best smartgauge

[micky1010]

I am looking for a smartgauge to keep an eye on my domestic batteries, the engine already has its own voltmeter, and there are a few around from the likes of victron, NASA and several others.

 

 

Which does anyone recomend, I would want it to show ah used and projected time remaining as well as voltage ideally?

[Tony Brooks]

Smartgauge - capital C - is a trade name for an exceptionally clever voltmeter that learns over time how well charged your battery is vis small voltage variations. The others are sometimes known as battery management systems that purport to have the ability to tell you how many amp hours of charge you have left in your battery. The better ones will be fairly accurate providing you get them set up correctly and fully charge your batteries on a very regular basis. The rest and even the better ones if just fitted and forgotten are a first rate way of being deceived into ruining your batteries.

 

The Smartgauge is easy to fit with just two thin wires. The others require a charging & supply lead (usually the domestic negative) to be cut, terminated and a shunt inserted.

 

Myself and others on here learnt to use an accurate voltmeter and ammeter to estimate the batteries state of charge but if you want a dedicated gauge the one least likely to tell lies is the Smartgauge but even that tends to be inaccurate for the first few charging/discharge cycles after fitting and when the battery capacity has reduced to more than 50% of original. There have also been reports that it may show an error code in certain circumstances when used with a large solar array but it seem to sort itself out.

[Top cat]

Well put Tony, I couldn't have said it any better, 100% agree.

I use a Victron BMV but just interpret the volt and ammeters for myself, the other numbers are mythical.

 

Top Cat

[musicman]

I put a Smartgague in our boat three years ago and have never looked back - it does what it says on the tin. Never once has it let me down and we have NEVER run the batteries down too low and been without power. It has my vote every time! Simple to install, simple to read, and simply great!

[bottle]

I think Tony has said it all, the only thing I would add is the Smartgauge admits to being up to 10% inaccurate when the batteries are being charged.

 

When the batteries are 'resting' or being discharged it is very accurate.

 

The others, in my opinion are totally inaccurate unless you accurately know the capacity of your batteries at any given time (they lose capacity as they age) and regularly ensure your batteries are charged to 100% of capacity and then adjust the gauge.

 

Smartgauge, fit and forget unless you need to know the state of charge of your batteries.

[Richard10002]

NASA BM1 or BM2 plus a Smartguage would be my ideal. I couldnt justify both so I have a NASA BM2, as I prefer to know cumulative Ah charged and discharged, and am happy to hazard a guess at State of Charge based on Voltage, Ah used, and the NASA stab in the dark at SOC.

[Arthur Brown]

There is ONE Smartgauge company, with a couple of products in their range. For a simple two wire device it's the easiest and most accurate way of reading directly the state of charge of the batteries, It is accused of errors in some situations BUT these are usually trivial.

 

Other battery monitoring systems exist.

 

The informed use of a good voltmeter is an easy and cheap alternative.

[Bod]

+1 for Smartgauge.

 

Bod

[Phil.]

This is probably the best if that's what you want but it will cost you.

 

http://www.merlinequipment.com/page/document.asp?id=524

[micky1010]

Thank you all for your advice, the smartguage seems to be the one for me.

[Sea Dog]

You pays your money and you takes your choice. I went for the Victron because I wanted the Ammeter functionality and all that brings. Charge and discharge current being valuable in itself, but also it's a short stretch from there to display Amp Hours in or out. I don't believe the percentage bit or the hours to go, but it's good to see what AH you've used since you moored up and you can see whether you were fully charged at that point from the V and A display. The Victron beat the NASA for me because it has a 500a shunt versus the 200a max on the NASA to supply the potential max draw from my inverter. NASA has the nicest display, Victron is neat, SG looks like something off Thunderbirds or an old pinball machine!

[1agos]

 

 

 

I love my solar controller, it has a smiley face sitting in the corner letting me know the battery's are happy. If it ever goes to a sad face I would turn the engine on to charge. The solars have been fitted two years now and I haven't seen the sad face yet.

 

This suits me as I am battery management incompetent all the v's & ah's numbers confuse the hell out of me.

 

 

 

[Chalky]

I have a Nasa BM-1. Its an amp counter however its accuracy is poor and I tend to rely upon the voltmeter and ammeter part to tell me the state of charge.

 

Amp counters count the amps into and out of the battery. Sound ideal however:-

• Batteries are not like buckets. 1 Amp into a battery doesn't mean 1 amp stored. The amount stored will vary on battery age, temperature, method of construction, state of charge etc. The amount stored is not constant and changes throughout the batteries life.
• When batteries charge it's like pouring a pint of beer. The battery initially shows one voltage (like the froth), the true voltage only appears once the froth has settled. (crude description of surface charge)
• Batteries loose charge (self discharge). This is not accounted for by most amp counters.
• The amount of power stored in a battery changes depending on how fast you take the power out (Pukert). Most gauges attempt to calculate this however the constants used aren't constant affected by same things as charging.
• To cope with the large range that the current sensing has to work with it's common to use a logarithmic input scale. The effect of this is that the units cope well with large currents but can get confused with small current inputs (e.g. solar, led lights etc). The result is that small but significant (over long periods) currents get ignored or over compensated for adding to the error.

[Richard10002]

I don't sense those difficulties with the NASA.Obviously, you need to put more in than you take out, but you can assume the batteries have taken almost as much as the can when the charging Amps figure falls below a certain level. In my case with about 400Ah capacity, I have settled on about 6A charging current to tell me they are full enough.

 

There is no doubt that you need some knowledge of how things work to use an amphour counter, whereas a Smartguage requires no knowledge....

 

except that a Smartguage gives you no idea of capacity and how it is changing, so you could be reading 95% on a 330Ah battery bank, think you have over 300Ah stored yet, in reality, you could have less than 100Ah stored.