Upgrade Options for RV

I have slowly built, piece by piece over the past year, a pretty decent system for our RV. We live in it 7 months of the year while snow birding. It consists of 3 250 watt panels on the roof, classic 150 w/WBjr. 4 each 6v agm Trojan for 12 volt system,2kw Exeltech inverter, 40 amp industrial charger and 2 each Honda 2000i for bad weather charging and backup. I have a second LA battery bank of 180Ah which I charge by back feeding from large bank. During cold months I have been using up to 150 Ah per night including coffee in AM. Using the general 50% DoD rule I have 1 to 2 days of autonomy. Non furnace months are greater. I understand furnace fan consumes a lot of juice. In New Mexico I may have excess array capicity. In Michigan I do not. I have been looking for more loads of opportunity such as modifying water heater with 12v element to use dump power to heat water. I would like to increase my rainy day capacity to 4 or 5 days. Looking to add a 4th panel to increase charging to 80 amps.I am not sure if Classic 150 can handle 5. I would like 6 2v cells rated at 1100 Ah but may have to settle for around 800 AH. What would be the best all around option?
1987 Avion 9.1 Metre with 5 Kyocera 270 watt panels, Midnite Classic 150 mppt controller, Approx 14.4 KW provided by 6 in series Fullriver dc1150-2 2 volt agm cells, Exeltech 2Kw pure sine inverter, Battery transfer switch to isolate pesky converter from solar components, 120 amp battery to battery charger to allow dc back up from tow vehicle and 2 Honda 2000 generators for the very rare need to back up. Networked with Cradle point AER2100 router ATT/ Verizon, WiFi as WAN on Exeltech 125 watt inverter. Microwave, 2 induction cook tops, Mr. Coffee and a pretty nice toaster.

Comments

  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    xmineman wrote: »
    I am not sure if Classic 150 can handle 5
    Use the Classic array sizing tool found here for the answer http://www.midnitesolar.com/sizingTool/displaySizing.php
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    Hi xmineman, Welcome to the Forum,

    The Classic should be able to handle four of the 250 watt PVs, but five would be a problem for your Classic 150. Most probably, with five PVs, the Voc would be too great, and on an RV, the lowest temperatures that the PVs might be exposed to may be uncertain.

    One issue with an odd number of PVs, is that they would need to all be connected in series.

    Here is the Link to the Classic String Sizer, if you have not seen it:
    http://www.midnitesolar.com/sizingTool/displaySizing.php

    A single string of 1100Ah batteries, like you are considering, is a smart idea, especially on a 12 V system. But, with only about 700 or so watts of PV output possibly available from four PVs, that might not work optimally.

    Just a drive-by post. Have Fun, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 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.
  • xmineman
    xmineman Registered Users Posts: 5
    I currently have the 3 panels wired in parallel using 6 gauge wire to combiner approx 12ft away in electrical closet (back trunk). I did this because of possible partial shading issues. Is that harmful?I thought I might wire 4 panels in series/ parallel
    1987 Avion 9.1 Metre with 5 Kyocera 270 watt panels, Midnite Classic 150 mppt controller, Approx 14.4 KW provided by 6 in series Fullriver dc1150-2 2 volt agm cells, Exeltech 2Kw pure sine inverter, Battery transfer switch to isolate pesky converter from solar components, 120 amp battery to battery charger to allow dc back up from tow vehicle and 2 Honda 2000 generators for the very rare need to back up. Networked with Cradle point AER2100 router ATT/ Verizon, WiFi as WAN on Exeltech 125 watt inverter. Microwave, 2 induction cook tops, Mr. Coffee and a pretty nice toaster.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    Shading is difficult for any solar electric panel. And how best to address shading (series/parallel) to some degree depends on solar panel layout and the type/location of shading (i.e., if you lay panels "landscape" orientation, then snow at the bottom of each panel only blocks 1/2 of the cells--So you will get 1/2 current until the sun melts the rest of the snow).

    Otherwise, if you can reduce shading (shorten vent pipe, move panels way from chimney, move antenna so they do not shade panels from ~9am to 3pm--at least)--You will be much better off.

