RV Battery System

Tom Cleary
Tom Cleary Solar Expert Posts: 37
Hello All:
If you have some time to review the diagram attached, and to make comments, that would be great. Many thanks to you experienced readers who have replied to my previous posts. I have learned a lot by figuring out questions to ask this forum. I may even be "almost there" at the end of my search for answers, unless of course I am not "almost there."

Attached is a diagram, drawn using MS Paint, which I learned how to use for the sake of constructing the diagram. If the panel/battery setup works the way I'm hoping, it will be set out in the sun 50 feet from the camper van, which will hopefully be parked in the shade. The panel will be in one location with the batteries, along with charge controller, TM 2025, inverter, etc.. AC electricity from the pv panel/batteries/inverter will be transferred through 50 feet of extension cord to the camper van.

Thanks for whatever comments you can provide. Best,
Tom

p.s. These are the parts to my proposed system:

Kyocera 24 volt 185 W panel with MC4 connectors
Two 12 volt deep cycle flooded cell batteries (Costco)
Rogue 30 amp controller
Bogart Trimetric 2025
Morningstar Sure Sine 300 inverter
Ironridge universal ground mount 1 panel-UNI-GR/02
#4 wire for battery interconnections L=?
#4 wire for battery connection to inverter L=?
50 feet 120vac 12 gauge extension cord
40 amp fuse "Square QO" for controller-to-battery connection
80 amp circuit breaker between inverter and batteries
30 amp fuse to connect panel and controller

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: RV Battery System

    Your picture did not show... If you can, convert to PDF (~700 kByte file size) or JPEG/JPG (~115/250 kByte), or BMP (~115 kByte) file types/extension (use the "Paper Clip" icon in the top of the editing pane to upload the files). I think MS Paint will save in any of those formats except PDF. Try file1.JPG first if not PDF...

    By the way, are you planning on a larger system? The Rogue is quite a bit larger than you need with the planned setup. Although a MorningStar 15 amp MPPT controller may be a better fit--it does not come with a display (added costs to read log files/etc.).

    And what Amp*Hour battery bank size?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Tom Cleary
    Tom Cleary Solar Expert Posts: 37
    Re: RV Battery System

    Thanks Bill:
    The attachment has been posted again, this time as a bit file (620x280) 16 color. Regarding your question about enlarging the system, I am considering adding a second Kyocera 185 watt panel and figured the Morningstar 15 amp model would be close to capacity with two Kyocera 185 watt panels. Although the 30 amp Rogue seemed like a large step up, it was the closest one I could find that was larger than 15 amp.

    My idea about batteries was to buy a "training bank" of two inexpensive batteries in case I kill the batteries prematurely. Costco sells the Kirkland Brand 12 volt deep cycle group 27 105 amp hour for $85 with a 3yr warranty.

    My setup includes a laptop (4 amps), an evaporative cooler (2 amps) and some led lights (1 amp) for a total of 7 amps per hour. It's not clear to me yet how many hours per day it will be running, probably not more than 5 hours total. Does this come out to 35 amp hours per day? Sorry, I am not sure if this is what you were asking. Thanks for the help.
    Tom
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: RV Battery System
    Tom Cleary wrote: »
    The attachment has been posted again, this time as a bit file (620x280) 16 color.
    Still don't see it (or in the albums).
    Regarding your question about enlarging the system, I am considering adding a second Kyocera 185 watt panel and figured the Morningstar 15 amp model would be close to capacity with two Kyocera 185 watt panels. Although the 30 amp Rogue seemed like a large step up, it was the closest one I could find that was larger than 15 amp.
    A nice maximum for the 15 amp MPPT controller at 12 and 24 volts:
    • 15 amps * 14.5 volts * 1/0.77 system derating = 282 watts
    • 15 amps * 29 volts * 1/0.77 system derating = 565 watts
    For 12 volts--yea, the 15 amp controller is a bit small.

    However, cut out some cardboard for your 185 watt panels and see how large they are... A pair of 135 watt panels may be more manageable by a single person (and for storage).

    Regarding the Kyocera panels... Their Vmp and Voc mean that for these "mid-range" input voltage charge controllers, that you can only use 1 panel per string and these will only charge a 12 volt battery bank. You cannot place two panels in series as their Voc=29.5 volts is too high (in cool/cold weather) for the 60-75 Voc input of the charge controllers.

