Humble and confused

gpspowellgpspowell Registered Users Posts: 18
I had a "critical needs" system installed just over a year ago and it appears the battery bank has already been damaged. Im now needing to replace batteries (?) and evaluate the system/settings.

History first: I live on the plains of NE Colorado with lots of good sunlight. The system (not designed or installed by me) is: 48v, 8 panels of 250W rating, Xantrex SW4048 inverter, Midnight Classic charge controller, 8 golf cart batteries. For backup I have a Honda 2000EU generator but the system is currently set up to automatically draw from the grid if needed (Not set up to FEED the grid at all). The intent of the installation was to get my feet wet in solar power with first, a system running "critical needs" (boiler, refrigerator, freezer, home office, and well pump) and second, a pseudo "stand-alone" system for learning preparatory to any possible extended use as a primary system in case of any future emergency (Our family farm was without electricity for 5 months after a severe blizzard in the late 70s).

In the last year I think I've learned three things: #1, No matter how "smart" the system was presented as, it won't effectively take care of itself, I need to take control of it(and learn how); and #2, The system may be under sized for need. At about 6 months I noticed the S.G.s dropping on the batteries and variations between cells. I called up the installer who came out and discovered he had botched a couple of charge settings allowing the batteries to go below 50%. He did a manual EQ and set the charge controller to auto EQ each month (No EQ had been done during the first six months). The S.G. issue has not resolved and, in fact is getting worse. So before I buy a new set of batteries I need to figure out WHAT batteries to buy, HOW MANY to buy, if my array is large enough for the coming battery bank, AND how to take care of the system so as to not have unnecessary issues in the future.

My average daily usage runs in the 4-5 kW range. It's higher in the summer months as I irrigate a small orchard and large garden but only during the middle of the day when solar gain is at its maximum potential.

I don't know if this is enough information to start a thread to help me proceed but I'll start here with hat-in-hand. Thanks in advance.

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Humble and confused

    Welcome to the forum.

    Let's look and see what you could expect.

    A string of golf cart batteries: 220 Amp hours @ 48 Volts. About 5kW hours stored capacity (DC) at 50% DOD. This could explain why they're dead if you were pulling 4-5 kW hours AC; the DC demand will be 10-20% more than this plus the inverter draw.

    You've got eight 250 Watt panels on an MPPT controller. Good for about 32 Amps on a 48 Volt system so should be enough to recharge the batteries on a sunny day.

    EQ is not the solution for everything. If the batteries have been killed, that's it; they don't come back to life no matter what.

    Yes, you are going to have to learn your system. Inverter Low Voltage Disconnect should be around 48, which ensures that the batteries won't go below 50% SOC (unloaded Voltage will be higher). You could stand to have a bigger battery bank, but beyond 320 Amp hours and you'll want more PV as well. You'll need to check the charging parameters as you cycle the system to make sure the batteries are getting fully charged - before you let it run for months on end.

    The Honda EU2000i will have a lot of trouble charging that much battery bank. Especially with an SW4048 and any concurrent loads. Ideally you should have a 3kW or 4kW generator for that system, and must have if you increase the battery bank size.

    So where do you go from here? I'd suggest the first thing to do is try and nail down that power consumption figure. The more exact that is the better the chance for a successful design. At the present estimated level it would be a good idea to have double the battery capacity, 1.5X the PV capacity, and double the generator size.
  • ScaleneScalene Solar Expert Posts: 25
    Re: Humble and confused

    Spent batteries do recharge, they don't reintegrate with new ones though. I guess one could use them for other things. One of the thing with Solar electricity, it recharges from dead, [but to new].
    Always troubleshoot with adequite sunlight.  Hi Ho Hi Ho
    2.3Kw  [10]Enecsys SMI 240-60 Gen1 inverters
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Humble and confused
    Scalene wrote: »
    Spent batteries do recharge, they don't reintegrate with new ones though. I guess one could use them for other things. One of the thing with Solar electricity, it recharges from dead, [but to new].

