How many Amps Hours do you use a day?

[rom]

Originally Posted by Ip485

Whichever way you cut it without shore power resorting to the Genset for a few hours a week would seem the absolute minimium, or, a night in a marina at least once a week.

Over say 7 years that will cost you more than a big Lithium battery pack !

[runnerman1]

60-20 ah/day it depends

[Ip485]

Rom - how true, but I dont want to live on the hook, so that works fine as a by product. I am very happy to have three or four days at a time mind you.

I did think about Lithium actually, it wasnt the cost but I just couldnt face replacing both chargers and all the cells - probably regret it at some point, but I am figuring with my new found knowledge the 660Ah Lifelines should be fine, as long as I can keep the Genset time down. I dont mind running it for a few hours at a time at all, I was beginning to worry it might have ended up being for a lot longer! I am going to figure out where to put one more panel to bring the solar up to 1,000W. I do have two suitable places, either on top of the davits which will happily take one panel or on the deck below the boom as it isnt a crossing point and there is a big expance of deck (not ideal I know as the shading will be greater).

Anyway my expereince with the Lifelines was very good before. I am only regretting I didnt check all the settings for the Rolls and left it to professionals. Still the supplier has been kind enough to come up with the Lifelines at cost and installed them as well together with setting all the chargers correctly (which I have double checked this time!! not that I had any doubt on this occasion).

[OceanSeaSpray]

Originally Posted by john61ct

Are you saying two meters in the same location are required because they are one-way?

Of course not. Read my previous post carefully. You need to measure two different currents and then you can deduct the third one and know how much you are: 1/ producing 2/ consuming and 3/storing.

Originally Posted by john61ct

Every battery monitor I've seen measures two way, net current result of both in and out from a single shunt.

Of course it does. This is not the point. It can't measure current it can't see because it is flowing elsewhere and bypassing the shunt.

[Maine Sail]

Originally Posted by Ip485

Maine Sail - that is a very useful link.

If I have read it correctly (only so far had a quick read) and assuming the results are scaleable it seems to me I might manage the .2C rate (I have 110Ah aside from solar and engine) but so far I have only seen what rate I can put in at 75% DOD. From memory it is well short of 110Ah. I have yet to establish, reagrdless of the chargers rating, what output they are actually capable of maintaining.

Never the less (again if I am understanding the results correctly) it would seem at .2C and 50% DOD, 110AH is sustainable for maybe around the first 1.5 hours (660Ah Lifelines) and then starts to tail of dramatically.

If this could be achieved from 50% DOD a good profile might be to run both chargers on the Genset for around 1.5 hours, and then drop over to solar which, if correctly spec'd might just about provide 240AH, so a combined 405Ah of the required 330Ah required from 50% DOD.

On the other hand with three panels close to 100% may be achievable, but without perhaps getting to 100% and with a much lower initial rate well below .2c - perhaps arguably ok in terms of battery life for 6 days out of 7 with a Genset augment charge once a week.

Whichever way you cut it without shore power resorting to the Genset for a few hours a week would seem the absolute minimium, or, a night in a marina at least once a week.

Are you saying you have 110 AMPS of charge current avaible or a 110 Ampere Hour (Ah) rated battery bank? You later state you have a 660Ah bank..??

[OceanSeaSpray]

Originally Posted by Ip485

Ok. So I use the gauge to measure the charge going in (with no load), and immediately switch off the charger, and read the charge going out (with a known load). Both pretty accurate we agree?

Correct. If you artificially force the load or the source current to be zero by switching off, then all current must go through the battery shunt and you can see all you are consuming or producing. Note that the source figure might change at this point if the battery can't absorb it all!
If you want to get this information continuously on a live system without disturbing it, then you need one more shunt and meter.

Originally Posted by Ip485

Then taking the readings with the same charge going in and out. You are suggesting there should be a difference which represents the charge not going through the batteries? Is there a percentage that you would typically expect or does this depend on the state of charge of the batteries.

Maybe, if I understand you correctly. One you have obtained your total load current (by switching off the chargers), you can work out how much of the load is supplied by the battery and how much directly by the charger by turning the chargers back on and reading the battery current. You may find that the charger supplies all the load current + some more charging the battery, or both the charger and the battery are powering the load together.

Think about it this way, intuitively:

1/ If you have your charger on, the fridge on and the monitor says you are charging the battery, does it mean that you are not currently using any energy on board?
Of course not. It means you are producing more than you are using and the difference Source-Load is going into the battery.

2/ How come you can't see your load consumption?
It is because that energy is not coming from the battery. You need to turn the charger off to address this, or add another ammeter measuring all consumers on board.

When the chargers feed into the (+) busbar, if any loads are on, the current might split. The split can be influenced by the state of charge of the battery indeed, but it mainly depends on the capacity of the charger and size of the loads:

If the charger can't supply all the current for the loads, the battery will make up for the difference. If it can supply more than the loads need, it will fully power the loads and also charge the battery.

Originally Posted by Ip485

Also you refer in particular to a solar charge, presumably you aren't distinguishing solar from any other charge source and would argue the same result should apply regardless?

