Need advice on setting up Solar for my 5th wheel

Hello,
Thank you for having this Forum and servicing it.
For a new guy, the Solar set-up is a bit daunting. I plan on travelling back to Arizona and New Mexico with Solar in the winter, a year from this coming winter.
I have been recharging my 6 (Sam's Club) 6 golf cart batteries and Inverting. I have a 2000 Watt Magnum, Transfer switch and 2 2000 Watt Honda generators, with a parallel kit, BUT I have been using only a single Generator to recharge. We would Invert in the afternoon, all night, then charge while underway the next day while travelling. The Magnum is a Inverter/Charger.
I feed the 50 amp panel, just flip off the 5th wheel's charger breaker, as it is not used. I flip off the breaker to the water heater and furnace. The refrigerator is on gas, not electric setting.
I did not see a need to install a sub-panel, just monitor my electrical usage. I do have a small dorm-type refrigerator and a small upright chest freezer. LED Lights and will have a single LED 32" TV, automatic sat. dish and direct or Dish Receiver 2 Laptop computers, 2 small ceiling fans. No microwave action..
I need help on solar panels,
SO, help needed here on panels. There are so many and it has got me confused I would like to get as high as I can as to wattage, because of the limited roof space, maybe 4? I haven't measured to see if I can get 6 up there. Also is it true that the cost for panels should be under $1.00 a Watt?
Thanks in advance
OzzJim
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Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Need advice on setting up Solar for my 5th wheel

    Welcome to the forum Jim.

    Well last questions first and all that ...

    It is possible to find panels for $1 per Watt or even less. But they are usually large "GT style" panels and you may have a hard time fitting them to your roof. You'd be looking at things over 3 feet wide and 5 feet long each there.

    With an RV application space becomes an over-riding issue. You can't put just any panel up there, it has to fit. So you're going to have to measure the free areas, plot it out on paper, and do a lot of thinking before you find the maximum you can get.

    You will probably find an advantage in monocrystaline panels as they take up less area per Watt, being a couple percent more efficient. They are also more expensive and not usually available in smaller sizes.

    If you've got six GC2's that's three parallel battery strings on what is most assuredly a 12 Volt system. That can be a problem if not wired correctly. This is another area where replacing them with fewer, higher-capacity batteries can be advantageous even though it costs more per Watt hour.

    The bank you have now is about 660 Amp hours @ 12 Volts. Ideally you would have 1000+ Watts and an 80 Amp MPPT charge controller for that. Chances are you can't fit 1000 Watts on the roof. Maybe half that? Which means you won't get full recharging ability from the panels, only extended battery time. You may also want to see if you can drop that third string. You'd be going from 3.9 kW hours @ 50% DOD to 2.6 kW hours @ 50% DOD. Depending on how much power you draw from the generators and how much you can get 'directly' from whatever solar you install that may be enough. Normally we tell people to measure their loads with a Kill-A-Watt meter, but that's not always easy to do in an RV because some significant loads can be DC and there's not always a handy plug to use for the AC items. You could run the whole thing from generator for a while and measure the power coming from that to the RV, but it may not be that accurate either (battery draw, converter - if equipped - usage, etc).
  • OzzJimOzzJim Solar Expert Posts: 37
    Re: Need advice on setting up Solar for my 5th wheel

    Thank you for responding quickly,
    I had to 'Google' DOD... Newby..... :) I understand now. I am not against replacing the batteries, but would prefer not to for financial reasons. Bottom line is that I want to do this right, just have to sell another Air conditioner :)
    What is the highest output compact panel I can get? Also you mentioned dropping the 3rd string... couldn't Google that.. Batteries maybe? I see the problems associated with a large battery bank, great to have the extension of power available, but the recharging is a problem on solar then. Need to have the 3 stage recharge needed for them. I am like the kids nowadays: I want it all... NOW :)
    What type and different makes of batteries would you suggest, so I can see if they available here in The K.C. MO. area?
    Thanks for your time helping me.
    Ozz
  • Mustang65Mustang65 Solar Expert Posts: 42 ✭✭
    Re: Need advice on setting up Solar for my 5th wheel

