Solar Electricity for A-Liner pop-up camper

Kamala
Kamala Solar Expert Posts: 452 ✭✭
in Off Grid Solar & Battery Systems #1
Attached are 2 PDF documents (zipped) describing my plans to add PV electricty to my camper. I first posted under the thread

http://forum.solar-electric.com/showthread.php?t=4894

I am unsure of my fuse selection and placement. The distance from the battery bank to the inverter and controller is less than four feet. Are fuses even needed for this short distance?

Craig
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #2
    Re: Solar Electricity for A-Liner pop-up camper

    I don't see any tables in the first one.

    In the second one, the wire sizes aren't labeled and "what size fuse" is a function of "what size wire".

    And yes, you need the fuses; 4' of wire - when it becomes a filament instead of a conductor - is plenty to ignite a fire.


    EDIT:

    I'm not sure the battery wiring is optimum. I remember someone posting a link in a thread here within the last couple of weeks which described a sort of "caddy corner" wiring scheme that fully equalizes the flow of current through the batteries.

    Unfortunately I didn't bookmark it as I meant to and can't seem to find the thread.


    Although it won't hurt to have that Blue Sea switch there, I think I might not do it that way...

    I think I would rather tie the output of the DC power supply parallel to the PV array and feed that into the charge controller - then use the batteries to feed the DC circuits and the inverter.

    You wouldn't need an inverter/charger in that case; just an inverter since the charging is being handled by the solar charge controller - whether or not you are connected to shore power.

    The way you have it now, when you are connected to shore power and the sun is shining, you have two different chargers trying to manage the battery charge. Unless I'm mistaken, the Prosine 2. 0 has a PWM charge controller, but the XW-MPPT (not XWPPT btw...) is an MPPT.

    I don't know the effect of letting PWM and MPPT controllers butt heads over the same battery bank, but I would just feed the juice from the DC supply to the MPPT along with the PV juice and let that one charger handle the batteries.
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #3
    Re: Solar Electricity for A-Liner pop-up camper

    Sorry about that. Maybe this link will work better.

    http://www.visi.com/~ch3dietz/solar/A-Liner Solar.pdf

    I think 4 or 6 gauge for battery interconnects and to inverter. 8 or 10 for the rest. Suggestions are appreciated. The longest run will be from the PV array to the controller. Less than 20 feet. And panels will probably be in series. All other lengths less than 5 feet.

    K
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #4
    Re: Solar Electricity for A-Liner pop-up camper
    dwh wrote: »
    I think I would rather tie the output of the DC power supply parallel to the PV array and feed that into the charge controller - then use the batteries to feed the DC circuits and the inverter.

    You wouldn't need an inverter/charger in that case; just an inverter since the charging is being handled by the solar charge controller - whether or not you are connected to shore power.

    The way you have it now, when you are connected to shore power and the sun is shining, you have two different chargers trying to manage the battery charge. Unless I'm mistaken, the Prosine 2. 0 has a PWM charge controller, but the XW-MPPT (not XWPPT btw...) is an MPPT.

    I don't know the effect of letting PWM and MPPT controllers butt heads over the same battery bank, but I would just feed the juice from the DC supply to the MPPT along with the PV juice and let that one charger handle the batteries.

    When the trailer is towed, the output from the tow vehicle's alternator is present across the output of the DC supply (I think.) Is this a problem for the MPPT or the PV Panels? Otherwise, I see your point regarding the two chargers.
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #5
    Re: Solar Electricity for A-Liner pop-up camper
    dwh wrote: »
    I'm not sure the battery wiring is optimum. I remember someone posting a link in a thread here within the last couple of weeks which described a sort of "caddy corner" wiring scheme that fully equalizes the flow of current through the batteries.

    Unfortunately I didn't bookmark it as I meant to and can't seem to find the thread.

    Might this be the link you have in mind?

    http://www.smartgauge.co.uk/batt_con.html

    Near the end it is stated:

    "Finally, if you only have 2 batteries, then simply linking them together and taking the main feeds from diagonally opposite corners cannot be improved upon."

