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Old 07-10-2016, 10:26   #31
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Re: Battery Monitor, which brand, which type

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Originally Posted by Dockhead View Post

The volts and amps readings are useful, but amp-counting state of charge is, in my opinion, worse than useless, for the reasons I stated above.
If you dock often to fully charge, amp counters work awesome. As they will reset. If you're in the hook for months with no full charges they will probably go out if Sync


As for the battery capacity dropping over time it's pretty much a non issue. evenently you're notice you get less from the bank. Actually with a soc meter you would never notice reduced capacity. Because it's not telling you capacity.

If the battery capacity drops 20%. And you start draining to an actual 40% when the meter says 50%. Yes you are hurting batteries more. But they are already garbage anyways. So it doesn't matter. As they need Replacing anyways.
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Old 07-10-2016, 11:52   #32
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Re: Battery Monitor, which brand, which type

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If you dock often to fully charge, amp counters work awesome. As they will reset. If you're in the hook for months with no full charges they will probably go out if Sync


As for the battery capacity dropping over time it's pretty much a non issue. evenently you're notice you get less from the bank. Actually with a soc meter you would never notice reduced capacity. Because it's not telling you capacity.

If the battery capacity drops 20%. And you start draining to an actual 40% when the meter says 50%. Yes you are hurting batteries more. But they are already garbage anyways. So it doesn't matter. As they need Replacing anyways.
I also run a 20 hr discharge once a year in the spring to see how many ah the bank can really provide. With golf cart wet cells the performance is pretty flat until near end of life.

An additional fun function of the Victron BMV702 is mid point voltage monitoring.

When the top to bottom voltage imbalance at the end of charge gets significant (say 1%) that appears to correlate well with hydrometer readings of the individual cells being out of balance. It is a great indicator of when to equalize the bank.

Interestingly, for fun, each of the two parallel strings of 4 golf cart batteries (24v system) has an independent BMV702 and independent mid point monitoring.

I have found that one string is extremely stable. The other side was always a bit "odd" tending to fall out of balance rather than converging. I could tell one of the batteries acted "different" from the first cycle. I did all sorts of parallel balancing at the 6v level (like one would initially balance a lithium bank) and that side tends to wander a bit. Voltages are very flat when in the low float victron calls storage. High current charging is flat until the last hour of an at the dock recharge. On discharge the bank is also very flat.

It's fun as I now have lots of interesting (and of questionable usefullness) data to contemplate.

I do have a fully victron system which talks across a common interface, thus the inverter knows the soc from the ah meter and the like. So I have a bias for "in family" solutions.

Sent from my SM-G935V using Cruisers Sailing Forum mobile app
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Old 07-10-2016, 12:44   #33
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Re: Battery Monitor, which brand, which type

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it's wired as a panel draw meter. like I said. it's in the correct spot for a panel draw meter. it's in the wrong spot for a battery monitor. if you add the victron the new shunt will go next to the battery instead. the existing one can be left as is.
Ok. This thread has really made me re examine what I am trying to do.

So it seems that what I have right now will actually show me Battery V and I can figure out SOC from tables for that.

The panel does show me A being consumed, not very accurately, but it does actually work. If I only turn on 1 switch at a time, it will show me the draw of say the fridge, or the electronics, or both.

The fact that I jumped the shunt on my solar (see diagram, my solar neg goes direct to battery, not top of shunt, and yes, there are fuses for each controller) is actually good in the sense that panel is reading only As being consumed, which is what I want to see.

I guess what I want to see more than anything is A being put in from the panels. Like I said, the controller shows this, but it takes 5 minutes and ripping the bed apart to get to.

So a simple A meter might do the trick. I guess what I need is a shunt between the controller and the battery to measure this? I am assuming there is a shunt in the controller to calculate As.

Is there anything wrong with my logic?
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Old 07-10-2016, 21:41   #34
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Re: Battery Monitor, which brand, which type

if you want to see the solar output then yes you need a current meter/ shunt on the solar line. or maybe move your controller where it is more visible? or maybe it has a remote viewing panel?

a battery monitor such as the victron will give you a net value. it goes right beside the battery and sees everything going in and out and gives you the net total. IE if you are drawing 10a and the solar is putting in 5. the battery monitor will say -5. so with the victron you wouldn't know what the solar was doing unless you turned off all loads to read it. (or turned off solar to see change)

the downside to panel draw meters is often inverters, heating systems etc are wired direct to battery so the panel gauge may be missing things. and you may be using more then you think. this is where a shunt right at battery is benifical and see's all loads. if you have a simple boat with everything off the panel then it's probably not a issue.
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Old 08-10-2016, 04:00   #35
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Re: Battery Monitor, which brand, which type

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if you want to see the solar output then yes you need a current meter/ shunt on the solar line. or maybe move your controller where it is more visible? or maybe it has a remote viewing panel?

a battery monitor such as the victron will give you a net value. it goes right beside the battery and sees everything going in and out and gives you the net total. IE if you are drawing 10a and the solar is putting in 5. the battery monitor will say -5. so with the victron you wouldn't know what the solar was doing unless you turned off all loads to read it. (or turned off solar to see change)

the downside to panel draw meters is often inverters, heating systems etc are wired direct to battery so the panel gauge may be missing things. and you may be using more then you think. this is where a shunt right at battery is benifical and see's all loads. if you have a simple boat with everything off the panel then it's probably not a issue.
I think it's really interesting to see how current is flowing in different places.

