 AH rated battery, and 300 AH would be better.

How long to recharge? If recharging off your propulsion engine and an alternator, as someone noted it doesn’t make sense to try to fully recharge the battery this way. One reason is that it is inefficient, as battery acceptance will taper to a small amount regardless of alternator rating and you’ll burn an awful lot of diesel. (And why does your super-duper alternator not put out “oodles” of amps? Battery acceptance rate is one factor, but another is that your alternator’s rating is based on an alternator shaft speed of 5,000 RPM (in most installations, alternator speed is twice that of engine speed, which means running the engine at 2,700 RPM. And your alternator rating is based on an internal case temperature of 70F (except for those made by Hehr Power Systems), whereas the real internal temperature of your alternator after a few minutes of running is closer to 175-200F.) Another reason is that running a 50 hp engine to spin a 2 hp alternator (that, in fact, may be imposing less than ½ hp of load) will eventually destroy your propulsion engine.

If recharging from a genset, the efficiency factors are similar, except that the genset is a smaller engine, so it will take longer to destroy it.

Some solar systems may be capable of fully recharging a battery; most aren’t.

So it is no coincidence that the folks who get 10 years or more out of a set of high grade deep cycle batteries are those who get to shore power at least one full day every two weeks and have a good three-stage shore-power powered charger.

Unfortunately, the AH line of monitors hasn’t been available for a long time, and the original Links for not quite as long. I’ve encountered a whole bunch of other products, some only casually, and I’ve been underwhelmed – in part by what they do (or don’t do) and in part by the ambiguity (if not outright fiction) in what they purport to display. If I were doing this again, I’d go for the Blue Sea Systems VSM.

Sorry for the long post, folks, if anyone is still awake.
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Old 14-06-2016, 22:46   #186
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Re: Which Battery Monitor ?

Quote:
Originally Posted by RKG View Post
I have just stumbled upon this thread. As an EE with extensive experience designing, installing and maintaining sailboat DC systems, I can tell you that there is a lot of detail in this thread, some of which is close – and a lot that is not.

For what it is worth (and that mayn’t be much) in our boat we run a Cruising Equipment Company AH-2+ (and have for the last 20+ years), and it is as good a monitoring system as they get. The AH series was the successor to the Quad Cycle (also a Cruising Equipment product, but primarily intended for use with flooded cells), and the original Link systems (sold by Xantrex) were essentially a repackaged AH system (after Cruising Equipment and Heart Interface were sold to Xantrex).

There is only one way to determine with any precision and accuracy the “state of charge” of a deep cycle lead-acid battery: measuring the specific gravity of the electrolyte. This is not possible (at least outside of a laboratory) with gels or AGMs, and not feasible in a sailboat with any battery type.

So what we do – and in the real world all we can do – is approximate when it is time to start charging by monitoring the amount of energy removed from the battery since it was last “full,” in units of amp-hours. In theory, if we know the nominal capacity of a battery (say 96 AH @ 20 hours for a G31 Sonnenschein-pattern gel), and if we know we have taken 29 AH out of it since fully charge at a rate not materially different from 5A, then the battery has been discharged about 30% (i.e., has about 70% remaining). I stress: “about.”

Any halfway decent AH meter will be perfectly accurate – at measuring and displaying integrated AH flowing through the shunts over time. What isn’t accurate or precise is what this means about state of charge, which is affected by factors the meter cannot evaluate. The dominant of these collateral factors is rate of discharge: your 96AH battery is only nominally capable of 96 AH at the 5A discharge rate: it is actually a smaller capacity battery at a higher rate and a (slightly) higher capacity battery at a lower rate. Other collaterals include temperature, plate warpage (caused by excessive current discharge) and sulfation (caused by allowing a partially discharged lead acid battery to sit for a long time with being fully recharged).

