Balmar SG-200 Battery Monitor

[Stu Jackson]

Originally Posted by john61ct

The point is the ability to record AH/24hrs usage for specific circuits, loads or sources, while systems are in production use, without having lots of shunts permanently wired in.

I certainly don't see how "a simple switch" would get you there, obviously just turning things off and on while systems are in use does not.

If you don't want that info, or think it's not worth the effort, fine. I was pointing out how it can be more useful than a single system-wide measurement.

The point I think you're missing is that the entire basis of using a cc, or any electrical tool for that matter, is to start with an energy budget and use the tool to confirm expectations or changes.


I discussed this earlier in this thread. Do the budget first. Don't use the tool as a starting point.


A good cc will tell you both instantaneous amp draw as well as accumulated ah. You can easily figure instantaneous loads by simple switching.

[Delfin]

Originally Posted by ontherocks83

I would argue for an option where the AH counter can be set to user reset only. With the SG200 giving me all of the other info I would need about the battery, I personally wouldn't really care about having it reset at the end of a charge cycle because I would want to control which time periods I was interested in monitoring. i.e. every 24 hours or overnights etc. without having to worry that it is going to reset in the middle of the day because I turned on the engine.

Totally agree.

I use a Link 20 as a cc, and installed a reset button so I can zero out the device after recharging the LFP bank. If I have both SoC and Ah used I can easily determine the capacity of the bank as it degrades over time. If both values are accurate, then if my 600 Ah bank has had 300 amps used but the SoC is 45%, I've lost capacity. Very useful information.

[a64pilot]

See, I’m going to argue the whole budget thing a little.
1. If your not actually cruising, then any budget will be at best a wild guess.
2. You have to have an amp counter, and be actually in your use case, cruising say to determine actual usage.
Once usage is known, then you can structure an electrical system that will support it.
Or, you do what most I believe that actually do any planning do, and that is install a system that covers worst case guess, or as big a system as is realistically possible, and then learn to live within that budget.

Although I’m convinced from talking to people, that most don’t have a clue. Talked to one couple in a boat like ours, that didn’t know if they had a battery charger or not.

[rgleason]

MaineSail information about use of SG200 to increase accuracy of SOG and SOH
http://www.cruisersforum.com/forums/...ml#post2780484

BTW I asked Chris W. from Balmar about using two shunts in series and he advised it would just cause a small drop in voltage and would not be a problem.

See http://www.cruisersforum.com/forums/...-a-211193.html
Also Mainesail advises about use of the BMV-712 shunt.

[john61ct]

SoG? should be SoC?

[rgleason]

Yes, a slip on the cell phone.
Thanks for the explanation CNB and MS.

[Stu Jackson]

Originally Posted by a64pilot

See, I’m going to argue the whole budget thing a little.
1. If your not actually cruising, then any budget will be at best a wild guess.
2. You have to have an amp counter, and be actually in your use case, cruising say to determine actual usage.
Once usage is known, then you can structure an electrical system that will support it.
Or, you do what most I believe that actually do any planning do, and that is install a system that covers worst case guess, or as big a system as is realistically possible, and then learn to live within that budget.

Although I’m convinced from talking to people, that most don’t have a clue. Talked to one couple in a boat like ours, that didn’t know if they had a battery charger or not.

We know some folks with a very nice IP350 who have never used their battery charger, have solar and wind, brand new Firefly batteries, and a Link monitor. They, too, have NO CLUE about how their system works. Unfortunately, they think they do...


a64, re the budget "issue"...As you know, there are two variables in the budget: actual load and time. Almost every device employed on boats has a pretty good track record of what the load is. Usually nameplate load is larger than actual use. We KNOW this now because after decades of teaching boat electrical stuff and reading, the use of ammeters and shunts with BMs has shown this to be true.


Therefore, the ONLY variable left is time. That is completely individual and except for known 24/7 run items like the ubiquitous "standard boat" fridges (5A, 50% run time, 60 ah per day).


That's why I suggest starting with a budget and modifying it based on use.


Of course, your last two paragraphs are ways to do it.


Over years I've done budgets and compared it to my meter.


Record of Daily Energy Use of 100 ah per day:

"Breaking In" New Wet Cell Batteries


This works for coastal cruisers like me with a fridge and a 400 ah house bank, but no solar or wind or generator. Any charging source other than ICE always helps.

[witzgall]

Originally Posted by noelex 77

The number of AHrs down tends to be a more important parameter than the SOC. It is also is a more accurate parameter than SOC.

This may be a reasonable argument for a traditional, shunt based system. The opposite, however is true for the SG200. The reason is that we are doing very different things to calculate SoC, and it is very much more accurate because of this.

Chris

[john61ct]

Chris,

Could you help us come up with a single term for

"the special things done by the SG200 to calculate SoC"

in other words **in addition to** coulomb-counting,

so we do not need to reference others' products' technology in discussing how the SG200 is different and more accurate.

