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Wiring & Installing A Battery Monitor

Feb 26, 2004
20,847
Catalina 34 224 Maple Bay, BC, Canada
Harry,

You're right.

Most battery monitors for recreational boats are NET charge monitors. They monitor the balance of what goes out to what comes it.

It's not a leap to figure out what you USE. That's so easy it's child's play. It's what goes back IN, based on battery acceptance, that most people don't get.

Hence, using a net monitor works for most folks.

If you want to get more detailed info, try this (please read both pages):

http://www.cruisersforum.com/forums/f14/need-help-setting-up-my-battery-monitor-83034.html
 
Feb 6, 1998
11,094
Canadian Sailcraft 36T Casco Bay, ME
You raise an intersting dilemma for those with always-on generating sources like solar and wind. One useful data stream for a battery monitor is consumed power. On a boat with no power sources, you can begin to get an understanding of power useage, such that when you check the panel in the AM and see it is down 50AH since the night before, you know that it is "typical" or "uh oh, something is unusual." You can even get a feel for your daily consumption, so that you know how big a battery bank might be appropriate. Also, with a constant awareness of consumption, you can start trying to see what you can do to get that 50AH overnight consumption down to, say, 45AH.

With solar or wind, it absolutely has to go through the monitor, or you loose the primary benefit, which is tracking SOC. But, when you run it through the monitor, it makes a mess of such useful data as daily consumption and ROI from those expensive panels (if you can't see how many AH they've made this week, you can't get all smug about how good a purchase they were!).

Intersting dilemma. Perhaps it could be partly solved by buying a 2-channel unit, and setting up one channel to monitor the solar panel, not the battery. Then channel 1 would monitor SOC, and channel 2 would give cumulative power generated. The shunts would have to be in series, if that would work.

Harry
With a properly calibrated monitor the important screen is % charged or SOC screen on a Victron. This screen calculates for Peukert and is more accurate than simply watching the A screen or Ah/CE screen. This is of course assuming one has actually programmed the Peukert number for the bank into the monitor.

We do have two ammeters we use. One ammeter is for all the DC loads and the other is the LinkPro. By simply glancing at both I can see what I am using and what the "net" loss or gain to the bank is.

In this picture the solar panel is producing 0.9A. Or -4.6A System Load - -3.7A Battery Load = 0.9A contribution via solar.
 
May 16, 2012
10
Hunter 40 Georgia
Thank you for this article! It sure saved me some time and frustration this weekend. We installed our solar, mppt and Victron Monitor in about 4 hours, including mounting and running wires. Your article stating the importance of placement of the bus bar and shunt helped me get it right the first time!
 
May 16, 2012
10
Hunter 40 Georgia
In four hours this past weekend my husband and I installed a 100watt Aurinco panel, blixt mppt controller and this victron 600s monitor. What a joy to install quickly and have it all work the first time! MaineSail's tip about the negative bus bar placement saved me hours of frustration. The Victron reads everything. WooHoo!
 

jviss

.
Feb 5, 2004
3,934
Tartan 3800 Westport, MA
AH display does compensate for CEF

The SOC screen corrects for the Peukert component and CEF the Ah screen does not.
I bought this monitor (MBV-600) as part of my current battery upgrade. I was disappointed when I read this, because it seems to me it would make sense, and be easy to compensate for both Peukert effect and CEF while Amp-hour counting. I checked the manual and found:

The BMV can display both the Amp-hours removed (compensated for
charge efficiency only) and the actual state-of-charge (compensated
for charge efficiency and Peukert efficiency). Reading the state-ofcharge
is the best way to monitor the battery.
So, still not perfect, but better that nothing at all!

I question the wording of the manual, though, since CEF would apply to Amp-hours added to the battery, not removed, no?

In addition, I wonder about the firmware design. One would think that a set of internal variables are stored, and the display values calculated from them, so any display regarding the state of the battery would reflect all of the correction factors.

jv
 

jviss

.
Feb 5, 2004
3,934
Tartan 3800 Westport, MA
Answered:peukert exponent for Duracell 24DCC 75AH batteries?

Peukert exponent for Duracell 24DCC 75AH batteries?

I have four new 24DCC batteries from Sam's Club, made by Deka/East Penn. Anyone know the correct Peukert exponent for these?

Thanks,

jv

Update: answering my own question - called East Penn (duh!) and customer support told me that the Peukert exponent for this batter is 1.1275.

jv
 
Last edited:
Feb 26, 2004
20,847
Catalina 34 224 Maple Bay, BC, Canada
Good thinking there, jv!

As to your post about the monitors, I think we should begin to realize that these monitors are NOT fancy :laboratory quality" measurement tools, but they DO give us a LOT more information than we ever had before.