    Nope.
    Drag a battery down low enough and/or often enough and it is dead.
    No amount of recharging will fix that.
  • gpspowellgpspowell Registered Users Posts: 18
    Re: Humble and confused

    Thanks, Cariboocoot. You're verifying what I was beginning to suspect. The only surprise there was the generator issue. I have the Honda 2000eu and its 2000W companion that can be linked to effect 4000 watts (3200 at my altitude). The footer I installed in the beginning has room for adding 4 more panels so that shouldn't be a problem. Now to figure out which batteries to buy, I'm thinking16 Trojan L16RE-A (325Ah) or Trojan J305P-AC (330Ah).
  • mike95490mike95490 Solar Expert Posts: 8,370 ✭✭✭✭✭
    Re: Humble and confused
    So before I buy a new set of batteries I need to figure out WHAT batteries to buy

    Unless you have FOR SURE diagnosed and corrected the charging and load situation, get another set of the cheap golf cart batteries. When you get 2 years out of them, then you have dialed the system in and can buy the REAL EXPENSIVE batteries, and be reasonably sure of getting 5 years out of them.

    3,200 watts at altitude is not going to be enough generator, you will be using it to it's max and it won't hold up too long.

    Find out if the Xantrex ComBox will work/talk with the SW4048, it will give you load information and the midnight classic will give you charge information via it's LocalApp.
    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 ,

  • SkiDoo55SkiDoo55 Solar Expert Posts: 414 ✭✭✭
    Re: Humble and confused

    Question is your Inverter an SW4048 or an XW4048, is it configured 240 split phase or has it been reconfigured to 120 output? SW will do 120 in to 240 out internally. To use the Honda's if inverter set for 240VAC, (120-N-120) you would need a transformer with XW to convert gen 120 VAC to 240 VAC. Is Grid Support enabled, and what are the settings for support set at, charger settings set for. Too bad you don't have the XW Mppt 150-60 controller, inverter can be set to follow it thru full charging cycle each day and draw excess required from grid. Don't know if it can be made to do that with your controller. evenwith the most advanced battery system they still need oversight on battery state of charge, water levels for flooded battery etc. There are experienced members here that have a vast amount of knowledge on solar/battery systems.
    You should have either the ComBox or an SCP to adjust the SW/XW inverter, the Combox is the most usable accessory.
    GT3.8 w/4600W Trina 230W, TX5000 w/5000W ET-250W, XW4024 w/1500W ET-250W, 4 L16, 5500W Gen. (never had to use) Yet!!
  • gpspowellgpspowell Registered Users Posts: 18
    Re: Humble and confused

    Already I'm glad I joined this group! Let the education begin. Mike95490, It seems the Xantrex ComBox won't interface with the SW4048. Bummer. I'll have to see if there is a monitor that will.

    SkiDoo55, The inverter is an SW4048 configured to 120volt (220v well pump runs off its own 240v inverter). Grid support is enabled. If I understand the settings correctly the grid support (menu 16) is set to transfer at 48.8v (this was set lower before the battery problem was noticed) and to cut in at 52.8. That follow-thru with a full charge cycle would be nice, I'll try to find that out. Learning to perform proper oversight on the batteries is a lot of why I've come here. Hopefully I'm up to the challenge.
  • SkiDoo55SkiDoo55 Solar Expert Posts: 414 ✭✭✭
    Re: Humble and confused

    went sideway on you, keep forgetting there are older SW's out there. New SW4048 not due to be released until sometime in 2015, it will as the current XW's/SW's work with the ComBox and there line of MPPT solar chargers, thru the Zanbus (cat 5e cable)
    GT3.8 w/4600W Trina 230W, TX5000 w/5000W ET-250W, XW4024 w/1500W ET-250W, 4 L16, 5500W Gen. (never had to use) Yet!!
  • ScaleneScalene Solar Expert Posts: 25
    Re: Humble and confused

    I am not sure but I think that if the battery was properly discharged [no element, heater, light bulbs, coffee maker.] it will keep coming back for a good long time...[And the proper load was proportioned
    Always troubleshoot with adequite sunlight.  Hi Ho Hi Ho
    2.3Kw  [10]Enecsys SMI 240-60 Gen1 inverters
  • icarusicarus Solar Expert Posts: 5,228 ✭✭✭✭
    Re: Humble and confused

    First, a dead (not simply discharged) battery will never take...and hold a proper charge. Over discharging a battery, could with lack of timely recharge is recipe to kill a battery. (see the attached battery FAQs for some great info:

    http://www.batteryfaq.org/

    http://www.solar-electric.com/deep-cycle-battery-faq.html

    Next, I agree with Mike's suggestion buy another cheap set before you buy an expensive set.

