generator/inverter charging setup...

hillbilly
hillbilly Solar Expert Posts: 334 ✭✭
ok this is probably a total newbie quandry that I am in, but here it is:
first off I am looking to up-size our whole system, but can only really do it one component at a time.  our current battery bank is made up of 8 6v surrette 350ah each, and we have 2 evergreen 110w solar panels, our power consumption is very low (and currently very limited), but backed up by a generator with an iota 30amp charger.  I was looking into some of the inverters with charging capabilities, in particular the outback vfx3524 (capable of charging at 85amps DC).  Three questions that I have which I could not tell from the specs that I've looked over:
from what I have heard it is not recommended to charge your battery bank at more than 10% of their rated capacity (this would be 70amps at 24v for us), and I am not sure if this inverter can charge at a lower rate than the specified 85 amps or not (ie: is that just the maximum capable output). 
secondly, I currently only have a 15amp rated cable running from the generator currently (that would supply about 75amps at 24V???), will this cause a problem or simply limit the charging capabilities of the inverter.
last, I am wondering is it possible to use the generator/inverter to equalize charge the batteries, or do I need to rely on the pv panels to do this.
Like I said, this is probably quite a greenhorn question, but I would greatly appreciate any and all advice.
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Comments

  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    Re: generator/inverter charging setup...

    the inverters charger of 85 amps is fully adjustable down to next to nothing.
    the 15 amp cable is going to need attention as it will be a severe week spot causing voltage drop to the inverter look into at least #10 copper depends on the length though.
    the inverter charger will equailize though you will need to buy the mate to go with it :x
    Xantrex makes a nice inverter no mate required look at there sw plus 2524 i have 2 and love them
  • hillbilly
    hillbilly Solar Expert Posts: 334 ✭✭
    Re: generator/inverter charging setup...

    Ok, thanks... that is kind of what I figured, but really wanted to make sure on all that. The 15amp cable is just what I have currently to connect the generator to my Iota charger, and it can be upgraded but it is a full 100ft away from the charger (the inverter would be about 10' closer most likely), so it will be a bit of cash to upgrade it and if I can only charge at 70amps anyways...
    thanks again for the help
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: generator/inverter charging setup...
    secondly, I currently only have a 15amp rated cable running from the generator currently (that would supply about 75amps at 24V???), will this cause a problem or simply limit the charging capabilities of the inverter.

    15 A x 120 VAC into the inverter would be 1,800 W. Assuming 90% charger efficiency and a maximum bulk charge voltage of 28.8 V, the charger could supply 1,800 W x 90% / 28.8 VDC = ~56 A. If you decide to buy the OutBack inverter, you'd just have to limit the input current ("aac", or Amps AC) to 15 A.

    HTH,
    Jim / crewzer
  • hillbilly
    hillbilly Solar Expert Posts: 334 ✭✭
    Re: generator/inverter charging setup...

    Thanks again for the help guys!
    quoting crewzer:
    "15 A x 120 VAC into the inverter would be 1,800 W. Assuming 90% charger efficiency and a maximum bulk charge voltage of 28.8 V, the charger could supply 1,800 W x 90% / 28.8 VDC = ~56 A."

    DOH! thanks, I knew that I was being a bit too quick and simple with my math (not my favorite subject). That does change things a bit, as that is a big waste of gas there... guess that I'll be upgrading that cable after all.

    Much appreciated.
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: generator/inverter charging setup...
    from what I have heard it is not recommended to charge your battery bank at more than 10% of their rated capacity (this would be 70amps at 24v for us), and I am not sure if this inverter can charge at a lower rate than the specified 85 amps or not (ie: is that just the maximum capable output).

    10% - 13% charge current seems to be the limit, according to Trojan Battery. Rolls / Surrette suggests 10% charge current for a battery at 75% SOC.

