Battery Monitors - Instructions for a nonelectrical engineer

[Steve O]

After a recent lightening strike my marina replaced my battery controls with a Magnum Energy System (inverter, combiner, monitor and Remote Control).

Now I am University educated but not in Electrical Engineering. Yes I have read the manual and contacted Support (who told me to read the manual) but it is not written for the sailor who just wants to know everything is working and I have power.

Is there anywhere that anyone has seen that describes (instructs) how to use this monitoring system which I and my wife would understand?

[Jon Hacking]

I don't know the Magnum specifically, but battery monitors are pretty cool. They monitor (& integrate) current in & out of the battery, & thereby provide a "fuel gauge" for your battery that's much more accurate than simply monitoring the voltage.

It's helpful to know how big your battery bank is. This is measured in Amp-hours (abbreviated Ah). A typical car battery might be 80-100Ah, a 4D truck battery is typically about 150Ah, & an 8D is usually 220Ah. For a 200Ah bank, you should be able to draw 2A out of it for 100 hours, or 4A for 50h, or 20A for 10h (although batteries aren't quite linear, & you really shouldn't drain your batteries past 50% or they won't last as long).

Your engine will typically have its own starting battery, & your "House bank" will usually have several 12v batteries wired up in parallel (+ to + & - to -, although there are many ways to make up a house bank). If you have several batteries wired in parallel, you can add their capacities to give you the capacity (in Ah) of your house bank. (6v batteries in series get treated differently, but aren't as common)

If you're sitting in a marina, the battery monitor won't do or tell you much, because your battery charger should be keeping the battery bank always full, & supplying whatever is needed for your power needs without actually having to draw any power from the batteries. The only thing you need to do is to tell the monitor when your batteries are full, which you should only need to do about once a year. Batteries are not 100% efficient, & their efficiency decreases with age & use, & this lets the battery monitor track that efficiency for you so you can replace them when they get too inefficient, instead of waiting until they die.

But when you're off the grid, the monitor will start showing how many amp-hours you've used, & when you're charging the batteries, it will show how full the batteries are (how many Ah down from fully charged).

This description is only to get you oriented. Electrical systems (& their care & maintenance) are huge subjects. But one of the joys of cruising (IMHO) is that you're constantly having to learn new stuff.

Hope this helps!

[Macblaze]

Not sure how far you want to go into this. I installed the Magnum Battery Monitor this summer.

You turn the knob/dial to 'meter' and press it.

INV/CHG gives you the voltage of your batteries. A rough guide of their state of charge but pretty useless unless your batteries have been resting

Turn the knob again and press

SOC is State of Charge. This, if set up correctly, should give you a percetage of where your battery charge is 80%, 60% etc.

Turn the knob again and press

Status BM Meters

This is the meters section. Initially it gives you the voltage again, this time to two decimal points

Turn the knob again and press

DC Amps: The number of amps remaining in the battery

Turn the knob again and press

AH I/O: The number of amps that have left or returned to the battery bank since your last full charge

Turn the knob again and press

rAH Out: a resettable meter that measures the amount of amps out since last time you reset it. Reset by holding the knob in for 10 seconds or so.

Turn the knob again and press

tAH Out: Total amps out since you installed the meter or it was last disconnected

I pretty much ignore everything else. Does this help at all?

:-)

[Stu Jackson]

Welcome.

None of us were born electricians, we all hadda learn.

That said I was in the same boat (pi!) as you back in '98 when we bought this boat.

As far as battery monitors are concerned, I wrote this handy thing to help me understand how they work and how they need to be programmed, the physical part is the easy part, the work is to figure out what all the settings and defaults that are concerned actually mean in Plain English, not engineer-speak (although I are one! )

So there's this:

For everyone installing a battery monitor: The "Gotcha Algorithm" thread, a "MUST READ"

Link-series Charging Algorithms -- The "Gotcha" Factor!

DEFAULTS are factory settings that are made to be modified to suit your setup.

Which comes from this:

Electrical Systems 101 Electrical Systems 101

Maine Sail also has a good one:

How to Wire a Battery Monitor by Maine Sail: Wiring & Installing A Battery Monitor | SailboatOwners.com Forums

It's for wiring but discusses programming, too.

Good luck & happy holidays.

Ask away if you have any more questions.

[Jon Hacking]

Originally Posted by Macblaze

...DC Amps: The number of amps remaining in the battery...

Many folks interchange Amps & Amp-hours, but they're very different. Amps are an instantaneous measure of current flow, not a measure of capacity. Amp-hours (Ah) multiply this by how many hours the current has been flowing, & is usually a measure of how much is still in the battery bank (or how much has been taken out).

Using the incorrect units is potentially confusing, especially for folks new to this whole business, so it really helps to use the correct units. For example, a good 80Ah starting battery can deliver 300A to a starter (for a brief period).

[Macblaze]

Originally Posted by Jon Hacking

.

Using the incorrect units is potentially confusing, especially for folks new to this whole business, so it really helps to use the correct units.

My bad. But the pesky software won't let me go back and edit my post...

[smac999]

the first screen is the voltage at the inverter / charger (not necessarily the same as the batteries do to draw / drop) and the amps is the amps in / out of the inverter charger only.


screen 2 is SOC in % (assuming it's been set up to correct AH)


3rd screen is actual battery voltage and net current in / out of battery measured from battery monitor. along with AH removed.


make sure the battery type, battery AH, and absorb time have been setup.


pretty much you can just leave it on the SOC page.

