1 bad battery? or all

So I have a small 48v system look at signature. My problem is this my batteries deka gels 4 12v in series are losing charge and gaining charge quickly. yesterday after charge controller no longer provided power to them I checked the individual voltage 3 where 12.85V and 1 was down to 10.85 all pretty quickly about 1 hour after full charge from sun. So do I have 1 bad battery or are they all bad? They are 3 1/2 years old and do get abused some. I got the gels as I have the potential for them to freeze.

Thanks kristine

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 1 bad battery? or all

    Well the first question I have is: how did you wire the five Kyocera 135 Watt panels to charge a 48 Volt battery bank? All in series I hope.

    The second question I have is: how much current are you seeing from the charge controller? It should be possible to get 10 Amps, which ought to suffice for a 94 Amp hour battery bank.

    Which brings us to question #3: why did you pick these tiny little gel batteries? That is a very, very small battery bank of a type not really suited to RE use. For example the VFX3648 on its own draws 20 Watts, or 480 Watt hours over a day. That's 10 Amp hours right there just to keep the inverter running. Charged batteries do not freeze, so there was no reason to select gels when flooded cells or AGM's would work fine.

    But you still wouldn't have much capacity as the array could really only handle 100 Amp hours or so. If you have any significant amount of load these would be deficit charged for 3.5 years and that will doom any battery. The symptoms you describe are consistent with lost capacity.

    In other words it's time to rethink the whole thing. Right now if the batteries were good you could manage about 960 Watt hours AC per day (at 25% DOD - not enough panel to recharge from lower). That's not very much and certainly if it were the amount used you wouldn't need a 48 Volt system to supply it.

    So let's start with the basic question: how many Watt hours per day do you need?
  • summitdwellersummitdweller Solar Expert Posts: 28
    Re: 1 bad battery? or all

    I use maybe 500 watts per day not much just some night time computer or a Netflix movie and 1 led light all maximum 5 hours in the winter summer much less other stuff to do! Also the inverter is only inverting maybe 6 hours a day the rest of the time on search 2.6 watts vs the 20 so much less amps used. Do all electric intensive stuff while sun is shining and can still recharge or plug in the generator. I was told to my dismay the gels were the way to go and have since learned and would love advice as to what batteries to purchase. want to expand as I can afford to include a real fridge not propane but everything else would be about the same. Thanks And yes the panels are in series could I add one more panel and be better off?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 1 bad battery? or all
    I use maybe 500 watts per day not much just some night time computer or a Netflix movie and 1 led light all maximum 5 hours in the winter summer much less other stuff to do! Also the inverter is only inverting maybe 6 hours a day the rest of the time on search 2.6 watts vs the 20 so much less amps used. Do all electric intensive stuff while sun is shining and can still recharge or plug in the generator. I was told to my dismay the gels were the way to go and have since learned and would love advice as to what batteries to purchase. want to expand as I can afford to include a real fridge not propane but everything else would be about the same. Thanks And yes the panels are in series could I add one more panel and be better off?

    Okay so 500 Watt hours per day. The "hours" part is important because Watts alone is a rate, whereas Watt hours is a quantity.

    For a 48 Volt system that would be (using known numbers for your inverter) 760 Watt hours DC. (BTW the VFX uses 6 Watts in search/standby). On a 48 Volt system that would be 16 Amp hours or a minimum 64 Amp hour battery.

    Looking at it from the other end you have five 135 Watt panels or 675 Watts which should produce about 10 Amps on an MPPT charge controller. Enough for a 100 Amp hour 48 Volt battery.

    Considering the power demand here, both your inverter and charge controller are overkill. Were you planning on expansion or did someone sell you these to make themselves a good profit?

