1st cycle 200amp hr battery bank/ 12 amps array 5 days to charge

UrbandialectUrbandialect Solar Expert Posts: 107 ✭✭✭✭
Ok, I just finished my first cycle, drain the battery from 12.5volt to about 9.5 volts, I was running my computer(desk top & monitor) a surround sound system hooked up to computer, and also a small fan for about 6-8 hours a day, took 5 days to run down the battery .... removed load then began to re charge the battery back up to 12.5 volts.. took 5 days to do it with no load, The max out put of the array is about 12 amps.


I guess this mean i need a 60amp array to re charge a 200amp hour battery bank that has been discharge to 9.5volts in one day?

60 amp x13.5 volts, so that's 810 watt array, is this correct?

Comments

  • PhotowhitPhotowhit Solar Expert Posts: 4,196 ✭✭✭✭
    Re: 1st cycle 200amp hr battery bank/ 12 amps array 5 days to charge

    No, more likely means you have damaged the battery by taking it down to such a low level...

    Was it at 12.5 with it still charging, no load, likely you haven't finished charging the battery yet.

    Might want to read through the Battery FAQ's http://www.windsun.com/Batteries/Battery_FAQ.htm, and get some attention for the hole in your foot.
    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.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 1st cycle 200amp hr battery bank/ 12 amps array 5 days to charge

    To expand on what Photwhit said:

    A "12 Volt" battery shouldn't be discharged below 10.5 Volts; it may never recharge after that.
    A 200 Amp hour deep cycle FLA battery needs at least 187 Watts of panel to recharge it: potential peak current of at least 10 Amps and a charging Voltage of 14.4.
    To "replace" 100 Amp hours (50% - maximum depth of discharge) would take that 187 Watt panel about 8 hours of "equivalent good sun". Since you normally only get about 4 hours per day, it should take two days (not exactly) to recharge.

    You can't judge a battery's performance by the number of days you ran some equipment; you need precise figures on power draw. Things like computers and stereos do not draw a steady current. For comparison purposes, that 100 Amp hours is roughly 1 kW hour.

    If you can't get that battery up to at least 12.5 Volts resting (left unconnected for at least an hour), it's toast. You should charge it to 14.4 Volts and keep it there until the charge current falls to <3%.
  • UrbandialectUrbandialect Solar Expert Posts: 107 ✭✭✭✭
    Re: 1st cycle 200amp hr battery bank/ 12 amps array 5 days to charge

    I gotta push it to the it's limit to see what it can do, but the battery is fine, and can still hold a charge
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 1st cycle 200amp hr battery bank/ 12 amps array 5 days to charge
    I gotta push it to the it's limit to see what it can do, but the battery is fine, and can still hold a charge

    Keep that up and it soon won't.
  • UrbandialectUrbandialect Solar Expert Posts: 107 ✭✭✭✭
    Re: 1st cycle 200amp hr battery bank/ 12 amps array 5 days to charge
    Keep that up and it soon won't.

    I know it's not good, but i'm running some test and then running my finding by you guys to see what yall think..

    what i'm trying to figure out is how many AMPS does my array need to pull in in an hour to charge the 200 amp hour battery bank back up in one day if it was discharged down to 30% - 50%, of course I don't plan to go pass 50%. I have 6 AMG batteries . I'm running all my test w/only 2 of them hooked up incase I screw something up. But once i hook all 6 batteries up that'll give me 300 amp hours before i hit 50%.. IF i'm configuring for 200amp hours i should be good with the load I intend to run.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 1st cycle 200amp hr battery bank/ 12 amps array 5 days to charge

    The target for potential peak current is 5% of the total battery bank Amps hours (at the 20 hour rate) minimum. In case of a 200 Amp hour battery, that's 10 Amps of charging current you're trying for. 20 Amps would be better. Charging Voltage on the deep cycle FLA is usually 14.4 Volts (some batteries, like Trojans, want more). So that's 144 Watts of power you're trying for. You have to derate panels somewhat; typically they produce about 77% of their "nameplate" rating under 4 hours of "equivalent good sun" thus you divide 144 by 0.77 and get 187 Watts for your minimum panel size. It's not precise, but it gets you in the ball park. If you try for 10% charge current you're almost certain to fall somewhere between 5% and 10% and have happy batteries.