As we have noted many, many times before, a good energy budget calculation will easily tell you what comes OUT of your house bank, but most of us rarely recognized that the battery acceptance meant that it took WAY longer to replace the amps than it did to draw them out. http://c34.org/bbs/index.php/topic,4787.0.html

For their intended use, they work just fine. You have made a very good point that reading the manual is extremely helpful (RTFM).

Maine Sail also points out that resynching the units when you know the bank is full is also very helpful to avoid creeping inconsistencies in the readings.
 

jviss

.
Feb 5, 2004
3,934
Tartan 3800 Westport, MA
Thanks Stu. Regarding re-synching them, yes, I am aware that Maine recommends this, but I am disappointed that this is necessary. I mean, I don't have to resynch my fuel gauge when I fill the tank, nor do I have to calibrate my voltmeter periodically. I had expected a battery monitor to tell me when the batteries are full, not the reverse. The fact that this battery monitor makes a strong assumption that when a charging source is present the battery is the current limiting component, and is fooled by current limited charging sources, e.g., solar; and that it doesn't account for Peukert's law when accounting for Amp hours is poor, uninspired design, in my opinion. But, it seems that all of the alternatives are similarly handicapped, so you have to program around it and live with it.

It's really quite frustrating. I mean, how is it that the BMV-600 can display state of charge which accounts for both Peukert's law and charge efficiency, and simultaneously display AH available that accounts for charge efficiency but not Peukert? (that's a rhetorical question).
 
Feb 26, 2004
20,847
Catalina 34 224 Maple Bay, BC, Canada
jv, in answer to your rhetorical question :): it's simply the algorithm. Why they didn't is beyond me, too. But at least knowing how it works is a step in the right direction.
 

jviss

.
Feb 5, 2004
3,934
Tartan 3800 Westport, MA
jv, in answer to your rhetorical question :): it's simply the algorithm. Why they didn't is beyond me, too. But at least knowing how it works is a step in the right direction.
Yes, of course, but it seems like lazy programming, or perhaps very poor product management, i.e., requirements development. I can imagine it would be pretty easy to account for Ah's flowing out with a Peukert's law correction, since we know that the value the user programmed in for total Ah capacity of the bank is the 20 hr. rate. I doubt, however, that there's a way of updating the firmware in this, let alone the manufacturer ever releasing a firmware update. You will most likely never see it, or have to buy a "new and improved" unit.
 
Nov 16, 2012
866
Catalina 310, 2000, #31 Santa Cruz
Quick question about the BMV600S shunt. What size are the connections? 3/8? 5/16? I'm ordering up pre made cables and can't find that info on the Victron site.

Thanks
 
Jun 6, 2006
6,982
Hunter 40.5 Harrington Harbor North, MD
Hey Jviss
You have hit upon the major issue I have with the gadgetry. It takes a lot of fussing with. If I have to understand what is going on to that extent what do I need the dang thing for? I have a volt and ammeter and do fine writing down the voltage in the boat log. After a few sessions of anchoring out you get the feel for what is and is not a "make it through the night" start voltage.
This might help:
http://www.scubaengineer.com/documents/lead_acid_battery_charging_graphs.pdf
 
Jun 6, 2006
6,982
Hunter 40.5 Harrington Harbor North, MD
On a related note: I'm kinda interested in what information most find useful.
Current SOC is only thing I can think of that would be of use.

The time till discharged is bogus as I would have to leave the load the same. Possibly useful right before I go to sleep but if the banks are that discharged I probably have not been doing good sailoring.
volt and amps are already available on the panel so that is redundant.
AH remaining is bogus for the same reason time till discharge is.

What else is available and how would that info be used other than informing the Admiral that we have xxx yyys left?
 
Feb 26, 2004
20,847
Catalina 34 224 Maple Bay, BC, Canada
Yes, of course, but it seems like lazy programming, or perhaps very poor product management, i.e., requirements development. I can imagine it would be pretty easy to account for Ah's flowing out with a Peukert's law correction, since we know that the value the user programmed in for total Ah capacity of the bank is the 20 hr. rate. I doubt, however, that there's a way of updating the firmware in this, let alone the manufacturer ever releasing a firmware update. You will most likely never see it, or have to buy a "new and improved" unit.
Not really. As I've mentioned many times before about these little computers, all they did was choose a DEFAULT value. Many folks have small battery banks of 200 ah. Lately, that's moved up to 400 ah for those of us with fridges.

It's simple: RTFM. :D
 
Feb 26, 2004
20,847
Catalina 34 224 Maple Bay, BC, Canada
On a related note: I'm kinda interested in what information most find useful.
Current SOC is only thing I can think of that would be of use.

