Meter for amp hours produced

quiquequique Posts: 252Solar Expert ✭✭
Hi guys...

Again with the wind turbine, we want to be able to measure how many amp-hours are produced in a day. What "electronic component" would I need to buy to measure accumulated amp hours during a day?

Comments

  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: Meter for amp hours produced

    You can do this with a battery monitor like the Trimetric if you just want to watch the turbine output or the Pentamtric if you want to keep track of turbine, solar production, and inverter usage separately.
  • BB.BB. Posts: 27,681Super Moderators admin
    Re: Meter for amp hours produced

    A Doc Wattson may work for you at $60... They are rated to 100 Amps and 60 volts... But I would be hard pressed to see putting more than 20-30 amps through them on a continuous basis without making modifications (14 AWG wires, too small, possibly a better shunt--not sure).

    They do have documents on how to modify the meters for other uses (note that these meters only "go forwards", the do not turn backwards if the power flow is reversed (such as on a battery where you have loads and charging currents). Should be fine for your needs.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • quiquequique Posts: 252Solar Expert ✭✭
    Re: Meter for amp hours produced

    Will these solutions, trimetric or Watson, work by simply connecting the turbine wires to it, or do I need them to be hooked up to the battery bank?
  • BB.BB. Posts: 27,681Super Moderators admin
    Re: Meter for amp hours produced

    They need DC power--But I believe they both can be wired to draw power from the battery bank, but record unrelated power (you always have to be careful--Many electronics assume that everywhere has the same DC ground.

    But, you should always have the turbine attached to the battery bank (except if you use the shunt switch to stop the turbine--and that will disconnect from the turbine side of the Doc Wattson.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ChrisOlsonChrisOlson Posts: 1,807Banned ✭✭
    Re: Meter for amp hours produced

    I have used Doc Wattson meters for several years on non-MPPT turbines with an external 100 mV shunt rated at 100 amps. I would not recommend using the Doc Wattson with the internal shunt with a turbine of any size (larger than 2.5 meters) on a 12V system since a 3.0 meter turbine will reduce a Doc Wattson to a smoldering pile of goo inside 30 minutes on a good wind site. What gives out in them is the solder connection on the source side of the internal shunt - it gets hot enough to melt the solder and anything else in the vicinity of it.

    Doing the external shunt modification is fairly simple - you have to split the case with a razor blade and unsolder the internal shunt, then solder on a twisted pair to the Kelvin sense pads under the shunt and run the twisted pair to an external shunt. They will handle 144 amps peak with an external 100A shunt, but no more than 70 amps continuous.

    The Doc Wattson is pretty good on accuracy below 20 amps. Above 20 amps they get increasingly optimistic up to about +10% error at 100 amps.
    --
    Chris
  • BB.BB. Posts: 27,681Super Moderators admin
    Re: Meter for amp hours produced

    I believe Chris' solution would be to use this external shunt (on the RC-Electronics site, they have some documents that talk about various alterations you can make the meters--iincluding adding an external shunt--as I recall):

    wind-sun_2257_21027425Deltec 100 amp, 100 millivolt current shunt

    That would keep the Doc Wattson screen readings "calibrated".

    NAWS has a 500 amp shunt too, but then you would need to multiply the Doc Wattson AH/WH/Amp readings by 10x for the correct number.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • gww1gww1 Posts: 963Solar Expert
    Re: Meter for amp hours produced

    I bought the doc watson and an external shunt. Do I really need to change the internal shunt to the external one if I am trying to capture the out put of two hugh piggott 500 watt 48 volt turbines? The amps at the turbines rated output would only be around 20 amps combined. Am I going to get smoke from the doc watson if I equalize the battery bank at over 60 volts?

    I ask cause I am lazy. Also if It would work standard I can't screw it up by getting it too hot trying to solder and such.
    Thanks
    gww
  • BB.BB. Posts: 27,681Super Moderators admin
    Re: Meter for amp hours produced

    I have not seen the inside of a doc Wattson, but it has a 0.001 ohm internal shunt. So:
    • P=I2R= 20 amps2 * 0.001 ohms = 0.4 watts

    A 1/2 watt "resistor" can get pretty warm in a small sealed plastic case.

    An external shunt like this one:

    wind-sun_2257_21027425Deltec 100 amp, 100 millivolt current shunt

    Would work nicely.

    The Doc Wattson is rated for 60 volts maximum... But it does not use much power. You could setup a small 48 volt to 12 volt (or whatever) power supply and connect it to the Doc Wattson directly (split the case, or connect to "red wire".

