Buying a Smartgauge

[fritzdfk]

I am looking into getting a Smartgauge monitor. The Smartgauge was originally developed by Merlin in the UK. You can order direct from UK for much less than USA prices, $120.00 vs $300. Am I missing something?
Battery Monitors: Merlin Smartguage Battery Monitor (19-1001)

[Dockhead]

Originally Posted by fritzdfk

I am looking into getting a Smartgauge monitor. The Smartgauge was originally developed by Merlin in the UK. You can order direct from UK for much less than USA prices, $120.00 vs $300. Am I missing something?
Battery Monitors: Merlin Smartguage Battery Monitor (19-1001)

Welcome to Balmar markup.

[rgleason]

http://www.smartgauge.co.uk/

[rgleason]

Are their any user experiences out there?

[Pete7]

Try a search, we will see you back in January after you have managed to read all the threads.

Pete

[AHoy]

Here is a review that gives the smart gauge very high marks:

https://marinehowto.com/smart-gauge-...nitoring-unit/

Also there is a good post here comparing the smart gauge and others here:

http://www.cruisersforum.com/forums/...co-192131.html

I was going to get the Smart Gauge but am now leaning towards the Simarine Pico because of the additional capabilities but am waiting for the test results from OceanPlanet on their test bench before I choose.

[fritzdfk]

I tried to post a link in the original post that didn't work.

Battery Monitors: Merlin Smartguage Battery Monitor (19-1001)

[a64pilot]

Your not missing anything, it’s excellent at giving you an accurate SOC when the batteries are being used, pretty much disregard SOC during charge.

[billknny]

Originally Posted by rgleason

Are their any user experiences out there?

The answer is, like so many others in the boat world, "It depends."

It depends on how you use your batteries. If you regularly bring the batteries up to full charge (REALLY full, like 36 hours plugged in to shore power) then the regular amp hour counting meters will do a better job for you than the Smartgauge--at least for 5 or 6 cycles after the full charge.

If on the other hand you are a full time cruiser who rarely gets the batteries REALLY full, then the amp hour meter is going to slowly walk away from giving you accurate information about battery state of charge. It has--to it's the nature of the beast. That application is where the Smartgauge works best. It is not a precise tool, but we don't really care about precision. Who cares if their battery is 74% or 76% full? We want to know if it is 40% or 60%.

I have both types of meters on my cruising boat. They give different information, and I do not think it is a case of one or the other. If I had to chose only one, it would be the amp-hour meter, because knowing instantaneous usage is so important.

[a64pilot]

I’m being argumentative. I do not think anything will tell you SOC better than a smart gauge of a lead acid bank, no matter how you charge your batteries. Lead acid only, not Life-Po
However besides voltage of two banks and SOC of one bank, it won’t do anything else, it won’t for example tell you your 660 AH bank is down to 500 AH, just what it’s SOC is, and it won’t tell you show many AH you used last night.
An amp hour counter along with the Smart Gauge you can interpolate the AH of the bank.
IE Smart Gauge says you used 25% of your bank, AH counter tells you you used 100 Ah, therefore you have a 400 AH bank, regardless of rating.

[sailinglegend]

Originally Posted by a64pilot

.....pretty much disregard SOC during charge.

I also have to be argumentative big time on your statement!

I have had a shunt based BEP Battery Monitor and a SmartGauge for ten years and I have now manage to synchronise them both during discharge AND charge and they are both within about 3% at all SOC.

Do do this I had to do a 20 hour discharge test on each battery and all 5 were down to 55% of original capacity (Lifeline AGM suggest change them at 50%). So inputing this into the shunt based BM dramatical improved the charge and discharge readings. Now I have tweaked the Peukert constant to get the discharge in line with SG after always manually setting the BM to 100% and not allowing it to automatically synchronise itself to 100% full.

I have reduced the Battery Charge Efficiency on the BM so that it now gets to 100% when the charge current is 0.5% of the current Ah capacity of the bank AT the absorption voltage - by switching the charger off and on again to force it back up to absorption voltage.

So now I can clearly state that the SG is following the BM within 3% - BUT the SG can jump to 100% when the BM says 95%, so a slightly larger error near 100% during charging.

All this contradicts your statement of ..."pretty much disregard SOC during charge."

[conachair]

Originally Posted by sailinglegend

I also have to be argumentative big time on your statement!

I have had a shunt based BEP Battery Monitor and a SmartGauge for ten years and I have now manage to synchronise them both during discharge AND charge and they are both within about 3% at all SOC.

Do do this I had to do a 20 hour discharge test on each battery and all 5 were down to 55% of original capacity (Lifeline AGM suggest change them at 50%). So inputing this into the shunt based BM dramatical improved the charge and discharge readings. Now I have tweaked the Peukert constant to get the discharge in line with SG after always manually setting the BM to 100% and not allowing it to automatically synchronise itself to 100% full.

I have reduced the Battery Charge Efficiency on the BM so that it now gets to 100% when the charge current is 0.5% of the current Ah capacity of the bank AT the absorption voltage - by switching the charger off and on again to force it back up to absorption voltage.

So now I can clearly state that the SG is following the BM within 3% - BUT the SG can jump to 100% when the BM says 95%, so a slightly larger error near 100% during charging.

All this contradicts your statement of ..."pretty much disregard SOC during charge."

Mainesail with a workshop full of lab grade test equipment only saw charging accuracy within 10-12%.

It means that I did see the Smart Gauge get a bit confused when the bank was being charged. It can't really track the capacity of a battery charger now can it...? However we are only talking about 10-12% variation from the Ah counters during charging

Smart Gauge Battery Monitoring Unit Photo Gallery by Compass Marine How To at pbase.com

[CatNewBee]

I consider the SmartGauge useless.

It simply cannot work accurately without a shunt - especially if you have a solar panel, that constantly adds charging voltage during the day. If you cannot measure the current and the direction it flows, you cannot guess the state of charge sole based on voltage measurements - no matter how often and how precise they may be taken, because the battery is never alone during the day.

Also the voltage drops on adding a load related to the batteries resistance. There is no way the SmartGauge can tell if the measured voltage results of the SOC of an idle battery or an battery under heavy load.

It simply cannot work.

[sailinglegend]

Originally Posted by conachair

Mainesail with a workshop full of lab grade test equipment only saw charging accuracy within 10-12%.....

The difference between my observations and Mainsail's is only 5%!!!! That small inaccuracy doesn't matter compared to a shunt based battery monitor that can be 50% inaccurate. Yes I have occasionally seen a 10% error above 90% SOC but I now have a 13 year old AGM battery bank and a 280 amp charger so we are expecting a lot from Smartgauge. Every two weeks I make sure the bank is 100% charged by monitoring the current at 14.4v.

Originally Posted by CatNewBee

I consider the SmartGauge useless....

You need to read Mainsails's article and the hundreds of other posting on this subject.

In theory it can't work and that is what Merlin boss said before he bought SmartGauge from Chris Gibson. Chris posted this on April 28, 2014:

"The thing I find quite amazing is that after all these years, after all the independent testing that has been done (Enersys, UK MoD, US DoD, TARDEC, TACOM, Balmar, Compass Marine...) I still see the odd comment that (paraphrased) reads "I don't understand (or "I don't see") how it works, therefore it can't". "I don't understand" means precisly that and nothing more.
It isn't perfect, nothing is, but it does meet the original design spec which was to solve the major problems with amp hour counters. Those problems really are a major issue to many people."

[sailorboy1]

5% seems a lot when you consider the 1,000s of thread pages aguring wheather batteries are fully charged or only 98% charged