URGENT! Who is right on battery re-charge question?

CBear42CBear42 Posts: 28Solar Expert
I have a new system. There are 4-250w panels connected to an Outback VFX3524 inverter connected to 4-250Amp batteries. Everything is brand new and has been in use less than a week. The Outback has a series of dummy lights to indicate battery status: green, yellow and red. Green equates to "full", yellow to "50%" full and red to "25% full". (I hate imprecise dummy lights... :-(

Because of the lack of sun the last week due to Sandy, my panels haven't been catching much sun - as you can imagine. Right now, I am pretty much running off of battery power. The conundrum is this: Everything I have ever read ANYWHERE says that you should not let your batteries discharge below 50% - and 80% is even better. I have read this multiple times in multiple venues. So - as soon as I see yellow - I have been topping up the batteries. It takes usually only 5-10 minutes with a 7500w Generac generator. However, twice I have seen the "Battery Temp" light go amber during a longer charge. Which is why I cut down the charging time.

My installer says that I am risking damaging the batteries by topping them off like this - back to "full". He says to let the light go to red - 25% - and only THEN charge the batteries. He says I am being "paranoid" about my batteries. (Well, yes - I probably am. I saw the mess the previous occupants made of their battery bank and know that batteries tend to be what is ruined first in a system. These are $500.00+ batteries...I can't afford to replace them readily.) He says I have a good inverter and I should have some "faith" that it will do its job correctly.

So - who is right? I am really confused and this is making me a little crazy. Which is worse? Occasional overheating? Or discharging to 25%?

Thank you so much in advance...!!!!
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Comments

  • ggunnggunn Posts: 1,973Solar Expert ✭✭✭
    Re: URGENT! Who is right on battery re-charge question?
    CBear42 wrote: »
    I have a new system. There are 4-250w panels connected to an Outback VFX3524 inverter connected to 4-250Amp batteries. Everything is brand new and has been in use less than a week. The Outback has a series of dummy lights to indicate battery status: green, yellow and red. Green equates to "full", yellow to "50%" full and red to "25% full". (I hate imprecise dummy lights... :-(

    Because of the lack of sun the last week due to Sandy, my panels haven't been catching much sun - as you can imagine. Right now, I am pretty much running off of battery power. The conundrum is this: Everything I have ever read ANYWHERE says that you should not let your batteries discharge below 50% - and 80% is even better. I have read this multiple times in multiple venues. So - as soon as I see yellow - I have been topping up the batteries. It takes usually only 5-10 minutes with a 7500w Generac generator. However, twice I have seen the "Battery Temp" light go amber during a longer charge. Which is why I cut down the charging time.

    My installer says that I am risking damaging the batteries by topping them off like this - back to "full". He says to let the light go to red - 25% - and only THEN charge the batteries. He says I am being "paranoid" about my batteries. (Well, yes - I probably am. I saw the mess the previous occupants made of their battery bank and know that batteries tend to be what is ruined first in a system. These are $500.00+ batteries...I can't afford to replace them readily.) He says I have a good inverter and I should have some "faith" that it will do its job correctly.

    So - who is right? I am really confused and this is making me a little crazy. Which is worse? Occasional overheating? Or discharging to 25%?

    Thank you so much in advance...!!!!
    It's not a simple issue. I'm not a battery expert, but battery companies provide charts that plot expected number of battery cycles in the life of a battery against depth of discharge, and it's not linear. The deeper you discharge the battery the fewer cycles you get and the lower the total energy throughput you will see.
  • john pjohn p Posts: 814Solar Expert ✭✭
    Re: URGENT! Who is right on battery re-charge question?

    Its simple . The least amount of discharge you do to the batteries the longer they will last.

    It goes something like this.(BUT DONT QUOTE ME)
    3000 cycles at 20%discharge
    2000 cycles at 30% discharge
    1000 cycles at 50% discharge
    400 cycles at 70% discharge.

    A blind dog with a hearing problem can easily see and hear that big discharges mean short battery life.
  • vtmapsvtmaps Posts: 3,738Solar Expert ✭✭✭✭
    Re: URGENT! Who is right on battery re-charge question?
    CBear42 wrote: »
    So - as soon as I see yellow - I have been topping up the batteries. It takes usually only 5-10 minutes with a 7500w Generac generator. However, twice I have seen the "Battery Temp" light go amber during a longer charge. Which is why I cut down the charging time.