    See: http://www.trojanbattery.com/Tech-Support/BatteryMaintenance/ChargerSelection.aspx
    and: http://www.rollsbattery.com/Bulletins/507.htm

    Note that a charger will typically only deliver its rated charge current during the bulk charging stage. Once the charger switches from bulk to absorb mode, it will gradually reduce charging current while maintaining target voltage and as the battery SOC increases. Rolls / Surrette recommends a 2 hour absorb mode for your S-430 batteries. A strategy to consider is to postpone external loads on the generator until the charger switches to absorb mode.

    HTH,
    Jim / crewzer
  • hillbilly
    hillbilly Solar Expert Posts: 334 ✭✭
    Re: generator/inverter charging setup...

    OK thanks Crewzer. As usual for me, one answer seems to bring up three questions. So I am a bit unclear on the whole concept of charging and using power; I saw there was a whole thread on this topic but I wasn't sure how it really would apply to our system. I understand that if you are consuming power that it takes away from available charging power, but what I am unclear on is weather it makes an actually difference when you consume as long as there is sufficient power to still fully charge the batteries up.
    In our case I am more curious how this might apply to daytime power consumption when we're at or near peak pv generation (we currently are running our generator about 1-2 times a week for about 3-4hours). In particular, say that I know that we are not going to have much (if any) time in float charge (our current charger is a 2stage charger, blue sky 2000E); so if I am just breaking even, or running a slight energy deficit one day does it make a difference what time of day/night I run loads? What we're doing now is basically looking at our energy use on a weekly cycle, and using the generator to make up any shortfall of solar energy production (or the rare times of extra consumption), thus we don't always reach float charge during the day (especially short, cloudy, winter days).
    Not sure if this makes sense, but I just sort of figured that it was pretty much amp hrs in- amp hrs out; if there are further considerations please enlighten me.
    ps. thanks so much for your help you guys, can't tell you how much this means to me; being off the grid, every little bit makes our home much more comfortable and enjoyable!
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: generator/inverter charging setup...

    hb,

    The best time to power your loads is when the inverter/charger or solar controller is operating in absorb or float mode. Two reasons:

    (1) Your flooded-cell batteries are only ~80% efficient (Wh out / Wh in). So, it takes less energy to power your loads from your energy source(s) directly than it does to power the loads from the batteries and then recharge the batteries.

    (2) There’s usually “unused” energy available when the charger is in absorb or float mode, especially when the energy source is a PV array. This is because the charger operates in “current limit” mode when in the absorb or float mode, so it typically uses only part of what’s available from the PV array.

    An example of this strategy is powering “opportunity” loads when the charger(s) is in absorb or float mode. Specifically, try running washing machine, water pump, and/or electric hand tools on a sunny afternoon after the charge controller has switched from bulk to absorb mode. The energy for these loads may well come from “extra” available from the array and not entirely from the batteries, if at all.

    Also, note that it’s important to regularly fully recharge your S-430 batteries (a full two-hour absorption cycle at least twice a week), and your flooded-cell batteries also require occasional equalization as well as periodic maintenance. Failure to fully recharge the batteries on a regular basis is called “deficit recharging”, and it invariably leads to hard sulfation of the internal battery plates, which in turn leads to reduced battery capacity (fewer useful Ah) and a shorter useful life (fewer charge/discharge cycles).

    See: http://www.rollsbattery.com/ , select “Site Map”, then select “Bulletins” for specific info on charging and manitaining your batteries.

    HTH,
    Jim / crewzer
  • hillbilly
    hillbilly Solar Expert Posts: 334 ✭✭
    Re: generator/inverter charging setup...

    Ok, that all makes sense, however:
    First of all in my case pretty much all of our bigger loads are run through the inverter (via battery), and most of the time we are charging with all of our available solar power meaning only some float time is ever available. In other words for the most part we only have any real extra power available would be while running the generator with loads connected directly to it (which at the moment the only items to connect are power tools). So in this particular instance are there other factors that I am missing, or would it sort of be a moot issue?
    I am well aware of the need to keep charging our battery bank, maybe I should have made it clear that by energy deficit, I am speaking in terms of a couple of days only at a time. We are not deep discharging our battery bank either, as our bank is currently very much oversized for our consumption (to allow for some days of autonomy for no sun/low sun); as far as I can tell I think that the deepest that we've discharged the bank thus far was about 25-30% at any point in our weekly cycle. Equalizing has been a bit tricky for the last couple of months, not so much now, but highly inefficient having to "boost" our batteries up first with our generator using our 30amp charger. Hence while we do want to double (and eventually triple) our pv array, it seems to make the most sense to first up our charging capabilities from our generator to reduce run times and maximize gas efficiency...
    Thanks again
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: generator/inverter charging setup...

