12/24 V Ah meter

[amiklic1]

I would like to have some info about how many Ah my devices "pull" out of the battery bank. That's something like Xantrex TM_500 power meter. The only thing is that I'll try to build something like that by my own. Can I change 220 W kwh meter to do theat instead of building totally new device?. If I change the coil, so it would turn with 12 volts load instead with 220, I think it would be OK.

Anny suggestions?

[drdongle]

If you talking about a KWH meter like the power company uses, no you can not convert it 12 VDC. You need an Amp meter which is placed in series withe the device under test and a volt meter parallel with the device under test. You then multiply the two readings together to get the watts. example: .3 amps ( 300 MA) x 12v = 3.60 watts

[nothing to lose]

As stated you need an amp hour meter, what you said (if power company type) is a Watt Hour meter.

I don't know if it will work or not, but if you have the meter already, you might be able to wire it on the AC side of your inverter. Ask someone smarter than me first though to be sure it works this way!!

 You know that you have steady 120Vac comming out of the inverter right. So if you use 1,200 Watts of power (1.2Kw) divide by 120V and you used  10amps from your  inverter, or divide by 12V and you used "about" 100 amps from your batteries.

 either 1,200watts / 120V = 10amps.

 or 1,200watts /12V = 100amps.

You will have inverter and wire losses and such not figured in that also, so it might be closer to 110amps from your batteries. It should get you a close Idea though.

Make sure the meter itself will work though, I don't know anything about the meters really for wiring up to a 120Vac source, they may not work this way off an inverter, but if they will work that is how I would use it myself.

You can get an Amphr meter to install in the lines from the batteries, I am thinking about getting one or more. I need to find out more about them, like my inverter is 5K/10K surge, and at 5K that is 416.66 amps draw from 12V batteries, 800amp surge?

Not sure how expensive an amphour meter I would need to handle that :0

[Dzisko]

Since Voltmeter is the first and the most necessary tool when comes to batteries, then all you need is just an amper meter - almost any kind of almost any old arrow tools (from the car or an old tape recorder) will be good enough.

Disassembe it, and plug your circuit directly to coil - and just tune shunt then - in the most cases that will be just a piece of iron wire. Be careful, try firstly with a small load like small bulbs.

But even in this case you will be not able to count AH - you wlii need clocks and lots of free time to sit and multiply volts, ampers and hours all the time! :-)

And you can take a kind of small DC motor, attach it through reductor to some old mechanical counter (from the old tape recorder or so) and operate him from the your battery with a small simply circuit, containing shunt, any op amplifier? a few resistors and an old  middle-power transistor (plugged as a follower, or included in the whole circuit with a feedback).

But why do you need to count the free electricity?

Just a small simple circuit (something like the car charge control) to control battery state will be good enough, maybe volt meter to check the battery estate manually.

[nothing to lose]

Well one thing is it is fun to count the free power your using

If one amp counter shows you used 150amps and another on the charging lines show you charged 125amps you will know alot more about your system total usage than just the Battery is charged at 12.25V

With just one amp counter wired in you could maybe see how far from zero you are as it rolls forward as you use power and backwards as you recharge, I geuss in that case staying at zero amps would be best.

If you start the morning with full charged batteries and end the night with full charged batteries, does that mean you used no power that day?

While many people probably don't need to count amps really, it could be nice also. Like above, you might have used 200amps during the day and charged 198 amps, but if you just read voltages you only know the batteries started and ended with the same volts. In a 1000amphr or larger system I dought 10amps would show up missing very fast by just reading volts.

Myself, if I get a large wind powered off grid system running I think I would actually like to have 3 amp counters. One for loads like Inverter and DC, One for dumpload, one for incomming power. If set up as I am thinking I would be able to see the amps I made, the amps I used, and any amps that were dumped as excess power when the batteries were full.

 If I had resetable counters I could look at daily or weekly amps, however I often I reset the counters. In this way I would know more about my system averages and if I should be using more power to stop dumping so much or if I am using a little too much and losing a few amps a day.

Also if I know the amps made and used I can figure my Kwhrs for a month if I want, or at least a pretty close geuss at them. That also lets me figure how fast the payback on my system is going by comparing  my Kwhrs to a neighbors grid bill. They pay perhaps $35 for 500kwhrs of power plus $15 monthly charge for a meter in the yard. If I use 500kwhrs then my system got a $50 payback that month, money the neighbors had to pay for their power that I did not have to pay.

Another thought on counting amps in and amps out, if you know your battery systems rate of self discharge normally and your watching amps roll around, you would probably notice a bit faster if you start to have problems with a battery as it drags the system down slowly and creates a larger gap in amps your reading on the meters.

In other words as a system weakens and self discharge becomes greater you have to put in more amps to maintian a full charge over time. If you see your amps used are the same average as always but your putting in alot more amps, and the dumpload amps are average, those extra amps in had to go somewhere and that could be battery problems.

You know you did not use those amps or dump them and batteries are not over charged, you could have a weak battery draging the system down.

So it's kinda like the amp counters are not needed but still nice to have for alot of reasons. I would like to have a few right now for other reasons but they are not high on my list of things to buy right now. I'll grab em if I find them cheap somewhere though.

[Dzisko]

Hi. The forum moderator has removed my post - it was containing just a link to image (I have designed it specially for this case), and no more.

What wrong was in the link???!!! Or in image itself?

What???!!!!!!!!!!!!!!!!!!!!!!

Ok, I honestly tryed attach it here, but this form does not work with my non-jawa Opera, may it be a thing to pay more attention than block messages with links to "bad" and "abusive" pictures?

Ok, another way to see that "bad" picture - see my files here - it is the only.

[amiklic1]

I can't imagine the principle of the device you got there. But, I am interested in more details, so I could try to build it myself.

Can you give more info?

Here, or post me an message to andjelo.miklic1@st.htnet.ht

Thanks!

[Dzisko]

The principle is simple - the more current - the more current throuht C1. After C1 charged to  Ustab. Zener diode, the monovibrator begin to work , it force relay to act and discharge C1 so all returns to beginning and C1 begins charge again.

The more current through load - the more frequency of the whole process and wheels rotate more quickly.

CAD soft shows a good linearity, but that system was never made in real parts - that is why I do not show values. I can not be calm untill will check it myself...

And in the picture my email is shown - yes, I answer all questions. In case lots of people will need this circuit, then I will build it and check thoroughly and publish its last edition - with defined values.

But if you are not so patient - ok, we shall build it together :-)

What a strange email - is it working indeed?

I will try to reach you, but you (and everyone here, of course) may also direct me letter to address on the picture, and I will answer.

I always give my address only as a picture and still have no spam :-)

[Dzisko]

I have slightly changed design for those who love ICs.

See new circuit -> dcah-mtr.gif in my files.