Without a lot of excess verbiage like "sophisticated proprietary mathematical algorithms comparing to internal database of known chemistries"

Say for example we called it

"AC impedance spectrography" (just an example)

So one could say something like

"The result of the usual AH counting technology, is compared or integrated with the results of the proprietary */AC impedance spectrography/* side, to not only provide a very accurate SoC measurement, but also - uniquely - a State of Health percentage estimate of remaining AH capacity at the 20-hour discharge rate"

?

[rgleason]

SG200 Manual on the 29th page (This is quoted.)

--------------------------------
"Converting Reserve Capacity to Amp Hours


"The following formula converts Reserve Capacity, typically expressed in minutes drawing 25 amp load, to amp hours at the 20 /hr rate."


RC (60) * 25/2600
Multiply Reverve Capacity by 60 to convert to sections.
Multiply by 25 to convert to coulombs.
Divide by 3600 to convert coulombs to amp/hours.


Example:
We have a battery showing reserve minutes of 130
130*60=7800
7800 *25 = 195,000
195,000/3600=54.16 ah"


End of quote

-------------------------------


(60*25)/3600= 1500/3600 = 0.4166 (factor to use)

so, 0.4166 * 130 minutes= 54.158 ah


So if you really need to have aH, just make the conversion.

[noelex 77]

Originally Posted by rgleason

(60*25)/3600= 1500/3600 = 0.4166 (factor to use)

so, 0.4166 * 130 minutes= 54.158 ah


So if you really need to have aH, just make the conversion.

That calculates AHrs left, not the Ahrs used.

[rgleason]

I said it was Reserve Capacity. So you want aH used? Example:

Actual Battery Capacity= 225ah new battery capacity x say 80% Soh = 180ah

180 ah - 54 ah = 126 aH used.

Actual Battery Capacity - (Minutes Left * .41) = aH used.

(If you have FLA batteries you just damaged your batteries a little.)

Eventually you'll just get used to the new measurement tool.

[Maine Sail]

Originally Posted by rgleason

SG200 Manual on the 29th page (This is quoted.)

--------------------------------
"Converting Reserve Capacity to Amp Hours


"The following formula converts Reserve Capacity, typically expressed in minutes drawing 25 amp load, to amp hours at the 20 /hr rate."


RC (60) * 25/2600
Multiply Reverve Capacity by 60 to convert to sections.
Multiply by 25 to convert to coulombs.
Divide by 3600 to convert coulombs to amp/hours.


Example:
We have a battery showing reserve minutes of 130
130*60=7800
7800 *25 = 195,000
195,000/3600=54.16 ah"


End of quote

-------------------------------


(60*25)/3600= 1500/3600 = 0.4166 (factor to use)

so, 0.4166 * 130 minutes= 54.158 ah


So if you really need to have aH, just make the conversion.

The only reason this is in the manual is for someone who purchases batteries not rated in Ah's and only rated in RC or RM at 25A. Batteries rated in RC or RM only are batteries that are very often not really a deep cycle design.

Also the formula is a guess, & often grossly inaccurate. There are a number of RC to Ah formulas out there. Some can get close but the only true measure is to get the 20h rate from the manufacturer.

For example lets look at the 12V Trojan T1275 rated at 150Ah and 280 minutes of reserve capacity at 25A.


280 * 60 = 16800
16800 * 25 = 420,000
420,000 / 3600 = 116.66Ah


For a battery rated at 150Ah.... At least it is airing on the side of caution...

A couple of formulas I have found that are a bit closer are;


RC / 2

280 / 2 = 140Ah (10Ah difference)

or

RC / 2 + 16


280 / 2 = 140 + 16 = 156Ah (6 Ah difference)


Bottom line, don't buy batteries that lack an actual Ah rating..

[noelex 77]

Originally Posted by rgleason

I said it was Reserve Capacity. So you want aH used? Example:

Actual Battery Capacity= 225ah new battery capacity x say 80% Soh = 180ah

180 ah - 54 ah = 126 aH used.

Actual Battery Capacity - (Minutes Left * .41) = aH used.

(If you have FLA batteries you just damaged your batteries a little.)

Eventually you'll just get used to the new measurement tool.

You are making a lot of assumptions and estimations to arrive at the final result.

A well set up, quality, conventional battery monitor will give a more accurate information about the AHrs used for example overnight, and of course will display the value without any mental arithmetic.

[john61ct]

Yes some confusion there.

"Reserve Capacity" is as MS states a formal units term, used in conjunction with Cranking Amps to compare Starter batteries, and can be a sign on 12V batteries in retail channels like the terms Marine Deep Cycle or Dual Use, that they are **not** actually suited for true deep cycling usage.

But in the case above used in a normal discussion context, it just means like the inverse of AH used, as with SoC as opposed to DoD.

So a 600aH bank, one person might say depleted by 400aH, whilean other that there are 200aH remaining "in reserve", no difference except POV, bit like half empty vs half full.

All in AH units, nothing to with "Reserve Capacity" in the sense above, which is the topic of that section of the SG200 manual.