Winter wrap-up

Chris11Chris11 Registered Users Posts: 61 ✭✭
Would it be better to ..............

  Leave batteries on float all winter ( zero loads ) 
  Or shut off the panels then go to the property every few weeks (snow allowing) and turn the panels back on for a few hours?

Thanks, Chris

Comments

  • mcgivormcgivor Registered Users Posts: 1,281 ✭✭✭✭
    edited October 27 #2
    I vote second choice, things other than the system would also  benifit from visiting every few weeks, if cold self discharge would be low and nothing connected means little chance of any electrical problems.
    + disconnect batteries 
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • 706jim706jim Solar Expert Posts: 169 ✭✭✭
    Leave the batteries on charge. NINETEEN years on my 12 GC's using this regimen.
    Island cottage solar system with 1400 watts of panels, Trace DR1524 MSW inverter, Trace C40 PWM controller 8 Trojan L16's. My 24th year.
  • EstragonEstragon Registered Users Posts: 1,545 ✭✭✭✭
    Three issues to consider:
    - Snow. Any chance the panels could get covered enough and/or shaded enough by low winter sun that snow can't melt off for ling period? It has been a problem for me depending on weather despite having panels at max tilt. With no charging, controller self-consumption gets to be an issue.
    - Freezing. Fully charged, batteries won't freeze, but the freezing point rises as state of charge gets lower. Only a problem if the snow issue arises or controller has a problem.
    - Stratification. Tall batteries like L16s especially can end up with stonger acid on the bottom and weak on top with ling term float. Periodic bulk/absorb will mix things up. OTOH, depending on age and settings, absorb will use some water, and you don't want them getting too low.

    I left my system on, and have classics set to absorb every 5 days. This year I also added small arrays mounted vertically where they should get some sun even on Dec21 as backup in case the main arrays have snow issues again. Also plan to go out and check on things after freeze-up.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • westbranchwestbranch Solar Expert Posts: 4,860 ✭✭✭✭
    If you leave the PV on and the CC is working you should not have any issues, mine is on 24/7/365..
    But be sure the PV is ON, left mine one winter without PV and heavily depleted my batteries! OOPS!! but was able to recover them...
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge, Hughes1100 Sat Modem
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Chris11Chris11 Registered Users Posts: 61 ✭✭
    Thanks all for your thoughts.

    My concern was if I leave everything on that each morning when the cc awakens it goes into bulk (charging) then into absorption for 2 hours (charging) then into float.  Sounds like a road to overcharging since there aren't any loads.
     I've been leaving the whole system on lately with no load and when I checked the SG it's always around 1290 in all cells.  So for 4 months it can't be doing the bats any good at that.

    I set the Outback at the rates suggested by the website clean energy brands.....30.6 for 2 to 4 hours absorption; and 26.8 float.  It did give 28.92 for bulk but I've yet to figure out how to set that on the Outback so I just set the abs. and float rates.  Oh, and set end volts for abs. at 4.  Without any loads and seeing the high SG, a couple of days ago I lowered float to 26 volts.

    This morning I was able to get in touch with customer service at Interstate (by the way, Interstate is just a distributor, not a mfg. )  The woman told me they recommend 29.4 for Abs. 2 to 4 hours, and 26.04 for float.

    I'm now tending to leave everything on after reading what you guys said ..... what do you think for the rates Interstate suggests?
  • HorseflyHorsefly Registered Users Posts: 258 ✭✭✭
    At the end of a visit to our cabin we disable the inverter and leave the panels and CC humming along.  From what I've seen, the batteries don't drop down enough overnight with no loads to drop out of float. So when the sun comes up they just stay in float all day.

    My intent (after asking similar questions here) is just to leave it be all winter, with the inverter turned off but the CC and PV array still connected.
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 4 x Vmax XTR12-155 12V, 155AH batteries in a 2x2 24V 310AH bank.
  • EstragonEstragon Registered Users Posts: 1,545 ✭✭✭✭
    The Interstate values are about what I'm using for my US battery L16s. End amps are generally set to 1-2% of capacity, which may need too be increased a bit incrementally as the bank ages.

    There is no bulk voltage setting in our context. The controller in bulk supplies whatever current is available and the battery will take until voltage rises to the absorb voltage setting. When absorb voltage is reached, it's held there until transition to float is triggered by end amps or timeout. The bulk voltage is variable from the initial voltage before charging begins to Vabs.