    If you fire up the gennie in the early AM, about 2 - 3 hours before max solar output, you can use gennie to bulk charge the batteries, and then, after they are into the adsorb mode, kill the gen, and let the solar "trickle" them for the final hour or 3
    As said before, you do not want to NOT finish fully charging the batteries. That will eventualy kill 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 ,

  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: generator/inverter charging setup...

    I like Mike's idea as well. If you have to run the generator, then shift some loads to it so that you don't have to run 'em off the batteries.

    Regards,
    Jim / crewzer
  • hillbilly
    hillbilly Solar Expert Posts: 334 ✭✭
    Re: generator/inverter charging setup...

      Mike you describe exactly what we are doing, but I was curious if it is an issue to only fully charge our batteries this way once or twice a week?  Again since our daily use is a very small % of our bank capacity it seems more efficient to me to only fire up the generator periodically (about every 2-3 days in the winter, maybe every 10 days in the summer depending).      Part of it is (correct me if I am wrong) that I understand that the batteries will absorb more rapidly when they have been discharged more than say 5-10%; meaning that if I would be using the generator more efficiently if I wait until the battery SOC drops to less than 70-80% and then let it run enough to top up the batteries to say somewhere in the 90-95% range and then let kill it to let the PV's trickle in the last bit.  Do any of you think that this is harder on batteries to go a couple of days to a week before getting fully charged back up (bearing in mind that they are still at a fairly high SOC all the time)?

    PS, after thinking it over I figured out how to rewire so that I can now temporarily switch all of our AC loads from our inverter to our generator while it is running.  Thanks for the input!
    ... now if I can just get that new inverter I could cut WAY back on the amount of time that I have to run that damned generator!
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: generator/inverter charging setup...

    The batteries should be topped off to 101% as often as you can stand to run the gennie.

    The longer they dwell at less than 100%, the faster the damage accrues, and the faster they die.
    At least run the charge up evrey 48 hours, if the solar can't keep up (wintertime).

    What's easier/cheaper dozen gallons of fuel, or a dozen batteries?

    Letting the batteries sit low for a week, takes months off their lifetime.
    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 ,

  • hillbilly
    hillbilly Solar Expert Posts: 334 ✭✭
    Re: generator/inverter charging setup...

    Ok Mike, wow I didn't realize that it made that much of a difference even over the course of a few days. Thanks for enlightening... I suppose that all this will be not such an issue in another month and a half with more solar avaiable+ another panel, and a more efficient means of generator charging via the inverter. Looks like in the mean time I better start running that generator a bit more often...
    Cheers
  • System2
    System2 Posts: 6,290 admin
    Re: generator/inverter charging setup...

    Quote: "wow I didn't realize that it made that much of a difference even over the course of a few days."

    According to Trojan's maintenance guide here: http://www.trojanbattery.com/Tech-Support/BatteryMaintenance/Discharging.aspx  Item (5) statess  "Many experts recommend operating batteries only between the 50% to 85% of full charge range. A periodic equalization charge is a must when using this practice."

      Do they say this because they want to sell more batteries to replace those that died prematurely from undercharging?  I don't think so because their reputation is at stake.  Do they want you to charge your batteries more than is required to keep them from sulfating because it makes their output specifications look better?  That's possible.  It seems to me that lead/acid batteries are very robust, just don't do anything to intentonally kill them.

       I'm no expert, but personally, if my eight three year old T-105's are at 90% I don't worry about them at all and they're working fine.  Another thing to consider if you are willing to go this route, the last 10% of charging is the most inefficient.  If you don't push your battery to 100% you don't lose that inefficiency.  Your investment in your Surrette's is quite a bit more than mine so maybe you need to be more anal about it than I am. 