Because of the configuration of my bank, I cannot unfortunately see current in and out of the battery bank. That's because my bank is split in two different places with no common ground cable. I could only do it if I could somehow aggregate the readings from two different shunts. I haven't found a way to do that, and don't feel it's worth the bother to watch two different ammeters and aggregate in my head.

I do monitor output of my alternator, and will probably add a hall effect sensor at my charger/inverter to monitor DC current going in and out.

That's on the DC side. On the AC side, I monitor current coming in from shorepower or generator, and separately I monitor current being consumed via the AC panel (the difference is battery charger consumption including DC loads).
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Old 08-10-2016, 08:24   #36
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Re: Battery Monitor, which brand, which type

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if you want to see the solar output then yes you need a current meter/ shunt on the solar line. or maybe move your controller where it is more visible? or maybe it has a remote viewing panel?

a battery monitor such as the victron will give you a net value. it goes right beside the battery and sees everything going in and out and gives you the net total. IE if you are drawing 10a and the solar is putting in 5. the battery monitor will say -5. so with the victron you wouldn't know what the solar was doing unless you turned off all loads to read it. (or turned off solar to see change)

the downside to panel draw meters is often inverters, heating systems etc are wired direct to battery so the panel gauge may be missing things. and you may be using more then you think. this is where a shunt right at battery is benifical and see's all loads. if you have a simple boat with everything off the panel then it's probably not a issue.
Thanks. Unfortunately, I have an inexpensive controller

https://www.amazon.com/ECO-WORTHY-Ch.../dp/B00FF1KGT4

and like I said, it's under the berth in a stateroom. No remote. Would need about 6' more of wire back to battery, which is located right next to it, to bring it out so it's always visible. From your suggestion, would be easier to just put a shunt and inexpensive analog meter. Do I lead this off the pos or neg terminal in my diagram above. I was thinking of putting the shunt from battery post direct to small bus bar, where I would put both wires from each controller, so just a 4 screw bus bar.

Appreciate you input. Thanks again.

@dockhead, impressed that you monitor each item. I am more concerned at the top level, to make sure enough As are going in as coming out, pretty much everything is at the panel. Boat is at a mooring, but when out, it hits a dock every few days, and 2 engines are run at least an hour a day. Currently, I don't have an inverter, so it is just fridge , electronics, and LED cabin lights that draw.
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Old 27-10-2016, 09:10   #37
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Re: Battery Monitor, which brand, which type

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I've tried all these things.

The SmartGauge is far more accurate, and accurate enough, but ..... it only works when you're discharging your batteries; it can't tell how much charge you've put in while you're charging.....
I've just caught up with this thread - after going sailing! This statement is wrong! It does follow the SOC when charging, but it only claims a 10% accuracy. Yes it is much more accurate on discharge. But 10% accuracy is far better than a shunt based Battery Monitor that is not keeping in sync with the battery SOC, or a voltage SOC chart that means nothing during charging.

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.....Previously I sort of liked the SmartGauge, but now I've become convinced that it is basically useless. ........
I think these are pretty strong words - especially from a moderator who should know better. To say something is useless without qualifying that is very irresponsible.

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This could be done using the SmartGauge alarm output function.... It's definitely an argument for having a SmartGauge instead of just a voltmeter.....
Ah now suddenly it might be useful to you! Read the manual and see how many alarms there really are - not just two.

There are much better and more accurate posts on SmartGauge.

Just to add a bit of background here.

The SmartGauge technology has just been installed on the M1 Abrahams tank refits by Merlin Equipment from the UK who own SmartGauge. They claim a 1% accuracy for SOC measurements. They also use their Datacell software with shunts to compare SmartGauge results to shunt based results and this gives them a Battery State of Health to within 2%.

So can the SmartGauge really be useless? I've had mine for 8 years and I think it does exactly what it says on the tin!
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Old 27-10-2016, 10:26   #38
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Re: Battery Monitor, which brand, which type

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I've just caught up with this thread - after going sailing! This statement is wrong! It does follow the SOC when charging, but it only claims a 10% accuracy. Yes it is much more accurate on discharge. But 10% accuracy is far better than a shunt based Battery Monitor that is not keeping in sync with the battery SOC, or a voltage SOC chart that means nothing during charging.



