Battery Monitor, which brand, which type

[Dockhead]

Originally Posted by conachair

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

I'm not sure why you think that "SOC is overrated" -- what else do you need to know about your batteries, which is so important? Actually I think this is the ONLY thing which is essential to know. Do I need to charge? Or can I carry on using them? That is the Big Question. For this the SmartGauge gives an extremely accurate answer, as does a voltmeter properly used.

This is like a fuel gauge. The fuel gauge doesn't tell you how many liters are in your tank, it just tells you % of total capacity remaining, and it tells you when you need to refuel.

Amps coming out of the bank can be useful to know -- tells you how fast you're using up your capacity and may alert you to switch something off, or understand your loads. But this is secondary information. The primary information is when to charge. The cost of getting it wrong is damaged batteries. This is the one really important thing.

The information which SmartGauge doesn't provide or rather, provides very inaccurately, is when you can stop charging. This is only important when running a generator -- when do I shut it off? Again, great accuracy is not needed here, so you can look at other signs (bulk charge over plus x minutes, etc.)

[conachair]

Originally Posted by Dockhead

I'm not sure why you think that "SOC is overrated" -- what else do you need to know about your batteries, which is so important? Actually I think this is the ONLY thing which is essential to know..)

What is much more important to know about your batteries if you want them to last is have they been they fully charged today
Which again an ammeter and voltmeter will probably tell you more accurately than a monitor if you've been cycling below 100% for a few days - volts high teens and little current going in, a good thing .

After a while it's quite easy to get a handle on SOC/battery health by looking at amps in or out and the voltmeter, though I would miss my bep battery monitor to check how many amps have gone out over night, these days I rarely bother looking at the SOC. Getting them fully charged as often as possible is something to be obsessed about, to the nearest percent how much you've used is a second. Imho

Ps. A voltmeter on its own is next to useless, without nan ammeter t see what's going in or out it takes so long for battery voltage settle it doesn't really tell you much unless you've just come back to the boat after a day or 2.

[Dockhead]

Originally Posted by conachair

What is much more important to know about your batteries if you want them to last is have they been they fully charged today
Which again an ammeter and voltmeter will probably tell you more accurately than a monitor if you've been cycling below 100% for a few days - volts high teens and little current going in, a good thing .

After a while it's quite easy to get a handle on SOC/battery health by looking at amps in or out and the voltmeter, though I would miss my bep battery monitor to check how many amps have gone out over night, these days I rarely bother looking at the SOC. Getting them fully charged as often as possible is something to be obsessed about, to the nearest percent how much you've used is a second. Imho

Ps. A voltmeter on its own is next to useless, without nan ammeter t see what's going in or out it takes so long for battery voltage settle it doesn't really tell you much unless you've just come back to the boat after a day or 2.

I suppose some very small banks, I mean small in relation to the loads, might need an ammeter in addition to a voltmeter in order to interpret whether there is so much load on that the system volts are indicating less than the real SOC.

For such a case, I wonder whether the SmartGauge will be telling something that the straight voltage is not telling -- interesting question. If so, then my comments about a voltmeter being enough might not apply to boats with smaller banks.

With a reasonable size bank, you don't need to know the amps. You just need to know that there are no big loads on. On my boat this has been extensively tested -- voltmeter vs. Smartgauge vs. specific gravity. During discharge, all three methods correspond extremely closely -- within a couple of %.

As to not needing to know when to charge -- I don't understand this. If you over-discharge your bank, you will damage it. It's like running out of petrol in your car -- you don't need to know when the tank is empty? This comment seems simply weird to me.

As to knowing when the bank is charged -- this is easy and you don't need gauges of any kind. The battery charger goes over to float, and that's fully charged. You'll never get there being off shore power. You will generally switch off the generator some reasonable time after the charger goes to absorption. Then when you have shore power, you don't stop at float anyway -- you want to leave it on for a while, and maybe do a bit of forced absorption or equalization.