Yes. I used a solar source for simplicity as an example. More generally, you are looking at the sum of all the energy sources feeding current into the system on one side and the sum of all loads consuming current on the other.

Bottom line: you can't look at a battery monitor and say "this is how much energy I use daily" if you charge and consume simultaneously. All it shows is how much came out of the battery.

[Ip485]

Originally Posted by Maine Sail

Are you saying you have 110 AMPS of charge current avaible or a 110 Ampere Hour (Ah) rated battery bank? You later state you have a 660Ah bank..??

House bank 660Ah Lifeline AGM

Chargers 50 Ah Victron and 60 Ah Charles

Currently 660W solar may increase to 990W from 2 to three panels

Balmar alternator

[Maine Sail]

Originally Posted by Ip485

House bank 660Ah Lifeline AGM

Chargers 50 Ah Amp Victron and 60 Ah Amp Charles

Currently 660W solar may increase to 990W from 2 to three panels

Balmar alternator

Above this is where the confusion came from. 110A of charge current on a 660Ah rated bank is an approximate .17C charge rate so the numbers from the article at .2C will be a decent guide....

[john61ct]

OK clear, and yes all that's self-evident to me.

Bogart's Pentametric is good monitor with some flexibility for those wanting a standing setup logging such data from multiple points.

It does not however control the solar charging like the more limited Trimetric.

I like the idea of a $20 meter with APP connectors able to be moved around as needed, plus a clamp meter to cross-reference.

[missourisailor]

I have and been using a two shunt/one meter system for years.

Both shunts are 500mv, positive shunts. One mounted on the battery lead and the other on the feed supplying the distribution panel. Both shunt sense leads go to a DPST switch and then to the meter. I have the meter set to read negative for loads and positive for charging.

Remember an Amp meter is nothing more than a volt meter. It read the voltage difference across the shunt. So flow one way (charging) it reads a positive voltage and the other way (discharging) a negative voltage. In mili-volts of course. The meter converts it to useful info., like amperes.

The distribution shunt always sees a negative value because electron flow is always in one direction. It’s the setting that I use to see true house loads.

On the other hand, the battery shunt can and does see flow in both direction.
So when the battery shunt shows a negative value, even with the charging sources running, the load is greater than the charging sources output. When it shows positive, load is lower than available supply.

Things start to get screwy is when the batteries start to reach full charge. The battery shunt will swing back and forth from pos to neg. Only a few tenths of a volt but still a swing.

At this point, the distribution shunt will show the reciprocal charge value.
I.E. when the battery shunt is swinging, a -5amp reading on the panel shunt means that the charging source is suppling 5 amps.

[Ip485]

Both shunts are 500mv, positive shunts. One mounted on the battery lead and the other on the feed supplying the distribution panel. Both shunt sense leads go to a DPST switch and then to the meter. I have the meter set to read negative for loads and positive for charging.

Do you mean 500mv or 50mv? I can see 50mv shunt are commonly available.

What meter do you use?

Presumably a 500A shunt is fine with 660AH house batteries?

Also do you mean 50mv, which seems to me the type commonly available?

The listings I have seen dont mention specifically it being a positive shunt.

[rom]

Originally Posted by Ip485

Do you mean 500mv or 50mv? I can see 50mv shunt are commonly available.

My bank is 660AH - so presumably the shunts should be rated at least at this? Again 500AH 50mv are commonly available but high AH seems more problematical?

The listings dont seem to mention the shunt being poistive? Is it the case most listed are?

What meter do you use?

I use 500A (not Ah) rated shunt. You're almost there !

[Ip485]

Rom - hehe, you will see I edited my post before you replied!

[missourisailor]

Originally Posted by Ip485

Do you mean 500mv or 50mv? I can see 50mv shunt are commonly available.

What meter do you use?

Presumably a 500A shunt is fine with 660AH house batteries?

Also do you mean 50mv, which seems to me the type commonly available?

The listings I have seen dont mention specifically it being a positive shunt.

!!!!BRAIN FART TIME!!!!
Ye,s I meant 50mV. However they are rated at 500A too.

The amp rating is only critical for total load rating. If you are going to use two or more shunts for one meter, you must have the same mV spec.

There really is no such thing as a positive or negative shunt. What makes the difference is the meter. It will determine whether or not to have the shunt in the pos or neg leg.

I use Blue Seas Digital A/V meter.
https://www.bluesea.com/products/824...ter_with_Alarm

But you will notice that it uses a neg shunt.
You need to use their shunt shifter to use it as a pos shunt.
https://www.bluesea.com/products/8242/DC_Shunt_Shifter


The reason that you need to use the shunt shifter is because the meter uses a common ground. with out the shifter, this common ground doesn't exist.

[Ip485]

I ike the sound of that system.

So I understand you have the shunt shifter on the positive supply into the house batteries and another shunter system (the same Blue Seas one) on the supply to the main distribution panel.

Both shunt shifters are connected to the one meter, with a rocker switch to select which shunt is being read?

I am guessing you could have two meters and do away with the switch?

Is this the ultimate system in terms of very accurately measuring the input and output of the house bank?

It makes me wonder why there isnt a "commercial" product configured in this way which uses the the information from both shunts as it seems to me it would be more accurate that the usual stuff on the market.