    BTW, most 12 Volt inverters have a low Voltage cut-off that shuts them down at 10.50 Volts (about 50% discharge). Does yours not? Another thing you might want to check is the quality of your DVM; if it's off by 1 Volt that can make a big difference to accurate readings.

    AGM's can take more current, but may want less Voltage (14.2); check manufacturer's specifications on that. If you had FLA's you can check them with a hydrometer and know the SOC by the SG reading; that's why cheap "golf cart" batteries are the best bet for a first set of batteries. With luck they'd still last 5 years or so - a good return for the $.

    As I recall your charge controller is a bit "suspect" too. :roll: If you had two meters you could wire one up for Voltage and pass the panel current through the other (make sure it can take the maximum expected Amps and then some) and get raw numbers to tell you what your panels are capable of.

    Déjà vu! I don't know if I already said all this to you or if the posts are all becoming blurred because the questions are so similar! :p
  • GreenPowerManiacGreenPowerManiac Solar Expert Posts: 447 ✭✭✭
    Re: 1st cycle 200amp hr battery bank/ 12 amps array 5 days to charge

    Nothing beats a system with a digital charge controller readout. I know exactly where to look when something is not right. Morningstar TS-45 has one, but the digital cover costs more. All worth it. Besides, I'll keep an eye on the bank voltage and won't let it fall below 12.5 volts consistently. I'll make sure that the charging rate is around 10-15% more than consumption continuously during sunny days.
    Nature's Design & Green Energy on FaceBook : Stop by and "Like" us anytime.. Many up-to-date articles about Renewables every day.
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  • bsolarbsolar Solar Expert Posts: 98 ✭✭
    Re: 1st cycle 200amp hr battery bank/ 12 amps array 5 days to charge
    I know it's not good, but i'm running some test and then running my finding by you guys to see what yall think..

    what i'm trying to figure out is how many AMPS does my array need to pull in in an hour to charge the 200 amp hour battery bank back up in one day if it was discharged down to 30% - 50%, of course I don't plan to go pass 50%. I have 6 AMG batteries . I'm running all my test w/only 2 of them hooked up incase I screw something up. But once i hook all 6 batteries up that'll give me 300 amp hours before i hit 50%.. IF i'm configuring for 200amp hours i should be good with the load I intend to run.

    i suck at figures and do tests about like you do to get a real world feel .. i think the gist of what everyone is saying is you are not getting an accurate feel for whats going on because you flogged the hell out the battery and likely hurt it .. this is "just my guess" from messing with my system but on a good sunny day you would want around 20 amps to get your fully drained battery back to speed in a prompt manner by the end of the day and by fully drained i mean no more than 50%, if you hurt the battery its likely going to act funny ...60 amps i could do (6) 200ah batts, as i said approx guessing .. i have figured 80-90amps for my 8 cell bank of 215ah batts and it does good .. cycling the batteries way down though is what you want to avoid from all i understand ..
  • UrbandialectUrbandialect Solar Expert Posts: 107 ✭✭✭✭
    Re: 1st cycle 200amp hr battery bank/ 12 amps array 5 days to charge

    Ok, I learned a lot by running my test.. First thing I learned is that you can fry the diode in the charge controller so it’s good to have diodes inside of the solar panels themselves..

    I also learned about resistances and currents… As the battery begin to charge it got to a certain point where the voltage that the panels were pushing into the battery with (13volts) wasn’t strong enough to charge the battery because the battery voltage had gone from 10 volts to 12volts and started pushing back, basically nothing was happening even doe the charge controller was showing it was charging, so the 2 bad panels that I had hooked up(the 2 coming in at less than 15 volts) had to be removed, after doing so it boosted the voltage from the charge controller from 13 volts to 14.5, which was able to push threw and continue to charge the battery.

    I also noticed a loss of power at night, as the battery worked it’s way back into the Green during the day the battery meter that I hooked up to it that shows the state of charge would show a lost of power at night from where it was during the day, I have no load on the battery so I first thought it was a standard discharge until I noticed it during the day while the panels where hooked up, as a cloud came over head and the voltage dropped that’s when I noticed the panels sucking power out of the batteries, the charge controller was blocking the reverse current but I think the diode inside it got fried some how during all my test.