    Anyway the quickest thing you can do to get back in business is replace those batteries. Regrettably the cheapest-per-Watt-hour batteries, the GC2's, would not be supported without at least doubling your array size. So see if you can find locally some true deep cycle 12 Volt batteries around 100 Amp hours. Something like these: http://www.solar-electric.com/repoba12vo95.html or the equivalent in another brand. Avoid Marine/RV batteries or anything that gives a rating in cold cranking Amps.
  • summitdwellersummitdweller Solar Expert Posts: 28
    Re: 1 bad battery? or all

    Why are the crowns so much cheaper than the sunxtenders agms? Yes I want to expand in the future but $ holds me back. I do want to double array size soon within a couple years. and then double again later. So a cheaper battery now may be the way to go.
  • zonebluezoneblue Solar Expert Posts: 1,218 ✭✭✭✭
    Re: 1 bad battery? or all

    I see two possible routes for you.

    a. Upgrade the weak components to support the vfx.
    b. trade the vfx for a smaller inverter

    This all depends on your loads. If they are as a small as you say then a 300-1000W inverter running at 24v is better suited to your pv. OTOH if you want to grow your pv and loads then stick with the vfx, its a great inverter, just doesnt have what it needs around it.

    If you go plan A, then you could do this in two steps, new batterys, and use the Honda to maintain them for a while. Then add pv to suit.

    But all of this requires a plan and a load budget.

    >I use maybe 500 watts per day

    Understanding load budgeting is the key to happiness in this game. You measure loads in Wh/day. That is something might use 100W and run for 5 hours/day, gives you 500Wh/day. You MUST set a design target load capacity. Its not like add a bit of this and bit of that and see how she goes. That wont work.

    IF your loads are changing then you have a draw a line somewhere. You mention wanting to run a fridge. Ok thats a place to start. That as a rule of thumb takes you into the 3kWh/day ball park. Here is a load budget for 3kWh/day

    Attachment not found.

    Take it and massage it to fit your lifestyle.

    In terms of those batterys one is dead, the others are certainly not far behind it. So theres some urgency.
    1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
    http://zoneblue.org/cms/page.php?view=off-grid-solar


  • summitdwellersummitdweller Solar Expert Posts: 28
    Re: 1 bad battery? or all

    Ok so I am at 500 watt hours per day, that includes the laptop for 5 hours no router and one led light OR 3 hours watching a movie and 1 led light. As I already have the inverter am going to stick with that. Plan to double panels and batteries soon then go to the GC2's?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 1 bad battery? or all
    Why are the crowns so much cheaper than the sunxtenders agms? Yes I want to expand in the future but $ holds me back. I do want to double array size soon within a couple years. and then double again later. So a cheaper battery now may be the way to go.

    Two different types of battery: AGM (Absorbed Glass Mat) vs. FLA (Flooded Lead Acid). AGM's are more expensive per Watt hour.

    If you double your array to 1350 Watts you should get about 21 Amps peak current and be able to support a string of 220 Amp hour 6 Volt GC2's which are now the best bargain in battery capacity to be had. In some of the warehouse stores they can be bought for <$100 apiece.

    The most array your FM60 will support at 48 Volts is about 3740 Watts. But you are going about this part of the expansion the wrong way, as you began with 135 Watt "12 Volt" panels. The Kyoceras are now 140 Watts and cost quite a bit more per Watt than completely different panels. Vis: five Kyocera 140 Watt "12 Volt" panels costs $1425 for 700 Watts ($285 each). That same money can buy almost 1440 Watts of all new panels if you get something like the Trina TSM 240 (six @ $238 each).
  • summitdwellersummitdweller Solar Expert Posts: 28
    Re: 1 bad battery? or all

    Sorry I missed the fla on the crowns! I may have this wrong but could I not do another string of higher watt panels as long as they closely match the voltage of the string of 135s or is this way off base? If I am going to double everything I am starting to think triple is better then I could support the fridge for sure who knows how long my used 30 year old propane fridge is going to last!
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 1 bad battery? or all
    Sorry I missed the fla on the crowns! I may have this wrong but could I not do another string of higher watt panels as long as they closely match the voltage of the string of 135s or is this way off base? If I am going to double everything I am starting to think triple is better then I could support the fridge for sure who knows how long my used 30 year old propane fridge is going to last!