    Instead of cutting back on the charging time, cut back on the charging amperage. You can program your vfx to limit the amount of AC amps from the generator that are available for charging the battery. If you have four 6 volt batteries in series, you have a 250 ah bank. If your batteries are heating up that much you should try limiting your AC amps to about 6 amps. That will give you a DC charging current of about 25 to 30 amps.

    Also, are batteries flooded? If so, I don't think it is a good idea to charge your batteries for only a short time. That will increase stratification. If you intend to do a partial charge, you need to get to point of gassing. Also, invest in a hydrometer or refractometer.

    Whether or not your batteries are flooded, you should look into getting a shunt-based battery monitor. Not a perfect solution, but much better than those dummy lights.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • CBear42CBear42 Posts: 28Solar Expert
    Re: URGENT! Who is right on battery re-charge question?

    Hi vtmaps - thanks for your reply.

    The inverter was "locked up" by the installer - and I haven't opened it - yet. I have 4 12v 250AmP batteries or a 1000 AmP bank - which is what I was recommended to purchase by the company selling the PVs and other equipment. The batteries are AGM sealed. Seems like I need a MATE to go with the Outback inverter and also (perhaps) a FLEXnet DC system monitor. (Anything is better than relying on dummy lights with expensive equipment!) Any thoughts on those monitoring options?
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: URGENT! Who is right on battery re-charge question?

    vtMaps is correct.
    First, you do need an Outback MATE or MATE II so you can program your inverter. It is not "locked up" by the installer; the lazy bum just didn't bother to change the default settings to suit your needs.
    Second, the MATE will tell you a lot more about the system than those LED's.
    Third, your have four 250 Amp hour 12 Volt batteries on a 24 Volt system: that is two in series to make 24 Volts X two in parallel for 500 Amp hours @ 24 Volts total. The maximum charge rate on this should be 50 Amps. Since the FX uses AC Amps for the charge rate this equates to 10 Amps on the MATE's charger settings.
    Fourth, that 1000 Watt array is insufficient for proper charging too. It will put out about 32 Amps peak using an MPPT controller (which controller do you have?) You actually need about 50% more panel there.

    You are absolutely going nowhere without that MATE. Worry about battery monitoring after you get that and see how things are set.

    One more hint: check the way those batteries are wired. With two parallel strings it should be as method #2 on the Smart Gauge page here: http://www.smartgauge.co.uk/batt_con.html
  • vtmapsvtmaps Posts: 3,738Solar Expert ✭✭✭✭
    Re: URGENT! Who is right on battery re-charge question?
    CBear42 wrote: »
    I have 4 12v 250AmP batteries or a 1000 AmP bank - which is what I was recommended to purchase by the company selling the PVs and other equipment. The batteries are AGM sealed. Seems like I need a MATE to go with the Outback inverter and also (perhaps) a FLEXnet DC system monitor. (Anything is better than relying on dummy lights with expensive equipment!) Any thoughts on those monitoring options?

    If your four 12 volt batteries are in a 24 volt configuration you have a 500 ah bank. You may double my previous recommendation to 12 AC amps resulting in 50-60 DC charging amps.

    You MUST get a mate. There are several good battery monitors on the market and the outback Flexnet DC is one of the best.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • CBear42CBear42 Posts: 28Solar Expert
    Re: URGENT! Who is right on battery re-charge question?

    Hi Cariboocoot,

    I have a TriStar MPPT-45 controller - dummy lights only on that as well...The whole system was sized for 1.5 KwH - but after the installer looked at the older panels (which would have supplied the "50% more panel"!) - he declared them essentially "dead" and not worth re-installing. So, the sylstem was sized correctly initially - but without those older panels...I'm in trouble, I take it. And this is one of those philosophical "why" questions: Why would a solar hardware company not include battery monitoring equipment as part of a normal quote? I mean, you are going to be in deep trouble if you can't monitor your system correctly!

    I will check the wiring per your suggestion/link asap.

    Thanks very, very much. Your help is very appreciated...
  • BB.BB. Posts: 27,699Super Moderators admin
    Re: URGENT! Who is right on battery re-charge question?

    For an emergency backup power system... Discharging to 50% (or even somewhat lower) State of Charge is not the end of the world. So, you only get 500 charging cycles--That would be 50 days without power for 10 years--Your bank will probably die of old age before that happens.

    Regarding battery charging... Flooded Cell lead acid batteries are pretty darn efficient at charging up to ~80-90% state of charge. Above that SOC level, then your battery converts a lot more of the energy to heat/gases (hydrogen/oxygen, using more water, etc.).