      This practice would not apply to AGM's since it requires an equalization charge and that's a no-no on them.

      This site http://www.batterystuff.com/tutorial_battery.html  states "*Sulfation of Batteries starts when specific gravity falls below 1.225 or voltage measures less than 12.4 (12v Battery) or 6.2 (6 volt battery). Sulfation hardens the battery plates reducing and eventually destroying the ability of the battery to generate Volts and Amps."  The battery State of Charge chart there states that is 75% SOC.
    The NAWS Deep Cycle Battery FAQ here http://www.solar-electric.com/deep_cycle_batteries/deep_cycle_battery_faq.htm puts that at about 65% SOC using specific gravity and about 80% SOC using voltage.

      If it's true that sulfation begins at 75% SOC then 90% SOC shouldn't be a problem, just food for thought.

    Cheers,

    Bad Apple


  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: generator/inverter charging setup...

    BA,

    My recollection of the original of the “50% to 85%” suggestion is that it’s based on total cost of ownership. Since, as you also point out, battery recharge efficiency is relatively low above ~85% - 90% SOC, the idea is that it’s cheaper to replace the batteries on a more frequent basis than to pay for the generator maintenance, fuel, and time required to charge the batteries all the way to 100% SOC. Generator maintenance and fuel are typically not issues in a well balanced PV energy system design.

    Accordingly, it’s my view of Trojan’s point #5 is that they are attempting to address the impact of the recommendation of other “battery experts” on lead acid batteries in general, and on theirs in particular. Rather than advocating this "50/85" protocol, I think Trojan is saying that batteries “must” be periodically equalized if they are operated in the manner described.

    Trojan’s concern is sound, in my opinion. Batteries recharged to only ~85% SOC will typically not gas while being charged, and the result will be stratification of the electrolyte as well as some level of sulfation. Their recommendation for periodic equalization is intended to vigorously bubble the electrolyte to mix it up inside the cells (de-stratify) as well as to de-sulfate the internal plates -- actions required to restore battery capacity and maximize useful life.

    Sandia Labs published the following interesting paper on this subject: http://www.sandia.gov/pv/docs/PDF/caploss.pdf

    I disagree with the notion that "*Sulfation of Batteries starts when specific gravity falls below 1.225 or voltage measures less than 12.4 (12v Battery) or 6.2 (6 volt battery).” Lead sulfate (PbSO4) is a by-product of lead-acid battery discharge, and it begins forming on both the positive and negative plates the instant a fully charged battery begins discharging, whether under load or during self-discharge. It is true, however, that the sulfate becomes more stubborn with deeper discharges, and some chargers (i.e., Morningstar) apply more aggressive recharge algorithms to compensate for such use.

    Regards,
    Jim / crewzer
  • hillbilly
    hillbilly Solar Expert Posts: 334 ✭✭
    Re: generator/inverter charging setup...

    :?
    Alright so now I am a bit unclear; crewzer and badapple, are you guys saying that you disagree with mike and that its fine (in your opinions) to go ahead and wait a couple of days or so until my soc drops down below say 80% or so before firing up the generator (that has been my logic for the very reasons that you listed). I am willing to spend a bit more on gas and such for the generator if it's worth it for my battery bank, but it seemed sort of inefficient to run the generator on an every other day sort of schedule.
    Another question that I have is about dual charging setups: from reading a bit further in some of the posts here I realize that I could just buy another iota charger and run them in parallel (hadn't figured that one out till yesterday!), so I may just do that (this would allow me to spend a bit more on pv panels sooner). In either case, if I am using multiple charging units (pv, iota's, inverters, etc...) is it best to connect them to separate ends of the battery bank, or should all charging current come into the same positive and negative posts? I had thought that it might make sense to "spread out" the various charging systems to even out the workload of my batteries, but I really don't know for sure what that would do.
    Thanks again for all the input!
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: generator/inverter charging setup...