You don't need any gauge for any of that. The only essential function of any battery monitor gauge is telling you when to stop discharging your batteries and find a way to start charging (like "time to find a petrol station"). Everything else is secondary.


Edit: I would add that for the OP's particular case, of course, an ammeter is very useful for the specific case of knowing how his solar panels are performing. This is different from operating a generator. But this isn't really a battery monitor function.

[UNCIVILIZED]

Originally Posted by jbinbi

My boat's setup is as follows.

1 house bank of 420Ah and 2 start banks, one for each engine.

The instrument panel has a battery monitor that lets me select each one of three to show its corresponding voltage level. It also shows As crudely on the top corner, though but only outflow, not inflow.

There is a shunt for the battery monitor.

Since adding solar, I am very keen on knowing how much is going into (and out of) the battery. The MPPT controllers have a LCD display that cycles between V and A, and AH, but the controllers are under a berth, to see them I need to unmake the bed, take off the mattress(es), slide back a piece of wood, and lean over. Not very convenient.

So I am thinking of adding a monitor. I have looked at the Victron, and Balmar Smart Gauge. The smart gauge would be easy to install, and also let me use my current setup to monitor both start batteries. I can leave all wiring in place, including the shunt, the Balmar just connectors to my house bank's terminals. BUT, it doesn't show Amps.

The Victron requires me to substitute its shunt for the current one, not a big deal, but then I can't monitor both of my starts, as the Victron only has the capability to monitor 1 extra battery. But it will show current in and out!

For those with solar, how important is it to know just SOC vs. current used as well. I have read reviews on both of these, mainesail highly recommends the Balmar for SOC. Sorry for the long post, but interested in hearing what others have used and pros and cons. Thanks.

Cut a "port" into the bunk front & add a piece of acrylic over the hole if you like. In conjunction with adding a mirror or prism over/in line with your current monitior's readout, & poof, no mattress moving needed. The mirror/prism will put the display's image wherever you aim it. Cost $10, time for mod', 2hrs. QED

[conachair]

Originally Posted by Dockhead

I suppose some very small banks, I mean small in relation to the loads, might need an ammeter in addition to a voltmeter in order to interpret whether there is so much load on that the system volts are indicating less than the real SOC.

It's not quite so bad getting pulled down, pulled up is much worse. You get a couple of big gusts and the wind gen will push the voltage up where it will take a while to slowly settle again. Meanwhile you glance over at the volts twenty minutes later and think your batteries are well charged.
An accurate voltmeter straight onto the battery terminals is great, wouldn't want to be without one but you need to know the limitations if using it to guess the state of charge.

As to not needing to know when to charge -- I don't understand this. If you over-discharge your bank, you will damage it. It's like running out of petrol in your car -- you don't need to know when the tank is empty? This comment seems simply weird to me.

That wasn't actually what was said, it was that SOC is over rated ( actually meant from a battery monitor) - with a smilie intended to show it was part in jest. Thing about knowing the state of charge to the nearest percent is that it will almost certainly be wrong - smartgauge seems to be accurate but gives no indication of the state of the batteries, they could be 100% of nearly nothing. without an ammeter you won't really know much better.
And a battery monitor will tell you that you're 80% - but again, 80% of what?
Voltmeter and ammeter can give you lots of info, though if fitting a counting ammeter why not go for a decent monitor anyway, not that expensive.

As to knowing when the bank is charged -- this is easy and you don't need gauges of any kind. The battery charger goes over to float, and that's fully charged.

Sorry, not so. Unless you've been in a severely tweaked the parameters it will switch to float before 100% fully charged. Plus the charger has no idea where the charge is going, it has no idea if your fridge is running and you're watching telly - next time it switches to float turn it off and on again and see what amps are going out, very likely much more that the 0.5% 0r 1%C at absorption voltage commonly mentioned as a full battery.