    As Chris said, the Doc Wattson only measures current on the negative (black) leads, so the voltage can be connected to other sources. The user manual has a lot of information on modifications:

    http://www.rc-electronics-usa.com/docs/wu100v2_user_manual.pdf

    What may be your best options--Use a resistor divider or regulator to limit the input voltage below 60 volts maximum (say 10% drop, would support 66 volt battery voltage and would under report voltage/watt hours/watt peak by 10%--not too bad).

    If you use an (for example) 12 volt source, then the Watt/Volts/Watt*Hours would be meaningless.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ChrisOlsonChrisOlson Posts: 1,807Banned ✭✭
    Re: Meter for amp hours produced

    That shunt that Bill showed is the ones I have used, although I get them from PowerWerx in Michigan. It is a high quality shunt and even correctly shows 100 mV drop across the shunt at 100 amps. There is some calibration error in the Doc Wattson itself, though, at higher amp readings.

    gww - the Doc Wattson is not really recommended for 48V systems because of its voltage limitation.

    If you do modify one be very careful not to lift the trace on the board for the kelvin sense terminals where the meter reads the voltage drop across the internal shunt. If you wreck it you'll have to make a new solder trace from the pad to the terminal, or solder the twisted pair directly to the kelvin sense terminals. Soldering directly to those kelvin terminals is very fine work. That board trace that runs from the shunt pads to the kelvin sense is as fine as a human hair.

    The best way to remove the shunt is to make an appointment with your bride to help you do it. Have her hold the shunt with a pair of needle nose pliers, and heat up two high thermal mass soldering irons. Touch the irons to the pads where the shunt is soldered on and the meter will fall right off leaving your bride holding the shunt with the pliers. If you try to do it yourself you'll find you don't have enough hands and if you only get one side to come loose it will bend and lift the trace on the other side.
    --
    Chris
  • gww1gww1 Posts: 963Solar Expert
    Re: Meter for amp hours produced

    Bill/Chris
    Dang, I had got some advice on this meter at the otherpower forum. I did mention it was for a 48 volt system. I paid $103 for the meter, external shunt and shipping. I see that it can be changed for voltage by what bill posted but it is above my head to what I might end up with. I wish I would have researched a bit better. I don't even know if I really need to know what the turbines put out as knowing won't really change what I get. I might just get some cheap amp meter and put on the turbines.

    Rather then use it I could try to sell it and get something that might work "better?" or just hook it up and load test it. I don't sell things well. I will just probly use it where I don't really need it. I have a twelve volt turbine hooked to two lawn mower/one car battery used for trolling moter. I also have 180w worth of solar and two car batteries at a rv parked on a creek. jeeeze.

    What would work better (Cheapest) to check my turbines output to my 48 volt battery bank ?

    Thanks
    gww
  • gww1gww1 Posts: 963Solar Expert
    Re: Meter for amp hours produced

    In english and dumbed down as much as possible, What does the below quote mean in real life?
    3. Remove internal power sharing diode. *** This is an Absolutely unsupported
    modification – don't even think of getting support for this or making a warranty
    claim on a meter whose case has been opened ***. With the case open, carefully remove
    diode D1. Once done, this will require powering the meter through the Auxiliary
    Connector, but will also make the meter more robust against overvoltage transients and
    remove the requirement that, to be the sole power source, the Auxiliary Connector voltage
    must exceed the measured SOURCE voltage.

    Thanks
    gww
  • NorthGuyNorthGuy Posts: 1,925Solar Expert
    Re: Meter for amp hours produced
    gww1 wrote: »
    In english and dumbed down as much as possible, What does the below quote mean in real life?

    I think this means the following:

    1. You can power the device from either "source" or "aux"
    2. The diode, called D1, is installed between the "source" and device. The idea is that if you get higher voltage on "aux", diode will isolate "source" from the device. If not, the diode will conduct and power device from the "source"
    3. Source may have transients, which may be bad for the device. Therefore, they recommend using "aux" for the power. To do that, obviously, the voltage on "aux" must be higher than "source"
    4. You want to use "aux", but you do not have a high enough voltage to connect to it
    5. The solution for you is to remove D1, thereby disconnecting "source" completely.
    6. You now can power the device from "aux" with low voltage without being afraid of transients on "source"
    7. If you dare to do that, your warranty is void
  • ChrisOlsonChrisOlson Posts: 1,807Banned ✭✭
    Re: Meter for amp hours produced
    gww1 wrote: »
    Bill/Chris
    Dang, I had got some advice on this meter at the otherpower forum. I did mention it was for a 48 volt system.

