Newbie with some questions

joehumpjoehump Registered Users Posts: 7
I just built a new solar panel. 36 cells, rated at .5 volt and 8 amp. From what I read these are the newest and best. I can get anywhere from 17.5 to 20 volts during the day.
I have a Xantrex c60. I have it set for charge controller. The bulk charge is set to 14.8 volts and the float charge is set for 13.5 volts.
Is this correct?

I have 2 T105 Trojan batteries in series. Rated at 225 amp hours.

I have a Cobra 1500 watt inverter.

The panel is located about 75 feet from the C60. I am using 14 gauge stranded. Is this ok? I measured the voltage at the panel and at the C60 and there was virtually no difference.

Do I need a 10 amp Diode? I believe the C60 has one built in.

I ran the batteries down to 11.3 volts the first night just to give everything a good test, but the highest I have been able to charge the batteries back to is only 12.2 volts. I had 2 full days of sun.

I think that I have everything hooked up correctly. I am using 4 gauge from Xantrex C60 to the batteries and 4 gauge from the batteries to the Cobra 1500 inverter.

Thanks in advance for any pointers. So far this has been a very informing and fun project. I plan on building 2 more panels.

Comments

  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Newbie with some questions

    Quick comment,

    I would guess that you would be LUCKY to ~ 9 amps out of your panel if I do the calcs right. A C 60 is a pretty big controller for only 9 amps. I would guess there is a fair bit of inefficiency there. Second, # 14 is pretty small to run 75'. There is a "sticky" with a voltage drop calculator in this forum. I suggest that you look at it. Third, running your batteries down to 11.3 volts is a really bad idea! Compound this by not FULLY charging them within a matter of a couple of days will put them on the road to scrap metal. I suggest you look at the following:http://www.batteryfaq.org/ http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries

    The important measurement is not how many VOLTS you get our of a panel, but how many AMPS you get at WHAT VOLTAGE (watts) 17.5 volts @1 amp= 17.5 watts, same 17.5 volts @ 10 amps = 175 watts. It is also important to remember that unless you use a MPPT controller, you will never get the stated WATTAGE out of any given panel unless your battery voltage were to rise to the Vmp of the panel, which in this case would cook the battery. So lets say you were getting 9 amps @ 17 volts, you would get 153 watts. Put that same 9 amps at 12.6 volts and you would only be getting ~113 watts.

    A rough rule of thumb is that flooded batteries need to be charged at a current between ~5-15% of ah capacity (11-23 amps) just to maintain charge.

    At this point I wouldn't worry about float or even absorb voltages as you are unlikely to ever get there.

    Finally, if you expect to run your inverter anywhere near 1500 watts you will not have nearly enough battery, except for very short term (minutes) loads.

    Welcome to the forum, good luck, and read all you can here and elsewhere. There are some pretty sharp folks here who have forgotten more than most of us will ever know. Using this resource allows us not to have to re-invent the wheel each time,

    Tony
  • mikeomikeo Solar Expert Posts: 386 ✭✭✭
    Re: Newbie with some questions
    The panel is located about 75 feet from the C60. I am using 14 gauge stranded. Is this ok? I measured the voltage at the panel and at the C60 and there was virtually no difference.
    You need at least #6 wire for this run from the panels to the controller to maintain a less then 3% drop at 8 amps.
    Do I need a 10 amp Diode? I believe the C60 has one built in.
    You are correct, no diode is needed.
    I ran the batteries down to 11.3 volts the first night just to give everything a good test, but the highest I have been able to charge the batteries back to is only 12.2 volts. I had 2 full days of sun.
    You will need 3 of these panels to properly charge and maintain this battery bank, any less and you will kill the batteries prematurely.
    I think that I have everything hooked up correctly. I am using 4 gauge from Xantrex C60 to the batteries and 4 gauge from the batteries to the Cobra 1500 inverter.
    at full load you will be drawing 125 amps. You will need at least 2 AWG to maintain less then 5% drop in voltage, 1 or 1-0 would be better.
  • joehumpjoehump Registered Users Posts: 7
    Re: Newbie with some questions

    Thanks for the info on this. It sounds to me like I need more panels for more watts to power the batteries. I was actually planning on getting 2 more T-105 trojans and building 2 more panels.

    What kind of amperage should I be putting into the charge controller in order to get those batteries back up to where they should be?

    I dont want to start off by ruining 2 perfectly good batteries.

