inefficiency/losses in system

mshen11
mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
in Solar Beginners Corner #1
i have a prosine 3.0 when it is charging it says something like 14.4V and 10A... my xantrex linkpro battery monitor says 14.35V and 12A... i know there can be discrepency because measurement is not taken at the same point. but this is variance minor? both are installed at the manual suggested location

if not... how do i make adjustment/corrections to better the reading?
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #2
    Re: inefficiency/losses in system

    Are there any loads on the battery while it is being charged? Are you using and battery temperature sensor?
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  • mshen11
    mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    #3
    Re: inefficiency/losses in system

    no loads.

    the prosine 3 came w/ a battery sensor. i tried to attach that sensor to the prolink and it didnt work so i kept it on the prosine (not sure why this question is relavent)?
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #4
    Re: inefficiency/losses in system
    mshen11 wrote: »
    no loads.

    the prosine 3 came w/ a battery sensor. i tried to attach that sensor to the prolink and it didnt work so i kept it on the prosine (not sure why this question is relavent)?

    Well, I guess I'm not either, now that I think about! :blush:

    I wouldn't worry about the 50mV difference in voltage readings. I see something similar when I compare the MSView voltage reading from my Morningstar MPPT to that of the Tri-Metric. It is possible that the couple of feet of 10 AWG wire that connects the CC to the buss bars is causing the drop. I was going to replace it with 8 AWG but the #10 stud lugs won't fit on the MPPT. :grr

    The 2A difference in current readings might be reason for concern. Looking at it from a power standpoint, you have:

    14.40V * 10A = 144.0W
    14.35V * 12A = 172.2W

    a difference of 28.2W. :confused:

    I just checked the NAWS site and the LinkPRO does have its own BTS. It can/should be used in conjuction with the BTS on the ProSine. IIUC, using the LinkPRO without its BTS should only affect how it determines AH capacity, not real time measurements. :confused::confused:

    Good Luck!
    K
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  • GreenPowerManiac
    GreenPowerManiac Solar Expert Posts: 453 ✭✭✭
    #5
    Re: inefficiency/losses in system

    Disconnect your battery monitor from the batteries for about 30 seconds. Leave it hooked up to the charging system. See if the two digital readout numbers stabilize. Yes, means there is a discrepancy between the batteries and the monitor. A false reading? No, means that it could just be the difference in digital equipment. My guess is the later is true.
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #6
    Re: inefficiency/losses in system

    A discrepancy of 2A is huge! A 20% error???:confused:

    With no loads on the battery (other than the monitor itself @ 7mA to 9mA,) I can't imagine what is causing the difference.
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  • mshen11
    mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    #7
    Re: inefficiency/losses in system

    what does BTS mean? see the glossary, niel

    i called xantrex yesterday - they said the prosine ACL is just an "approxmate" and the Linkpro reading is more accurate. reason? because the latter measures across a shunt and the former does not. im not sure if i trust that answer because the guy said some stuff other i know wasnt quite true.

    this weekend i will use a meter to measure the current across difference places of the wires and compare (will report back). will also try GreenPowerManiac's suggestion this weekend.

    well its not exactly no load on the battery... other than the battery monitor, the prosine is also sucking power when charging. could that be the answer?
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  • GreenPowerManiac
    GreenPowerManiac Solar Expert Posts: 453 ✭✭✭
    #8
    Re: inefficiency/losses in system

    I believe you just answered your own question. If a charger is still hooked up and turned on, yes, it consuming power, but it must be in-between the two meters.

    The charger should channel more power to the batteries in order to charge them as needed. The battery monitor should say 12amps, not 10a. Always need more power going in depending on what the batteries require. If you have a 3rd amp meter to check the current flowing through the hot wire, then you'll get another reading from it. 3 different readings would suggest nothing is wrong and is just a discrepancy between meters.
    Nature's Design & Green Energy on FaceBook : Stop by and "Like" us anytime.. Many up-to-date articles about Renewables every day.
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  • mshen11
    mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    #9
    Re: inefficiency/losses in system

    prosine 3.0 *IS* charger/inverter and gives the read outs via their ACL

    but like you said i should have less amps on the battery monitor, not 2A more. so is xantrex telling us the answer - the prosine ACL is "inaccurate"?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,639 admin
    #10
    Re: inefficiency/losses in system

    RBTS is Remote Battery Temperature Sensor...

    20% error is a bit large... But 5-10% is not unusual. Also, we are used to meters that have x.xxx accuracy--but that is really resolution (i.e., meter can report those decimal places).

    A 3kW inverter at 12 volts can take upwards of 300 amps. And if it is accurate to 2 amps--that is better than 1% accuracy at 300 amps. Most meters tend to be less accurate at near zero readings (at low range readings, there can be offset errors in the electronics that make readings less reliable).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #11
    Re: inefficiency/losses in system

    mshen11,

    Correct me if I am wrong, but you are using the ProSine in charger mode only (plugged into 120VAC,) correct? If true, it would not present a load to your batteries.
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #12
    Re: inefficiency/losses in system
    mshen11 wrote: »
    ... the latter measures across a shunt and the former does not....