    from what i'm reading it is crewzer that moreso agrees with mike. i also agree with mike and crewzer that the deeper and the longer the time intervals the batteries sit below 100%, the shorter their lifespan. btw, it takes the same amount of gas into that generator to get the batteries to 85% from say 80% as it does in letting them go farther down below 80% and then run the genny longer so do what's better for the batteries if you can. that would mean running the genny more often for shorter time intervals. running it up past the 90% level to 100% is desirable for the lifespan of the batteries and if you could time it right you could be using that excess power the batteries aren't using because they're into the absorb stage to power other items. this saves on using that hard gotten 100% soc right away. let's not forget that your pvs will be able to continue some of that charging in the 90-100% range in the abscence of the genny as well as adding to the bulk current with the genny running putting you nearer to the 10% charge rate than i've stated below here.
    now i did not see you mention the capacity of your genny, but by all means use 2 iotas if the genny can handle it as this puts the bulk charge in faster. this will be an 8.5% charge rate rather than about 4.25% for the iota chargers alone and will save some on the lifespan of the batteries by allowing less time in a deeper discharged state. you will either have to go with a larger wire or use seperate wires from each iota as this is above the 56amps previosly mentioned. also as was stated, the sulphation occurs in all batteries as soon as they are discharged below 100% soc, ie, the moment you use the batteries and i fully agree. it is time and the severity of the discharge that makes that harden. once hardened it is more difficult for the recharge process to convert it back to useful electrolyte. this is the reasoning they are saying that it has to get a big charge periodically(periodic eq).
  • System2
    System2 Posts: 6,290 admin
    Re: generator/inverter charging setup...

      The paper abstract of the cited Sandia Labs document on page (1) states: "Recovery of the PV battery after extended periods in a deficit charge condition may or may not be possible depending on the extent of battery degradation and the resources available for recovery".

      Page (2) PV Batteyy Capacity Loss:  "In PV systems a compromise between battery capacity and maintenance is reached by using a temperature compensated regulation voltage that maintains the battery to at least 80% of its initial capacity"

      Using the trendline in Fig. 1 on page (3), the Vrr at 80% is ~ 14.2V, Vr would have to be interpolated from the given data points, perhaps 14.4V.  The "Vrr" in the graph could be equated with "absorb" and "float" voltage on PMW or MPPT controllers being set to ~14.4v.  Many would say this is battery murder, I feel that this paper argues that it is acceptable.  Just be sure to equalize per the manufacturers recommendations.

      On page (5) under the "Excessive Sulfation" heading it states ""Hard" sulfation as a capacity loss mechanism can be identified by a long history of under charging (usually months) and a low specific gravity (<1.250) after heavy gassing for sevaral hours during a full recharge to the equalization voltage."

      To me this says that sulfation isn't a cause of permanent capacity loss until it has undergone weeks or months of undercharge, becoming the "hard" type of sulfation.  The article states that the test is to equalize and then check specific gravity.  It seems to me that if SG remains low, the lead sulfate is "hard" and resistant/unable to convert back into positive plate material and sulfuric acid, resulting in low SG and capacity.  Likewise, if it is "Soft", the lead sulfate will combine readily with available water and convert back to lead oxide on the positive plates and sulfuric acid, thus increasing SG and returning the battery to normal capacity, no harm no foul.  Makes sense to me.

      Page (6) under the "Hard" Sulfation Battery Recovery heading goes even further and states "Desulfation tests based on the battery manufacturer's recommended recovery procedures have demonstrated that vented deep-cycle lead-antimony golf cart batteries could be recovered after approximately 6 months of cycling in a deep discharge state between 20% and 30% capacity."

      I'm not certain but it seems like they are saying they charged golf cart batteries to 30% SOC and discharged them to 20% SOC, recharged them to 30%, etc. for six months.  Their wording could be a little more clear though.  If  that is in fact their test method, it tells me that as long as the battery is being cycled you have much more leeway in removing the "soft" sulfation.