    Hi Ozz,
    Once you get your solar set up, you will love it!!! I have had mine about 18 months and have not used the TT's battery charge controller since installing solar.
    (I rewired the TT charge controller to its own 110 AC breaker, and it has been OFF since SOLAR day 1). As for the number of panels on your roof, you will need to be a little creative. I currently have 1 250Watt Grape solar panel and it is working great, for our current needs. We plan on increasing our dry-camping time next year so I will be adding another panel or 2, and 2 more batteries.

    As for additional panels, I am looking at adding additional panels by stacking them. What I mean is I have a base panel mounted to the roof of the RV, and mounting a second panel to the existing one (hinged) and opening it like a book, when we get to the camp site. So, while traveling it would fold over the roof mounted one and latched to it while traveling. While at the site the unhinged end of the second panel would be secured to the roof

    So I could actually have 4 panels on the roof with only 2 mounted to the roof.

    Just my thoughts,

    Don

    2013 Jayco Eagle 284BHS
    250Watt Grape Solar Panel, MorningStar MPPT 60 Charge Controller
    1500 Watt Ramsond PSI, 2 Trojan T145 Batteries (260Ah)
    2 - AirSight Wireless IP Cameras (used as rear view cameras)
    EnGenius WI-FI extender, D-Link wireless (n) modem
    MagicJack Internet Phone
    2012 Ford F150XLT, EcoBoost w/3.73
    157" Wheel base, HD Towing Package
  • OzzJimOzzJim Solar Expert Posts: 37
    Re: Need advice on setting up Solar for my 5th wheel

    Thanks Don,
    That is a very creative idea when you don't have the room needed. I have wanted Solar for a long time, our 5er is a 2007 year, I have managed with the generator quite well, but need to go to the next level. Been working hard this Summer to get the money needed for Solar.
    That Jayco is a nice unit. We have a 3400RL Montana. Hauling that anchor around the country getting a marvelous 10 MPG most of the time.
    ozz
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Need advice on setting up Solar for my 5th wheel
    OzzJim wrote: »
    Thank you for responding quickly,
    I had to 'Google' DOD... Newby..... :) I understand now. I am not against replacing the batteries, but would prefer not to for financial reasons. Bottom line is that I want to do this right, just have to sell another Air conditioner :)
    What is the highest output compact panel I can get? Also you mentioned dropping the 3rd string... couldn't Google that.. Batteries maybe? I see the problems associated with a large battery bank, great to have the extension of power available, but the recharging is a problem on solar then. Need to have the 3 stage recharge needed for them. I am like the kids nowadays: I want it all... NOW :)
    What type and different makes of batteries would you suggest, so I can see if they available here in The K.C. MO. area?
    Thanks for your time helping me.
    Ozz

    I can't help you with what's available in Kansas City, Missouri; I live quite a long ways away in a different country. Sometimes very different. Brands that I have seen work well: Crown, East Penn/Deka/US Battery (three different labels but the same battery), Trojan (pricey). Also, believe it or not, some people have got good value out of 'warehouse' GC2's from places like Costco.

    Yes, DOD is Depth Of Discharge. We have a whole glossary of terms, but no one ever looks at it. http://forum.solar-electric.com/showthread.php?6136-Glossary :D

    Three parallel battery strings can be trouble. Not will be; can be. http://forum.solar-electric.com/showthread.php?15989-Battery-System-Voltages-and-equivalent-power If you can use fewer batteries and less total capacity it's better all around.

    You are still faced with the limitation of what will fit on the roof. Panel brands don't matter much in terms of output because they all use the same basic technologies. Monocrystaline gives the highest output for a given area, polycrystaline (now being called "multicrystaline' just to confuse people) comes in second, and thin film amorphous panels a distant third.