    Not a problem if 12 volts is what you want--just configuration choices.
    My idea about batteries was to buy a "training bank" of two inexpensive batteries in case I kill the batteries prematurely. Costco sells the Kirkland Brand 12 volt deep cycle group 27 105 amp hour for $85 with a 3yr warranty.
    Hard to beat.
    My setup includes a laptop (4 amps), an evaporative cooler (2 amps) and some led lights (1 amp) for a total of 7 amps [not per hour--just amps]. It's not clear to me yet how many hours per day it will be running, probably not more than 5 hours total. Does this come out to 35 amp hours per day? Sorry, I am not sure if this is what you were asking. Thanks for the help.
    At some point you need to measure your loads... You can use:
    A Trimetric Battery Monitor is a good choice for truly monitoring your battery bank's state of charge. The DC Amp*Hour meter is fine for a lab bench or manually monitoring loads (the DC Amp*Hour meter only logs current flow in one direction, the Battery Monitor totalizes flow in both directions, charging and discharging at ~2x the cost).

    A DC Current Clamp meter is great for checking out your system (looking for unequal current flow with parallel battery strings, solar panels, etc.)... But DMMs and current clamps do not measure current flow over time (Amp*Hours and Watt*Hours)--sort of like driving a car without a fuel gauge--just using the odometer and speedometer to guess at fuel tank levels.

    Also, make sure you have appropriate fusing/breakers. Boat suppliers also have some nice options too... A shorted wire can ruin your day with the large amount of current a shorted lead acid battery bank can output.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Tom Cleary
    Tom Cleary Solar Expert Posts: 37
    Re: RV Battery System

    Hello Bill:
    Posted a png file this time, looks like it will go judging by preview mode. Thanks for the feedback. Will respond to your comments later, just wanted to get the attachment up for now. Best,
    Tom
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: RV Battery System

    Looks OK as a beginning...

    Note that the Battery Monitor has two sets of connections... One is the current shunt which goes between the battery negative post and all other connections (ground, negative bus, etc.)... You want all the current into/out of the battery bank to go through the shunt for proper current measurement.

    The second set of leads go right on the +/- bus common points for powering the meter and so it can measure battery voltage.

    You really do not need a fuse/breaker between the pair of solar panels and the charge controller... You can put a breaker or switch there if you want to be able to shut down power to the controller if you want to do some work during the day (nice to have but not needed--although code does require a switch/breaker/fuse).

    You only need to fuse the solar array if you have three or more parallel strings--then you need a series fuse per string to protect against array shorts (you only have two parallel strings, so series fusing/combiner boxes are not needed).

    -Bill

    PS: Your JPG attachment worked OK for me too...
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • scrubjaysnest
    scrubjaysnest Solar Expert Posts: 175 ✭✭✭
    Re: RV Battery System

    Looking at your block diagram, it is good for a start but you will need to get a better usage figure since you have the camper on the inverter output. Your camper converter will be drawing power to feed everything in the camper. This means co/propane monitor, if you have one; propane heater blower fan, and other items may be loads on the system.
  • Tom Cleary
    Tom Cleary Solar Expert Posts: 37
    Re: RV Battery System

    Thanks for noting there are two sets of connections on the Battery Monitor. Did not know that. I will refer back to your notes when it comes time to install it.

    Thanks also for the suggestion to cut some cardboard in the shape of the Kyocera 185 watt panels to see how large they are -- I will try that.

    I understand your information about the need for load factor measurements and will attend to that using the TM 2025.

    Can I ask another question, one I haven't asked? How can I make sure the system is grounded? I planned to run a 50 ft extension cord from the pv panel and battery assembly, where the power will be produced, to a power strip inside the van.

    Appliances will be plugged into that power strip, but a power strip wouldn't be grounded in the chassis, of course, unless there is a way to do that. It is usually the case to have an electrical system grounded to an RV chassis. Is it possible to ground the power strip some way?

    Also, does the panel and battery assembly that produces the power need to be grounded separately?

    Thanks again, as always for whatever time you have, and whatever comments you can provide.
    Tom
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: RV Battery System
    Tom Cleary wrote: »
    How can I make sure the system is grounded? I planned to run a 50 ft extension cord from the pv panel and battery assembly, where the power will be produced, to a power strip inside the van.

    Appliances will be plugged into that power strip, but a power strip wouldn't be grounded in the chassis, of course, unless there is a way to do that. It is usually the case to have an electrical system grounded to an RV chassis. Is it possible to ground the power strip some way?
    Ah--the $64 question...

    So I will ask you a couple... Is this for electrical safety (shock hazard) or because you have a strong chance for lightning in the area?

    And is this a fixed installation (RV used as cabin and/or fixed pad on property) or is this a purely portable setup that will move around the area?