    With a generator, as you get above 80-90% SOC, the current falls and the generator operates at much lower fuel efficiency (once your loads fall below ~50%, the fuel flow stays at about 50% for most gasoline powered/standard gensets).

    So--For an emergency, I would not feel bad at all turning on the genset at 50% SOC and recharging to ~85% SOC--Then turning the generator off.

    What you do not want to do is let the battery set for days on end below ~75% SOC--They will start to sulfate (and die) at that point. Ideally, if the battery is below 75% SOC the next day, start the generator.

    You do want to get a hydrometer and accurate DC volt meter to monitor the battery bank Specific Gravity and voltages. They will let you know how the battery is being treated.

    I would suggest you get a DC Current Clamp meter (this one from Sears is "good enough" and has all the normal DMM functions too). You will want to monitor the current through your parallel battery string (during heavy charging/discharging) to ensure that they are properly sharing current. And you can measure actual charging/discharging current (until you get the Mate) and see what is going on.

    Longer term, you will probably want some sort of Battery Monitor and/or a Voltage Monitor that is designed for supporting a battery bank.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmapsvtmaps Posts: 3,738Solar Expert ✭✭✭✭
    Re: URGENT! Who is right on battery re-charge question?
    CBear42 wrote: »
    I will check the wiring per your suggestion/link asap.

    That smartguage site show how to hook up four batteries in parallel. Here is a diagram that is more exactly suited to your configuration:
    http://forum.solar-electric.com/showthread.php?p=129205#post129205

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: URGENT! Who is right on battery re-charge question?
    Why would a solar hardware company not include battery monitoring equipment as part of a normal quote?

    Because it is not essential to operation.
    On the other hand they left the meter off the TriStar and didn't include a MATE so maybe they're stupid and don't know the value of these things or they're cheapskates who sell minimum equipment at maximum price.
    If he didn't actually check those panels individually I'd go with the analysis that he doesn't actually know what he's doing. Or is a crook (checking panels takes time; why do it for free?)

    These are flooded cell batteries, yes? If so you should definitely get a hydrometer and check the specific gravity of each and every cell now. There's no better way to tell the state of an FLA and you need to know that before they are ruined from under or over charging.
  • icarusicarus Posts: 5,108Solar Expert ✭✭✭✭
    Re: URGENT! Who is right on battery re-charge question?

    Read and try to under stand the following:

    http://www.batteryfaq.org/

    http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries


    Running a genny for a few minutes is doing little except wasting gas and adding cold start wear to the genny IMHO.

    Tony
  • BB.BB. Posts: 27,699Super Moderators admin
    Re: URGENT! Who is right on battery re-charge question?

    I should add a few links for reading:

    Battery FAQ
    www.batteryfaq.org

    Many (most?) people end up killing (murdering) their first battery banks--Think of it as a right of passage to solar. :cry:

    The battery is the "heart" of your system... Charging/discharging/etc. should all be slanted towards keeping your battery bank happy.

    But, do not get too paranoid--The batteries are there for you to use. If you get them >90% SOC a couple times a week (perhaps not during this emergency), avoid cycling them below 50% (long term life), avoid cycling below 80% DOD (can kill almost immediately), and do not let them sit below ~75% SOC for days/weeks/months on end--You should be OK.

    Check wiring for loose/dirty connections (you can measure voltage drop under load across each wire/connection when heavy current is flowing), keep tops of batteries clean, refill ~1/2 way full with distilled water (do not over fill), do not ever let plates get exposed to air (cover plates with water, recharge, then fill to full level to avoid having electrolyte spill out).

    Get a good hydrometer (or two, one usually breaks when you need it). Keep track of 100% SOC (log temperature corrected SG numbers). And you should be good to go.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • vtmapsvtmaps Posts: 3,738Solar Expert ✭✭✭✭
    Re: URGENT! Who is right on battery re-charge question?
    These are flooded cell batteries, yes? If so you should definitely get a hydrometer
    BB. wrote:
    You do want to get a hydrometer

    Bill, Marc,
    I suggested a hydrometer in post#4. In post #5 the OP says he has AGM batteries. --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: URGENT! Who is right on battery re-charge question?
    vtmaps wrote: »
    Bill, Marc,
    I suggested a hydrometer in post#4. In post #5 the OP says he has AGM batteries. --vtMaps

    ARGH!
    The prime reason why AGM's shouldn't be the first set of batteries! These probably cost $$$ and is now in imminent danger of being scrap metal. Leaving out a battery monitor for these is practically criminal. Although it sounds as though the installer wouldn't have programmed that right either. Bet he's got the charge Amps set at maximum (AGM's can take more current, so if they're getting hot ...)