    The MPPT solar charge controllers usually work most efficiently around 2x battery charging voltage (~14.8 volts charging means ~Vmp-array in the range of 30 volts or so--Or 2x "12 volt" panels in series for Vmp-array ~ 36 volts).

    While the MPPT charge controller can run upwards of Vmp-array ~ 100 VDC (for "high end" MPPT charge controllers), the losses inside the MPPT controller can increase--Instead of being 96% efficient with Vmp~30 volts on a 12 volt battery, a 100 Vmp on a 12 volt battery may be down around ~93% efficient or so... The MPPT charge controller will run hotter (need good ventilation).

    Typically we use "high" Vmp-array voltages when the solar array is 10's to 100's of feet from the charge controller/battery box... It allows the use of much smaller diameter copper wire from the array to the charge controller.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    BB. wrote: »
    Shading is difficult for any solar electric panel. And how best to address shading (series/parallel) to some degree depends on solar panel layout and the type/location of shading (i.e., if you lay panels "landscape" orientation, then snow at the bottom of each panel only blocks 1/2 of the cells--So you will get 1/2 current until the sun melts the rest of the snow).

    Typically we use "high" Vmp-array voltages when the solar array is 10's to 100's of feet from the charge controller/battery box... It allows the use of much smaller diameter copper wire from the array to the charge controller.

    -Bill

    Hi BB Bill,

    Great point about RVs often encountering numerous shading issues, and that series strings can greatly magnify the issue.

    I should stick to stationary systems. Thanks - Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 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.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    Vic,

    Your answers were fine... There is the difficulty of using a Prime number of panels (3, 5, etc.) that cannot be mixed/matched for series/parallel applications. If I had 5 panels and that was all I could fit, I probably would bite the bullet and just put them all in parallel. 12 foot run to a combiner box (plus breakers or fuses per panel) should work fine. At the expense of a comber box plus a spool of of heavier copper wire (if needed) to keep the voltage drop from getting too large (less than a 0.5 volt drop on a Vmp~18 volt set of panels).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • techntrek
    techntrek Solar Expert Posts: 1,372 ✭✭✭
    Suggestion, to move this to the RV sub-forum.
    4.5 kw APC UPS powered by a Prius, 12 kw Generac, Honda EU3000is
  • BB.
    BB. Super Moderators, Administrators Posts: 33,433 admin
    OK... Moved thread to RV Forum.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • scrubjaysnest
    scrubjaysnest Solar Expert Posts: 175 ✭✭✭
    xmineman wrote: »
    I have slowly built, piece by piece over the past year, a pretty decent system for our RV. We live in it 7 months of the year while snow birding. It consists of 3 250 watt panels on the roof, classic 150 w/WBjr. 4 each 6v agm Trojan for 12 volt system,2kw Exeltech inverter, 40 amp industrial charger and 2 each Honda 2000i for bad weather charging and backup. I have a second LA battery bank of 180Ah which I charge by back feeding from large bank. During cold months I have been using up to 150 Ah per night including coffee in AM. Using the general 50% DoD rule I have 1 to 2 days of autonomy. Non furnace months are greater. I understand furnace fan consumes a lot of juice. In New Mexico I may have excess array capicity. In Michigan I do not. I have been looking for more loads of opportunity such as modifying water heater with 12v element to use dump power to heat water. I would like to increase my rainy day capacity to 4 or 5 days. Looking to add a 4th panel to increase charging to 80 amps.I am not sure if Classic 150 can handle 5. I would like 6 2v cells rated at 1100 Ah but may have to settle for around 800 AH. What would be the best all around option?
    Good answers above. Here are some additional thoughts. We boil the coffee on the gas stove so that would be a big power savings if it would work for you. Running the water heater on gas will also be a big savings over a 12 volt element. We actual had better solar this last summer in MI then this winter in AZ with out 2 80 watt panels. I don't know what you run the heater at but ours uses 2.25 amps, call it 30 watts. It is rarely used at night and we are quite comfortable at setting the thermostat at 55. You might want to look at your usage and see how/where you can conserve. LED lighting will give about an 80% savings over incendensent lights. Just some other thoughts that may save you a panel.