    For electrical shock, the MorningStar 300 watt TSW inverter 120 VAC output is actually isolated by an internal transformer from any other electrical connection... So, by design, you could touch either lead (by itself) and it will not shock anyone. Of course, touch across the leads and you get 120 VAC. For a temporary setup, I would not do more.

    There are a few items that need a ground and/or grounded neutral lead (what is done with power in North America) like some florescent tube fixtures that need a grounded fixture to start reliably. You can connect the green wire to your RV chassis ground and even tie the neutral lead to RV chassis ground if you wish (make your own power strip with a metal box and outlets from the home store to wire your ground and neutral together--permanently ground metal box to RV frame).

    If this is because you have lightning in the area--That is another whole bunch of fun... Is this a permanent or mobile setup? Do you have water pipes in ground feeding the RV pad?

    If this is a mobile setup, then I would just do the metal boxed grounded power strip as described above (hard ground green wire and neutral to RV chassis).

    If this is a fixed setup--Do as above and place one or two 8' ground rods at the RV pad and ground the RV frame (whatever proper grounding is recommended in your region).

    You can also ground the battery negative terminal, solar panel frames, and inverter chassis back at the PV station (via ground rods). If you do this, do not connect the AC output green wire to anything. Let the green wire float between the shed and the RV. Use the RV green wire as ground (and make the neutral/ground connection in the RV as above).

    If you have the option--simply disconnecting the AC connection from your RV and pulling the cord back 6+ feet from the RV when lightning is forecast (and you don't need the AC power) is also a good option to reduce the risk of damage to your devices.
    Also, does the panel and battery assembly that produces the power need to be grounded separately?

    The battery does not need to be grounded to work correctly...

    You only need to ground the metal framework/panel frames against lightning strikes. And even then, that is not clearly the best solution. Just grounding the metal frame of the panels and let everything else float is another theory.

    The end result of grounding for safety is, where you use the power (inside the RV) that all metal components/wiring never become energized with respect to each other. Grounding everything at the RV (with or without a ground rod) is the first step (in a lightning region). Being inside a metal box is one of the safest placed to be.

    A couple threads about Lightning:

    Off Grid Grounding Technique?
    Another Question, this time about Lightning

    Note, the above are discussions, not a do A, B, and C--and you will be "safe". There probably is no such thing with lightning. Several different techniques are discussed--and a few of those posters even have experience with lightning. :cool:

    And our host's consolidated FAQ page:

    www.windsun.com
    Lightning Protection for PV Systems

    From other past posts here, Windsun (admin/owner of NAWS), he said that most of lighting induced failures he saw were in the Inverters' AC output section.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • scrubjaysnest
    scrubjaysnest Solar Expert Posts: 175 ✭✭✭
    Re: RV Battery System

    You might also check the electrical codes in your area. The usual code is ground the green at the source, ground the neutral, white, at the source. Attache the green to the frame but not the neutral. Your inverter may have different instructions though. As for the disconnect the cord for lighting. Did that once at both the RV and the house. The lighting strike blew a chunk out of the porch wall and the concrete pad the RV was sitting on. The cord was toast. My suggestion is roll the cord up after unplugging and put it away.
  • Tom Cleary
    Tom Cleary Solar Expert Posts: 37
    Re: RV Battery System

    Thanks for the help. Your message was clear and helpful in distinguishing between the two different ways of grounding a solar array, grounding it against lightning hazard versus shock hazard. I'd like to take the two types one at a time, with lightning first.

    Disconnecting the ac cord and moving it and the powerstrip 6 feet back from the RV during a thunderstorm is a good option. There will usually be warning of lightning storms -- and I definitely will remember to move the equipment. Thanks for the tips about grounding the pv/battery array with ground rods. It is a possibility that I will keep in mind as I do dry camp on private property and could have the option of doing that.

    You asked the question whether I am more concerned about shock hazards than lightning hazards, and my answer has to be 'yes,' mainly because lightning is rare where i live. For electrical safety against shock hazard, I was wondering about grounding the extension cord and powerstrip in the van.

    Is it true that if you ground your solar system properly and run a 3 wire extension cord to your camper, that that will ground everything to the camper chassis assuming that the electrical system in your trailer is grounded to the chassis? Is it necessary for my purposes to wire a powerstrip to RV chassis?

    Thanks again, as always.
    Tom
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: RV Battery System
    Tom Cleary wrote: »
    Disconnecting the ac cord and moving it and the powerstrip 6 feet back from the RV during a thunderstorm is a good option.