    I felt that I could treat the two batteries in series as one battery.
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #6
    Re: Solar Electricity for A-Liner pop-up camper
    Kamala wrote: »
    When the trailer is towed, the output from the tow vehicle's alternator is present across the output of the DC supply (I think.) Is this a problem for the MPPT or the PV Panels? Otherwise, I see your point regarding the two chargers.

    Okay, that's not shown in the diagram, and I forgot you said that in your original thread.

    It wouldn't be a problem for the PVs, but as for the MPPT... I probably wouldn't run the output from an automotive charging system into the input of any solar charge controller (but that's just senseless blind habitual caution...there might not be any reason why it would be a bad idea).

    The automotive voltage regulator is a very simple charging system. I would probably hook it directly to the batteries and let it do what it can when the tow vehicle is running. I would also use a battery isolator on the tow vehicle.

    The presence of voltage from the engine alternator (on the battery side of the MPPT, not the PV side) might make make the MPPT act a bit strange trying to charge the batteries, but maybe not...if the MPPT reacts quickly enough, it might not have any problems at all.

    This is a question for Solar Guppy I think, and since I'm going to be doing something similar on my camper van I'm interested in the answer.
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  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
    #7
    Re: Solar Electricity for A-Liner pop-up camper
    Kamala wrote: »
    Might this be the link you have in mind?

    http://www.smartgauge.co.uk/batt_con.html

    Near the end it is stated:

    "Finally, if you only have 2 batteries, then simply linking them together and taking the main feeds from diagonally opposite corners cannot be improved upon."

    I felt that I could treat the two batteries in series as one battery.

    Yes, that was the link, thanks. And you may be right and have it done correctly. I'll have to stare at it a while and try to figure out why it looked strange to me. :)
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #8
    Re: Solar Electricity for A-Liner pop-up camper

    The output of the Elixir DC PS is 13.2 volts at full load (25A.) As I understand the MPPT would adjust this to properly charge the AGMs. But... it's output is tied to chassis ground and as I have been reading in another post, the input to the XW-MPPT should be connected only to the PV array.
    Solar Guppy wrote: »
    The XW-Mppt is a 4 wire Mptt controller. The Solar Panel leads must ONLY connect to the chargers "+" and "-" solar input, not anything else. Then the output of the chargers "+" and "-" go to the battery's
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #9
    Re: Solar Electricity for A-Liner pop-up camper

    Regarding parallel charge controllers (battery outputs only--not any other wiring to the soalr panel inputs--other than solar panels)... They will share the charging of the battery based on their own internal set-points and what stage of charge they think the battery is in.

    Typically, a deep cycle solar charge controller is programmed to charge a storage battery to a higher voltage than the tow vehicle is--so depending on what kind of isolation there is (relay, blocking diode, etc.)--the solar charge controller will attempt to charge the house battery to a higher finish voltage--and it may try to charge the tow vehicle battery to a higher voltage too (not a good idea if the solar charge controller is trying to equalize the battery bank--too high of voltage for tow vehicle.

    Also, there is usually a pretty substantial voltage drop from the tow vehicle to the house batteries in the trailer--voltage is lower, and current is not that high. If there is a lot of camping and driving--placing an Inverter in the tow vehicle and an AC charger in the trailer may give better on-the-road charging.

    Regarding AGM--always check the specifications... But from what I have seen, there should not be a big issue with charging by the tow vehicle.

    The grounding of the XW 60 MPPT Xantrex charge controller. The "grounding issue" (as far as I know) is around the PV Inputs... Those must be "floated" (+ and - terminals must only connect from the solar panels to the XW MPPT solar panel inputs). Other controllers can work OK if the solar panel "-" is connected to chassis ground. But not the Xantrex XW MPPT DC charge controller.
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #10
    Re: Solar Electricity for A-Liner pop-up camper
    dwh wrote: »
    I think I would rather tie the output of the DC power supply parallel to the PV array and feed that into the charge controller...

    Apparently not a good idea with the XW-MPPT.

    It appears that it is not a problem to connect the output of the charge controller and the output of the PROsine charger in parallel to the battery bank.
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  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
    #11
    Aimin' so long, can't wait to fire

    Me again.

    Need help on wire and fuse size.

    K
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