    I guess the only thing he can do to check charge now is disconnect them and let them sit over night then check the resting Voltage. A method that is far from accurate, unfortunately.
  • WxboyWxboy Posts: 70Solar Expert ✭✭✭✭
    Re: URGENT! Who is right on battery re-charge question?

    CBear42, what brand batteries do you have? I'm just curious since I'm in the market for some new AGM's. Thanks.
  • vtmapsvtmaps Posts: 3,738Solar Expert ✭✭✭✭
    Re: URGENT! Who is right on battery re-charge question?
    ARGH!
    The prime reason why AGM's shouldn't be the first set of batteries! These probably cost $$$ and is now in imminent danger of being scrap metal. Leaving out a battery monitor for these is practically criminal. Although it sounds as though the installer wouldn't have programmed that right either. Bet he's got the charge Amps set at maximum (AGM's can take more current, so if they're getting hot ...)

    The system is only a week old. Not yet scrap metal.

    I just reread this thread and noticed in the OP:
    CBear42 wrote:
    However, twice I have seen the "Battery Temp" light go amber during a longer charge. Which is why I cut down the charging time.

    What "Battery Temp" light? I don't think my system has one. (I will be embarrassed if I have one and don't know about it). Also, CBear, do you have a remote battery temp sensor? That is very important. As the batteries heat up the charger should reduce the charging voltage. If you don't have a remote sensor you run the risk of thermal runaway.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: URGENT! Who is right on battery re-charge question?
    vtmaps wrote: »
    The system is only a week old. Not yet scrap metal.

    I just reread this thread and noticed in the OP:

    What "Battery Temp" light? I don't think my system has one. (I will be embarrassed if I have one and don't know about it). Also, CBear, do you have a remote battery temp sensor? That is very important. As the batteries heat up the charger should reduce the charging voltage. If you don't have a remote sensor you run the risk of thermal runaway.

    --vtMaps

    The FX doesn't have one, however the Tristar controller will sequence the yellow and red LED's if it detects too high a battery temp through the RTS. I presume that's what he means.
  • ggunnggunn Posts: 1,973Solar Expert ✭✭✭
    Re: URGENT! Who is right on battery re-charge question?
    john p wrote: »
    Its simple . The least amount of discharge you do to the batteries the longer they will last.

    It goes something like this.(BUT DONT QUOTE ME)
    3000 cycles at 20%discharge
    2000 cycles at 30% discharge
    1000 cycles at 50% discharge
    400 cycles at 70% discharge.

    A blind dog with a hearing problem can easily see and hear that big discharges mean short battery life.
    That part is simple, sure, but from a systems application point of view, not so much. You need to balance how much power you need at once, how much energy you will need over how long a time, how often you need it, etc. As someone else pointed out, if you only need them a few times over a 10 year period you can take the batteries just about as low as you want. They will be dead after that long, anyway.
  • VicVic Posts: 2,908Solar Expert ✭✭✭✭
    Re: URGENT! Who is right on battery re-charge question?

    One added comment is that Voltage readings of batteries is a very inaccurate measure of SOC. A Battery Monitor is almost essential for Sealed batteries, but it must be carefully calibrated, and then rechecked fairly often, especially when the battery bank is young. Good Luck with the new system, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: URGENT! Who is right on battery re-charge question?

    i'm wondering how the controller is set and what specs are those batteries calling for for charging? we also don't know which agm batteries you have.
  • CariboocootCariboocoot Posts: 17,615Banned ✭✭
    Re: URGENT! Who is right on battery re-charge question?
    niel wrote: »
    i'm wondering how the controller is set and what specs are those batteries calling for for charging? we also don't know which agm batteries you have.

    That's the big problem here: they sold him a system with no meters at all! :grr
    Talk about groping around in the dark ...
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: URGENT! Who is right on battery re-charge question?

    i don't think i'd trust an installer to that degree.:roll: if he thinks the batteries are overheating then i would think the installer should explain some things if not at least double check everything. have faith? not in installers, thank you.:-)
  • john pjohn p Posts: 814Solar Expert ✭✭
    Re: URGENT! Who is right on battery re-charge question?
    ggunn wrote: »
    That part is simple, sure, but from a systems application point of view, not so much. You need to balance how much power you need at once, how much energy you will need over how long a time, how often you need it, etc. As someone else pointed out, if you only need them a few times over a 10 year period you can take the batteries just about as low as you want. They will be dead after that long, anyway.