    6' was just a suggestion--A lightning strike that just went through a couple miles of air is not going to be slowed down much by 6 extra feet. Obviously, the further away, the better (assuming a lightning strike on your array). But since the cord is not inside your RV--the risk is dramatically reduced (metal RV is like a Faraday Cage).
    You asked the question whether I am more concerned about shock hazards than lightning hazards, and my answer has to be 'yes,' mainly because lightning is rare where i live. For electrical safety against shock hazard, I was wondering about grounding the extension cord and powerstrip in the van.

    Do you ground your van when you use an extension cord at home (working on van, charging battery, etc.)? Probably not.

    1) Excluding the lightning issue--the reasons not to ground:
    • Your MS 300 watts TSW inverter has a fully isolated output (should be ~2,000 VAC worth of isolation). Basically, touching any one lead--you cannot get shocked. More or less like a 12 volt battery... You can touch one post with your finger, metal, etc. and there will not be any current flow. You must touch both leads to get current flow.
    • If all of your AC equipment is in good shape, not permanently mounted, and either two or three prong plugs--The equipment itself is not supposed to expose the user to electrical shock hazards--So, should not be a general shock hazard (combined with above. The devices (if of modern vintage) should also be tested when new at the factory to ~2,000 volts AC (HiPot testing).
    • If either L1 or L2 become shorted to metal in the van--there will still be no current flow (isolated transformer output from TSW inverter).
    2) Reasons to think about grounding at the Van chassis (ground green wire of inverter output to van chassis).
    • Classic grounding scheme. Keeps PV equipment and inverter chassis all at the same potential and reducing the chance of static build up between PV system and your 120 VAC power strip in the van. More of an issue if lightning is possible in the area, or if there was a tall antenna mast connected to the PV array (static charge build up).
    • If you don't disconnect the AC plug from the van, then it is bit safer to have the Green Wire grounded to the body of the van (direct much of the energy to the outside chassis of the van instead of bringing it inside.
    • Remember lightning is a lot of energy--a direct hit--probably nothing you can do (remember old warnings of not using a phone or TV during a lightning storm).
    Tying Green Wire to Van and "Neutral" wire to Earth Ground (at Inverter tie to ground rod if fixed installation):
    • Classic ground technique (confirms to NEC Code if green wire/neutral wire is tied to earth ground too.
    • Better lightning protection. Get a power strip with surge suppressors or add AC surge suppressors (like this one) to your "Hot Wire".
    • Probably Over Kill and unneeded unless you are making a "fixed home" type situation.
    • With this type of grounding (green, white, earth rod)--You can then use a GFI equipped extension cord. Very nice if you are working out in the rain, near a pond, etc. If there is AC return current that "leaks to ground" (i.e, through you to a puddle) the GFI will turn off the AC power.
    Now--what would I do (discussion, make your one decisions)...

    If you don't ground the AC Neutral (option 1 or 2 above), you cannot get shocked by stepping into a puddle because there is no electrical connect between the puddle (earth) and the inverter.

    Option 3) grounding inverter/neutral now creates the possibility of you getting shocked. The L2 black lead of the inverter is at 120 VAC relative to the "earth" (dirt). So, now if you want shock protection, you need a GFI (or even an isolation transformer) to work out in the rain/wet.

    Ether is a valid safety technique... Option 1 is perfectly safe, except you have to test the system once in a while to make sure the AC output is still floating (pinched AC lead to a metal clamp can incidentally create a short/ground reference--and you would not know it).

    Option 3 is good because if the black wire insulation fails, the inverter will short out to neutral. If you get current flow to earth ground (or grounded metal) the GFI will sense and trip--preventing hazardous shock. Plus there is a test button on the GFI to make sure it is working correctly.

    If this was a purely portable setup and lightning is not a big concern... Don't bother grounding anything.

    If you want a reasonably reliable / safe setup... Get a grounded metal power strip and attach that to a metal wall (or heavy green wire to van chassis). Wire to external weather proof plug on the outside of the van. Drive a ground rod and or bury some bare cable at the PV array tided to the solar panel frame and metal framework.
    Is it true that if you ground your solar system properly and run a 3 wire extension cord to your camper, that that will ground everything to the camper chassis assuming that the electrical system in your trailer is grounded to the chassis? Is it necessary for my purposes to wire a powerstrip to RV chassis?

    Depends on the Van is wired. The Van chassis would only be grounded if somebody made the electrical connection to the green wire.

    If this was just an extension cord and power strip--then, unless it was a metal power strip bolted to the van--The van would not be electrically connected to anything.

    In general, the Neutral wire will not be grounded inside the van. It will be grounded by the House (at the main panel, neutral to earth ground).

