Time for batteries ?

wimbledon83wimbledon83 Posts: 3Registered Users
Hello , 
I need some advice before I commit to some hard earned cash .. 

Our system (purchased with house) is in need of new batteries. We have killed the 9 year old ones because the bank was to small. 

Our current system and storage .  4.1kw solar : 2.6kw through 2 x VT80 studer variotracks. 1.575 kw through an older V60 unit.  24V system consisting of 12 x 2V gel 1000Ah batteries. 1 x 4000W x 24V Latronics invertor, 1 x 2000W x 24V Latronics Invertor , Woods Battery charger , 11KVA diesel generator as standby. Plus a small 300-450W wind turbine .
Our usage : summer 13kWh / day . 3095Ah     winter 12kWh / day 2857Ah . 

The two quotes both recommend we purchase 24 x 2V 1660Ah Gel batteries. (exide Sonnenschein 2RPG1660) at least. 

Is this apprx what we need ?. 

we are talking around $21000 AUD for this battery bank. 

Your advice would be appreciated. 

our generator is running overtime ... 


Comments

  • littleharbor2littleharbor2 Posts: 914Solar Expert ✭✭✭✭
    For starters, it looks like you really need to go to a 48 volt system. That's a huge battery bank. You can easily make it 48 volts. Why do you have two inverters? One properly sized 48 volt inverter should do the job.
     Your daily Ah. usage numbers don't look right. 13kw /24 volt = 542 ah.
     Your array looks undersized for this size battery.
     Wind power adds a negligible amount on a good day it really shouldn't factor in to your charging calculation. 
     The battery bank you have is close to enough for your daily needs, although at it's age ready to go, especially if it was chronically undercharged.
     It would behoove you to start from scratch review your system, replacing the pair of inverters and ensuring your solar array  covers your daily needs and battery is sized properly 13,000 wh a day is 270 ah @ 48 volts., multiplied by 5 = 1354 ah. @48 volts so you need a 1354 ah battery. You may be able to reduce your daily requirement and downsize the battery if you haven't taken energy saving steps already. You really shouldn't have to run your generator very often. possibly just periodically in winter when the sun, or clouds rather, aren't cooperating.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • mcgivormcgivor Posts: 1,746Registered Users ✭✭✭✭
    edited May 28 #3
    The 4.1 Kw array is probably sized about right for the existing battery for full time offgrid, the useage is drawing batteries down to 50%, based on figures supplied. Increasing the bank capacity will help with the depth of discharge,around 30% , but charging would be at a deficit, so perhaps a little more PV would help. Flooded batteries are more robust with a longer life, at the cost of a little more maintenance, that would be my choice but that's a personal opinion. With the consumption mentioned 48v would be a better configuration but naturally that would involve changing inverters, perhaps not within budget.
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • EstragonEstragon Posts: 2,310Registered Users ✭✭✭✭
    I pretty much agree with LH2. A close look at loads may help. Running any sort of electric heating appliance on solar/generator can be pretty costly.

    Assuming you really need 13kwh/day, you should have on the order of 4x the size of solar array for the proposed size of battery bank if generator use is to be mostly avoided.

    There are pros and cons to gel (or AGM) type batteries. Among the cons is they tend to be more expensive to buy than flooded, and tend not to last as long in this application because problems can go unnoticed and/or unremediated as regular checks of SG and equalization aren't possible. The lack of routine maintenance is also a main feature.
    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
  • mcgivormcgivor Posts: 1,746Registered Users ✭✭✭✭
    @Estragon said. 
    Assuming you really need 13kwh/day, you should have on the order of 4x the size of solar array for the proposed size of battery bank if generator use is to be mostly avoided.