      It goes on to say that "... In this case the battery is clearly suffering from "hard" sulfation as indicatedd by the low battery specific gravity of 1.230 after an equalization charge to 7.65 volts (2.55 vpc) for 3 hours.  ...The result after nearly 600Ah recharged into the battery was a recovery to normal specific gravity (~1.277) and 80% of the battery's initial capacity after 2years of normal PV service and 6 months of cycling between 20% and 30% capacity."

      Taking two year old batteries and then "abusing" them for six months and recovering like that is pretty robust in my book.

      I suspect a battery in a discharged state that is being cycled and that does not have "hard" sulfation, that one day molecules A - M of "soft" sulfation gets reconverted back to positive plate material and sulfuric acid, the next day molecules N - Z gets reconverted and so on.  No molecules stay in the "soft" form long enough to harden.  Again, just a suspicion and I do not recommend operating a battery at this SOC as a practice.

      In my first post on this topic I was not trying to imply that equalization is unnecessary, equalization is necessary which is why I stated that this strategy would not be suitable for AGM's.


      I don't feel that chasing the elusive "100%" SOC is worth losing sleep over.  Why is 1.277 SG selected as "100% SOC" anyway?  You can charge a battery to 1.287 if you like, why isn't that considered 100% SOC?  At that SG, capacity would be greater but battery life might be lessened.  Perhaps 1.277 SG is slanted toward more capacity with decent life.  Maybe 1.267 SG would lean towards more longevity but less capacity.  There seems to be plenty of evidence in the paper that it isn't that big of a deal, at least that's how I read it.  Don't overly discharge them, "opportunity" charge them when you can, equalize them per the manufacturers recommendations, keep them watered and clean and I think they will serve you well.  Again, I'm not an expert and my T-105's aren't that expensive compared to Surrettes.

    Nomex on.

    Cheers,

    Bad Apple
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: generator/inverter charging setup...

    I tend to be pretty conservative about this issue.
    On page (5) under the "Excessive Sulfation" heading it states ""Hard" sulfation as a capacity loss mechanism can be identified by a long history of under charging (usually months) and a low specific gravity (<1.250) after heavy gassing for sevaral hours during a full recharge to the equalization voltage."

    This says to me that just one winter (several months) of abuse (cold batteries, relatively deep discharges, undercharging due to insufficient charging resources, and/or rare equalization) will lead to hard sulfation and resulting reduction of battery capacity and useful life.

    I don't see any need for Nomex... it seems to me like we're having a thoughtful and civil discussion.

    Regards,
    Jim / crewzer
  • System2
    System2 Posts: 6,290 admin
    Re: generator/inverter charging setup...
    crewzer wrote:
      On page (5) under the "Excessive Sulfation" heading it states ""Hard" sulfation as a capacity loss mechanism can be identified by a long history of under charging (usually months) and a low specific gravity (<1.250) after heavy gassing for sevaral hours during a full recharge to the equalization voltage."

    This says to me that just one winter (several months) of abuse (cold batteries, relatively deep discharges, undercharging due to insufficient charging resources, and/or rare equalization) will lead to hard sulfation and resulting reduction of battery capacity and useful life.

    To me, that just describes how to identify a battery that is suffering from "hard" slufation, not whether or not it can be removed to regain capacity or what it does to useful life. 
     

      My statement "Nomex on" was simply to acknowledge that my opinion runs counter to the majority on this forum and like the entire post, it wasn't directed to anyone in particular.

      Cheers,

    Bad Apple
  • hillbilly
    hillbilly Solar Expert Posts: 334 ✭✭
    Re: generator/inverter charging setup...