    Some RVers solve the space problem with 'portable' panels set up in the sun while they park in the shade. These have issues too: easier to steal, easier to damage, long wire runs to deal with (trip hazard, damage hazard, Voltage drop). But it can work to have a few hundred extra Watts out there.
  • OzzJimOzzJim Solar Expert Posts: 37
    Re: Need advice on setting up Solar for my 5th wheel

    Attachment not found. This is my wiring on my 6 T-105 225 AH each. I looked at the Rolls? but they are too tall for my compartment, looks like I am stuck with what I have as far as batteries are concerned.
    I like the extra battery power idea, if I can't get enough room for 6 panels on the roof, I might just use the Honda for recharge, but that isn't ideal set up I am looking for. Would 6 Panels be enough for the 3 stage charging? I won't go with external panels for the reasons you stated. I might have to scale down on the batteries, Ponderous, just ponderous
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Need advice on setting up Solar for my 5th wheel

    Wiring diagram: that should work fairly well. Best is for equal lengths off each battery pair to bus bars, with a fuse for safety on each pair. Like the attached diagram, except the battery strings would be only two in series instead of eight.

    Rolls Surrette batteries are expensive and in my opinion not worth the money. There have been a lot of problems reported with them of late. BTW companies do make 6 Volt batteries of slightly higher capacity that take up a similar amount of space. I'm using some that are 232, Trojan makes 225's (and other sizes), and Crown has listings up to 240 Amp hours. If your batteries are still good I wouldn't think about replacing them with something else; wait 'til they need replacing.

    The number of panels has nothing to do with 3 stage charging: that is a function of the charge controller and almost every single one will do it. The number of panels also has nothing to do with if there's enough power to charge or not: it's the Watts they add up to and the specifications.

    For example: to get 66 Amps peak current @ 12 Volts for your battery bank you'd need either 1155 Watts of 'standard' panels (Vmp around 17.5) on a PWM controller (two in fact, as they only go up to 60 Amp) or 1028 Watts on an 80 Amp MPPT controller. In the latter case they can be any kind of panel so long as the array Vmp is above 17.5 (minimum needed for charging a 12 Volt system): the controller will down-convert the higher Voltage into greater charging Amps.

    Why does this make a difference? Here's a system design I was working on yesterday for someone, comparing two ways of getting the same amount of charging power:

    Three 130 Watt panels @ $285 each = $855 (390 Watts)
    plus Xantrex C35 controller $85 = $940
    22 Amps output for two GC2's

    Two 190 Watt panels @ $218 each = $436 (380 Watts)
    plus MidNite Kid 30 Amp MPPT controller @ $285 = $721
    24 Amps output for two GC2's


    As you can see the higher Wattage panels are cheaper per Watt so when you get near 400 Watts using an MPPT controller becomes less expensive. With even larger panels the difference is more dramatic.

    A 130 Watt poly panel is 58" x 26". A 260 Watt mono panel is 66" x 40". Do a little math and you see that two of poly panels have the same power but take up 3016 square inches whereas the one mono panel is 2640 square inches. 376 square inches or 12% less space for the same power. But you may not be able to fit large panels to your roof.
  • OzzJimOzzJim Solar Expert Posts: 37
    Re: Need advice on setting up Solar for my 5th wheel

    I have a lot to learn.. I appreciate your explaining this to me, I would have thought the 'boiling' of the electrolyte stage, would require more amps of draw than a smaller panel array would put out, as you stated the Watts they add up to is the key.
    Yep, I am stuck with the batteries until I have problems. They are all the same age also. 225 AH is good. I will diagram the roof space available and get that info to you.
    I have asked for a couple of quotes from some dealers for the equipment, but they were not too helpful, seemed like they just wanted to throw some prices out without asking the needed questions. That is the good thing about this Forum, and the benefit of your knowledge and other members input.
    Thanks again.
    Ozz
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Need advice on setting up Solar for my 5th wheel
    OzzJim wrote: »
    Attachment not found. This is my wiring on my 6 T-105 225 AH each.