    The site recommending a bulk voltage may be using an extra stage, with the "bulk" voltage really a slightly lower voltage absorb, and a higher voltage finish stage, which is sort of a routine equalization. Using the Interstate values and periodic manual EQ as needed seems to work well for me.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • Chris11Chris11 Registered Users Posts: 61 ✭✭
    Horsefly....I didn't know the cc would continue with float from wakeup.  Good to know, thanks.

    Estragon... I'm thankful you confirmed  Interstate's rates.  I always like confirmation from the real world.

    I am going to continue using 26 volts as float.....It just seems to me without any load and just replacing the overnight loss from whatever the natural loss is called, that 26 volts should be adequate.  We'll see.

    I also have three smaller systems, all with small Morningstar controllers that I can't manually change the rates.  I'll just have to trust the smart engineers who input the rates in those.  


  • mike95490mike95490 Solar Expert Posts: 7,286 ✭✭✭✭
    be sure that water usage wont run the batteries dry. 
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • EstragonEstragon Registered Users Posts: 1,545 ✭✭✭✭
    I don't think my Classics work like Horsefly describes. They have a "rebulk" setting that triggers a bulk/absorb cycle when voltage drops below a set level, but I think that's meant for situations where loads exceed charging current which reduces battery SOC to the point a new cycle is needed.

    If I don't have "skip days" set >0, I'm pretty sure the Classic will start a new bulk cycle every day from whatever voltage it's at in the morning. With a full bank, that's not a huge problem, as it will get to Vabs pretty fast, and also taper to end-amps quickly.

    With skip days set, the bulk cycle gets triggered by the sooner of either the passing of the skip days, or hitting the rebulk voltage.

    If your small systems aren't AGM or gel, default values are probably ok. If AGM, most have low self-discharge and may be better left disconnected.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • HorseflyHorsefly Registered Users Posts: 258 ✭✭✭
    @Estragon is way more of an expert than me, so I'll defer to him every chance I get.  :)

    Here's why I said what I did.  I have a voltage logger on my batteries, and it logs the voltage once per hour. The float voltage is set to 27.1V, and the absorption voltage is 29.1V. What I see in the log is that when no one is there the voltage sits at 27.1V (temp adjusted, sometimes higher) until about when I would expect the sun to go down. Over night, the voltage drifts down a bit, generally to between 26.0V and 26.3V. When I finally see it rise, it doesn't get above the 27.1V float voltage. I would assume this means it stayed in float, even though the CC shut down with no light and started back up.  Truth is, I guess it is possible that it rose up to 29.1V between the 1 hour measurement intervals, but I'd have a hard time believing that.

    Now, having said that... I do see every so often (maybe once a week or so?) the voltage drops to more like 25.6V before the CC kicks in, in which case the voltage returns to 29.1V for generally one measurement before it drops back to float.

    Most importantly, I designed my system to be a bit "over paneled" because the darned panels were so cheap. That tends to mean I don't spend very much time in bulk or absorption, so I may be missing all the fun parts in my log.

    I really haven't cross checked the hourly measurements against the for-certain dates that someone is there using the system, but I think I could tell if someone is there. 
    Off-grid cabin: 6 x Canadian Solar CSK-280M PV panels, Schneider XW-MPPT60-150 Charge Controller, Schneider CSW4024 Inverter/Charger, Schneider SCP, 4 x Vmax XTR12-155 12V, 155AH batteries in a 2x2 24V 310AH bank.
  • EstragonEstragon Registered Users Posts: 1,545 ✭✭✭✭
    @Horsefly - I'm no more expert than you, just sayin what I see. :-)

    Not being there with no loads, and with no hourly voltage logs (yet), I can't say for sure what happens when I'm not there. All I have to go by is what I see when I am there, and the daily values in the classic logs when I'm not.

    With no loads, and a full bank, I wouldn't be surprised if a bulk/absorb/float cycle completed in less than an hour. My 12v "night" bank sometimes goes with no loads if we're running the 48v system 24/7 to run AC fridge etc anyway, and it floats fast when full like that. I also have a pretty good amount of panel relative to battery.

    That said, if it's doing a bulk cycle, it's a bit surprising hourly logging wouldn't catch it in mid-cycle at least once in a while.

    The classic daily logs show max battery voltage, among other things. With skip days set > 0, max voltage will be ~ Vfloat for ~ skip days (depending on weather), then be ~ Vabs for a day, then back to Vfloat. I haven't tried running with skip days =0 and no loads though. I think it would bulk daily, but I don't know for sure.
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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