    ....sooooo, just to clarify how this might affect our charging routine... If we are really only running an extremely small deficit charge from day to day, would it really make that much of difference to wait another day or so to fully charge them up.  BTW our current set up with the 8 batteries is 12V 1400AH (I had been talking about them earlier with the idea of changing them to 24V to up-size the inverter), and our typical Daily use is anywhere from 50-150AH and our pv input is currently around 55-65AH (these are rough calculations).  So on a moderate use day we might end up "short" something like 50AH or so (about 3-4% of our capacity), usually it takes about about 3-4 days before our SOC drops down to about 85% or so, at which point I charge them all the way up again. The lowest SOC that I've seen thus far was after about  75%, which was after about 9 days of not running our generator (long story).  I do understand the basic theory that I need to fully charge our batteries and I have been equalizing them once a month, just curious if ours was a somewhat unique situation...
    Cheers
    Thanks for the enlightening discussion
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: generator/inverter charging setup...

    getting a 2nd Iota Charger, so you can "bulk up" the batteries faster, is a great idea, if your gen will handle the extra load. That should cut your gen run times down. Charge off the genset, till you get indications that you have dropped off of Bulk Mode, and then let your solar do the final top off charge.

    Recovering batteries from hard sulphated conditions - usually a messy proposition. I think it used to involve dumping out acid, fill with distilled, and over charge till you break the sulpher off the cell plates, then dump out water, and refill with fresh acid. Almost easier to buy new batteries, or keep the original ones in good condition. There are "Pulse Conditioners" that are supposed to be able to recover a battery, but they only work on 1 battery at a time, not a whole bank.

    Whatever you decide, have fun.

    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 ,

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: generator/inverter charging setup...

    hillbilly,
    i was thinking along the lines of every 2-3 days, but i don't see any real problems with 3-4 days.
  • System2
    System2 Posts: 6,290 admin
    Re: generator/inverter charging setup...

    Hillbilly,

    However you boost your charging capabilities, you should only run a generator with a rectified load (transformer/rectifier chargers) at 70% of it's rated capacity. I'm not familiar with the Iota charger's manufacture, or the Outback inverter/charger's for that matter, so don't know if this is pertinent to your thread.

    I run a 10kw diesel genset at 7kw, charging with my Xantrex 4048 and a Vulcan lift truck charger (100amp dc). THis has greatly reduced my gen run times, but does require monitoring the genset load. It's easy to overload and shutdown the genset if you over do it.

    THe Vulcan has no input or output controls and reduces output amps as battery voltage rises, so to keep the total load on the genset below 7kw i use a clamp meter on the genny input wires and adjust the total load with the Xantrex charging control input menu. Works like a charm, but not for an unsupervised charging run. Adjustments are made every 30 minutes or so over a 3-4 hour charge.

    Usually the downrating of a genset is moot since the charge capabilities of an inverter/charger won't exceed the genset's capabilities. My X-company unit on it's own will only draw 3800 watts or so, easily handled by a 5 or 6 kw gas/Lp/diesel genset. Running 2 inverter/chargers would necessitate 10-12kws of gen capacity to be safe...IMO.

    ralph
  • hillbilly
    hillbilly Solar Expert Posts: 334 ✭✭
    Re: generator/inverter charging setup...

    Ok, thanks guys that's great. That is kind of what I had been hoping, as we had deliberately oversized our bank to give us some days of autonomy, and I was starting to worry that might damage the battery bank. All clear now. Already ordered 2 Iota chargers (55amp), and I think that we'll skip the inverter upgrade for now and put our "extra" money into some more solar panels. Is there anything wrong with running all 3 chargers at once (30amp, and 2 55amp)?
    Cheers!

    Offinontario: we have a 7.5KW Gen, so I don't think that the chargers should be a problem (probably just need to be careful about trying to run too many tools at the same time (I usually try to schedule in any work projects to coincide with generator charging sessions).
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: generator/inverter charging setup...

    do know that if you get charge current from the 3 iotas and your pvs that this could total around 200amps. 200/1400=14.3% which is over the recommended top end charge rate of 13%. 13% of 1400ah would be 182amps, with the better 10% rate being 140amps. i contend the 30amp iota, the 65amp pvs, and the 1 55amp iota would be 150amps and a rate of 10.7% to your batteries. the only time it would work with the 2 55amp iotas with the 30 amp iota and the pvs is if you can make sure you are using that excess power at the time of generation. this isn't always possible and you could boil the batteries or drain them down farther.
  • hillbilly
    hillbilly Solar Expert Posts: 334 ✭✭
    Re: generator/inverter charging setup...