    I have to wonder: how then does it measure measure current?
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  • mshen11
    mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    #13
    Re: inefficiency/losses in system

    its a charger/inverter. i should know how much current it pushes/pulls?
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #14
    Re: inefficiency/losses in system

    Yes, I know. And also a 30A auto transfer switch. But you are not using the inverter, correct? You have it connected to 120VAC, correct?

    If it is connected to 120VAC, the inverter is disabled and the batteries get charged.

    Also, I assume that you have the ACS panel and using it (not the LED bar graph on the ProSine itself) to read the current.
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  • mshen11
    mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    #15
    Re: inefficiency/losses in system

    correct. am connecting shoreline to 120VAC to charge the battery. nothing on the auto transfer switch/inverter.
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #16
    Re: inefficiency/losses in system

    Back to your OP...
    mshen11 wrote: »
    i have a prosine 3.0 when it is charging it says something like 14.4V and 10A...

    What do you mean by "something like." When trying to determine the relevance of, what I am now beginning to believe is a minor discrepancy, one should strive for accurate measurements.
    mshen11 wrote: »
    my xantrex linkpro battery monitor says 14.35V and 12A... i know there can be discrepency because measurement is not taken at the same point.

    Not taking "measurements at the same point" is a factor only for voltage measurements. Current is equal at all points in a series circuit, which is what you have in your charger to battery connection (including shunt.) As stated earlier, the 50mV difference in voltages is negligible. However, this is only true when comparing the accuracy (or perhaps resolution*) of the measurement devices. 50mV can be significant in the charging profile of an AGM battery. In this case trust what the LinkPRO says.
    mshen11 wrote: »
    but this is variance minor? both are installed at the manual suggested location

    Yup. I think that the variance is minor.
    mshen11 wrote: »
    if not... how do i make adjustment/corrections to better the reading?

    You don't. Use the readings from the Link PRO. As in most cases, you get what you pay for (from reputable, established vendors; and I believe that Xantrex is such a vendor,) and you paid plenty for the LinkPRO. I have a Tri-Metric and it works well. I like the temperature compensation feature of the LinkPRO. It should deliver a more accurate "fuel gauge" capability. The Tri-Metric is not temp compensated.

    Good luck!

    K
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  • mshen11
    mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    #17
    Re: inefficiency/losses in system

    "something like" means im trying to recall the exact numbers. but the discrepency (hard fact is 2A and 0.5V difference)

    does anyone know if you can use the same temp sensor on both the prosine and prolink (xantrex said no but i have a feeling they wanted me to buy another one - theyve been wrong on a lot of things about their product when i call in). IF SO, can one easily splice the telephone jack on the sensor and make it have two end connectors - so the prosine and the battery monitor share the same battery sensor?
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #18
    Re: inefficiency/losses in system

    You can't use a single sensor for two different products, even if they are identical make and model. BTS's work by the change in resistance in a multi-resistor network. Connecting to two units would in essence change the networks as they would be paralleled. You also have noise and ground issues to contend with.
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  • mshen11
    mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    #19
    Re: inefficiency/losses in system

    can you go into more details? of course i know next to nothing but it seems like the battery sensor (yellow piece) is a digital thermometer that pushes the information through the telephone jack (one way information push) to the jack.

    am interested in learning about the internals of these devices. thanks
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,639 admin
    #20
    Re: inefficiency/losses in system

    You can read a bit about "thermistors" here.

    It sounds like SG is typing about a Wheatstone Bridge setup (in the chargers, not at the BTS) for measuring the changes in resistance of the thermistor.

    While it is certainly possible these days to make a digital version of the RBTS--it sounds like they are still all some sort of thermistor instead. They could also be thermocouples--but that is not what is being used here.

    In any case, virtually nothing in the engineering world starts out digital... Everything is pretty much an analog signal that needs an Analog to Digital Conversion (basically a "digital volt meter").

    And while the guts have been miniaturized and put on single chips--the insides of those chips are usually still recognizable as those components used for the last 30-100+ years from times past.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #21
    Re: inefficiency/losses in system

    For the technically challenged, most battery temp sensors are simple Thermistors. These are simple variable resistance resistors that change their resistance as the temp changes. Some thermistors increase resistance with temp rise, some decrease with temp rise. With in a certain range, it does so with a predictable curve.

    Tony
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  • mshen11
    mshen11 Solar Expert Posts: 185 ✭✭✭✭✭
    #22
    Re: inefficiency/losses in system

    did not know that about battery sensors

    anyone have a definite answer on whether the prosine 3.0 battery sensor can be used on the linkpro?
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #23
    Re: inefficiency/losses in system

    In an earlier post you said that you tried it and that it didn't work. Keep the temp sensor on the ProSine. It needs it more than the Link PRO.
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