RV System questions

System
System Posts: 2,511 admin
in Advanced Solar Electric Technical Forum #1
I have (2) 110w solar panels (16.40 volts 6.7amps) charging (3) Group 31 Lifeline AGM batteries and controlled by a Solar Boost 2000 with temperature monitoring. In reading the instructions for the controller; charge voltage is set at 14 volts from the factory. Is this sufficient voltage to fully charge the AGM's? Are the batteries float charged after that? Not sure I understand how the controller works. :|

Thanks for the help...

:-D


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  • BB.
    BB. Super Moderators, Administrators Posts: 33,680 admin
    #2
    Re: RV System questions

    With the Web now-a-days, going to the vendor's site will usually be the best place to start looking for information. For the Batteries:

    http://www.lifelinebatteries.com/

    From their generic graphs:

    http://www.lifelinebatteries.com/rvgraphs.php

    At 77F, the float voltage should be 13.38 VDC (I think it is 13.38--the numbers are not clear), and for bulk charging, add 1 VDC to 13.38 (or 14.38 VDC at 77F).

    Bulk charge is intended to get the batteries almost fully charged as quick as possible. Float is for long term storage and the voltage should be lower. If you left your batteries on Bulk charge voltage forever, then you would overheat the batteries and boil the electrolite away (even for sealed AGMs).

    So, 14 VDC at 80F would seem to be fine for bulk charging, but too high for float charging (storage) for the AGM batteries.

    http://www.blueskyenergyinc.com/pdf/SB2000ManualE.pdf (SB2000 manual in PDF form)

    From reading the manual, the SB 2000 does not support Bulk and Float charge modes--it would need a second charge controller to support this function (6210 AC charge control system???).

    I will leave it to others who know more about these controllers and batteries than I to make the definitive recommendations... But I would suggest that (assuming that you have the battery temperature probe) that you set the SB 2000 to around 14 VDC at 80F while camping/using the batteries, and set it to 13.3 vdc or so when the batteries are to be kept in long term storage...

    -Bill

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #3
    Re: RV System questions

    Here's a link to Lifeline Battery's owner's manual: http://www.lifelinebatteries.com/manual.php

    Recommended charging voltages are shown on page 2. I suggest you use the single stage specs for your SB2000 controller, for, as Bill indicated, the SB200 does not include a float stage.

    DO NOT follow the equalization instructions in the manual -- they will ruin your batteries, as AGM batteries a very sensitive to overcharging. Concorde makes a very good product, but I have no idea what (if?) they were thinking when this manual was published.

    Note that when setting the charging voltage, you should confirm the setting by measuring the charge voltage at the battery terminals near the end of the absorption stage. This method compensates for any voltage drop in the wiring, connections, fuses and/or breakers between the controller and the battery terminals.

    HTH,
    Jim / crewzer
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,680 admin
    #4
    Re: RV System questions

    And note that for single stage chargers (set at 14.2-14.4 VDC), that "Once the battery is fully charged, remove it from charger."...

    Or, setting the SB 2000 back to 13.2-13.3 VDC for long term storage would be the other option.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • System2
    System2 Posts: 6,290 admin
    #5
    Re: RV System questions

    I guess I was under the impression that the solar controller was a little more automatic than that.

    So if I'm following you on the two replies; once the battery's reach 14 volts (the factory setting) then the voltage to the battery holds the same after that and is not regulated /reduced some how at all? Guess I will need to install a switch to turn off my solar panels or risk overcharging the AGM's ? ...Is that what this means?

    Are there solar controllers made that take care of all of that automatically?

    Which solar controller would be best for managing Lifeline AGM battery's (automatically) using the proper voltages in your opinion?

    Thanks again for the replies...
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,680 admin
    #6
    Re: RV System questions

    Bmats,

    You are exactly correct... The SB 2000 is a 1 stage controller... Look for a 2 or three state controller for you next system (since you currently have AGM batteries, you do not need the "Equalize" function that is used in flooded cell lead acid batteries to fully charge all cells and stir up the electrolite).

    I will leave it to others here to recommend alternative controllers... But going to our host's web site store would not be a bad place to start looking.

    From Wind-Sun's FAQ:
    All of the charge controllers that we stock are 3 or 4-stage PWM types, including the MPPT units. (in reality, "4-stage" is somewhat advertising hype - it used to be called equalize, but someone decided that 4 stage was better than 3). And now we even see one that is advertised as "5-stage"....

    So, I would start browsing this page and look for 20-30 amp controllers:

    http://store.solar-electric.com/chco.html

    You are going to see a lot about MPPT controllers as being better than PWM or other types of controllers... Yes, they are more efficient at getting power from solar panels to the batteries--but usually only in cold weather or for long wire runs where you run the panels at 60 VDC and run the batteries at 12-24 VDC (lower current means less I^2 * R heating losses and/or smaller gauge wire can be used)...