    Four times the current array of 4.1Kw, so 16.4Kw.... 164000W × 0.75 (average output) =12 300W ÷28.8 (average charging voltage ) = 427A
    Battery Capacity 1660Ah needs 10% minimum charging current versus capacity, so 166A.
    So the 4× array over the course of a day, let's use a  conservative figure for Australia  of 4 hours average, 4 × 12300W = 49200Wh or 49Kwh.
    Round trip efficiency of 13kwh at 50%  is 26Kwh, so based on this around 9000W array would be sufficient, naturally actual location would help in this calculation . Perhaps @BB could use his magic in this,  so I formally invite Bill to weigh in. Not an argument but rather a debate. My calculations are sometimes eronious  :#
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • 706jim706jim Posts: 201Solar Expert ✭✭✭
    I would scrap the wind generator for starters. It will do little but make noise unless you have gale force winds. And I would go with a 48 volt flooded battery. It will be cheaper and you can check the electrolyte periodically. Do you have propane fueled stoves or furnaces? Just wondering where all that power is going.
    Island cottage solar system with 1400 watts of panels, Trace DR1524 MSW inverter, Trace C40 PWM controller 8 Trojan L16's. My 25th year.
  • EstragonEstragon Posts: 2,310Registered Users ✭✭✭✭
    @mcgivor - I think the proposed bank was 24x2v 1660ah gel cells, which would be two strings at 24v so 3320ah. With 50% DOD, that would be 3320 x 24v nominal x 50% = ~40kwh - about 3 days no sun at 13kwh/day. A bit much maybe, but not totally unreasonable.

    [email protected]%=332a x 28v=9.3kw, so about 2x current array. I think I messed up by thinking 48v nominal at that amperage, which is was mentioned and is probably the way to go, but not right for the above arithmetic. :blush:
    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
  • BB.BB. Posts: 27,432Super Moderators admin
    My guess is somewhere around Perth:

    Perth
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 58° angle from vertical:
    (For best year-round performance)
    Jan Feb Mar Apr May Jun
    7.51
     
    7.31
     
    6.53
     
    5.46
     
    4.29
     
    3.89
     
    Jul Aug Sep Oct Nov Dec
    4.05
     
    4.69
     
    5.80
     
    6.54
     
    7.06
     
    7.39
     
    Lots of sun there... A "nominal" design system may look like (2 days of storage, 50% maximum battery discharge for longer battery life) (note will do calculations at 24 volts, but suggest a 48 volt bank would be nicer--Save money on charge controller and copper wiring):
    • 13,000 WH * 1/0.85 AC inverter eff * 1/24 volt bank * 2 days storage * 1/0.50 max discharge = 2,549 AH @ 24 volt battery bank (based on C/20 discharge rate)
    Then there is charging the battery bank... 5% to 13% solar works well. 5% for weekend/seasonal usage and 10%+ for full time off grid:
    • 2,549 AH * 29 volts charging * 1/0.77 panel+controller losses * 0.05 rate of charge = 4,800 Watt array minimum
    • 2,549 AH * 29 volts charging * 1/0.77 panel+controller losses * 0.10 rate of charge = 9,600 Watt array nominal
    • 2,549 AH * 29 volts charging * 1/0.77 panel+controller losses * 0.13 rate of charge = 12,480 Watt array "typical cost effective" maximum
    And based on loads and hours of sun per day... Using June 3.89 hours of sun per day (still a lot of sun for winter) as "break even point" (still may need genset depending on daily weather conditions for a bit in winter):
    • 13,000 WH per day * 1/0.52 off grid end to end system eff * 1/3.89 Hours of sun per day = 6,427 Watt "break even for June" Array
    The above numbers are just starting points. If you have long streaks of sunny weather--Then the 2 days of storage may be 'excessive' for your needs. On the other hand, If you deep cycle a lead acid battery bank (towards 50% state of charge every day), there may not be enough "hours of sun" to fully recharge the battery bank (recommended to recharge >95% state of charge once or twice per week).