    You would not want to ground the Neutral inside the van. That would be in conflict if you ever plugged into Grid Power (NEC grounds the neutral at the main panel near the meter).

    Using a GFI breaker/extension on a floating setup (option 1) will not normally do anything useful (hot to ground current flow possible if everyhting working correctly.).

    If you where to green wire to neutral wire connect inside the van AC wiring box (ground reference neutral)--that would cause problems if you plugged your van in to utility power--You would have a ground loop and if there was a GFI to the home power--you would probably have GFI trips.

    Sorry for all of the typing... Grounding for safety can be a fairly complex issue.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Tom Cleary
    Tom Cleary Solar Expert Posts: 37
    Re: RV Battery System

    Hi Bill:
    Your description of the problem of grounding electrical systems has been great ... breaking it down in terms of shock versus lightning strike protection. I wrote some individual responses to the points, and even though overall I basically decided not to ground at this time, I wanted to check my understanding in case I missed something important. It took me awhile to absorb all of the information given, sorry it's been a few days since I posted.

    *

    Disconnecting the ac cord and moving it and the powerstrip 6 feet back from the RV during a thunderstorm is a good option. 6' was just a suggestion--A lightning strike that just went through a couple miles of air is not going to be slowed down much by 6 extra feet. Obviously, the further away, the better (assuming a lightning strike on your array). But since the cord is not inside your RV--the risk is dramatically reduced (metal RV is like a Faraday Cage)

    *

    Thanks for the advice about keeping the pv/battery array away from the van. I was considering storing the pv/battery array inside the camper van during thunder storms, but it sounds like this is the worst thing a person could do. I didn't know about Faraday cage effects.

    *

    Do you ground your van when you use an extension cord at home (working on van, charging battery, etc.)? Probably not.


    *

    I haven't done that no, and it does make sense when put that way ... guess I will not attempt to ground the system to the camper van for reasons of shock.

    *

    1) Excluding the lightning issue--the reasons not to ground:

    Your MS 300 watts TSW inverter has a fully isolated output (should be ~2,000 VAC worth of isolation). Basically, touching any one lead--you cannot get shocked. More or less like a 12 volt battery... You can touch one post with your finger, metal, etc. and there will not be any current flow. You must touch both leads to get current flow.


    *

    Basically, don't complete the electricity loop with one's fingers or metal, etc..

    *

    If all of your AC equipment is in good shape, not permanently mounted, and either two or three prong plugs--The equipment itself is not supposed to expose the user to electrical shock hazards--So, should not be a general shock hazard (combined with above. The devices (if of modern vintage) should also be tested when new at the factory to ~2,000 volts AC (HiPot testing).

    *

    All of my components will be new, from NAWS warehouses.

    *

    If either L1 or L2 become shorted to metal in the van--there will still be no current flow (isolated transformer output from TSW inverter).


    *

    I am not sure what L1 or L2 mean, but since there will still be no current flow even if they do short, I take it that precautions do not have to be taken against their shorting.

    *

    2) Reasons to think about grounding at the Van chassis (ground green wire of inverter output to van chassis).

    Classic grounding scheme. Keeps PV equipment and inverter chassis all at the same potential and reducing the chance of static build up between PV system and your 120 VAC power strip in the van.


    *

    Okay, I get the idea of grounding the van chassis against static electricity discharges. In southern california, where I live, the weather is dry as can be, and even just putting on a sweater can invite a drastic discharge of static electricity. For reasons you mentioned, static electricity wouldn't seem to be a huge problem though. My van doesn't have a tall antenna mast connected to the PV array, for example. Maybe too a problem with static electricity discharges will be something that will become apparent over time, much like day to day living in southern california teaches me to put on sweaters slowly in the winter time when the weather is especially dry. So I don't have to take precautions against this type of electrical discharge, I am thinking anyway, until static discharges seem to be occurring. Is that correct?

    *

    More of an issue if lightning is possible in the area, or if there was a tall antenna mast connected to the PV array (static charge build up).


    *

    Lightning discharges here are unusual. We don't get a lot of lightning in So California, we don't get a lot of storms at all usually (our recent record setting winter rain storm not withstanding.) I will keep on top of the lightning situations where I travel, however.

    *

    If you don't disconnect the AC plug from the van, then it is bit safer to have the Green Wire grounded to the body of the van (direct much of the energy to the outside chassis of the van instead of bringing it inside.

    Remember lightning is a lot of energy--a direct hit--probably nothing you can do (remember old warnings of not using a phone or TV during a lightning storm).


