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Old 04-06-2014, 12:18   #1
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Solar Charging and Measuring Total Amps

I've finally gone the solar route and have 375W of solar panels on the way. I don't need to know the charging voltage, since I've already got a Xantrex and the boat panel telling me that. If I install a DC ammeter then I'd be seeing the current charging value, but I would like to have an idea of how many amps in total have come from solar. I've done a quick search in Google and haven't found anything along those lines. I suppose, in a pinch, I could install a Xantrex or similar and only measure current going in one direction, but that is a bit of overkill.

Does anyone know of something on the market that can do this?
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Old 04-06-2014, 12:50   #2
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Re: Solar charging and measuring total amps

I assume you mean you have a Xantrex battery monitor installed that measures total amps and amphours used and you want to do the same, but just for the panel's output.

The only device I know that totals amphours is....another Xantrex battery monitor.

If you just want to temporarily know what the total amphours are from the panel for a single day, just shut off all internal boat DC loads. The difference in amphours for the period will be that which the panels provided.

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Old 04-06-2014, 12:53   #3
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Re: Solar charging and measuring total amps

I'm a little confused by your question. 'Amps' refers to a rate of flow of current. When you say 'how many amps in total have come from solar' do you mean amp hours, or do you mean how many amps your solar system is pumping in to your batteries in real time?

Either way yes there are plenty of battery monitor products that will measure such things. Xantrex makes a couple. Personally i'm a big fan of morningstar, who make excellent products. If you haven't already purchased a charge controller i would highly recommend the Rogue Systems MPT-3048 available as of June last year. I have one. It's brilliant. It doesn't give you quite as much information on the screen as a dedicated battery monitor but it will tell you voltages, currents, daily usage, how many amp hours (or watt hours) have been put in by the solar array and a host of other information that can be nice to know. There is also a bit of PC software that will talk to the controller and tell you everything you could ever want to know about the system in real time as well as historically. I've never actually tried the software as i'm happy as it is but it looks good if you're interested in really getting deep with it, and it's free i believe.
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Old 04-06-2014, 14:12   #4
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Re: Solar charging and measuring total amps

DefinitelyMe - thanks, I should have said total Amp-Hours rather than amps.

I happen to have hardware aboard to let me breadboard this (an ACS712 circuit and an Arduino with LCD display) but the darn thing only measure up to 5A, and my panels will put out just over 16A - plus if the monitor is cheap enough I'd rather buy one than play with progamming the IC.

I already have Genasun controllers for the panels, so don't need another MPPT.

You said that there a lot of monitors out there. Could you give me a brand name of one that measures and displays total amp-hours and current amps? I haven't found one that does that, and only that. As mentioned in the original post, if I find nothing I might get another Xantrex and use only parts of its functionality.
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Old 04-06-2014, 14:19   #5
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Solar charging and measuring total amps

I think what you're looking for is called an amp hour totalizer. Lots of companies make them.

You made the right choice, we've been sitting here in Florida for 4 weeks and haven't had to touch our engine to charge.
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Old 04-06-2014, 15:41   #6
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Re: Solar charging and measuring total amps

Quote:
Originally Posted by Zanshin View Post
DefinitelyMe - thanks, I should have said total Amp-Hours rather than amps.

I happen to have hardware aboard to let me breadboard this (an ACS712 circuit and an Arduino with LCD display) but the darn thing only measure up to 5A, and my panels will put out just over 16A - plus if the monitor is cheap enough I'd rather buy one than play with progamming the IC.

I already have Genasun controllers for the panels, so don't need another MPPT.

You said that there a lot of monitors out there. Could you give me a brand name of one that measures and displays total amp-hours and current amps? I haven't found one that does that, and only that. As mentioned in the original post, if I find nothing I might get another Xantrex and use only parts of its functionality.
Could you put two branches of known resistance in parallel and then measure the current through one? If one was 3 times the resistance of the other, it would put 1/4 of the amps down one branch and you could use your existing totalizer on that one.
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Old 04-06-2014, 17:45   #7
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Re: Solar charging and measuring total amps

ebay and other sites have several 20-30A amp hour meters for a few bucks

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Old 05-06-2014, 04:23   #8
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Re: Solar Charging and Measuring Total Amps

Do you really need anything more then what you have.

My old charge controller died. It would display panel voltage, battery voltage and current amp output.

Replaced it with a Blue Sky MPPT which has a very simple display but I placed it an area that is not readily accessed. Blue Sky builds a monitor device that connects via twisted pair wires to the charge controller which will display what you are asking for but I have yet to install it.

I have a Victron battery monitor and can pretty easily tell from monitoring its values about where the batteries are and how well the solar panels are performing.

The Victron shows be current net Amp flow. From this I can deduce how many amps are being generating. If the refrigerator is running I may shut it down from its breaker for a moment to get a better idea of the amps being generated. The Victron also has a State of Charge reading for the batteries which is an attempt to monitor the net amp-hours (or energy) into the batteries and out of the batteries. When off the grid I use this reading as an indication of how well the solar panels are doing in keeping the batteries charged. Typically the value will drop overnight to about 85% and sometime in the early afternoon will be back up to 100%. Your Xantrex should provide similiar information. Read elsewhere about the Balmar State of Charge monitor which apparently supplies a better indication of State of Charge as it has a better method of calculating the current capacity of your battery bank.

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Old 05-06-2014, 04:31   #9
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Re: Solar Charging and Measuring Total Amps

Thanks for all the posts. I know I can deduce how much solar energy is coming in using my current Xantrex monitor, but I'd have to shut off devices and I don't want to do that; and getting a total Amp-Hour input from solar would still require additional hardware.
Once I stopped looking at chandleries and boat supply stores, I did find this device which fits my requirements perfectly. I'll get that and still program my own device for the fun of it, though.

Thanks.
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Old 05-06-2014, 04:41   #10
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Re: Solar Charging and Measuring Total Amps

Hello,

I live on my vessel full time, and I picked up a gadget called "WattsView". I found it at www.wattsview.com

It has a current transformer the plus cable passed thru from the controller to the bank. I connect the module to my computer and it logs in real time the full production of my solar. I even have one on the wind turbines.

It is a handy gadget, and the monitoring software works on a Mac !!!

Alan
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Old 06-06-2014, 15:08   #11
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Re: Solar Charging and Measuring Total Amps

Well, I've ordered parts to complete my installation. I was surprised (but not shocked) at how expensive cables are, but in order to prevent line losses I chose bigger cables than absolutely necessary. I've also found some ACS712 hall-effect sensors and am programming an Arduino micro to perform the "totalizer" function and give me total Ah charged since reset and per day. For those interested, here is my installation schematic:



Since the 3 panels are monitored separately, I can also cycle that display to show me values per panel and perhaps be able to reposition panels for optimization and detect when they are under-performing. And for electronics purists the Arduino power supply is 5V, so there are some small caps and a DC-DC converter in there to supply regulated voltage for the IC and as a regulated reference voltage so it can compute volts and watts correctly.
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