    For example, 5% rate of charge into a 50% discharged battery bank may require upwards of 10-15 hours per day of charging... A typical fixed array will get most of its power from ~9:00 to ~15:00 hours, or ~6 hours of "decent charging current" per day--Fewer hours than required to recharging a 50% SOC (state of charge) lead acid battery bank. A mechanical tracking array can help a lot to extend charging current into early morning and late afternoon, as well as "virtual tracking" (1/2 your array pointing ~North East, and the other 1/2 pointing ~North West).

    In the US/North America--We have "issues" with GEL batteries. If charged too quickly or with too high of charging voltage, gas pockets from in the batteries and they don't dissipate. Permanently reducing battery capacity. The warranty (from one vendor) requires that deep cycled (50% SOC) batteries be fully recharged overnight to maintain warranty:

    Two Year warranty
    GNB warrants to the original user, that Energystore GEL batteries will be free from defects in material and
    workmanship for a period of two years from the date of shipment. Installation should occur within three months
    of date of shipment.
    Four Year Warranty
    GNB further warrants to the original user, that Energystore GEL for four years from their date of shipment when
    used in accordance with the operating instructions and the following conditions as specified below.
    Should GNB find that any cell is in breach of this warranty, it will repair or replace the cell, and allow a credit on
    a pro rata basis, of that portion of the warranty term remaining. The pro rata credit shall be based on the original
    purchase price of the cell and this credit will be applied to the normal list price of a replacement GNB battery at
    the time of claim.
    Conditions
    Warranty is applicable if the cell/ battery fails to meet the requirements when tested in accordance with IEC 896-
    2 and subject to following conditions.
    · Maximum of one cycle per day 50% DOD at 25C and recharged fully there after before next discharge.
    · Deep discharges (to 1.80vpc) to be limited to twice a year provided the batteries are fully recharged with in
    two days of such discharge.
    · Maintenance and operations logs to be maintained as per the operating instructions and such records are
    made available for inspection by GNB.
    · GNB to be advised immediately if any of the above parameters exceed the reportable limits.
    · In the event of a warranty claim, only GNB or their authorised representatives to effect any evaluation and
    repairs on the batteries.
    · This warranty is applicable on return to base basis.
    Limitations on the Guarantee and Warranty:
    In no event shall GNB be liable for consequential or incidental losses or damages. GNB further disclaims all
    implied warranties of merchantability and fitness.

    That your batteries lasted 9 years is very good--Especially if this is a hot climate (25C = nominal temperature and design life; 35C = 50% reduction in design life). Keeping batteries cool helps extend their life (every 10C increase = 1/2 reduction in life. Every 10C drop in temperature = 2x increase in life).

    Looking at the Exide battery manual--These have a maximum charging current of 35 Amps / 100 AH capacity... So, they should be able to take a good charging current.

    I will stop here. Enough text for one post.

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mcgivormcgivor Posts: 1,746Registered Users ✭✭✭✭
    Thanks for your input Bill, valuable as always.
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • mike95490mike95490 Posts: 7,642Solar Expert ✭✭✭✭
    GEL and AGM batteries are NOT the same.    Gel batteries have glop in them, like stiff pudding.  It does not flow and if charged quickly, will develop gas bubbles and the pudding will not flow back and the bubbles become permanent voids.  Not Good

    AGM batteries have liquid electrolyte, but packed with fiber glass batting, which prevents any spillage, and prevents voids.  AGM can be charged and discharged quickly.  Nice batteries, but expensive and not as long-lived as flooded.
    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 ,

  • wimbledon83wimbledon83 Posts: 3Registered Users


    Hello Gents, 
    thank for some valuable information. 

    Location is Bathurst NSW Australia. 

    The house had the smaller invertor and the 9 x 175W panels when we moved in . An older lady lived here. Hence the smaller system. 

