Rule of Thumb #1 Get a DC Clamp Meter

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feedhorn
feedhorn Solar Expert Posts: 103 ✭✭
Thought I would post some of my many rules-of-thumb that I use to manage my solar/battery power system.

#1 is: Get a DC Clamp Meter!

Most clamp meters you see in the stores will measure only AC Amps you need to get one that measures DC amps too. Sears has them as does most professional electrical stores. They cost almost twice as much as the ones that measure only AC amps but they will save your system $$.

With a DC clamp meter you can easily measure the current in each battery string, each solar panel, or each load element and know exactly what is going on in your system.

Knowledge is Power and a DC clamp meter will put true knowledge in your hand. Use it daily until you totally understand your system.

I had to replace an entire battery bank due to one bad connection that a DC clamp meter could have found in seconds. I learned the hard way.

FH

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,476 admin
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    Re: Rule of Thumb #1 Get a DC Clamp Meter

    I post this Extech Model MA 220 as a low cost example--It is about $100 USD and one poster here found one for $50 on EBay.

    As with most DC Clamp Current Meters--They do not hold Zero well... You may have to keep adjusting them every few minutes if you are trying to read small currents accurately.

    And how about adding some other tools that people "should have" for off-grid solar systems:
    • Accurate Digitial Multi-Meter (at least 1XX.XX five digit accuracy)
    • Hydrometer + Thermometer (for flooded cell specific gravity measurements)
    • Battery Monitor (for measuring AH/WH in/out of a battery bank--almost required for AGM/Sealed Battery real time monitoring)
    • Remote Battery Temperature Sensor (highly recommended for solar charge and AC battery chargers that support the function).
    • Safety Glasses / Shield for working on battery banks (keep acid from eyes/face)
    • DC Current Clamp Meter (per original poster)
    Anything else I forgot?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • feedhorn
    feedhorn Solar Expert Posts: 103 ✭✭
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    Re: Rule of Thumb #1 Get a DC Clamp Meter

    Oh, you could add an IR Temp Meter that you can point at each cell and see if it getting hot or not.

    FH
  • BB.
    BB. Super Moderators, Administrators Posts: 33,476 admin
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    Re: Rule of Thumb #1 Get a DC Clamp Meter

    Extech Instruments also makes AC/DC Current Clamp meter with IR Thermometers too (don't know cost). 8);)

    I do like monitoring battery wiring (when under heavy load)--Frequently, you can find a hot spot in the wiring/connections... Either high resistance (corrosion or loose bolt)--Or that cable/bank is carrying more current and the other has an "open" circuit or high resistance is is carrying only a little bit current.

    A reason why I like large capacity one string battery banks vs a bunch of batteries in parallel--it is easier to find connection/cell problems with one bank (all current must flow through that one path).

    With parallel banks, a DC Current Clamp Meter does make it very easy to see when a string is carrying more or less than its proper share of current.

    I highly recommend a DC C.C. meter too... They are also very "safe" to use (you cannot set them up or connect them wrong, no exposed metal to measure voltage/current required). Even if you do not have much experience with electricty--It would be very difficult to get in trouble using one (make sure to remove all jewelry, rings, bracelets, necklaces, metal watch bands, etc. before working around a battery bank--Batteries are capable scary/dangerous amounts of current into a dead short).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • keyturbocars
    keyturbocars Solar Expert Posts: 375 ✭✭
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    Re: Rule of Thumb #1 Get a DC Clamp Meter

    I just ordered this Elenco AC/DC Clamp Ammeter for $52 and free shipping.

    http://www.testequipmentdepot.com/elenco/clamp-meters/st3030.htm

    I haven't received or used it yet, but the one review I read about it online seemed good. The specs (+/- % error) were better than most other DC clamp ammeters I researched. Good price too.

    Edward
  • KeithWHare
    KeithWHare Solar Expert Posts: 140 ✭✭✭
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    Re: Rule of Thumb #1 Get a DC Clamp Meter
    BB. wrote: »
    Anything else I forgot?

    Not so much tools as techniques:
    • Download and read all of the documentation -- I've been able to find documentation for just about everything online. Reading it carefully has been very helpful.
    • Ask questions both here on the NAWS forum and directly to the manufacturers -- I've found people in this field to be very helpful.

    Keith
  • XRinger
    XRinger Solar Expert Posts: 529 ✭✭✭
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    Re: Rule of Thumb #1 Get a DC Clamp Meter

    I got the Sears. If it wasn't what I wanted, Sears is just 2 miles away..

    http://www.sears.com/shc/s/p_10153_12605_03482369000P?prdNo=3&blockNo=3&blockType=

    I think that I paid about $60 for it.
    It comes with a standard looking temperature sensor that works pretty well.
    You do have to pay attention to the Zero.. It can drift out of cal on you.
    Just have to keep hitting the button, when you see 0.1A floating in and out.
    I guess it wouldn't be such a problem, if I was running more than 7A max. :blush:

    297364826_o.jpg

    They have one that looks just like this one, for about $40 /w no DC amps.
    You don't want that one..
  • feedhorn
    feedhorn Solar Expert Posts: 103 ✭✭
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    Re: Rule of Thumb #1 Get a DC Clamp Meter

    DC clamp meters are affected by the Earth's magnetic field and once you zero one its a good idea to try and keep in the same orientation when taking various measurments.

    FH
  • XRinger
    XRinger Solar Expert Posts: 529 ✭✭✭
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    Re: Rule of Thumb #1 Get a DC Clamp Meter
    feedhorn wrote: »
    DC clamp meters are affected by the Earth's magnetic field and once you zero one its a good idea to try and keep in the same orientation when taking various measurments.

    FH


    I've been wondering about that, because I've been checking the PV current
    going into the heating element in my boiler..

    The boiler is all steel. And a lot of it. I've learned not to be moving the probe
    around while zeroing it.

    I'll try to be more careful with the orientation, I'll bet it helps..

    Thanks,
    Rich
  • zeuspaul
    zeuspaul Solar Expert Posts: 59 ✭✭✭✭
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    Re: Rule of Thumb #1 Get a DC Clamp Meter

    I paid a little more to get a clamp meter with inrush capture.

    http://www.amazon.com/Amprobe-ACDC-100-Digital-Clamp-Multimeter/dp/B001C6P38U

    I watched the inrush current with the kill-a-watt for my freezer and it was 8 amps. During the same startup the clamp meter captured 12.9 amps.

    Zeuspaul