    The wires that run from the battery bank to the inverter are labeled in your diagram as being "equal length cables". Those two cables do NOT need to be equal length. If you can make one of them shorter it will be to your benefit.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • OzzJimOzzJim Solar Expert Posts: 37
    Re: Need advice on setting up Solar for my 5th wheel

    vtMaps, I found this diagram on the Internet somewhere, it is not my exact wiring, just how it is wired. Never have figured out how to make neat diagrams of my own. Not one of my skill-sets :blush:
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Need advice on setting up Solar for my 5th wheel
    vtmaps wrote: »
    The wires that run from the battery bank to the inverter are labeled in your diagram as being "equal length cables". Those two cables do NOT need to be equal length. If you can make one of them shorter it will be to your benefit.

    --vtMaps

    Just to clarify:
    The wires from inverter to battery bank do not need to be equal length just as vtMaps says.
    The wires between the batteries in each battery string do need to be equal length.
    The wires paralleling the battery strings do need to be equal length.

    Thus the string on top has zero extra positive wires and two extra negatives, the string in the middle has one extra positive and one extra negative, and the string on the bottom has two extra positives and zero extra negatives: each string has the same number of (equal length) extra wires.
  • OzzJimOzzJim Solar Expert Posts: 37
    Re: Need advice on setting up Solar for my 5th wheel

    Good info, thanks. I just found the diagram on the Internet, mine is not wired as the diagram states in that detail, just didn't make that clear.
  • OzzJimOzzJim Solar Expert Posts: 37
    Re: Need advice on setting up Solar for my 5th wheel

    I measured my RV Roof, I can put 5 SolarWorld Sunmodule 315 Watt Monocrystalline Panels on it, giving me 1720 watts, would that get me where I need to be with my six batteries? I am also changing out my RV reefer with an energy star household refrigerator, as it is 7 years old, and I want to switch to the electric... or will that be too much on the system?
    Thanks.
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Re: Need advice on setting up Solar for my 5th wheel

    The solar world 315 watts are actually under 15.5% conversion efficient. They use lower grade cells, almost about the same equivalent as buying topoint mono panels.
    Arizona wind and sun actually has a few of the solar world 280's 16.7% conversion efficient. I'm willing to bet if you buy 3 or 4 they might aim to give you a deal on the panels.
    As for me I continually buy the solar world 275's as the 280's have been discontinued due to cell sorting and mix matching and because of the positive 5% tolerance the 275's are, they actually round out to about 277watts, not 275.

    Ebay has slightly used sunpower 325's available that are roughly 10 months old. You can see if you can work a deal with that vendor.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Need advice on setting up Solar for my 5th wheel
    OzzJim wrote: »
    I measured my RV Roof, I can put 5 SolarWorld Sunmodule 315 Watt Monocrystalline Panels on it, giving me 1720 watts, would that get me where I need to be with my six batteries? I am also changing out my RV reefer with an energy star household refrigerator, as it is 7 years old, and I want to switch to the electric... or will that be too much on the system?
    Thanks.

    Those are some of the largest panels there are. If you can fit five of them you can fit just about anything.

    You do not want to use five of this type of panel. The reason being they would all be in parallel due to the odd number. That will require a combiner box box capable of taking all five panels; a six position box.

    But it does appear you have a lot of roof space available. If you can fit 1720 Watts you can get 110 Amps of charge current on a 12 Volt system. That would also mean a need for two charge controllers.

    For two parallel strings of 225 Amp hours @ 12 Volts (450 total) you only need 700-ish Watts and one MPPT controller.