    *

    I definitely get your meaning although with my skeleton rig I won't have either device; nevertheless, it sounds like a good guideline to follow. During lightning storms I will disconnect the AC devices and powerstrips.

    *

    Tying Green Wire to Van and "Neutral" wire to Earth Ground (at Inverter tie to ground rod if fixed installation):

    Classic ground technique (confirms to NEC Code if green wire/neutral wire is tied to earth ground too.

    Better lightning protection. Get a power strip with surge suppressors or add AC surge suppressors (like this one) to your "Hot Wire".

    Probably Over Kill and unneeded unless you are making a "fixed home" type situation.

    With this type of grounding (green, white, earth rod)--You can then use a GFI equipped extension cord. Very nice if you are working out in the rain, near a pond, etc. If there is AC return current that "leaks to ground" (i.e, through you to a puddle) the GFI will turn off the AC power.

    *

    In the event I do wind up having a situation this describes, like working in the rain with electricity from the camper van power source, I will install GFI. At this point I don't envision that, but it's good to know.

    *

    Now--what would I do (discussion, make your one decisions)...

    If you don't ground the AC Neutral (option 1 or 2 above), you cannot get shocked by stepping into a puddle because there is no electrical connect between the puddle (earth) and the inverter.

    Option 3) grounding inverter/neutral now creates the possibility of you getting shocked. The L2 black lead of the inverter is at 120 VAC relative to the "earth" (dirt). So, now if you want shock protection, you need a GFI (or even an isolation transformer) to work out in the rain/wet.

    Ether is a valid safety technique... Option 1 is perfectly safe, except you have to test the system once in a while to make sure the AC output is still floating (pinched AC lead to a metal clamp can incidentally create a short/ground reference--and you would not know it).

    Option 3 is good because if the black wire insulation fails, the inverter will short out to neutral. If you get current flow to earth ground (or grounded metal) the GFI will sense and trip--preventing hazardous shock. Plus there is a test button on the GFI to make sure it is working correctly.

    If this was a purely portable setup and lightning is not a big concern... Don't bother grounding anything.


    If you want a reasonably reliable / safe setup... Get a grounded metal power strip and attach that to a metal wall (or heavy green wire to van chassis). Wire to external weather proof plug on the outside of the van. Drive a ground rod and or bury some bare cable at the PV array tided to the solar panel frame and metal framework.


    *

    I like this idea, it makes intuitive sense to me to ground the solar array with a ground rod in this way, and also to ground the power strip with a heavy green wire to the van chassis. I will work on these ideas once I get my solar rig up and running.

    ***

    Grounding certainly is a complex issue: thanks for breaking it down for me! I hope other readers get as much help (and peace of mind) out of this discussion as I have. Hope I am not repeating myself, but can't say it enough, I appreciate your input very much.

    Can I ask another question? Would it be okay to wire the three different loads, the controller, the monitor, and the inverter as pictured, between the positive terminal of one battery and the negative terminal of the other battery, or would a bus bar work better in this instance? If a busbar would be better, do you have a recommendation for type of busbar that would work best?

    I am still working on my system, but almost there, thanks for the advice. Best luck in the new year.

    Thanks,
    Tom
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: RV Battery System
    Tom Cleary wrote: »
    Hi Bill:
    Your description of the problem of grounding electrical systems has been great ... breaking it down in terms of shock versus lightning strike protection.
    You are very welcome Tom--I will try to keep these answers on the short side to avoid being repetitive--please ask if I am confusing (or confused:roll:)
    Thanks for the advice about keeping the pv/battery array away from the van. I was considering storing the pv/battery array inside the camper van during thunder storms, but it sounds like this is the worst thing a person could do. I didn't know about Faraday cage effects.

    Don't get me wrong here--Storing inside your van (Faraday Cage) would actually be a very safe thing to do (excluding the issue of battery gassing, acid, and possibly of electrical shorts).

    I understood that your Array needed to be 100'+ away... Your van+array (plus the distance across the ground which also carries lightning strike current) just makes you a bigger target. I was recommending disconnecting the 120 VAC extension cord from your van when lightning is in the area to avoid a strike near the array+inverter from bringing energy into your van through the extension cord.

    It is a game of chance. People's power lines get hit near their home all the time (and frequently they have to replace appliances when that happens). It is just reducing what, hopefully (in your area) is already a smallish risk, to even less.
    Do you ground your van when you use an extension cord at home (working on van, charging battery, etc.)? Probably not.

    Again, the risk catagory... You probably don't work on the van in a lightning storm either. With you living in the van, that is your "safe spot" and the exterior cord is what "could" bring the energy from outside into your van.

    1) Excluding the lightning issue--the reasons not to ground:

    Your MS 300 watts TSW inverter has a fully isolated output (should be ~2,000 VAC worth of isolation). Basically, touching any one lead--you cannot get shocked. More or less like a 12 volt battery... You can touch one post with your finger, metal, etc. and there will not be any current flow. You must touch both leads to get current flow.

    All of my components will be new, from NAWS warehouses.

    Nice to support our host :D. And please ask them questions too... They have been in this game much longer than I with much more experience too.
    I am not sure what L1 or L2 mean, but since there will still be no current flow even if they do short, I take it that precautions do not have to be taken against their shorting.

    The "power lines" (typically the black and white wires) from the inverter (as opposed to the green safety ground wire).

    Normally, we would say Hot and Neutral--but Neutral is only created when one side of an inverter (or transformer) is grounded to earth ground.

    Sol I was just trying to be generic talking about your Line 1 and Line 2 power leads from your inverter.
    Okay, I get the idea of grounding the van chassis against static electricity discharges. In southern California, where I live, the weather is dry as can be, and even just putting on a sweater can invite a drastic discharge of static electricity. For reasons you mentioned, static electricity wouldn't seem to be a huge problem though. My van doesn't have a tall antenna mast connected to the PV array, for example. Maybe too a problem with static electricity discharges will be something that will become apparent over time, much like day to day living in southern california teaches me to put on sweaters slowly in the winter time when the weather is especially dry. So I don't have to take precautions against this type of electrical discharge, I am thinking anyway, until static discharges seem to be occurring. Is that correct?

    Yep--There is actually a ~100-500 volt per meter DC field for the Earth--and so if you had an (for example) ungrounded CB Radio antenna+tower 30 feet or more in the air--You can get hundreds or even thousands of volts of static charge on metal. The current is very small--but it slowly charges the tower/antenna like an capacitor--just waiting to bite.
    In the event I do wind up having a situation this describes, like working in the rain with electricity from the camper van power source, I will install GFI. At this point I don't envision that, but it's good to know.

    With an isolated inverter (floating, no ground neutral)--adding a GFI is a belt and suspenders approach. Nothing wrong, and can save your life...
    I like this idea, it makes intuitive sense to me to ground the solar array with a ground rod in this way, and also to ground the power strip with a heavy green wire to the van chassis. I will work on these ideas once I get my solar rig up and running.

    Just remember that entering or leaving the van with lightning activity is the dangerous time for you... Either in the van or away from tall objects is better (so standing next the van in a lighting storm is not good).
    Grounding certainly is a complex issue: thanks for breaking it down for me!
    I hope other readers get as much help (and peace of mind) out of this discussion as I have. Hope I am not repeating myself, but can't say it enough, I appreciate your input very much.
    Again, my pleasure.

    And remember, if there is every a close or direct strike--you probably will be buying, at least, a new inverter and probably some appliances. Just too much energy / cost to make it bullet proof--just safe as practical is what we are aiming for.
    Can I ask another question? Would it be okay to wire the three different loads, the controller, the monitor, and the inverter as pictured, between the positive terminal of one battery and the negative terminal of the other battery, or would a bus bar work better in this instance? If a busbar would be better, do you have a recommendation for type of busbar that would work best?

    For your use the bolts on the battery bank or a bus bar are fine--a bus bar is just a convenient hunk of metal to tie your electrical connection to:

    wind-sun_2137_5403217


    You have already wired your battery bank (if some parallel batteries) for optimum current sharing (batteries each each carry ~1/number of batteries worth of current). So all of your charging sources and loads should "attach to the same point". (don't put your charger in one place and your loads in another--it should not be needed).

    Take care,
    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Tom Cleary
    Tom Cleary Solar Expert Posts: 37
    Re: RV Battery System

    Hi Bill:

    Your description of the problem of grounding electrical systems has been great ...

    *

    welcome Tom--I will try to keep these answers on the short side to avoid being repetitive--please ask if I am confusing (or confused)

    *

    Thanks for the advice about keeping the pv/battery array away from the van. I was considering storing the pv/battery array inside the camper van during thunder storms, but it sounds like this is the worst thing a person could do. I didn't know about Faraday cage effects.

    *

    Don't get me wrong here--Storing inside your van (Faraday Cage) would actually be a very safe thing to do (excluding the issue of battery gassing, acid, and possibly of electrical shorts).

    *

    well, thanks for the correction, even though it is possible to keep it in the van, forgot about the gassing, the solar array doesn't seem like something you want to share space in a thunderstorm with . have to find a place under a tarp outside for it.