    Finally (probably not finally), ideal battery discharge is in the range of 20-25% daily, followed by a full recharge for best batty life. Ocassional discharge to 50% is fine, but any further and you are courting early battery failure. The problem usually isn't solved with bigger batteries, but rather bigger batteries usually exacerbates the issue.

    All design calcs stem from the loads. The loads define the battery bank size, the battery bank size defines the charge regimen. Bottom line, acurately calculate your loads, and proceed from there.

    Finally, (told you it probably wouldn't be the last!) there are two basic rules of solar that folks ignore at thier peril. First, they over estimate thir solar potential, second, they at the same time underestimate thier loads, leading to deficit charging. Chronic deficit charging is the number me cause of battery failure.

    Good luck, welcome tot he forum, and keep in touch. There are some pretty smart folks here who have forgotten more about PV than most of us will ever know, and they re very willing to help,

    Tony
  • gpspowellgpspowell Registered Users Posts: 18
    Re: Humble and confused

    Okay, here's what I think I know so far: After a year of recording usage I find that I consistently use 4kW of power per day. Occasionally I see 3kW or 5kW but not often. In the summer months I drip irrigate a small orchard and a large garden. I irrigate during the middle of the day when I'm seeing 1600-1800W being produced from my 8 250W panels. According to the installer the charger was consistently taking the battery bank (8 golf carts) below 50% due to a botched initial setting. This condition persisted for about 9 months. Now the battery bank is pretty much shot.

    This morning the temperature in my battery house was -8ºF. I'm guessing here but, an average temperature here in NE Colorado (day/night/winter/summer) is probably in the area of 50ºF. At 50ºF my 220Ah battery bank was probably capable of supplying (at 50%) about 2.6-2.8kW of stored power....AND I'm using 4kW/day. If my assumptions are correct (including the botched setting) this battery bank didn't stand a chance.

    So.... I'm questioning the idea of buying more golf cart batteries (16 golf cart batteries storing 5.2-5.6kW) for $2000 (+/-) that still are marginal????? I'd like to be able to switch to grid backup no lower than 60% SOC, have roughly 2 days storage in that first 40% draw, and enough charging capacity to return to 100% SOC as often as possible. What I'm thinking is: installing 16 Trojan J305P-AC batteries @ 330Ah each giving me nearly two days storage (temperature corrected) and increasing my array by 4 panels (1000W total) to give me enough charging capacity for the larger battery bank, especially when running the well pump in the summer (draws 1200W).

    All this is, of course, an invitation for more critique and advice.
  • Alaska ManAlaska Man Solar Expert Posts: 252 ✭✭
    Re: Humble and confused

    I would not store my bank in a place that cold. you are seriously decreasing their capacity. I would hope that a Battery Temp Sensor was installed and has been configured for use with your charger and charge controller.
  • 2twisty2twisty Solar Expert Posts: 199 ✭✭✭
    Re: Humble and confused

    What is the recommended low-temp cutoff? Right now, my batteries are outside in 25F ambient temps. How much capacity is lost?

    My chargers DO have temp sensors on them, fwiw. We will be building a box around them in the next week to protect them (they are covered with a tarp right now) and I am wondering if I need insulation. I live in the desert, so ambient temps can get over 100F in the summer.
  • BB.BB. Super Moderators, Administrators Posts: 29,489 admin
    Re: Humble and confused

    From the battery FAQ;

    http://www.solar-electric.com/deep-cycle-battery-faq.html

    Attachment not found.

    Or at 25F, you have approximately 85% capacity.

    What you want is the battery bank to be somewhere between 50 and 75F ideally. You may need insulation in the winter, but lots of ventilation in the summer (or insulating during the day, venting during cool nights).

    Cellar or earth berm walls for your battery enclosure can help stabilize the battery temperature too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • gpspowellgpspowell Registered Users Posts: 18
    Re: Humble and confused

    Thanks, BB. Something weird is going on here with the forum. Your post, and one other showed up on the main forum page but not in the string???? We'll see if this one shows up? The temperature fluctuation here is part of the reasoning for the larger battery bank I'm considering. My Charge controller (Midnight Classic) is temp compensated but, after reading the FAQ you included I'm wondering if I shouldn't look into a direct sensor on one of the batteries as well as seeing if there is some way to moderate the temps in the battery house (insulation?). It may be that the batteries aren't fluctuating as much as the air temp.
  • BB.BB. Super Moderators, Administrators Posts: 29,489 admin
    Re: Humble and confused

    Batteries do/can heat, especially when being charged. So, a modest amount of insulation (or even just a small wooden box around the batteries) may be enough in the winter to keep them warm enough.