    Down-size the panel choice a bit and save yourself some money and grief. You should be able to fit four 240 Watt panels (960 Watts), for example. No combiner needed if you run two parallel strings of two in series (although the higher Vmp of the arrau would be slightly less efficient). If there are going to be a lot of protrusions possibly casting shadows on the panel, then put them all in parallel on a four position box.
  • OzzJimOzzJim Solar Expert Posts: 37
    Re: Need advice on setting up Solar for my 5th wheel

    Thank both of you for your responses, I am working to keep my 6 T 105 batteries so don't I need at least 1500 watts? I can actually get a 6th panel up there if needed. That would get me back to one controller. Obviously, I want to spend the least amount on the panels as possible, but want to do it right. Keeping that in mind, what do you both suggest? I would lean toward A W & S to the purchase, since this is their Forum and I trust the brand.
    What is your opinion on changing the RV frig to the energy star residential model?
    Thanks Ozz
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Need advice on setting up Solar for my 5th wheel

    Last question first. :D

    There's a difference between an RV 'frige and a residential unit, and not just size. RV types are usually propane with 120 VAC back-up for the heater. If you shift to residential you lose the propane ability, although that's not necessarily a bad thing. But it does mean that all your refrigeration requirements must be met with electric power. You have just about enough capacity to do that. Given the difference in design and the huge number of different refrigerators in general it's hard to say if the all-electric would be more efficient than propane. The off-grid rule-of-thumb is the longer you stay out there, the more worthwhile the investment in electric over propane.

    You really do not need a huge array for the battery bank set at 450 Amp hours @ 12 Volts. You will have some fall-off due to less-than-perfect insolation that RV's suffer from (can't always control the panel angle to the sun). Think of it like this: if you max out a single 80 Amp controller on a 12 Volt system you'd only have 1250 Watts of array. More than that and you'd need another controller. Even at one you could be producing more Amps than the batteries can safely handle: 80 into 450 is 17% charge rate and would really stress them.

    It used to be possible to recommend panel brands. Now manufacturers come and go like the weather. They're all made pretty much the same, so as long as they meet specs and certification and have a sop towards warranty they're all the same.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Need advice on setting up Solar for my 5th wheel

    If you can live with the 8.5 cu size and price, heres a AC/DC compressor ( amps @ 12 V, 4.5 amps @ 24V, 2.25 amps, 28 watts Average duty cycle ) Dometic that ppl I know seem to be happy with. $1,500.00. I am sure Norcold makes one also.

    http://www.dometic.com/enus/Americas/USA/Marine/Refrigerators/Refrigeration/?productdataid=74828
    .
  • OzzJimOzzJim Solar Expert Posts: 37
    Re: Need advice on setting up Solar for my 5th wheel
    If you can live with the 8.5 cu size and price, heres a AC/DC compressor ( amps @ 12 V, 4.5 amps @ 24V, 2.25 amps, 28 watts on AC ) Dometic that ppl I know seem to be happy with. $1,500.00. I am sure Norcold makes one also.

    http://www.dometic.com/enus/Americas/USA/Marine/Refrigerators/Refrigeration/?productdataid=74828

    YIKES!
    Nope too much money!! If I can get a cheap Energy Star 120 volt medium size refrigerator I will fit it into that space. With my 6 batteries and whatever system I end up with, the power needed for the refrigerator will be there. I will see what I can find. Thanks for the choice, I appreciate your input.
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Need advice on setting up Solar for my 5th wheel
    If you can live with the 8.5 cu size and price, heres a AC/DC compressor ( amps @ 12 V, 4.5 amps @ 24V, 2.25 amps, 28 watts on AC )

    The DC amps you quote are the actual amps that it draws while running... it draws 12 volts X 4.5 amps = 54 watts while the compressor is running.

    The AC watts you quote is the AVERAGE watts that it draws. It draws more than 28 watts while the compressor is running.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Need advice on setting up Solar for my 5th wheel
    OzzJim wrote: »
    YIKES!
    Nope too much money!! If I can get a cheap Energy Star 120 volt medium size refrigerator I will fit it into that space. With my 6 batteries and whatever system I end up with, the power needed for the refrigerator will be there. I will see what I can find. Thanks for the choice, I appreciate your input.
    It's pricey for sure, most big motor coaches have two side by side. I think there some Inverter refrigerators out there, there was a thread on here. This one may not be available in the USA, but there is one.

    http://www.samsung.com/latin_en/consumer/home-appliances/refrigerators/top-freezer/RT38FEAKDSL/AP
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Need advice on setting up Solar for my 5th wheel
    vtmaps wrote: »
    The DC amps you quote are the actual amps that it draws while running... it draws 12 volts X 4.5 amps = 54 watts while the compressor is running.

