New Amp Clamp

Rngr275
Rngr275 Solar Expert Posts: 127 ✭✭
My posts from the last couple of weeks has been about my battery struggles and my generator craping out. New generator installed today and should commission it in a day or 2. Re-did my 48v 8 battery in series and another 8 in parallels to a single 8 battery series using the best batteries until I decide what I want to do, probably biting the bullet and put together a new battery bank. Similar set up using Crown RE batteries instead of Trojans (whole different story).

Check SG just after the sun went off my panels and the bank looked good except for a couple cells that were reading 1.283, not sure why but as I said the sun had just gone down. Currently, doing a 3.5hr absorb (was doing 4hr for my full bank).

So I just received my DC amp clamp. It has been recommended to have one (I guess I should have years ago), but I'm not sure how to use it as an analytical tool for the battery bank.

Could someone comment on my battery SG/charging and how to I put the Amp Clamp to work for me?

Thanks
McD

Comments

  • Surfpath
    Surfpath Solar Expert Posts: 463 ✭✭✭
    Hi Rngr275,
     I’m going to bump this thread up for you because I saw that it did not get a reply.
     Have you used your new clamp meter yet? I’m also thinking of getting one. Mainly it seems like a good diagnostic tool.  Id like to also be able to measure the current coming from each of my pv strings to the combiner.
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Rngr275 said:
    My posts from the last couple of weeks has been about my battery struggles and my generator craping out. New generator installed today and should commission it in a day or 2. Re-did my 48v 8 battery in series and another 8 in parallels to a single 8 battery series using the best batteries until I decide what I want to do, probably biting the bullet and put together a new battery bank. Similar set up using Crown RE batteries instead of Trojans (whole different story).

    Check SG just after the sun went off my panels and the bank looked good except for a couple cells that were reading 1.283, not sure why but as I said the sun had just gone down. Currently, doing a 3.5hr absorb (was doing 4hr for my full bank).

    So I just received my DC amp clamp. It has been recommended to have one (I guess I should have years ago), but I'm not sure how to use it as an analytical tool for the battery bank.

    Could someone comment on my battery SG/charging and how to I put the Amp Clamp to work for me?

    Thanks
    McD
    Hi McD,

    Regarding the few cells at 1.283 Sg (if this is not a typo),  this is not far from the target SG of some of the Trojan RE batteries (1.277 SG for full).   What are the SGs of the other cells?  What is the spec for full charge on the batteries that you are using?

    Most Hydrometers are not ultra accurate or repeatable.  Refractometers are a bit more accurate,  generally,  though.  If the 1.283 cells are high,  perhaps they are a bit low on electrolyte.  Many Hydrometers would be lucky to be within +/- 5 points of the reading, and/or for repeatability.

    A Clamp DC Ammeter is great for monitoring charge/discharge balance,  between multiple strings of batteries in parallel,  measuring current of each PV string (as Surfpath noted),  and measuring CC output current,  if your system does not have a shunt type battery monitoring device   ...   and so on.

    Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • MichaelK
    MichaelK Registered Users Posts: 234 ✭✭✭
    edited July 2021 #4
    I can add a thing or two about clamp meters.  I have two, a very expensive Fluke meter, and also this one.
    they are both accurate to within 1% of each other.  The Uni-T is far cheaper
    They both have features that other cheaper clamps do not.  Besides measuring both AC and DC amperage, they both also can read "inrush current".  That's the current draw a lot of big motor equipment draws for about 1 second right at startup.  Your standard AC clamp is not fast enough to get an accurate reading of inrush.
    I used the inrush feature to measure the starting surge of my well-pump, which runs at ~9.5A at 240V, but inrushes at 38A just at startup.  I used that information to purchase my XW inverter, which has the surge capacity to handle 12,000W.
    When you clamp a wire, you must clamp only one wire, either + or - for DC, or live or neutral for AC.  So, you can't put the clamp around the electrical cord of a lamp to read the amperage the light bulb is using.  You need to split open the line and separate the two wires so the clamp only reads one wire.
    If you don't like taking a razor blade to your electrical cords, you can buy one of these handy AC splitters, which does the separation for you.  One advantage the spliter has is that it has two clamping loops, one at 1X and the other at 10X.  So, you can get an accurate rating for very low-amperage items.
    When you use the clamp, it will be polarity sensitive.  Clamp a wire in one way, and it will give a positive amperage reading.  Flip the clamp over 180 degrees, and measure again, and it will give the same reading, but as a negative number.
    System 1) 15 Renogy 300w + 4 250W Astronergy panels,  Midnight 200 CC, 8 Trojan L16 bat., Schneider XW6848 NA inverter, AC-Delco 6000w gen.
    System 2) 8 YingLi 250W panels, Midnight 200CC, three 8V Rolls batteries, Schneider Conext 4024 inverter (workshop)
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    edited July 2021 #5
    Just a quick note--The + and - current clamp polarity reading only applies to DC current flow... The clamp meter cannot measure the direction of AC power flow (without using voltage measurement and the ability to "do the vector math").

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset