Smartgauge and ammeter

[pessimist]

I am an electrical simpleton, please bear with me. The new boat came with a Smartgauge system along with a Smartbank, which I think is just a fancy VSR with the ability to pair batteries. I rather like the instant SOC readout of the Smartgauge, which I'm led to believe is accurate, but would like to fit an ammeter. Two questions -

1. I have a headless BM1 which enables me to check battery Volts/Amps remotely (have it up and running in the office). This requires a shunt. Will fitting a shunt annoy the Smartgauge/Smartbank?

2. If the answer to 1 is O.K.. then is it possible to "daisychain" shunts so that I can fit a normal panel ammeter? I'd like to do this so that I can check charge/discharge at a glance rather than trying to remember where I left my 'phone to check the BM1.

Please don't suggest ripping it all out and fitting a battery monitoring system - we had one on the last boat and it and me never saw eye to eye, particularly in terms of SOC.

TIA

 

[pvb]

No problem adding a shunt for the BM1, it won't upset the Smartgauge stuff. And you can add another shunt in series to run a panel ammeter.

A proper battery monitor can be very useful. Your previous experience suggests your monitor may not have been correctly programmed. If a decent monitor is correctly installed and programmed, it will give an accurate SOC.

 

[Alan S]

Someone will correct me if I'm wrong, but I see no reason why one shunt could not be used for two or more instruments as long as the milliohm resistance matches. Fewer potential points of failere and lower voltage drop.

 

[sailinglegend420]

If a decent monitor is correctly installed and programmed, it will give an accurate SOC.

Yes it will give an accurate SoC but only when the batteries are new and the BM is programmed with the correct information.

The information needed is the Ah capacity of the bank, the Charge Efficiency of the batteries, and the Peukert value for the batteries - this modifies the calculated Ah discharge based on the size of the current drawn. (Not availablele on all BMs)

The problem is ALL these parameters change as the batteries age - especially the Ah capacity - so all shunt based BMs get more and more inaccurate. This is why the SmartGauge was developed, because the military were demanding a better and much more accurate Battery Monitoring system. The technology is now central to the Abrams tanks electrical system in the USA.

 

[pvb]

The problem is ALL these parameters change as the batteries age - especially the Ah capacity - so all shunt based BMs get more and more inaccurate.

It's easy to reprogram a monitor with a lower Ah capacity figure for older batteries.

 

[Hoolie]

I have a similar system that I fitted. The only point I would make is the Smartgauge must be connected directly to the battery terminals, so any shunt must be connected downstream of the Smartgauge connection.

 

[Poey50]

Yes it will give an accurate SoC but only when the batteries are new and the BM is programmed with the correct information.

The information needed is the Ah capacity of the bank, the Charge Efficiency of the batteries, and the Peukert value for the batteries - this modifies the calculated Ah discharge based on the size of the current drawn. (Not availablele on all BMs)

The problem is ALL these parameters change as the batteries age - especially the Ah capacity - so all shunt based BMs get more and more inaccurate. This is why the SmartGauge was developed, because the military were demanding a better and much more accurate Battery Monitoring system. The technology is now central to the Abrams tanks electrical system in the USA.

I have a SmartGauge and appreciate the more accurate state of charge but it's not a complete solution as the batteries age since it becomes relevant to know what the present total capapacity is. 60% SOC is reliable only if you can answer "60% of what?".

 

[GHA]

Someone will correct me if I'm wrong, but I see no reason why one shunt could not be used for two or more instruments as long as the milliohm resistance matches. Fewer potential points of failere and lower voltage drop.

Just did a quick test. I just installed a new victron smartshunt and the old BEP meter is still there, with the charger on the smart shunt showed 6.99A going into the batts dropping down to 6.93A if the BEP leads are connected across the smartshunt, so yes, should be possible if the 2 monitors have similar shunts. BEP was showing 249A so obviously it's shunt is different to the smartshunt!

What is interesting is having a smartshunt and a smartguage fitted, dropping the capacity of the smartshunt down a little it's possible for the 2 to track quite well giving a rough stab at capacity though more playing is required, may well be that peukerts is set a bit wrong as well. The smartshunt seems to save the current data then apply peukerts afterwards so you can adjust it and see the capacity left change.
Also the only tests I've seen for the smartguage are for constant temperature & current, but seems fairly safe to assume it will do well for changing temperatures and constantly fluctuating current.