What is a fully charged battery? There is one easy way to tell – and, apart from specific gravity readings, only one way: put the battery on a competent three-stage shore-powered charger for an extended period of time. When at float voltage, the battery acceptance goes to 0A (which may indicate on the meter as much as 0.1A input, on account of noise), the battery is fully charged. Your battery monitor may indicate a positive number of AH, but that is meaningless; the “extra” AH “into” the battery was actually spent as heat. A good monitor will begin counting “down” from a full battery as soon as load is put on it. (That is to say, it will not take credit for the positive AH number.)

When to recharge? At least by the time the battery has been discharged to the 50% point, and in real life the life of the battery will be far longer if you recharge sooner. So if you figure you’ll need about 100 AH between charging sessions, you need at least a 200 AH rated battery, and 300 AH would be better.

How long to recharge? If recharging off your propulsion engine and an alternator, as someone noted it doesn’t make sense to try to fully recharge the battery this way. One reason is that it is inefficient, as battery acceptance will taper to a small amount regardless of alternator rating and you’ll burn an awful lot of diesel. (And why does your super-duper alternator not put out “oodles” of amps? Battery acceptance rate is one factor, but another is that your alternator’s rating is based on an alternator shaft speed of 5,000 RPM (in most installations, alternator speed is twice that of engine speed, which means running the engine at 2,700 RPM. And your alternator rating is based on an internal case temperature of 70F (except for those made by Hehr Power Systems), whereas the real internal temperature of your alternator after a few minutes of running is closer to 175-200F.) Another reason is that running a 50 hp engine to spin a 2 hp alternator (that, in fact, may be imposing less than ½ hp of load) will eventually destroy your propulsion engine.

If recharging from a genset, the efficiency factors are similar, except that the genset is a smaller engine, so it will take longer to destroy it.

Some solar systems may be capable of fully recharging a battery; most aren’t.

So it is no coincidence that the folks who get 10 years or more out of a set of high grade deep cycle batteries are those who get to shore power at least one full day every two weeks and have a good three-stage shore-power powered charger.

Unfortunately, the AH line of monitors hasn’t been available for a long time, and the original Links for not quite as long. I’ve encountered a whole bunch of other products, some only casually, and I’ve been underwhelmed – in part by what they do (or don’t do) and in part by the ambiguity (if not outright fiction) in what they purport to display. If I were doing this again, I’d go for the Blue Sea Systems VSM.

Sorry for the long post, folks, if anyone is still awake.
Talk about a necropost! That thread died down five years ago.

A much more recent thread:

Energy Monitors and true battery state question


I think you have described pretty well what can go wrong when counting amp/hours in and amp/hours out to determine state of charge of a battery bank. But in my opinion you don't go quite far enough with the implications of all of that. In fact empirical testing (by our own MaineSail, and by the British Army) shows that the factors you describe make counting amps either totally useless or nearly useless (depending on your point of view) for determining state of charge of a lead acid battery bank.

The root problem is that a lead acid battery simply does not contain a fixed amount of amp-hours of power, which can be related to the nominal capacity of the battery. It varies greatly according to Peukert, condition of the battery, temperature, and other factors, and is changing all the time.

And what is worse, the errors in this method all tend to OVERSTATE the bank's state of a charge, which means that there will be a tendency to draw it down further than you think you are, which can damage it. When I was using an amp-counting meter, I programmed in a discount for this -- I set the battery capacity to not 100% of nominal capacity but 50%. And I tried not to draw the bank down to less than 30% of this. In other words, I fudged the capacity down, since I knew I couldn't know it. This worked to prevent damaging overdischarge, but I was not using the bank's capacity very well.


I realized all this a few years ago and basically abandoned the amp-counting method (and sold my Victron battery monitors on Fleabay). I went back to basics and made a chart of Open Circuit Voltage vs State of Charge vs Specific Gravity, based on data from the Trojan manual, and stuck it on my nav table.

The logic of doing this was that although allowing the batteries to settle without load or charging for 24 hours (or whatever) to get a true open circuit voltage reading is obviously not practical on a daily basis, any error of just reading the current voltage with no big loads on, will UNDERSTATE the state of charge of the bank, which is a harmless error other than you might be charging somewhat earlier than you otherwise could do.

