Bulk Absorption Chg Finish Selltogrid

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  • pcguy2upcguy2u Solar Expert Posts: 139 ✭✭✭
    Re: Bulk Absorption Chg Finish Selltogrid

    Not the way I see it. All batteries will fluctuate to some extent and if in the case of the surge, the voltage level was/is on the cusp of the sell voltage, it would be expected of any battery bank. Recall that this unit performs quite properly after every fault, which includes most fault warnings and all of which conclude with a test of the grid, which it also does at the beginning of the day at times, but the AC charger has to be off.

    That is the confounding issue. To me, there is a firmware bug with the way the AC charger interfaces with the system.
  • pcguy2upcguy2u Solar Expert Posts: 139 ✭✭✭
    Re: Bulk Absorption Chg Finish Selltogrid

    I may be premature with this post since it’s only been 2 weeks since I put up the new firmware on the 6048.

    On 8/22/11 I installed the new firmware and all has gone smoothly since then, sans a need to reset some of the variables. Since then there have been zero faults and the system has been acting as should be expected. And at the moment, the current state seems to boil down to a lack of transparency on the part of PG&E and Schneider/Xantrex.

    PG&E seems to be hiding its methods of operation (and lying to the PUC about having tried to contact me – the PUC cancelled my complaint in the form of a letter) and Xantrex may not be providing a totally clear picture of what is contained in the way of updates in the latest release of firmware for the 6048 (Version 1.07). As I read the semantics for this release, there are no direct references to grid impedance and/or any particular faults. Obviously this is not to say that some changes were made that enter into the unknown equation contributing to the issue here.

    During the process of trying to understand what may have been happening in my situation, I happened on the following statement that seem to be relevant:

    http://www.pvpower.com/pdf/datasheets/pv%20powered/pvp%20install.pdf - “To avoid an increase in AC voltage to unacceptable values while the inverter is exporting power, the grid impedance value at the connection point should be as low as possible. By keeping the grid impedance value low, the inverter will achieve higher system efficiency and avoid nuisance shutdowns. The total impedance of the grid plus the interconnecting AC wires should be less than 1.25 Ohm.”

    Seems universal enough to be relevant in my case, especially because of my distant proximity to 60 or 120KV stations. I have to assume that the greater the distance, the greater the potential impedance and the introduction of some huge piece of equipment that is not properly connected to the grid will certainly increase the impedance.

    I realize that the best that can be expected is for the link to the grid to be free from degraded connections between the meter and the inverter, but once on the grid everyone is subject to the quality and locations of the utility provided facilities. In my case, we are at the end of potentially two different 12KV feeds from PG&E. In one case we are 4 miles and in the other I’m not sure, but it may be 18 miles or more. The sad part is you never know if the feed is currently from one or the other or both.

    Clearly, something has been happening frequently on the grid at 8:03AM on weekday mornings – at least once every week some fault was incurred on the system at that time and occasionally at other times during the day.

    Now, in conjunction with the new firmware, things may be ok. Or could it be that the PG&E is in a state that doesn’t cause the problem? There have been a couple of times where I have not noticed a fault (or did not record the fault) where the time between faults was more than a few days. In any case, no faults now in 14 days.

    Does anyone know if two feeds from distant stations could be (regrlarly are) connected to a high voltage feed at the same time?

    Time will tell what is really happening here.
  • Joe_BJoe_B Solar Expert Posts: 318 ✭✭✭✭✭✭
    Re: Bulk Absorption Chg Finish Selltogrid

    I dont know what version of firmware that you upgraded from but somewhere on the Schneider website there is an extensive list of changes through the ages. IIRC, there was some stuff about selling and grid impedance.
  • pcguy2upcguy2u Solar Expert Posts: 139 ✭✭✭
    Re: Bulk Absorption Chg Finish Selltogrid

    Thanks for that Joe. Here's what appears in the release notes for all versions of the inverter - it's the only reference to "impedance".

    "Improved charge voltage regulation in a multiunit installation where more than
    one unit is charging a Gel type battery bank. Previously, the battery bank can
    be over-charged and damaged due to the low impedance present in the Gel
    type batteries."


    This particular note is the same note provided for all inverters/revisions and doesn't seem to relate. However, it shows to be initiated in V1.05 - I missed that update, my last version was 1.03.
  • BB.BB. Super Moderators, Administrators Posts: 32,005 admin
    Re: Bulk Absorption Chg Finish Selltogrid
    pcguy2u wrote: »
    "Improved charge voltage regulation in a multiunit installation where more than one unit is charging a Gel type battery bank. Previously, the battery bank can be over-charged and damaged due to the low impedance present in the Gel type batteries."
    This sounds suspiciously like the over voltage during charging on the "small" battery bank issue... (48 volt battery bank >72 volts during charging)

    Apparently, many MPPT controllers dump all available solar energy power into the battery bank during MPPT sweeps. The over voltage causes over current (i.e., low impedance) into the gel batteries which (can/may/does) cause the Gel to out-gas at the plate interface--which creates a void at the plate that can never recover (and causes capacity loss).

    But, I would guess, that this is solar charge controller problem, not a XW hybrid inverter issue. Perhaps, the XW during AC charging was also not controlling current well enough/monitoring battery bank voltage well during charging?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • pcguy2upcguy2u Solar Expert Posts: 139 ✭✭✭
    Re: Bulk Absorption Chg Finish Selltogrid

    Well, like I thought, at 8:03AM this morning (Tues) another F25 grid incident. Unlike some other times though, this incident was handled normally and the system recovered as it should have in 5 minutes. Rocevering normally is not unusual, so in terms of the effect seen with the new firmware there is nothing to report.

    Clearly there is something on the grid that is effecting the 60 cycle frequency.
  • pcguy2upcguy2u Solar Expert Posts: 139 ✭✭✭
    Re: Bulk Absorption Chg Finish Selltogrid

    Updated to version 1.07 on 8/22/11 (almost one year ago). The only anomaly that continues is the issue with PGE and one of its commercial customers in the neighborhood - the issue of AC cycle being out of range.

    All other issues have disappeared, including the issue described by others of using a battery bank that is too small.

    The system appears to be performing perfectly, sans PGE.
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