State of Charge Monitors

MurrayM · Feb 28, 2014

Used the search function and couldn't find a thread devoted to SoC monitors, so here we go...

We managed to keep our promise to ourselves by not buying anything for Badger in the first year (except for a get-home kicker, a larger anchor, and a longer rode).

One of the first things on our shopping list is a State of Charge (SoC) monitor for our starter and house bank wet cell batteries.

Do you have one? Happy with it? Would you recommend it, or do you have your eye on another?

N4712 · Feb 28, 2014

I've heard good things about Victron's BMV-600.

markpierce · Feb 28, 2014

BMV-501 works for me.

Steve · Feb 28, 2014

I have a Link Lite Battery monitor and am happy with it. The link Pro has a few more features, not much more money. I have had no problems with it.

FlyWright · Feb 28, 2014

MurrayM · Mar 1, 2014

Thanks for the tips, and Al for the links to past threads.

Anybody have a SmartGauge?

In USA; smartgauge-layout

In England; SmartGauge Electronics - SmartGauge battery monitor

av8r · Mar 1, 2014

We have had a Bogart 2010 on 2 boats and the units have been fine. The Victron is probably prettier and the Bogart requires either a larger box or a larger hole, but they have similar specs and capabilities.

Peter B · Mar 1, 2014

I'm thinking of getting one of these. Cruzpro has a good name, and I have really liked their chain counter.

CruzPro VAH30 and VAH60 Volts/Amps/Amp-Hour Monitor with Alarms and NMEA 0183

Insequent · Mar 1, 2014

I am using Victron's "VE.net" and Blue Power Panel. Its a great system, gives you a lot of information. I mostly keep an eye on the Amp-hours, but can also see the amperage into the batteries, the inverter draw on them and AC input and loads - all on the one display.

Aquabelle · Mar 1, 2014

I am also a big fan of Victron. The models referenced above are fine, but Panbo recently carried a review of a new Victron model you might want to consider: Panbo: The Marine Electronics Hub: Victron Color Control GX, more than a power display

fryedaze · Mar 1, 2014

Installed the Victron 602 last year. The install in a breeze. The wiring from the shunt to the display in a plug in cable like a Cat 5 or phone cord. Its small and gives all the data needed to monitor the batteries. IMHO

jleonard · Mar 1, 2014

I have a Link Lite and it seeems to do what I need.

Bendit · Mar 3, 2014

We have a CruzPro VAH110
CruzPro VAH110 Three bank digital Volts/Amps/Amp-Hour Monitor
It has a large display in the wheel house that I can read from the saloon. It tells me all I need to know about 3 battery banks: Start 24V, House 24V, House 12V. Our batteries are 18 years old (gel) and I'm hoping for 30yrs so good monitoring and charging regime seem to work .

DavidM · Mar 3, 2014

I am not sure where and when the term State of Charge Monitor got started. But I have sure seen it a lot recently. But I prefer the term Battery Monitor.

A Battery Monitor measures current (in and out, positive and negative) from a battery and then time integrates it to give amphours used (by house loads) or replaced (from charging sources). Only when you start from a full battery and subtract amphours used and then divide by the battery(s) capacity do you finally get pct SOC.

And it is just an approximation. In addition to the overall capacity of the batteries which can be very different from nameplate, particularly for older batteries there is something called the Peukert coefficient. This is a fudge factor that relates actual capacity to amphour discharge rate. It varies from 1.1 to about 1.5.

So overall the state of charge can easily be off by 25% when measured by a battery monitor.

It also gives instantaneous amperage useage (+ or-) and an accurate voltage reading of the batteries.

I have used several brands and all seem to work well, even the Xantrex unit. But don't buy a dual battery bank monitor. There is no point in measuring amphours used by a starting battery (as the second bank). It will always be near zero as the amphours required to start are very low and it gets recharged quickly.

David

timjet · Mar 4, 2014

Thanks Dave for that exclamation. I just bought a victron 2 bank battery monitor. The battery monitor only monitors voltage on the second bank. This will allow me to remove my current digital v meter and insert the battery monitor. They are the same size making it an easy install.
My current v meter monitors all 3 banks (house, eng start, genny start) with a rotary selector switch. My plan is to monitor the house bank with all the features of the victron monitor and using my current rotary switch monitor the eng and genny start banks voltage with the 2nd bank voltage feature of the new monitor.

DavidM · Mar 4, 2014

Yes, voltage monitoring of the second battery is useful. Hooking up a second shunt to measure current isn't useful.

I didn't know about that feature on the Victron. Makes sense.

David

caltexflanc · Mar 4, 2014

djmarchand said:
I am not sure where and when the term State of Charge Monitor got started. But I have sure seen it a lot recently. But I prefer the term Battery Monitor.

A Battery Monitor measures current (in and out, positive and negative) from a battery and then time integrates it to give amphours used (by house loads) or replaced (from charging sources). Only when you start from a full battery and subtract amphours used and then divide by the battery(s) capacity do you finally get pct SOC.

And it is just an approximation. In addition to the overall capacity of the batteries which can be very different from nameplate, particularly for older batteries there is something called the Peukert coefficient. This is a fudge factor that relates actual capacity to amphour discharge rate. It varies from 1.1 to about 1.5.

So overall the state of charge can easily be off by 25% when measured by a battery monitor.

It also gives instantaneous amperage useage (+ or-) and an accurate voltage reading of the batteries.

I have used several brands and all seem to work well, even the Xantrex unit. But don't buy a dual battery bank monitor. There is no point in measuring amphours used by a starting battery (as the second bank). It will always be near zero as the amphours required to start are very low and it gets recharged quickly.

David

This is not exactly or always the case with modern battery monitors. The better ones will make calculations for charge efficiency and discharge rate factors that go beyond merely measuring amps in and out. I cross checked my Magnum many times using a proper hydrometer test on battery banks of all ages and SOC% was spot on. A friend who used a newer Trimetric (Bogart) had did the same experience. The units that measure a second bank typically just report volts, fine for a starting bank which is just why they are designed that way.

A snip from my Magnum manual:

"The battery monitor is shipped with the charge efficiency set to Auto. This allows the battery monitor to automatically calculate variables that affect the charging efficiency such as battery type, battery age, and how the batteries are maintained – which is not always constant. With the Auto setting, the efficiency is recalculated each time the batteries reach a 100% state of charge." So virtually all batteries, you don't reach 100% SOC until you have put more amps back in than you took out.

State of Charge Monitors

MurrayM

Guru

N4712

Guru

markpierce

Master and Commander

Steve

Guru

FlyWright

Guru

MurrayM

Guru

av8r

Senior Member

Peter B

Guru

Insequent

Guru

Aquabelle

Guru

fryedaze

Guru

jleonard

Guru

Bendit

Senior Member

DavidM

Valued Technical Contributor

timjet

Guru

DavidM

Valued Technical Contributor

caltexflanc

Guru

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