I think these are pretty strong words - especially from a moderator who should know better. To say something is useless without qualifying that is very irresponsible.


Ah now suddenly it might be useful to you! Read the manual and see how many alarms there really are - not just two.

There are much better and more accurate posts on SmartGauge.

Just to add a bit of background here.

The SmartGauge technology has just been installed on the M1 Abrahams tank refits by Merlin Equipment from the UK who own SmartGauge. They claim a 1% accuracy for SOC measurements. They also use their Datacell software with shunts to compare SmartGauge results to shunt based results and this gives them a Battery State of Health to within 2%.

So can the SmartGauge really be useless? I've had mine for 8 years and I think it does exactly what it says on the tin!
I am describing my experiences and expressing my opinion after using various battery monitors over significant periods of time. YMMV.

The SmartGauge is the best of the lot -- as I've said. It gives an extremely accurate reading of SOC when the battery is discharging -- I have checked it against hydrometer readings -- have you?

While charging, on the other hand, it has no clue and is not within 10% or even 20%, at least not on my boat. It might be able to do better on boats with different charging profiles, but on my boat it is really clueless in this situation. This is inherent to the technology.

But the bottom line is that it does not tell you anything which an ordinary voltmeter tells you. It saves you from looking up against the table, and it has an alarm output which could be very useful to some. AND the price is more than fair -- IF you buy in the UK (rather than through Balmar, who mark it up double). Another big point in its favor is that it will not mislead you like amp-counting meters inevitably will that your batteries have a higher state of charge than they actually have -- meaning, it will do no harm.

So I wouldn't say it's pointless to have, but unless you really need the alarm output, it's not doing much.

This is just my opinion, but it was formed not out of thin air and good feelings, but on the basis of very many data points comparing the raw voltage reading to the units statement of SOC, and tests of battery specific gravity. This testing shows that you can get the same information from a $5 voltmeter, if it's properly wired.
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Old 27-10-2016, 11:06   #39
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Re: Battery Monitor, which brand, which type

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....While charging, on the other hand, it has no clue and is not within 10% or even 20%, at least not on my boat. It might be able to do better on boats with different charging profiles, but on my boat it is really clueless in this situation. This is inherent to the technology......
Thanks for very much for your quick response.

So please explain how you can compare accuracy. How can you tell the SOC from your voltage readings - when the charger has reached the absorption stage - and it is siting there for maybe 5 hours at the same voltage. The SmartGauge will give you a rising SOC - your constant voltage tells you nothing. SmartGauge is constantly learning and correcting itself. So if the charging started at 50% it can work out the rise in the SOC. If the charging stated at 80% it will increase accordingly - within 10% accuracy.

It is doing 1100 voltage measurements a second - far more than you can do - and it is not just measuring voltage, but doing small load tests and AC impedance spectrography tests. Please see the other SmartGauge threads for more info on this.
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Old 27-10-2016, 11:16   #40
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Re: Battery Monitor, which brand, which type

I have followed this thread with great interest and would like to add my thoughts to the subject. There are many ways to skin this cat as the posts show but to go back to the beginning the original idea was to monitor the output of the solar panels. My boat sits at the dock and I rely on my solar panel to keep my batteries charged. I installed a Tri-Metric battery monitor (Bogart Engineering Model TM2030) and find that it is perfect for this task. You can program it to suit your particular batteries/charging regimen etc and it allows you to go back and look over a period of time (history function) to see what has gone in/out of the batteries. Yes, I do monitor the specific gravity, equalize and all the other good stuff from time to time and tweak the programming as the batteries age but for the sheer convenience to see just how my panel is working its pretty hard to beat.
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Old 27-10-2016, 11:33   #41
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Re: Battery Monitor, which brand, which type

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Thanks for very much for your quick response.

So please explain how you can compare accuracy. How can you tell the SOC from your voltage readings - when the charger has reached the absorption stage - and it is siting there for maybe 5 hours at the same voltage. The SmartGauge will give you a rising SOC - your constant voltage tells you nothing. SmartGauge is constantly learning and correcting itself. So if the charging started at 50% it can work out the rise in the SOC. If the charging stated at 80% it will increase accordingly - within 10% accuracy.

It is doing 1100 voltage measurements a second - far more than you can do - and it is not just measuring voltage, but doing small load tests and AC impedance spectrography tests. Please see the other SmartGauge threads for more info on this.
The bolded text is the answer why the SmartGauge can't read SOC during charging.