The time till discharged is bogus as I would have to leave the load the same. Possibly useful right before I go to sleep but if the banks are that discharged I probably have not been doing good sailoring.
volt and amps are already available on the panel so that is redundant.
AH remaining is bogus for the same reason time till discharge is.

What else is available and how would that info be used other than informing the Admiral that we have xxx yyys left?
Not really. In my Link 2000, the time remaining is based on the settings for amps being used. That can be programmed for instantaneous up to a rolling average of 4, 16 or 32 minutes. Since most fridges, once cold, only operate for 30% to 50% of the time, this is a pretty realistic measurement.

You can stick with your ammeter and voltmeter, but don't discount the usefulness of these instruments for many other sailors.

There's a good reason that many folks suggest that battery monitors should be the first thing skippers buy when they're updating their electrical systems.

I find mine very helpful.
 
Jun 6, 2006
6,982
Hunter 40.5 Harrington Harbor North, MD
So time till discharged (presumably to some % level you set) is based on an assumed load (presumably the "standard load")
Not at all sure how I would know the standard load if I did not have an ammeter in the first place. Perhaps you hone in on the downrange variables as you use the unit. aka fussing
Also if you have a wind or solar does not all that go out the window? I suppose it would read negative time till discharge if the sun was out or wind was blowing. does it have a (assumed again standard charging amps) time till charged function?
 
Jun 6, 2006
6,982
Hunter 40.5 Harrington Harbor North, MD
For the record: I don't have anything against monitors or the folks that use them. I've been trying to understand what they provide that is SO useful. After reading the rest of the posts it seems that SOC is what most are using. That makes sense to me as I use that info too.

Given that they cost some hundreds of bucks I'm thinking that is a lot of beer or perhaps a new bikini for the First Mate.
 
Feb 26, 2004
20,847
Catalina 34 224 Maple Bay, BC, Canada
So time till discharged (presumably to some % level you set) is based on an assumed load (presumably the "standard load")
Not at all sure how I would know the standard load if I did not have an ammeter in the first place.
No, Bill, it is based on the measured amps and calculates the time remaining based on the "period" (i.e., instantaneous, 4, 16 or 32 minutes) that the instrument is set for. The battery monitors measure amperage, so given the battery capacity, it can easily calculate the time remaining. The Link 2000 that I have shows amps, volts, and amp hours (actually converted from KwHrs).

I respect you for doing your thing with volts & amps. All I've ever said is that it's a useful instrument for many skippers. Like all things in boating, different strokes...

I've also said, probably earlier in this thread, and in many others, that most skippers can easily tell what their amperage draws are and calculate amps OUT. What is most difficult, because of battery acceptance, is what one PUTS BACK IN in terms of amps, and I contend that simpler instrumentation simply cannot do so.

$160 is hardly "hundreds of dollars." I've always felt it has a great ROI since it saves batteries, which themselves are costly.
 
Feb 6, 1998
11,094
Canadian Sailcraft 36T Casco Bay, ME
So time till discharged (presumably to some % level you set) is based on an assumed load (presumably the "standard load")
Not at all sure how I would know the standard load if I did not have an ammeter in the first place. Perhaps you hone in on the downrange variables as you use the unit. aka fussing
Also if you have a wind or solar does not all that go out the window? I suppose it would read negative time till discharge if the sun was out or wind was blowing. does it have a (assumed again standard charging amps) time till charged function?
Bill,

How are YOU calculating for Peukert...???? These monitor / capture amp in/out based on a re-set at 100% SOC and proper programing..

They also calculate the Peukert effect and preset the % charged on the screen. Are they 100% accurate? No, there is no such thing when it comes to batteries, but they are as close as can be.

In every single instance where I have installed a battery monitor, including numerous monitors on customers boats who are EE's, they got considerably LONGER battery life.....

They pay for themselves in nearly every instance where I have installed them... For the $155.00 - $185.00 they cost it is hardly a bad boat buck expenditure. I don't have a single customer who regretted it. I just looked at my Victron data and I sold a LOT of them last year. Not one single complaint and only glowing reviews...

Some who were ADAMANT they could manage their bank by voltage alone, mostly my EE's, were very surprised to find out they were doing a poor job of it....

You've argued against them for years because you claim to be able to monitor your bank based on voltage only. Well, the VAST MAJORITY of boaters can NOT do this and RUIN battery banks trying... You've even told us how you were going to build us an "affordable one" because the commercial ones were a waste of money and these devices were "simple" to build, but as of yet we've seen nothing......... Build me one and I will sell boat loads of them IF it tests accurate....