    In theory you could do a parallel string of higher Watt panels to match the ones you've got in Voltage. In practice this is not so easy. Right now your Vmp is (17.5 * 5) 87.5. Most of the "GT" panels have a Vmp around 30, so three in series would be 90 Vmp for that string. For example a Solarworld 245 has a Vmp of 30.8 so a string of three would be 92.4. That's a difference of 4.9 Volts or 5.6%. Not perfect, but pretty close. It would add 735 Watts bringing the total to 1410. Cost $756.

    The greater the Voltage difference in parallel strings the more power will be lost as the higher Voltage string tries to pull the lower one above its Vmp. And this is largely theoretical as what will actually happen in the real world is not so easily predictable.

    Now what about the next time you want to expand? This is the whole problem with trying to expand a system after its initial install.

    BTW I can run my electric 'frige from 700 Watts and 232 Amp hours @ 24 Volts, but seasonally. The refrigerator uses about 1.2 kW hours per day. Best thing you can do is use a Kill-A-Watt meter to measure the average daily power draw of whatever you've got now and see what the real numbers are.
  • summitdwellersummitdweller Solar Expert Posts: 28
    Re: 1 bad battery? or all

    I have no problem in the summer it is the winter that kicks my butt! Still need to cut a couple trees for the low sun also! Other question if I double the system do I need a bigger generator to charge in the winter on the snow days? when I get a real fridge do I just take my kill a watt meter to the store or is there a way to know for sure what power they use? What percentage of difference in the string vmps should I try to achieve? yes all new panels would be great...and yes I started this all wrong!! Have much to think about Thank you
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 1 bad battery? or all

    Yes, Winter can be a pain. Up here the daylight drops to 6 hours a day and the sun tries to hide beneath the horizon even at midday.

    Your generator size depends on how many Amps you need to charge your batteries. Larger battery bank = more Amps = larger gen. The good thing here is that the VFX has a really good built-in charger even though you have to interpret the AC Amps setting as DC Amps by multiplying by 2.5 (i.e. 10 Amps Charging is in AC and equals 25 Amps DC going to the batteries).

    So let's say you have a 220 Amp hour 48 Volt bank and you want that 25 Amps (its okay to go higher than 10%, just not extremely). That's 10 Amps AC * 120 VAC = 1200 Watts. At that point your Honda EU2000i will not have much power left to run anything else because it's only capable of 1600 Watts. Refrigerator kicks on; inverter will drop gen. Not much margin to work with. You could buy a second 2000 and parallel them, or go for a 3000 and get yourself another kilowatt to work with.

    It would be nice if you could take the K-A-W meter to the store and test things. Dollars to donuts they won't let you. You can sort of get an idea from the power ratings, but remember they are optimistic (slanted to look good). I've actually measured a few (look under energy & conservations for the "just how bad a small 'frige is" thread) and found them disappointing.

    As far as string Vmp difference is concerned, less than 10% is desirable and less than 5% is better. 0% is ideal. :D You could probably sell those 12 Volt panels to recoup some money.
  • summitdwellersummitdweller Solar Expert Posts: 28
    Re: 1 bad battery? or all

    was looking at my paper work for the panels they are vmp of 17.7*5=88.5 looked at the Kyocera 250gx they have vmp 29.8 *3=89.4 so 1% difference? Would that work? then a combiner box? anything else I would need I am not thinking of? But if I expand again will I be screwed they don't make the correct vmp panels anymore?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 1 bad battery? or all
    was looking at my paper work for the panels they are vmp of 17.7*5=88.5 looked at the Kyocera 250gx they have vmp 29.8 *3=89.4 so 1% difference? Would that work? then a combiner box? anything else I would need I am not thinking of? But if I expand again will I be screwed they don't make the correct vmp panels anymore?