    We took our previous grid house power bill to the electricians and said we need this. Without replacing batteries then (they advised against adding another 12 to give 48V) we were confined to 24V . So the old 2000W invertor was split from the house and only feeds shed lighting and our tank waterpump . So this smaller invertor is usually in stand by. The new bigger invertor feeds the house. We added the 8 x 325W panels, the 2 x studer VT80, change over switch to bring generator straight into large invertor on low battery level (23V) . This cost us nearly $20K to do upgrade .

    All hot water and cooking is on GAS .
    Wood fire with a small 130W convection blower motor - fan only used for a few hours on cold nights. 
    We have added a pool , but used the Davey Powermaster eco pump. 170W for 5 hrs a day.
    I work from home for 3 days a week. Laptop etc runs up the power usage.
    Two young boys/wife  watching large TV for 4-6 hrs per day. 
    This is where our power goes. 

    All the panels face north and get good sun . I clean them with a hose every 6 months  (dust from other farms) 

    The old battery system worked fine . In summer we didnt need/use the geni at all . In winter it used to run for about 1-1.5 hrs per day if we had constant cloudy days . With the price of diesel this is of no concern . 

    So as I am reading BB ,  we need more panels ? . (building a large shed , plan is more panels on that shed) 

    But the battery bank one solar company and our electrician has recommended is about right ?. 
  • Organic FarmerOrganic Farmer Posts: 128Solar Expert ✭✭
    Sometimes the lifestyle you lived on-grid, is no longer practical when you go off-grid.

    I have had to force myself, and my wife, to only be turning things on when the sun is shining. She would turn everything on at night.

    Since we began living off-grid, our power consumption has grown a great deal. And it is not conforming to during sun-light hours.
  • EstragonEstragon Posts: 2,310Registered Users ✭✭✭✭
    edited May 29 #13
    It seems to me it would be a good idea to get a sense of what your actual load needs are now. Taking what you used in a grid home before isn't likely very representative of what you need now. I use ~30kwh/day on grid, vs ~ 3kw/day off-grid, for example. Knowing what you actually need will go a long way towards getting a system that meets your expectations.
    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
  • wimbledon83wimbledon83 Posts: 3Registered Users
    New question . 

    we are going to put grid power to the house.  Can some give details/recommendation for a 80A 240V single phase automatic (as in on a timer) change over switch?. 
    We want to run grid power at night and our solar system during daylight hours.  
  • mcgivormcgivor Posts: 1,746Registered Users ✭✭✭✭
    edited June 10 #15
    An automatic transfer switch with a definite purpose normally open contactor upstream of the transfer switch, which interrupts the grid, whose coil is is powered via grid power through a timer also grid powered, preferably with memory, would take care of the takeover. Next task would be to shut the inverters down after transfer is complete, wouldn't want to run them overnight consuming power unnecessarily. 
    There are hybrid inverter chargers which can perform all this seamlessly  without a custom design, but I'm assuming you would like to keep the existing equipment, correct? 

    Here is an example of such a contactor, there are many examples https://www.schneider-electric.com/en/product/GC10040M6/tesys-gc---modular-contactor---100-a---4-no---coil-220...240-v-ac/
      1500W, 6× Schutten 250W Poly panels , Schneider 150 60 CC, Schneider SW 2524 inverter, 8×T105 GC 24V nominal 

  • bill von novakbill von novak Posts: 731Solar Expert ✭✭✭✭
    New question . 

    we are going to put grid power to the house.  Can some give details/recommendation for a 80A 240V single phase automatic (as in on a timer) change over switch?. 
    We want to run grid power at night and our solar system during daylight hours.  
    I would recommend not doing this for a few reasons.

    One, you will be making two unsychronized switches a day.  That's hard on motors, like the motors in your fridge, water pump and A/C (if you have one.)

    Two, you are going to be switching this based on a timer or something similar without regard to your battery state.  That's not a good way to run your system.

    There are plenty of hybrid inverters on the market that will do this automatically, using good information (state of charge) and by synchronizing phases.  You are much better off with one of them.

    Even better - get a grid tie inverter.  That way you always export as much power as possible.
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