    But, if you have less than (a guess) 500 watts of solar panels, have short wire runs, a standard installation, and don't do much snow camping, don't feel like you have to pay any extra money for the MPPT controller.

    However, purchase the battery temp sensor option (batteries are very sensitive to temperature--as they get cold, their voltage requirements rise), and mount the charge controller(s) close to the batteries with good sized wiring... The lower the voltage drop between the controller and the battery, the more accurately they can measure charge voltage.

    Call, write, post to Wind-Sun if you have any questions for them about their controllers.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • System2
    System2 Posts: 6,290 admin
    #7
    Re: RV System questions

    Thanks Jim and Bill.

    I talked to Rick Cullen over at Blue Sky Energy. His description of the way the SB 2000 works is about the same as yours. He said if it was a "cycling" system that the batteries would likely not be at full charge for very long anyway. He said the worst thing I could do would be to park my camper in the sun and then not use it (no-electrical load). I have a 12 volt refrigerator in my camper so there will be a fairly consistant discharge of the batteries going on over a 24 hour period. Combine that with the rest of the electrical loads and it is probably a non-issue as Rick suggests. I think with a good understanding about how this controller works and a little commom sense it will be fine with the AGM's. Thanks again for the help guy's.

    Now...let me take a look at that Blue Sky 2512 (3) stage w/pro remote :-D
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #8
    Re: RV System questions

    While I recommended that you use Lifeline's "single stage" specs for the SB2000, I would actually argue that from a functional perspective it's at least a two stage controller, and, forgetting about the EQ stage, it may even be a sort-of three stage controller.

    The first stage is the bulk stage, and the SB2000 operates in that mode as it delivers all current available while trying to push the battery voltage to the absorption setting.

    The second stage is the absorption stage, during which the controller holds constant voltage by limiting charge current.

    The sort-of third stage is a silent stage encountered when the Sun sets and the controller is no longer charging the battery at all. This to me is similar to disconnecting the charger when the battery is full, especially in the case of AGM batteries which typically require a long, slow absorption stage.

    I think Rick gave you generally sound advice. However, you might want to occasionally check how long the absorption stage lasts. If it's regularly longer than ~three hours, then you may want to lower the absorption voltage setting to the lower range of the Lifeline recommendation.

    HTH,
    Jim / crewzer
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #9
    Re: RV System questions

    i'll agree it's a 2 stage controller as it has bulk and absorb. i discount the shutdown or disconnection from the pvs as a charging stage, but is more a feature of preventing battery discharge at night through the pvs. 14v is an odd place to have the voltage set for and is a tad low even for the agms. lifelines and sun xtenders have a charge range of 14.1v to 14.4v.
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  • crewzer
    crewzer Registered Users, Solar Expert Posts: 1,832 ✭✭✭✭
    #10
    Re: RV System questions

    Fair enough. Perhaps it should be called a third "state", as it's not operating in either bulk or absorb mode. I think the point I'm really trying to make, and I admit that I'm fumbling with the words, is that the SB2000 shouldn't be considered a single stage controller that charges to a set voltage point and then stays there forever, kind of like a single stage charger operating from AC might. Accordingly, it may well be OK to treat the night time "non-charging" state as the functional equivalent of disconnecting the charger.

    Until sunrise, of course...

    HTH,
    Jim / crewzer

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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #11
    Re: RV System questions

    We recommend setting the voltage down a bit for AGM's in the 2000/2000e.

    There is a pot inside where you can adjust it.

    The SB2000 is the only controller we sell that only has two stage charging, it might be about time for Bluesky to retire it or upgrade it.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #12
    Re: RV System questions

    "The SB2000 is the only controller we sell that only has two stage charging, it might be about time for Bluesky to retire it or upgrade it."

    whoops. you mean the only 2 stage mppt charge controller you sell. sunsavers are 2 stage too.
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  • System2
    System2 Posts: 6,290 admin
    #13
    Re: RV System questions

    Thanks again guys.  As an upgrade, later down the road, I'll be looking at something like the Blue Sky 2512 (3) stage w/pro remote. In the mean time I'll stick with the SB 2000 because that what I stipulated when I ordered the camper. I'll keep an eye on the way it is working as suggested; the 14 volts seemed low to me too. I don't think you can adjust the "absorb" stage such as it is. I don't want to reset the pot each time I get to the absorb stage. ...Maybe that why it is set at 14 volts. Kind of an in between setting that's safe?  :roll:

    Live and learn I guess...
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  • Windsun
    Windsun Solar Expert Posts: 1,164 ✭✭
    #14
    Re: RV System questions
    niel wrote:
    "The SB2000 is the only controller we sell that only has two stage charging, it might be about time for Bluesky to retire it or upgrade it."

    whoops. you mean the only 2 stage mppt charge controller you sell. sunsavers are 2 stage too.

    SunSavers are .. 2-1/2 stage :D

    They have the 3rd stage as they call it that uses PWM
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #15
    Re: RV System questions

    i'll argue that one as it is only the method of regulating the absorb stage.
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