[wrwakefield]

Hi Steve,

I installed a Magnum inverter, remote, and battery monitor kit earlier this year.

The Magnum Remote accommodates several add-ons sold by Magnum, and has programming built-in for each. (e.g., Battery monitor kit, generator remote start, etc.)

If you delve into the menu system on the remote for one of those add-on systems it will tell you that system is not available- but sometimes in a confusing way...

So, do you know if they also installed the Battery Monitor Kit? (BMK) If so, they will also have installed a shunt on the negative bus feed, and you will have access to very accurate battery information. Without the BMK (and per tech support at Magnum) the remote only estimates all the battery read-outs and is not nearly as accurate.

Once you determine what other add-one they may have installed I'll be able to provide more refined feedback.

You have a good system. With patience for yourself you will become an expert.

Cheers!

Bill


-Bill
SV Denali Rose

[Steve O]

Yes Bill I have a BMK.

I realize there is a lot of information being presented by the system. The problem with the manuals is really two fold. One: They use one heck of a lot of unfamiliar short forms and/or initials (SOC, BTS etc) and Two: There is no explanation of what the importance of the various readings is.

I must say that I am still working my way through the myriad of links that have been provided by this forum. Thanks everyone

[TranceNT]

Reference the nice Latin quotation: Gaudeamus igitur iuvenes dum sumus..

What about us elderly people ? I didn't do Classics, and when I first read " Carpe Diem" I thought immediately of some people I had met who were constantly carping every day.
Then I found out how hard it was to comply with those two words.

Onto battery monitors and beyond.

One thing a good battery monitor needs to show (and few do) is leakage current to metal hulls. Both polarities in cases where a properly isolated DC system is the goal. The house battery can easily become a silent assassin.

Sure, there are systems dedicated to corrosion measurement and management, but the technology is available and so cheap to include and the fascia of your instrument panel is becoming a crowded piece of real estate these days.

Cheers, Terry (an Electrician in a past life)

[Macblaze]

Originally Posted by TranceNT

Reference the nice Latin quotation: Gaudeamus igitur iuvenes dum sumus..

What about us elderly people ? I didn't do Classics, and when I first read " Carpe Diem" I thought immediately of some people I had met who were constantly carping every day.
Then I found out how hard it was to comply with those two words.

Onto battery monitors and beyond.


Cheers, Terry (an Electrician in a past life)

The iuvenes part has long since become a state of mind... :-)

And I agree that the monitors are often less a true inductor than a crutch. But it's a crutch I like ...

[facciatosta]

What about simple DC amp meter connected in series( or via shunt)? Like in old times. This should cover all needs. If current is positive - battery is charging, if current is negative - battery is discharging. By observing amount of discharging current you can estimate how long the battery will last. If there are no loads connected but amp meter shows negative current then there is leakage somewhere.
The capacity of the battery can be derived from the charge time. If, for example, it takes one day to charge new battery but only one 1 hour to charge old battery with same charging current then it is evident that old battery has no capacity. Once again, whether battery is being charged or not can be determined by amp meter.

[Jon Hacking]

Originally Posted by facciatosta

What about simple DC amp meter connected in series?...

Facciatosta, first let me say Welcome to Cruisers Forum!

Don't knock amp-hour meters until you've tried one. As an EE from way back, I didn't think I needed one (until I replaced what was probably a perfectly good battery bank too soon). Amp-hour meters (battery monitors) are wonderful! If a bit spendy...

To go with the old water analogy: If you have a tank (your battery) with hoses going in & out, you can see (with an amp meter) when water (electricity) is going into or out of your tank, & maybe you can see when the tank overflows (is full) or is empty (no lights). But it's very difficult to say, at any given time, how much water is in the tank. Not only does an amp-hour meter give you that visibility, but it also tells you when your tank is leaking so much that it should probably be replaced, before it splits a seam & all the water runs out (the battery dies catastrophically).

[Stu Jackson]

Originally Posted by Jon Hacking

Amp-hour meters (battery monitors) are wonderful! If a bit spendy...

Good points, Jon, But spendy? The Victrons are less than $200 and simple to connect. $200 isn't small potatos, but there are a lot more things on a boat that cost more. Like a bunch of batteries...

[wrwakefield]

Originally Posted by Steve O

Yes Bill I have a BMK.

I realize there is a lot of information being presented by the system. The problem with the manuals is really two fold. One: They use one heck of a lot of unfamiliar short forms and/or initials (SOC, BTS etc) and Two: There is no explanation of what the importance of the various readings is.

I must say that I am still working my way through the myriad of links that have been provided by this forum. Thanks everyone

Thanks, Steve,

Your mention of the alphabet soup in Magnum documentation brings back similar memories. I had forgotten how poorly written the docs are (poorly in that it is considered vary bad form to include acronyms without definition, and function without background.)

Management shortcomings are typically to blame- not the (obvious) techie who was delegated the task.

I'm traveling these next few days, but as soon as I can I will check to see if I annotated my copies of their docs as I sussed-out the mysteries of their acronyms, and if so share it here.

Otherwise, you are taking a valid approach: list the functionality and capabilities your Magnum system has currently and explore third-party resources for understanding the meaning of those capabilities.

Cheers!






-Bill
SV Denali Rose