    gww - with 48V systems you have to be careful with equipment because the 60V stuff can't be used. It's like using SquareD QO boxes and breakers - fine on 24V, but not on 48 because they're only DC rated to 60V. I'm not totally certain what will happen if you try to push a Doc Wattson over 60V (maybe nothing?). I've never tried it.
    --
    Chris
  • NorthGuyNorthGuy Posts: 1,925Solar Expert
    Re: Meter for amp hours produced
    NorthGuy wrote: »
    I think this means the following:

    1. You can power the device from either "source" or "aux"
    2. The diode, called D1, is installed between the "source" and device. The idea is that if you get higher voltage on "aux", diode will isolate "source" from the device. If not, the diode will conduct and power device from the "source"
    3. Source may have transients, which may be bad for the device. Therefore, they recommend using "aux" for the power. To do that, obviously, the voltage on "aux" must be higher than "source"
    4. You want to use "aux", but you do not have a high enough voltage to connect to it
    5. The solution for you is to remove D1, thereby disconnecting "source" completely.
    6. You now can power the device from "aux" with low voltage without being afraid of transients on "source"
    7. If you dare to do that, your warranty is void

    Oh, looks like you're just trying to put too much voltage on the source (48V). In this case, you should read 3 and 4 in the above as follows:

    3. "source" voltage is too high and will be bad for device, so you cannot use it to power it
    4. You want to use "aux" to power the device with lower voltage, but you can't becuase "source" voltage is higher.

    Bottom line is that you will need a separate source of low voltage power on "aux", which is capable of powering the device. Then you can remove D1, thereby disconnecting the "source". Now "source" will be used only on measuring circuits. This is unlikely to damage the device, but if it is above the device measurement ceiling, the voltage data may be screwed.
  • gww1gww1 Posts: 963Solar Expert
    Re: Meter for amp hours produced

    Northguy
    If I understand what you are saying, If I powered the auxilary with a 4 volt wall wart or small battery, with the d1 diode removed, it will measure the source to battery bank but as it is a 60 volt measuring device it may cap the mesurements to that value or lower?

    Or not?

    I was going to void the warrenty when I placed a sturdier external shunt anyway.
    Thanks
    gww

    PS
    gww - with 48V systems you have to be careful with equipment because the 60V stuff can't be used. It's like using SquareD QO boxes and breakers - fine on 24V, but not on 48 because they're only DC rated to 60V. I'm not totally certain what will happen if you try to push a Doc Wattson over 60V (maybe nothing?). I've never tried it.
    --
    Chris

    If I aint smart enough to adjust it, I might just try it to see what happens. If I do I'll report how it worked.
    gww
  • NorthGuyNorthGuy Posts: 1,925Solar Expert
    Re: Meter for amp hours produced
    gww1 wrote: »
    Northguy
    If I understand what you are saying, If I powered the auxilary with a 4 volt wall wart or small battery, with the d1 diode removed, it will measure the source to battery bank but as it is a 60 volt measuring device it may cap the mesurements to that value or lower?

    That's what they say. Except that 4 volt might not be enough. You need to find out what minimum voltage they need. I guess that's something around the minumum battery voltage they support.

    The most important thing is not to mix + and - of your aux power connection. Reverse polarity is likely to kill the device immediately.

    As to the capping, the best way to find out is to try to measure the real voltages. The cap might be above what you need.

    As an alternative, if your device supports 24V and you have only one battery string, you can use it to monitor voltage of half-bank. As long as your batteries are balanced this will give you comparable results. You may be able to do that even with multiple strings, but the error will be higher.
  • BB.BB. Posts: 27,681Super Moderators admin
    Re: Meter for amp hours produced

    Connect the black wire (source) of the Doc Wattson to your wind turbine native wire.

    Connect the black wire (load) of D.W. to your battery bank negative bus.

    Connect the red wire (source, probably don't care to load) to "something". For a first time test, I would connect it to the +24 volt poin-Bilt on your battery bank (meter draws so little power, I would not worry about the 7mA (0.007 amp) load unbalancing the battery bank). You should have a small fuse/breaker on the wire from the battery bank +24 to the D.W. positive lead (you could even use a switch here to "reset" the D.W. every month back to zero).

    Basically, the first drawing in their FAQ:

    http://www.rc-electronics-usa.com/ammeters/amp-meter-connection.html

    All should work fine. You Watt/WattHour reading should be x2 to get the "real numbers".

    If you are concerned about drawing 7mA from your battery bank, we can talk about more options.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • gww1gww1 Posts: 963Solar Expert
    Re: Meter for amp hours produced

    Northguy/bill
    I intend on 16 sams club batteries. As long as it measures even a little close I will be happy. I don't mind having to double the recorded values to see what I am getting. Unless some one else knows something I don't, I believe the small mid-bank draw will not ruin my batteries much worse then my inexperiance will. Lastly, and I have to say this alot on this site, THANKS.
    gww
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