    I do have a better understand of what Voc is and VMP, I think I fried the Diode by going pass the VMP rating on the charge controller for a 12 volt system.. to get your Vmp you count the number of cells then times it by .5, I tried wiring my 2 low voltage panels together in series to boost the voc to 18 to 20 volts so I can wire it in parallel with my other 2 good panels. After wiring the panels together in series the voltage did go up to 21 voc, but the VMP was over 30 because each cell REGARDLESS of what the Voc is, is .50 VMP, the charge controller I have can’t go over 30 vmp with a 12volt configuration, so one panel with 40 cell another panel w/36 cells, wired in series is 76 cells times(X) .50= 38 vmp, which equals a fried diode.. lol

    Anyway, I working on my 2nd generation of solar panels, these panels are going to have blocking diodes and will be encapsulated in clear resin epoxy. They will not have any backing on them, so they won't get as hot as the first gerenation, so no wood at all. And I’m making the frame out of Aluminum L channels
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 1st cycle 200amp hr battery bank/ 12 amps array 5 days to charge

    Yes, you probably did short out some part of the cheap charge controller allowing battery Voltage to leak back through the panels over night resulting in discharge. A good charge controller won't have that problem, nor will it need blocking diodes on the panels. Remember; diodes rob a bit of power themselves. The Schottky type are your best bet for blocking diodes: http://www.solar-electric.com/blocdiod8amp.html

    If the Vmp per cell is 0.5 Volts, then multiplying by the number of cells in series gets the panel Vmp. That's not necessarily where it will operate at, though; more of a "ideal" Voltage. The Voc is often far different (25% higher, depending on the exact panel) and is important for not exceeding the controller's Vmax in. You found that out a bit late.

    Now, think about what you're going through and multiply it into enough panels for even a 1 kW system.
    Some fun, eh? :roll:
  • waynefromnscanadawaynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Re: 1st cycle 200amp hr battery bank/ 12 amps array 5 days to charge

    Wow! My heart hit the floor when I read how those batteries had been run down dead:cry: If only questions had been asked first. And "no backing on the panels this time"? Sounds like home made panels. Are these mounted, or to be mounted on your roof? If so, do you have another place where you can live:confused: And no, I'm not being sarcastic.
  • UrbandialectUrbandialect Solar Expert Posts: 107 ✭✭✭✭
    Re: 1st cycle 200amp hr battery bank/ 12 amps array 5 days to charge

    the panels will not be mounted on the house, i'm building a ground mounting system out of wood, I found out as the panels get hott power is reduced by quit alot, to fix this problem during the heat of the day you can spray them off with a water hose and cool them back down, another reason I'm not mounting them on the house is because they are home made panels, and I don't know how long they'll last, so i feel being able to easly replacement them is important. and last but not least, FIRE!!! remember i almost burned one of the panels up because i had 2 cells that were side by side that were slightly touching.

    This is a good learning experience, I want to know how ALL of this works.. Solar power is awesome when u can do it yourself and you understand how it all works,

    Once i learn what i'm doing with this solar power i'm moving to wind mills, or wind generators to work in conjuction with my solar, I plan to start building them too, I've been looking on craigslist and someone is always given away a free treadmill. :) I figured I can bust up an old office chair that spins 360degrees as the top mount.. but right now i'm still in the beginning stages of solar
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 1st cycle 200amp hr battery bank/ 12 amps array 5 days to charge

    Please note:

    1). Spraying panels with water tends to use more energy than the slight panel temperature reduction to be had will supply.

    2). Panel temperature is generated internally; you need significant thermal difference to realize any gain as glass does not conduct heat very well.

    3). Water on panels can act as a lens and focus the sun's rays resulting in very intense insolation in spots; not good for panels.

    4). Water is never pure; it will conduct electricity. Spraying it on panels means you'd better be sure every possible hole and potential leak is well-sealed.

    5). The three main failures for wind turbines: A). the site location does not have sufficient sustained wind to make an installation viable; B). the turbine is not installed properly (too low, too many things causing turbulent air); C). the turbine itself is a non-viable, over-rated piece of junk. Oddly, homemade turbines often tend to fair better than commercial ones: the exact opposite results of homemade PV's. This is probably due to the builder's efforts to customize his turbine to suit the site/needs, rather than a commercial unit's specifications which are meant to work in some idealized locale.
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