    I will replace the cable tommorrow with the correct gauge wire from the panel to the charge controller.

    Thanks again in advance.
  • mikeomikeo Solar Expert Posts: 386 ✭✭✭
    Re: Newbie with some questions
    What kind of amperage should I be putting into the charge controller in order to get those batteries back up to where they should be?
    I would shoot for around 10% of your battery capacity, in this case around 22 amps. A 20 amp battery charger would do the trick very well, you could get by with a 10 amp battery charger if you have one available to get the batteries charged back up. A 8 amp panel is just not enough.
  • joehumpjoehump Registered Users Posts: 7
    Re: Newbie with some questions

    Thanks MikeO.

    Im living and learning. My cells should be delivered by aboaut Tuesday so hopefully by about Friday I can have them put together.

    I fortunatley still have my day job.

    Thanks again for the info. Its all starting to make more sense.
  • joehumpjoehump Registered Users Posts: 7
    Re: Newbie with some questions

    One other thing that I have noticed and dont really understand.

    I measured the voltage on the batteries before the sun went down and measured 12.2 volts. I measured again a couple of hours later and I measured 12.0 volts.

    Is this normal? I have everything turned off. Just wondering.

    I have the cables from the panel going to the C60 and then from the C60 to the Batteries. I am measuring from the C60 and from the Batteries. Both show 12.0 now.

    Is this correct?

    Thanks
  • KamalaKamala Solar Expert Posts: 452 ✭✭
    Re: Newbie with some questions

    It might be correct, but is definitely not good. 12.0V is indicative of a significant depth of discharge. Does the C60 have a standby current draw?
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: Newbie with some questions

    Batteries need about 3 hours to "rest" (no charge/discharge current). The electrolyte next to the plates is more concentrated than the balance of the fluid during charging.

    The problem is that the batteries sound like they are somewhere around 50% discharged (Deep Cycle Battery FAQ) from undercharging (not enough solar panels for size of load/battery bank)/over discharging (too much load for the panels/hours of sun per day)... Flooded Cell batteries will die a pretty quick death if stored for days/months below ~75% state of charge).

    Of course, this is assuming your batteries are filled with standard strength electrolyte, are at/near standard temperature (~77F), and that your volt meter is calibrated (even digital ones can go bad).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • joehumpjoehump Registered Users Posts: 7
    Re: Newbie with some questions

    Im not sure about the current draw. It does have a green blinking light so I am going to assume that it does.

    Sounds more like I need to pump up the amps.

    Hopefully by next week when I get my other 2 panels installed it will be enough to charge them back to normal.

    The batteries are only about 1 week old. Hopefully I havent ruined them.
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: Newbie with some questions

    Get a good Hydrometer and log the cell S.G. levels.

    Also, get a charger on the batteries and get them at least to 90% State of Charge. Take them home, put them on a genset, or something.

    And once you get the batteries fully charged--again log the S.G. and battery voltages (after a 3 hour rest). You can use these numbers later on to ensure that you are keeping the batteries well charged.

    Generally, most charge controllers should not put much of a load on the batteries (if you have some solar panels attached--you should be charging the batteries unless there is a problem elsewhere).

    8 Amps a few hours a day is probably not going to do a very good job of recharging the batteries. You are, right now, probably just staying ahead of self discharge. I guess you are not drawing any loads from the batteries at this time?

    Not enough panels, long (small gauge) wiring reducing current flow/peak voltage, and relatively large bank for the solar panels--Needs more help.

    One quick warning--Home Made solar panels at higher power levels can catch fire from high resistance connections (solder tabs, etc.) if build with typical materials (Plexiglas, wood, etc.). Make sure they are installed over non-flammable surfaces (metal, gravel, bare ground, green vegetation etc.) to ensure something does not go wrong when you are not around.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Newbie with some questions

    Here's an old joke. What's the voltage volt battery? If you measure 12 vdc you have a "dead" 12 volt battery. As has been suggested, using battery voltage as measure of health is not a good technique. A battery will show higher than "real" voltage when coming off charge, and lower than "real" voltage under or just after loading.

    Also realize that most folks wreck at least one set of batteries as they learn how to charge and discharge them in a way that leads to longevity. (Also again, I urge you to read the battery Faqs linked below). A common misconception about "deep cycle" batteries is that they are boxes which you pour electricity into, and out of. In reality they are pretty special chemical plants that require fairly specific charging/discharging regimens to balance life cycles with power available.