Pretty much impossible to do an accurate capacity test on a boat which makes things a bit trickier but for a cruising boat having boat having both could give some valuable info.

Boat battery health is usually measured in quite low resolution - brand spanking new ----- seems OK so will ignore ------ dead.

 

[GHA]

Yes it will give an accurate SoC but only when the batteries are new

Not quite, batteries need to be cycled a fair bit when new before they reach full capacity.

 

[pessimist]

Thanks, everyone - particularly for answering my next question before I asked it. If I can run two BM1s, one headless for remote access and one with a local display from the same shunt all problems are solved. I accept that SOC is a joke on these instruments but that's what the Smartgauge is for

 

[sailinglegend420]

It's easy to reprogram a monitor with a lower Ah capacity figure for older batteries.

It may be easy for you, but not for most readers here.

You have to do a capacity test by discharging to 10.5v at the battery designed current draw, and you have to maintain that exact current draw by turning on more loads as the voltage falls. (Ohms Law) and you have to do this for 20 hrs! For a 100 Ah battery that's 5 amps at the 20 Hr rate. 5 X 20 = 100Ah.

That's the relatively easy bit, but knowing the new efficiency and Peukerts values is the hard bit. The only way is to discover these is to experiment with them during charge and discharge. But you have to reset the BM to 100% when you know the batteries are at 100%, the trouble is most users think the batteries are at 100% when the charger drops to float mode. I played with re-programming my BEP BM for three years and finally gave up and bought the SmartGauge.

Gibbo, who was the guy who worked for Lynx battery monitors, got so fed up explaining to unhappy customers that their BMs could never be very accurate that he left and designed SmartGauge which Merlin in Poole bought from him and licensed to Balmar in the USA.

 

[Poey50]

A slight tangent. For anyone wanting to test their remaining capacity (maybe an annual task), there are plenty of inexpensive electronic capacity testers on the big Chinese sites. I bought one for capacity testing my lithium pack, but it would be very straightforward to do a C20 test down to 10.5v on a 12 volt lead acid (as long as it is charged straight back up again when the test is over). I have the 180 watt version of this one. You can set a minimum cut-off voltage, the amperage (e.g. 5 amps for a C20 test on a 100ah battery) and it runs happily on its own, automatically maintaining the load, and recording all the data on display which it holds in memory.

8 In 1 150W/180W Digital Battery Capacity Tester Voltmeter Adjustable Constant Current Electronic Load Charger USB Meter Indicator

 

[lustyd]

I feel like we're in danger of saying that if the capacity isn't accurate then it isn't useful. That's absolutely not the case. The reason I bought a monitor was to avoid damaging my battery bank. To achieve this I just have to tell it what I think the capacity is, and the max discharge I find acceptable. I then get a full and empty and somewhere in between. Am I using the maximum capacity possible? No, but I am avoiding damage. If you're bothered by using lots of the available capacity then you'd probably be using Lithium anyway.

 

[pvb]

It may be easy for you, but not for most readers here.

You have to do a capacity test by discharging to 10.5v at the battery designed current draw, and you have to maintain that exact current draw by turning on more loads as the voltage falls. (Ohms Law) and you have to do this for 20 hrs! For a 100 Ah battery that's 5 amps at the 20 Hr rate. 5 X 20 = 100Ah.

That's the relatively easy bit, but knowing the new efficiency and Peukerts values is the hard bit. The only way is to discover these is to experiment with them during charge and discharge. But you have to reset the BM to 100% when you know the batteries are at 100%, the trouble is most users think the batteries are at 100% when the charger drops to float mode. I played with re-programming my BEP BM for three years and finally gave up and bought the SmartGauge.

Gibbo, who was the guy who worked for Lynx battery monitors, got so fed up explaining to unhappy customers that their BMs could never be very accurate that he left and designed SmartGauge which Merlin in Poole bought from him and licensed to Balmar in the USA.