    This is not really true. And its a wrong assumption.
    If a battery that you expected to last 10 years is discharged say 2 times down to 20 %remaining in first year it will NOT last 10 yrs . You be lucky if it lasts 3
    years.
    In testing batteries I have found a 12v battery can be seriously life shortened in just 2 or 3 cycles discharged down to 11v.. You can soon tell as they wont fully recharge and then discharge faster than previously for same load..

    In my opinion its bad advice from you and the other poster that said it.
    I certainly would not recommend that to anyone.
    If you have both done that and got away with it and the batteries were still ok at 8yrs then you both had more than average good luck.
  • BB.BB. Posts: 27,699Super Moderators admin
    Re: URGENT! Who is right on battery re-charge question?

    Sorry, that is 80% depth of discharge or 20 % state of charge.

    I may have to wait to edit when I get to a real computer.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • nielniel Posts: 10,311Solar Expert ✭✭✭✭
    Re: URGENT! Who is right on battery re-charge question?

    it's now fixed.:D
  • BB.BB. Posts: 27,699Super Moderators admin
    Re: URGENT! Who is right on battery re-charge question?

    Thank you Niel.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PhotowhitPhotowhit Posts: 4,662Solar Expert ✭✭✭✭
    Re: URGENT! Who is right on battery re-charge question?
    icarus wrote: »

    Great advice, once you've gone through and understand the ways of monitoring your batteries and state of charge, the better the understanding of your situation. Those dummy lights your watching are basicly a voltage reading. You can make your battery bank appear to be running low, by simple putting a huge load on the bank. Like wise you can see a full charge when they are just reaching the absorb stage and may only be 80% charged. Once you've learned what's going on you may be able to relax, but without the knowledge I'd install a good quality battery monitor and have someone properly set it up for you.

    I would also not abandon your old solar panels, I have some 30 year old panels still producing 80% of their rated current when stored 4-5 years ago. They may no longer work with the new panels, but very likely are still working to some degree. If your helpful installer hauled them off for you, I'd go talk with him.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, ForkLift battery. Off grid for @13 of last 14 years. 1000 watts being added to current CC, @2700 watts to be added with an additional CC.
  • CBear42CBear42 Posts: 28Solar Expert
    Re: URGENT! Who is right on battery re-charge question?
    These are flooded cell batteries, yes? If so you should definitely get a hydrometer and check the specific gravity of each and every cell now. There's no better way to tell the state of an FLA and you need to know that before they are ruined from under or over charging.

    These batteries are sealed AGM batteries - so no checking of the acid levels.

    However - I spent several hours on the phone with Morningstar Corp (makers of the charge controller MPPT-45) yesterday. I installed their View software so that I could monitor the array and the battery bank's performance. His analysis was that the batteries are not even coming close to being fully charged - and probably never HAVE been fully charged since they've been here. He had me run the generator for two hours straight. The battery voltage hit 28.63 and then dropped in the middle of the experiment to 25.43 - and never rose again.

    He suspects two things - both a problem with the panel not pushing adequate volts through the controller (it measured a less than an Amp at times, and only went to 9 amps after charging for an hour). He said the array should be getting 13-15 A coming in (he knows the latitude of where I live, etc.) He doesn't know what is going on with the batteries at this point except that they won't seem to sustain a charge.

    So, not sure how to proceed today - but reading all the posts now.

    CBear
  • CBear42CBear42 Posts: 28Solar Expert
    Re: URGENT! Who is right on battery re-charge question?

    Hi -

    I got them from Battery Stuff - UB8D 12v 250 AMP batteries. They cost $526.00 each about six weeks ago.
  • CBear42CBear42 Posts: 28Solar Expert
    Re: URGENT! Who is right on battery re-charge question?

    I have installed the View software from Morningstar for now - and that is giving me so data to work with at least.

    What is puzzling to me is why the Charge Controller sits at 0-35% SOC - according to our infamous dummy lights...and why the inverter can be green (95%-100%)?

    If this is an abysmally dumb question - I apologize...I am learning as fast as I can. :-)

    BTW, installer called last night and insisted that HE did it right. That Grape Solar, Morningstar Corp, Outback and battery people were all wrong.

    As Grape Solar put it: "This is stupidity beyond incompetence."

    CBear
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