    A few of things you should consider getting to keep your system healthy. The first is a good digital voltmeter. Second, a good (not cheap auto parts store) temperature corrected battery hydrometer. The third is at the very minimum a ammeter so that you can at least log current in and current out of your system. Idiot lights on a charge controller or inverter don't tell much of a story. A system may be "charging" but it may only be charging at .5 amps which is as effective as not charging at all. I would suggest that you buy a "real" battery monitor like the Bogart Tri-meteric. This tool will allow you to see in real time what is going in/out as well as see over time how much you have put in/taken out of the battery bank. (It will pay for itself in battery life many times over).

    Finally, almost all battery based systems occasionally need charging from some outside source (grid or generator). I would suggest that you invest in a good charger NOW so that you can keep these batteries charged until our solar system is up and running properly. Most automotive chargers do not work very well on battery banks such as yours. I suggest that you look into a good three stage charge, (IOTA or Xantrex TC come to mind). I also wouldn't buy any more batteries until you are able to keep the ones you have properly maintained.

    What is it you intend to use this system for?

    Once again, Good luck and shout when you have other questions,

    Tony
  • joehumpjoehump Registered Users Posts: 7
    Re: Newbie with some questions

    Thanks for all the valuable info Tony. There really was no intent when I started this. I thought that I could cut off about 20-30 dollars a month from my power bill but Im finding "that aint gonna happen". Its still a very interesting project. Its getting a little more costly than I anticipated but I dont really have any other hobbies and this is kind of fun. How much time do you think that I have before my batteries are DOA? What are your thoughts on the time that I have. I looked at some battery chargers and they are a little costly so Im hoping that I can revive these with the new panels. Bill has me a little worried about the panel "catching on fire".
    I did build it on wood and covered it in Plexiglass and soldered the connections. I have it on my roof.
  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Newbie with some questions

    In an absolute pinch, go to the discount Auto parts store tomorrow, and buy a 15-20 amp battery charger. Buy a gallon of distilled water and a cheap hydrometer. Plug the battery in and charge it until the specific gravity rises to ~1.25-1.26 or thereabouts (a bit above the green in a cheap hydrometer). Once the batteries get to the right SG, take them off the charger. Put them back on your Pv, but don't load them until you can keep them charged. Check them every couple of weeks and top them up as needed. Once you get your Pv going, you can begin to play with the loads and the charge rates.

    Be advised, that Pv solar is rarely "cheaper" than grid power, and battery based systems are even more expensive on a watt/hour basis.

    Tony
  • joehumpjoehump Registered Users Posts: 7
    Re: Newbie with some questions

    Will do. Thanks again for the info.
  • mike95490mike95490 Solar Expert Posts: 9,359 ✭✭✭✭✭
    Re: Newbie with some questions

    The C-60 blinking green light, indicates state of charge. There should be a chart on the controller, 2blinks=20%, 5blinks=90% or something like that. Solid green=full charge.
    Red blinking/solid is bad.
    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 ,

  • icarusicarus Solar Expert Posts: 5,433 ✭✭✭✭
    Re: Newbie with some questions

    Make sure you check the water in the battery often, and remember to be careful around batteries, both due to hydrogen gas, as well as acid. Wear old clothes and SAFETY GLASSES!

    Good luck, keep in touch,

    T
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: Newbie with some questions

    Joe,

    Fires are a real issue with any electrical system--that is why the "codes" and UL (Underwriter's Laboratories) was created in the first place.

    You can read a thread here about non-UL rated panels installed by a contractor which failed (and ended up catching fire). We still do not know the details of the failure (cheap imported non-UL plastic backed panels, or whatever)--And "we" (us) may never know (I would suspect that there are a few lawyers involved at this time).

    In the end, you will have to make your own decisions... There are many people that have built panels as they don't like the costs of factory panels--but for piece of mind and long life (25-40 years)--factory panels with 25 year warranties at $3-$5 per watt retail pricing for the 100+ watt panels are hard to beat.

    Note that NAWS is a Solar RE retailer/wholesaler out of Flagstaff Arizona and the host of our forum here. Other than Windsun (the Admin)--none of us here have any business relationship with NAWS. Please feel free to research the best delivered to your door price (and good service) as you see fit.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • KamalaKamala Solar Expert Posts: 452 ✭✭
    Re: Newbie with some questions
    joehump wrote: »
    ... a little worried about the panel "catching on fire". ...

    You should be! Pay heed to Bill's comments.

    K
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