The SmartGauge is ideal for people who just want a simple, cheap, easy to fit, way of getting a vague idea of what the SOC is. There's no programming to do, no complex manual to read. But a proper battery monitor can give a lot of additional useful information, and potentially be even more accurate.

 

[Hoolie]

The SmartGauge is ideal for people who just want a simple, cheap, easy to fit, way of getting a vague idea of what the SOC is. There's no programming to do, no complex manual to read. But a proper battery monitor can give a lot of additional useful information, and potentially be even more accurate.

I have a SmartGauge and I agree. It's an indication and IMO is very non-linear particularly at the top end. However for me it's enough; I really can't spend all my time worrying about the precise state of the batteries.

 

[sailinglegend420]

The SmartGauge is ideal for people who just want a simple, cheap, easy to fit, way of getting a vague idea of what the SOC is. There's no programming to do, no complex manual to read....

I really have to challenge this because it is full of errors. After 42,340 posts I expect you to know what you are talking about.

Simple - wrong - It has a very clever algorithm that has about 260 variables that it evaluates by reading the voltage over 1000 times a second. It learns the battery and increases its accuracy. It measures the voltage over one thousand times a second, but it also uses other “propriatory means" which are a strict trade secret, but it seems to use AC impedance spectrography to calculate the % depth of discharge of the batteries. It is very accurate - a poster above complained because it is not accurate "at the top end". I assume he means SmartGauge may be saying 90% charge when he "thinks" his bank is 100% charged - just because a little charger light turns green when his battery drops to Float mode.
Cheap - wrong - it's not like the cheap Ah counters from China that probably can't programme the Charge Efficiency or the Peukert constant and so would be very innacurate. It is the same price as Nasa but a bit cheaper than other decent large shunt Battery monitors like Victron and Mastervolt.
Easy to fit - YES - that is the key to its success - there is no shunt and therefore no large battery lugs to crimp, just two 14 gauge (AWG) cables. Shunt based battery Monitors are often very inaccuarte because of installation errors where every load or charge source does not go through the shunt. Often extra kit is added later that also does not go through the shunt. A very well known electrical Engineer called Maine Sail in the USA, who used to post on here, currently states on his website:
…that about 90% of Ah Counters I come across are NOT properly installed & wired and about 98% of Ah counters I come across are NOT properly calibrated/programmed.
A vague idea of what the SOC is - wrong. It has been tested by many independent organisations who upheld its claim of 5% accuracy at all times. It was also proved by Enersys, who make Odyssey batteries, to be much more accurate than any shunt based Battery Monitor.
No programming to do - wrong. SmartGauge needs one simple piece of data, the battery type, FLA, AGM, etc.. This data never changes. Shunt based battery monitors need programming with 2 or 3 pieces of data which change as the batteries age,
No complex manual to read - again wrong - it has a 29 page detailed manual and can set alarms and has a relay output.

The one and only disadvantage of this device is it doesn’t measure current, knowing the charge/discharge currents at all time is very important on a boat. A cheap digital current meter can be sourced from another supplier. But beware buy one that measures both charge and discharge current.

After repeated requests Merlin Smartgauge refused to add a current meter because it was not needed to improve accuracy. It is worth following the new Balmar SmartGauge, the SG200, to see all the problems they are having with both a SmartGauge device and a shunt-based device in one unit.

 

[halcyon]

I really have to challenge this because it is full of errors. After 42,340 posts I expect you to know what you are talking about.