    In the summer, cooling is going to be a bigger issue. Keeping sun off during the day, and venting at night may help... I live in a moderate climate--Perhaps others here can give you better information than I.

    Your post showed up fine for me.

    For me, I perfer to use the "New Posts" button vs the "Whats New" function.

    Also, play with your reading options... under Settings (upper right of page) or click here:

    http://forum.solar-electric.com/profile.php?do=editoptions

    And scroll down to Thread Display Mode: and pick Linear/Oldest first... Usually works well for our forum. I do not like "threaded" display, it causes "new posts" to appear in the middle of the thread sometimes (depending on where the person hits the "reply" button).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 8,370 ✭✭✭✭✭
    Re: Humble and confused
    Right now, my batteries are outside in 25F ambient temps


    One thing to beware of, is low temperature charge voltage, needing to increase. This may (depending on the temps) make the inverter upset with the extra voltage needed to charge cold batteries.
    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 ,

  • inetdoginetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Humble and confused
    BB. wrote: »
    Batteries do/can heat, especially when being charged. So, a modest amount of insulation (or even just a small wooden box around the batteries) may be enough in the winter to keep them warm enough.

    In the summer, cooling is going to be a bigger issue. Keeping sun off during the day, and venting at night may help... I live in a moderate climate--Perhaps others here can give you better information than I.

    Your post showed up fine for me.

    For me, I perfer to use the "New Posts" button vs the "Whats New" function.

    Also, play with your reading options... under Settings (upper right of page) or click here:

    http://forum.solar-electric.com/profile.php?do=editoptions

    And scroll down to Thread Display Mode: and pick Linear/Oldest first... Usually works well for our forum. I do not like "threaded" display, it causes "new posts" to appear in the middle of the thread sometimes (depending on where the person hits the "reply" button).

    -Bill

    Bill: See additional suggestions at http://forum.solar-electric.com/showthread.php?25885-Forum-malfunction
    SMA SB 3000, old BP panels.
  • BB.BB. Super Moderators, Administrators Posts: 29,489 admin
    Re: Humble and confused

    Thank you Inetdog.

    I have mine set to maximum number of posts (40 or something) on Firefox browser. I have not seen the problem--But understand that it can happen.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,228 ✭✭✭✭
    Re: Humble and confused

    Remember, that while battery CAPACITY drops with temp, battery longevity actually rises.

    Batteries will "self heat" to a limited extend by both charging and discharging. A battery box that is insulated will keep batteries significantly above ambient temps.

    Tony
  • gpspowellgpspowell Registered Users Posts: 18
    Re: Humble and confused

    Great info here. Thanks to all who have offered advice. I think I have a plan and I hope some of you will weigh in on it before I commit. The only advice I’ve gotten here that I’m reluctant to follow is that of purchasing cheap batteries again to test out the new system configuration. I understand the reasoning behind that idea but since 16 golf cart batteries would still be an undersized bank (IMHO) I feel I would just be throwing away $2000 on a temporary test. So, here goes:

    As I posted earlier, I’d like to install 16 Trojan J305P-AC batteries, for a theoretical 660Ah of storage which would give me close to a two day storage using 40% (I consistently use 4kw/day) and I will set the grid support to cut in at 60% SOC. Then add 4 more 250W panels to bring my array up to 3kw for charging the enlarged battery bank and to supply more watts when irrigating in the summer time. My battery house is a detached structure and moving the batteries and controllers isn’t a feasible option so I’ll plan on increasing the ventilation for summer with closable venting and insulate the building for winter. If possible I’ll add a remote temperature sensor to one of the batteries to more accurately control the Midnight charge controller. Lastly, in case of grid failure I’ll look into purchasing a larger generator (my paired Honda 2000s only put out 3200W).

    Does this sound appropriate?
  • mike95490mike95490 Solar Expert Posts: 8,370 ✭✭✭✭✭
    Re: Humble and confused

    If you have GRID, then you should be floating your batteries 95% of the time (after plate forming) And if you have a grid failure, you get to use the batteries. But otherwise, the expensive batteries are just sitting and dieing. So go with the cheapest, and when the grid is down, beat them to 60% discharged. And run your genset monthly.
    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 ,

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