Wizbang Jr amp hour reset?

verdigoverdigo Solar Expert Posts: 428 ✭✭
So when I first set up my wizbang jr for battery bank capacity evedently the batteries were not fully charged and was off a bit. When I attempt to reset the capacity after a full charge the capacity is always more than the setting. Anyone know if there is something else to reset in the Classic menu to get this thing corrected. Right now after a full charge using end amps at 4.6 amps for a 464 amp hour bank the amp hours remaining reads 491 ah. Not a huge deal as I rely mainly on a hydrometer but It would be nice to know at a glance I if the bank is charged or not.

Thanks

Dennis

Comments

  • VicVic Solar Expert Posts: 3,113 ✭✭✭✭
    verdigo wrote: »
    So when I first set up my wizbang jr for battery bank capacity evedently the batteries were not fully charged and was off a bit. When I attempt to reset the capacity after a full charge the capacity is always more than the setting. Anyone know if there is something else to reset in the Classic menu to get this thing corrected. Right now after a full charge using end amps at 4.6 amps for a 464 amp hour bank the amp hours remaining reads 491 ah. Not a huge deal as I rely mainly on a hydrometer but It would be nice to know at a glance I if the bank is charged or not.
    Thanks
    Dennis

    Hi Dennis,

    Am not quite certain just what is your situation, ... but ...

    If your batteries are above the Reference temp that you have set (usually 25 C), the Capacity of the fully-charged battery will increase a small amount. And, this small change will be shown in remaining Ah on the Classic's display and in the Local App (Ibelieve). Is your battery temperature above the Ref temp? You can find the Classic BTS temperature reading in the ' Temps ' menu.

    And do agree, that a few Ah difference is essentially meaningless, in the scheme of things. There can be significant variation in actual capacity verses Ah tabulated by any meter or monitor, as the rate at which the battery was discharged, and charge rate will affect C. Constructing an accurate Model of the behavior of any battery is daunting, and small changes in the chemistry can affect the behavior of any single battery design, let alone the broad range of battery designs and construction.

    So, IMO, considering any Metering device to be accurate within several percentage points, is placing a bit too much faith in the accuracy of most of these instruments.

    Measuring SGs is the best measure of SOC. And the WBjr is a great, inexpensive (FREE with Standard Classics) device that can report a reasonably accurate snapshot of remaining Capacity.

    Most battery monitoring devices are approximate, and will never be any more accurate than the settings the user inputs to them, and, over time, these settings need to change as the battery ages, and as use patterns or the battery change.

    ALL my Opinions, FWIW, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 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.
  • verdigoverdigo Solar Expert Posts: 428 ✭✭
    Thanks for the reply Vic.

    With the warmer weather with the battery bank at 80 degrees and fully charged (according to hydrometer) my 464 ah bank according to the wizbang on the Classic display is reading 500 + amp hours remaining. If I reset the base amp hours in setup downward the display changes accordingly but when I set it to 464 the display for amp hours remaining continues to read too high. It seems like amp hours remaining should read 464. I guess I could enter a lower setting until it reads correctly.

    Your opinion?
  • VicVic Solar Expert Posts: 3,113 ✭✭✭✭
    Hi again Dennis,

    There are several points in this ERRONIOUS reading;

    First, the Capacity of most/all batteries increases with an increase in temperature. Almost all batteries that we use in energy producing systems have a reference temperature of 25 degrees C (77 F), or in some cases, 27 C, about 80 F. This is almost certainly the case with your batteries. In setting up the WBjr, you probably either accepted the Default battery Reference temperature (usually 25 C), or perhaps you changed this value a bit. But, you mentioned that the temperature of your batteries is about 80 F. This has increased the Capacity of your bank a bit, if you have set or used the Default Ref temp of 25 C. .And, the accuracy of the Battery Temp Sensor (BTS) has some tolerance which will affect the accuracy of compensation applied to the battery Capacity. Furthermore, where, and the way in which the BTS is installed will also affect its accuracy.

    The increase in C that you are noticing, is not really an error, the small increase in temperature of the battery had increased the C by a small amount (if you have used 25 C as the Reference).

    But, candidly, this is essentially meaningless. As I tried to state above, battery SOC Monitoring devices cannot really be very accurate, as there are SO MANY variables, that they cannot keep track of, and essentially every battery is a bit different from almost all other batteries. And even if one had a perfect mathematical Model for your exact battery, the way it is used, and normal aging would mean that this Model of the battery would need to be changed a number of times per year. Such a Model of batteries has so many variables that we do not know about, that the once perfect Model would be substantially wrong, over a period of time.

    Battery Monitoring devices CAN be a useful tool in indicating, ROUGHLY, approximately, what is the SOC at any one time. We can help make them a more accurate by inputting correct variables for the ones that we have control over. BUT, still, they are approximating, not absolute devices, IMO.

    In the WBjr setup, believe that there is a setting for the temperature coefficient of Capacity verses changes in temperature -- a percentage, I believe. If you were to set this to zero, believe that the WBjr would not report any C change vs changes in temperature (above or below) from that of the Reference temp that is entered into the Firmware that runs the WB.

    The above are my opinions. And, believe that you may be looking at the WBjr as an absolute indication of actual battery Capacity. It, and all of the other battery monitoring devices, are only able to report a rough approximation of ACTUAL battery Capacity, again, IMO. FWIW, YMMV, and so on. Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 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.
  • verdigoverdigo Solar Expert Posts: 428 ✭✭
    Thanks again for the reply. So in short battery monitors are not much use. I'll play around with it this weekend if time allows and look into changing the temperature coefficient in the setup. I would like to see if I can get it close to a known full charge but as you say it probably won't stay that way. The battery bank being a couple of years old and being a grid interactive setup where while selling the batteries are constantly being discharged and recharged as clouds go by will only further confuse things. I guess at best it is something to tinker with.

    Thanks again

    Dennis
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