    Niel, my PV input current usually max's out at around 12-13apms, once went up to 16.3 on a sunny morning with the roof covered in snow. So I am not so worried about that just yet... 65 PV AMPS would be a dream!!!
    cheers
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: generator/inverter charging setup...

    I'm not sure we finished our discussion about battery sulfation and possible recovery. I went and did a bit more research on the issue using this Google search string: http://www.google.com/search?q=battery+capacity++hard+sulfate+OR+sulfation&hl=en&lr=lang_en&as_qdr=all&start=60&sa=N

    There are plenty of sites that indicate hard sulfation to be irrecoverable. However, they may be drinking their own bath water. There's no doubt that Sandia's report concluded that hard sulfation may be recoverable. But, I still find their conclusions to be a stretch.

    For example, VRLA battery capacity was found to be recoverable because of unique battery chemistry (phosphoric acid appears to minimize hard sulfation), and "repeated deep cycles using an extended charge time of 24 hours at a regulation voltage of 14.1 (2.35 vpc) or 14.4 volts (2.40 vpc)." This technique is probably beyond the interest and/or resources of most users.

    Flooded-cell battery capacity was found to be recoverable from hard sulfation to ~80% of capacity, and this was deemed full recovery when compared to comparable capacity of similar age batteries maintained in a normal fashion. This is pretty murky logic to me, as I wonder how the reference batteries would have behaved if they had been maintained in a manner as aggressive as the recovery technique used.

    We may end up agreeing to disagree on this issue. A great discussion though, a there wasn't even any Nomex required! :wink:

    Regards,
    Jim / crewzer

  • arcandspark
    arcandspark Solar Expert Posts: 63 ✭✭✭✭
    Re: generator/inverter charging setup...

    Hillbilly, You stated: "Already ordered 2 Iota chargers (55amp), and I think that we'll skip the inverter upgrade for now and put our "extra" money into some more solar panels.  Is there anything wrong with running all 3 chargers at once (30amp, and 2 55amp)?"

    I found that there can be problems with hooking up more than one charger at a time. The chargers usually pulse the charge and they look at the battery voltage during the charging time to monitor battery condition. I found with two chargers going at the same time one charge can read the pulsed charge of the other charger and see a higher voltage than the actual battery voltage and it can cause that charger to reduce the its output. If both chargers can not communicate between each other they dont know what the other is doing and you end up with a mixed up charge instead of a true Bulk, Absorb, Float charge. I found this true with a Dual Trace SW4024 system. Both inverters were set up to put out 60 amps each, sometimes the current reading when the inverters would start charging would be a little over 100 amps and many times it would only be around 60 amps. Trace could not give me a real answer for the problem. I figured having both inverters set at 60 amps each would give me 120 amps but it never reached 120 amps. The batteries on that system require a minumum of 120 amps as their minimum charge current, so for over five years now they have only been able to receive around 60 amps. They receive a three to four hour 60 amp charge every day. The system has been working perfect over five years. I am adding a third SW4024 inverter and a third 24 volt 1500 amp hour battery bank to the system, as the owner is building a 2500 sq ft home on the property. I am working on issues with the neutral wire size and grounding with the addition of the third inverter. Not 100% sure of the best way to do it yet. I am installing a fork lift battery charger which will be able to give the maxumum charge current to the battery bank, and also looking at being able to switch different battery banks in and out of the system, get a little complicated, but I want to install a PLC controller to monitor the battery banks and switch them in and out of the system as they need to be able to give each of the three battery banks a complete and separate charge. Just a thought. I would highly recommend you go with one large three stage charger or DC generator instead of mulitple chargers. Dave R. (arcandspark)
  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    Re: generator/inverter charging setup...

    Dave,

    Bad news about the interference between the Trace 4024 inverter/chargers. However, Brock operates a couple of Iota chargers in parallel, and his posts on both this forum as well as over on the OutBack forum indicate they work as expected, and with no problems. In fact, Iota's website specifically states that "Multiple units can be operated in series or parallel to increase amperage for additional power."

    Regards,
    Jim / crewzer