    Those panels should work that way.
    Combiner box may be a difficult thing as your old panels will probably have MC3 connectors and the new ones will have MC4, so some adapting needs to be done to get the two connected. With two parallel connections you won't need fuses on them, but if you plan to expand to three ... That's why you have to think about these things in advance.

    And you're right the next time you go to buy panels you may have the same trouble again.
  • summitdwellersummitdweller Solar Expert Posts: 28
    Re: 1 bad battery? or all

    Was thinking this MidNite Solar MNPV4-MC4 Solar Array Combiner then I could add to it later? Or something else? The Kyocera panels, and 8 220AH 6 volt batteries? anything else as I may just do this now instead of later! As for the connections already thought of that, I can make it work. Seems dumb to get batteries without doubling everything when I want to double soon anyway, then just wasting batteries.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 1 bad battery? or all

    Eight 220 Amp hour 6 Volt batteries = 220 Amp hours @ 48 Volts.
    25% DOD = 2640 Watt hours DC, about 2.2 kW hours AC.
    22 Amps * 48 Volts would need 1371 Watts of array. You've got 675 Watts and are adding 750 Watts for 1425 Watts so it should work fine.

    The MidNite MNPV4-MC4 can take four strings of panels; they just plug in. What else? Well there's always something else, isn't there? Mounting hardware for the new panels for example.

    If you can afford it taking the leap to the 220 Amp hour batteries and providing the PV they need now is better than changing the gel batteries out and then having to change them again with the later expansion.

    As it is you'll be no place near the maximum the controller can handle (about 3740 Watts, enough to recharge 600 Amp hours @ 48 Volts).
  • mike95490mike95490 Solar Expert Posts: 8,614 ✭✭✭✭✭
    Re: 1 bad battery? or all

    My take on this, for the short term, is to simply get a 4 pack of 12V, 95Ah, $85, marine "deep cycle" batteries, and expect to get 2-5 years out of them.
    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 ,

  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: 1 bad battery? or all

    Although it seems like the gels are toasted by now, I wonder what your controller's absorb voltage is set for? For Gel's, that would be about 14.0 to maybe 14.1 max for a nominal 12v system..
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: 1 bad battery? or all
    The MidNite MNPV4-MC4 can take four strings of panels; they just plug in.

    True enough. That item has four 600 volt fuses... perfect for a high voltage grid tie system. You can order that same box, (pre-wired or not) with up to six 150 volt circuit breakers. If you don't need high voltage, you will be happier with breakers.

    It's a shame that Midnite does not publicize their pre-wired MC4 combiners with breakers for the low voltage off-grid market. I guess they know the market, and THE market these days is for grid-tie. (same applies to solar panels... grid-tie panels dominate the market).

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 1 bad battery? or all

    One of the little details of expansion: wiring.

    If you're going to be doubling or tripling the panels connected to the controller you're also going to be increasing the current, and that means you need to check and make sure the wires from the combiner to the controller can take the increase. Also check the wires from the controller to the battery, as that current will be going up too. While you're at it, make sure the wires from the battery to the inverter are up to snuff. And of course the appropriate over-current protection on each circuit.
  • summitdwellersummitdweller Solar Expert Posts: 28
    Re: 1 bad battery? or all

    Okay so I am going with the Eight 220 Amp hour 6 Volt batteries = 220 Amp hours @ 48 Volts and adding the panels. got the combiner box basic midnight one with room for expansion. Wiring is good did get more interconnect wires. My question is venting? can I use just the Zepher 12 volt power vent off the inverter for less wattage use or do I want/need the full 48 volt one off the inverter and the batteries which has more consumption with the amount of batteries I have?
    Thanks for all the information
  • summitdwellersummitdweller Solar Expert Posts: 28
    Re: 1 bad battery? or all

    The 48 volt one needs an additional 12 volt relay basically if I do use this one have NO idea how to set it up....do I really need the bigger one or just do 12 volt one right off the inverter? If I need the 48 volt how do I wire it? Just don't get it!
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