    The AC watts you quote is the AVERAGE watts that it draws. It draws more than 28 watts while the compressor is running.

    --vtMaps
    Works for me, if it works for you. All I did was copy the specifications.

    Attachment not found.
  • OzzJimOzzJim Solar Expert Posts: 37
    Re: Need advice on setting up Solar for my 5th wheel
    Last question first. :D

    There's a difference between an RV 'frige and a residential unit, and not just size. RV types are usually propane with 120 VAC back-up for the heater. If you shift to residential you lose the propane ability, although that's not necessarily a bad thing. But it does mean that all your refrigeration requirements must be met with electric power. You have just about enough capacity to do that. Given the difference in design and the huge number of different refrigerators in general it's hard to say if the all-electric would be more efficient than propane. The off-grid rule-of-thumb is the longer you stay out there, the more worthwhile the investment in electric over propane.

    You really do not need a huge array for the battery bank set at 450 Amp hours @ 12 Volts. You will have some fall-off due to less-than-perfect insolation that RV's suffer from (can't always control the panel angle to the sun). Think of it like this: if you max out a single 80 Amp controller on a 12 Volt system you'd only have 1250 Watts of array. More than that and you'd need another controller. Even at one you could be producing more Amps than the batteries can safely handle: 80 into 450 is 17% charge rate and would really stress them.

    It used to be possible to recommend panel brands. Now manufacturers come and go like the weather. They're all made pretty much the same, so as long as they meet specs and certification and have a sop towards warranty they're all the same.


    I must be missing something on the AH. You said my battery bank was 450 AH, but with 6 @ 225 wouldn't that be a total of 1350?
    But, you state that an 80 amp controller will calculate that I have only a 1250 watt array, the max my batteries can safety charge.
    I am learning here, so be gentle. We are all experts in our field, hard to know everything about everything :)
    So.. what do I need for my batteries, the 1250 watt array?
    What do you suggest I buy for the 1250 if so? How many of what size, and which controller.
    Thanks for your help, hope I am not sucking all the oxygen out of the room with my questions.
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Need advice on setting up Solar for my 5th wheel
    Works for me, if it works for you. All I did was copy the specifications.

    I read the specs for "AVERAGE POWER" on the web page link you provided. Since it uses a DC compressor, when it runs on AC it is using a power supply to make the DC. Therefore it is slightly less efficient on AC. Let's say (to make the calculations easier) that the power supply wastes 1 watt. That means the compressor uses 27 watts average.

    Since the compressor draws 54 watts when running and 27 watts average, the duty cycle is 50%.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Need advice on setting up Solar for my 5th wheel
    vtmaps wrote: »
    I read the specs for "AVERAGE POWER" on the web page link you provided. Since it uses a DC compressor, when it runs on AC it is using a power supply to make the DC. Therefore it is slightly less efficient on AC. Let's say (to make the calculations easier) that the power supply wastes 1 watt. That means the compressor uses 27 watts average.

    Since the compressor draws 54 watts when running and 27 watts average, the duty cycle is 50%.

    --vtMaps
    Again, what ever works for you, enjoy it. The duty cycle is what ever it is, maybe more maybe less.
  • AuricTechAuricTech Solar Expert Posts: 140 ✭✭
    Re: Need advice on setting up Solar for my 5th wheel
    OzzJim wrote: »
    I must be missing something on the AH. You said my battery bank was 450 AH, but with 6 @ 225 wouldn't that be a total of 1350?