It can learn all it wants -- but with no data, it can't tell anything. Just watch your own SmartGauge in action and you will clearly see how it works. It estimates -- very conservatively -- that some charge is going in, when the voltage is constant during absorption, and will let the calculated SOC rise slowly. Take the charge off (shut down the generator) and it will continue to read 65% or whatever for about an hour, then it will jump to 90% or whatever. It clearly has a timer which will hold it back from drawing conclusions about SOC until a certain amount of time has passed for the surface charge to come off. When you observe this jump, you see how far off it is, until it gets its feet.


As to impedence spectrography -- if any additional data is being gathered this way, I have not been able to observe any sign of it. During discharge, the correspondence between SmartGauge calculated SOC and SOC calculated from system voltage (even with a small load on) and the Trojan battery table is practically 100% .

If you understand how impedence spectrography can be used practically for determing SOC, I would be glad to be enlightened. I actually own an expensive Argo EIS device, which I use for measuring internal resistance and latent capacity of batteries, to keep up with how they are aging and how consistent they are between them. But this device does not read SOC this way.
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Old 27-10-2016, 22:47   #42
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Re: Battery Monitor, which brand, which type

it can't tell how much charge you've put in while you're charging.....

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I've just caught up with this thread - after going sailing! This statement is wrong!.......
Am I missing something here?

As far as I am aware the smartgauge can do a good job of telling how full the bucket is but has no idea how big the bucket is. Can it also tell you how much has gone into the bucket?
Can it track how many Ah (how much charge you've put in) have gone in to the batteries?

Fantastic if it could, I'd fit one for sure.
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Old 27-10-2016, 22:56   #43
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Re: Battery Monitor, which brand, which type

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it can't tell how much charge you've put in while you're charging.....



Am I missing something here?

As far as I am aware the smartgauge can do a good job of telling how full the bucket is but has no idea how big the bucket is. Can it also tell you how much has gone into the bucket?
Can it track how many Ah (how much charge you've put in) have gone in to the batteries?

Fantastic if it could, I'd fit one for sure.
No, SmartGauge does not measure current and does not count amp/hours going in or out. That's its claim to fame -- it's a different approach.

It works far better than amp-counting meters, but with certain limitations which I have described.

Amp-counting meters are not really any good for determining state of charge, because of two factors -- Peukert factor, which means that the amount of battery power used to produce a given number of amp/hours of electrical power varies depending on the strength of the current; and secondly, the fact that the capacity of a given battery varies greatly over its lifetime. The better ones try to roughly compensate for Peukert, and you can keep measuring the real capacity of the bank and adjusting the settings, but only the very diligent users will get a result which is anywhere close to reality. Worse, amp-counting meters will generally err on the dangerous side -- they will overstate the SOC, which increases risk of damaging your batteries by overdischarging them. The SmartGauge cannot do this; any error will be on the conservative side

Amp-counting gauges are good for showing current going in and out of the battery bank, but an ordinary ammeter can do the same thing. They are also good for showing you the cumulative A/h which you've put in or taken out -- IF you are interested in that. In my opinion, that's not really all that useful information, unless you are in the process of actively optimizing your power consumption.

SmartGauge is far better than amp-counting gauges as a way to measure SOC, but in my experience, an ordinary volt gauge, properly used, will give you the same quality of information.
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Old 27-10-2016, 23:27   #44
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Re: Battery Monitor, which brand, which type

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..............However, I really want to know if the solar is outputting and how well. I have learned that even though my panels each output 20As, I have hit this only once, when the sun was directly overhead at the stern. Other times I have checked the controllers, which I explained getting to them is a major major PITA, it turns out I am getting 1/4 to 1/2 of that because the mainsheet is shading or the sun is not direct, etc. etc. issues of solar.....................

For this i installed two Victron 100/15 MPPT Controllers and two Victron BlueSolar MPPT control units.

These remote units gives you info about the status of your panals.

See https://www.victronenergy.com/blog/2...-mppt-control/
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Old 27-10-2016, 23:45   #45
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Re: Battery Monitor, which brand, which type

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No, SmartGauge does not measure current and does not count amp/hours going in or out.
............
SmartGauge is far better than amp-counting gauges as a way to measure SOC, but in my experience, an ordinary volt gauge, properly used, will give you the same quality of information.
Thats what I thought, pity it didn't include an ammeter as well.

The rest for someone living on a boat usually at anchor is familiar terrain

As for a voltmeter directly onto the battery terminals - Big fan a large display visible from your favorite seat and the cockpit is a very good thing and an accurate one costs about a beer on ebay


But on it's own not that much use, you need to know what amps are going in /out as well to get a feel for how happy your batteries are.
Also, imho, state of charge is overrated - what you want is that your batteries back up to full charge as often as possible. Something I think is a rarity on many cruising boats. This might be where a Smartguage could help for those less obsessed , amp counting falls apart quickly it you don't get back to 100% regularly.
The ideal battery monitor would be one which could instil a deep sense of guilt in you every day you didn't get you batteries up to very near 100% SOC
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