I did this for about three years, and occasionally checked the specific gravity of the bank to see how accurate a picture I was getting this way. The answer was -- surprisingly accurate. Different banks on different boats behave in different ways -- if you have a very small bank with very large loads this method will not work as well, because the voltage will be more influenced by the momentary loads, but my experience shows that with a reasonably large bank (in my case, 420a/h * 24v), even with fairly large loads, it works very well indeed, and far better than an amp-counting battery monitor. Better in two ways -- it's more accurate, and because any error is harmless.

The only drawback to this method, in my opinion, is that even if you have a very good picture of the state of charge of the bank during discharge, you have no picture at all during charging, and you won't know how much charging you've managed to do with a partial charge until the surface charge is off some time after you stop charging. If you ONLY charged with a battery charger, you might overcome this by mapping how the voltage rises with your particular charger vs state of charge achieved as measured by SG, but if you charge with multiple sources then this won't work.


And that was why I ended up installing a Merlin SmartGauge (now sold by Balmar, as the Balmar Smartgauge, the same device but marked up 100%). This has been thoroughly tested by MaineSail (Smart Gauge Battery Monitoring Unit Photo Gallery by Compass Marine How To at pbase.com), and is also the device now being used in most new military and emergency vehicles to measure state of charge. It works by comparing voltage with voltage curves which it "learns" on your vessel. It has been shown to be far more accurate than amp/hour counting battery monitors, HOWEVER --

As MaineSail discovered, it does not do a very good job in figuring out how much charge you've gotten INTO the batteries with a partial charge -- the same thing I am unable to figure out with my own voltage-watching method.


Maybe someday someone will invent a battery monitor which BOTH watches amp/hours in and out, and also watches voltage as the SmartGauge does. If you made voltage curves based on amps going in, and then have the device "learn" what state of charge is being achieved by comparing to the state of charge measured by the plain voltage curve after surface charge is gone -- then you would have accurate information about that.


So meanwhile in my opinion although the SmartGauge is more convenient, you really can hardly beat intelligent voltage watching, for which you don't need any equipment at all other than an accurate volt meter, connected directly to the batteries.
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Old 15-06-2016, 13:44   #187
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Re: Which Battery Monitor ?

And I thought the Link system was the be-all-to-end-all.

Since I have sold the boat and have only a couple of batteries I use for the Jon boat etc I use a Voltmeter. Nice to know I am ok.

All that stuff sold (think if the money!) in that past to people like me.....
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Old 15-06-2016, 13:55   #188
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Re: Which Battery Monitor ?

Had a battery monitor... once. That was enough for me! Never used anything more than a voltmeter since. You use about the same everyday, you put back in what you need. it doesn't vary that much. You'll know if something has changed.
However if you are bored and need something to do, trying to figure out, adjust and keep up with a monitor can fill that time.... assuming you have one of those boats that never needs maintenance.... :>)
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Old 15-06-2016, 14:46   #189
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Re: Which Battery Monitor ?

This is an absurd obsession. I have Link.. it read each bank voltage accurately for my use... and tells me amps in and amps out. I've never been stuck with dead batteries... and I imagine few are.

I can tell when my batts are nearing the end of the service life by how soon they need charge and how quickly they appear to recharge.
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Old 18-06-2016, 14:12   #190
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Re: Which Battery Monitor ?

I read for months about battery SOC, and eventually bought a Victron. Mainly because I wanted an ammeter, that showed me +ve and -ve, and they were nearly as expensive as the Victron.
The ammeter helps find the last rogue power users, and let's me reduce engine rpm when charging at anchor, as the amps accepted by the battery fall as SOC goes up, resistance goes up, and I can reduce rpm as more rpm is not 'pushing' more amps into the battery. I often start charging at 1700rpm or so and can reduce to about 1200rpm after only 20 or 30 minutes. I'm sure without an ammeter some would be revving their engines way beyond what is needed for max alternator output. if it's unclear, I might get 25A from the alternator, and increasing revs, does NOT increase Amps. Simple ohms law.
(I only have a 130AH battery and a 45A alternator but the same applies to any basic battery/charging)


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