    Using six 6V batteries to build a 12V battery bank, you would have three parallel strings, each consisting of two batteries in series. Two 6V/225AH batteries in serial equals 12V @ 225AH (in series wiring, you add the voltages together). When you wire those three two-battery strings in parallel, that gives you a 12V battery bank with a total of 675AH (in parallel wiring, you add the Amp-hour capacities together). The 450AH figure you're quoting is based on the fact that it's generally ungood (probably not doubleplusungood, but ungood) to have three parallel strings; with two parallel strings of these batteries, you get a 450AH battery bank.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Need advice on setting up Solar for my 5th wheel
    OzzJim wrote: »
    I must be missing something on the AH. You said my battery bank was 450 AH, but with 6 @ 225 wouldn't that be a total of 1350?
    But, you state that an 80 amp controller will calculate that I have only a 1250 watt array, the max my batteries can safety charge.
    I am learning here, so be gentle. We are all experts in our field, hard to know everything about everything :)
    So.. what do I need for my batteries, the 1250 watt array?
    What do you suggest I buy for the 1250 if so? How many of what size, and which controller.
    Thanks for your help, hope I am not sucking all the oxygen out of the room with my questions.

    Six 6 Volt batteries? I thought you had four. Six is a bigger number.

    Two in series per string to get 12 Volts. Amp hours does not go up; only the Voltage does.
    Three such strings in parallel = 3 * 225 or 675 Amp hours @ 12 Volts.

    Ideally to recharge that you'd want a peak current of 67.5 Amps. The formula for sizing an array on an MPPT controller is: Amps * nominal Voltage / efficiency factor. In this case that would be 67.5 * 12 / 0.77 (typically) = 1052 Watts.

    The most an 80 Amp MPPT controller can handle at 12 Volts is the same formula only at its maximum current: 80 * 12 / 0.77 = 1247 Watts. (Sometimes I round numbers. Usually upwards.) You could go with that maximum size on 675 Amp hours @ 12 Volts and achieve a peak charge rate of just under 12%. It wouldn't hurt anything.

    Most people have very similar questions about their systems. Often I'm answering two or more similar questions at the same time and get confused as to the subtle differences.
  • animattanimatt Solar Expert Posts: 295 ✭✭✭
    Re: Need advice on setting up Solar for my 5th wheel

    Being panels will not be optimally pointed at sun most of the time some one may want to install 6 panels. This is more charge than the mppt controller could use but would allow charging a full mppt capacity for longer amounts if time.

    Being that there is the consideration of moving to a standard electric fridge, having more power even at somewhat reduced collection effiency maybe desired. Less collection effiency because there will be times the mppt controller would not be collecting all the power available. I would also recomend paralleling all panels, as to reduce shadowing issues.
  • OzzJimOzzJim Solar Expert Posts: 37
    Re: Need advice on setting up Solar for my 5th wheel

    I want to place an order for panels, controller and associated wire, brackets and such. Need to do this before my wife sees we have a couple extra bucks and heads for Bed, Bath and way beyond..
    Do I have this correct: 80 Amp MPPT Charge controller, an array consisting of a total of 1052 watts... or more because of shading. Doesn't matter which wattage as long as the total is around 1052 or more. I do have room for 6, but higher wattage and fewer panels would be my goal.
    Mono panels are the best?
    I think I will shy away from the tilting panel kit, don't want to go up and down to the roof, also high winds need to be figured in. Opinion on that?
    I got a couple of bids a week or so ago, one had a 60 amp MPPT Charge controller and 6 250 watt panels. One bid had a 40 amp controller and 600 watts of array, you can see why I am a bit confused. Aren't these folks selling these systems schooled in what a customer needs?
    I can install it with no problems, but I want to order the right equipment.
    Thanks.
  • vtmapsvtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    Re: Need advice on setting up Solar for my 5th wheel
    OzzJim wrote: »
    Aren't these folks selling these systems schooled in what a customer needs?

    Sure they're schooled... just like automobile dealers. Would you ask a car dealer what car you should buy?

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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