Simple - wrong - It has a very clever algorithm that has about 260 variables that it evaluates by reading the voltage over 1000 times a second. It learns the battery and increases its accuracy. It measures the voltage over one thousand times a second, but it also uses other “propriatory means" which are a strict trade secret, but it seems to use AC impedance spectrography to calculate the % depth of discharge of the batteries. It is very accurate - a poster above complained because it is not accurate "at the top end". I assume he means SmartGauge may be saying 90% charge when he "thinks" his bank is 100% charged - just because a little charger light turns green when his battery drops to Float mode.
Cheap - wrong - it's not like the cheap Ah counters from China that probably can't programme the Charge Efficiency or the Peukert constant and so would be very innacurate. It is the same price as Nasa but a bit cheaper than other decent large shunt Battery monitors like Victron and Mastervolt.
Easy to fit - YES - that is the key to its success - there is no shunt and therefore no large battery lugs to crimp, just two 14 gauge (AWG) cables. Shunt based battery Monitors are often very inaccuarte because of installation errors where every load or charge source does not go through the shunt. Often extra kit is added later that also does not go through the shunt. A very well known electrical Engineer called Maine Sail in the USA, who used to post on here, currently states on his website:
…that about 90% of Ah Counters I come across are NOT properly installed & wired and about 98% of Ah counters I come across are NOT properly calibrated/programmed.
A vague idea of what the SOC is - wrong. It has been tested by many independent organisations who upheld its claim of 5% accuracy at all times. It was also proved by Enersys, who make Odyssey batteries, to be much more accurate than any shunt based Battery Monitor.
No programming to do - wrong. SmartGauge needs one simple piece of data, the battery type, FLA, AGM, etc.. This data never changes. Shunt based battery monitors need programming with 2 or 3 pieces of data which change as the batteries age,
No complex manual to read - again wrong - it has a 29 page detailed manual and can set alarms and has a relay output.

The one and only disadvantage of this device is it doesn’t measure current, knowing the charge/discharge currents at all time is very important on a boat. A cheap digital current meter can be sourced from another supplier. But beware buy one that measures both charge and discharge current.

After repeated requests Merlin Smartgauge refused to add a current meter because it was not needed to improve accuracy. It is worth following the new Balmar SmartGauge, the SG200, to see all the problems they are having with both a SmartGauge device and a shunt-based device in one unit.

Just use a Hall Effect shunt.

Brian

 

[pvb]

I really have to challenge this because it is full of errors. After 42,340 posts I expect you to know what you are talking about.

It's likely that most people would agree with what I said. If you think selecting a battery type counts as "programming", you're nit-picking.

 

[Hoolie]

It is very accurate - a poster above complained because it is not accurate "at the top end". I assume he means SmartGauge may be saying 90% charge when he "thinks" his bank is 100% charged - just because a little charger light turns green when his battery drops to Float mode.

I didn't mean that at all. It falls rapidly initially when loaded off charge, then levels out; I have correctly set the battery type. Nevertheless it's a very useful device to have.

 

[Mistroma]

I didn't mean that at all. It falls rapidly initially when loaded off charge, then levels out; I have correctly set the battery type. Nevertheless it's a very useful device to have.

The technical support guys will admit the issue when charging, mine always dropped rapidly initially but quickly gave a correct reading. It would show 100% too early and revert to a lower figure soon after solar charging stopped. It wasn't really much of a problem as I wasn't using it to stop charging. I was getting to a real 100% once I had more solar and the initial drop became much less noticeable.

Smartgauge always matched actual SOC very closely in the morning when the reading was most useful. It almost always agreed very well with SOC from temp. corrected SG measurements. The only real problem was a sudden drop in accuracy after a voltage spike. I gave my detailed measurements to their tech. guys and they were interested in testing it. I sent it off and got a new unit back for a modest cost.

Coulomb counters have many problems in estimating battery capacity and impact of significant discharge/charge current
Battery age e.g. T105 capacity increases for ~50 cycles and then starts to drop off. Actual capacity is always a guess
Temperature has a significant effect on capacity
Capacity is affected by magnitude of discharge current (Peukert)

Charge efficiency also varies greatly at different SOC for manty of the same reasons

Modern units are certainly better than older ones because they are "smarter". i.e. Manufacturer has improved how to reset to 100% on full charge and allow for other errors. However, there's still some guesswork and configuration needed to get the best out of them.

I decided that Smartgauge would be fine to monitor SOC wrt acceptable threshold for additional recharging after some cloudy days. However, I like to have more data and fitted a £20 eBay unit to give a lot of data on Ah,Wh,V etc. on charge/discharge. It isn't available now but was a great buy with LCD display and an Android app. for remote display.

Smartgauge/Smartbank works well to control charging for a mixture of T105/ low. maint & AGM. All three are connected when charging but disconnected when low. maint & AGM are fully charged and T105s charging continues to 14.8V. I also use Smartgauge to control the battery ventilation fan speed in relation to charging voltage. I've never bothered to use it to boost alternator output but might get around to it eventually. Quite a useful piece of kit.