    *

    I understood that your Array needed to be 100'+ away... Your van+array (plus the distance across the ground which also carries lightning strike current) just makes you a bigger target. I was recommending disconnecting the 120 VAC extension cord from your van when lightning is in the area to avoid a strike near the array+inverter from bringing energy into your van through the extension cord.

    It is a game of chance. People's power lines get hit near their home all the time (and frequently they have to replace appliances when that happens). It is just reducing what, hopefully (in your area) is already a smallish risk, to even less.

    *

    Ok, that makes sense. Did not know that a wire spread over a distance connecting two objects enlarges the risk factor. Disconnecting the 120 VAC extension cord seems like good protection.

    *

    Do you ground your van when you use an extension cord at home (working on van, charging battery, etc.)? Probably not. Again, the risk catagory... You probably don't work on the van in a lightning storm either. With you living in the van, that is your "safe spot" and the exterior cord is what "could" bring the energy from outside into your van.

    1) Excluding the lightning issue--the reasons not to ground:

    Your MS 300 watts TSW inverter has a fully isolated output (should be ~2,000 VAC worth of isolation). Basically, touching any one lead--you cannot get shocked. More or less like a 12 volt battery... You can touch one post with your finger, metal, etc. and there will not be any current flow. You must touch both leads to get current flow.

    *

    All of my components will be new, from NAWS warehouses.


    *

    Nice to support our host . And please ask them questions too... They have been in this game much longer than I with much more experience too.

    *

    I am not sure what L1 or L2 mean, but since there will still be no current flow even if they do short, I take it that precautions do not have to be taken against their shorting.

    *

    The "power lines" (typically the black and white wires) from the inverter (as opposed to the green safety ground wire). Normally, we would say Hot and Neutral--but Neutral is only created when one side of an inverter (or transformer) is grounded to earth ground. So I was just trying to be generic talking about your Line 1 and Line 2 power leads from your inverter.

    *

    Thanks for explaining the terminology, makes sense now.

    *

    Okay, I get the idea of grounding the van chassis against static electricity discharges. In southern California, where I live, the weather is dry as can be, and even just putting on a sweater can invite a drastic discharge of static electricity. For reasons you mentioned, static electricity wouldn't seem to be a huge problem though. My van doesn't have a tall antenna mast connected to the PV array, for example. Maybe too a problem with static electricity discharges will be something that will become apparent over time, much like day to day living in southern california teaches me to put on sweaters slowly in the winter time when the weather is especially dry. So I don't have to take precautions against this type of electrical discharge, I am thinking anyway, until static discharges seem to be occurring. Is that correct?

    *

    Yep--There is actually a 100-500 volt per meter DC field for the Earth--and so if you had an (for example) ungrounded CB Radio antenna+tower 30 feet or more in the air--You can get hundreds or even thousands of volts of static charge on metal. The current is very small--but it slowly charges the tower/antenna like an capacitor--just waiting to bite.

    *

    So that's why a tower of metal can generate a shock, it could be charged by the ground itself and develop its own voltage potential waiting to discharge. a camper van on the other hand presumably wouldn't be charged because the only contact with the ground is through the tires, which would prevent that from happening.

    *

    In the event I do wind up having a situation this describes, like working in the rain with electricity from the camper van power source, I will install GFI. At this point I don't envision that, but it's good to know. With an isolated inverter (floating, no ground neutral)--adding a GFI is a belt and suspenders approach. Nothing wrong, and can save your life...

    *

    It makes sense to ground the solar array with a ground rod in this way, and also to ground the power strip with a heavy green wire to the van chassis. I will work on these ideas once I get my solar rig up and running.

    *

    Just remember that entering or leaving the van with lightning activity is the dangerous time for you... Either in the van or away from tall objects is better (so standing next the van in a lighting storm is not good).

    *

    Ok. Got to be vigilant in thunder storms when you see them flashing, stay out of the open, best place sounds like it's inside the van, at least if there aren't any buildings around.

    *

    Grounding certainly is a complex issue: thanks for breaking it down for me! I hope other readers get as much help (and peace of mind) out of this discussion as I have. Hope I am not repeating myself, but can't say it enough, I appreciate your input very much.

    *

    Again, my pleasure.

    *

    And remember, if there is every a close or direct strike--you probably will be buying, at least, a new inverter and probably some appliances. Just too much energy / cost to make it bullet proof--just safe as practical is what we are aiming for.

    *

    I don't mind a bit of risk to the equipment. The main thing is to avoid catastrophe, and thanks for outlining a program for that here.

    *

    Can I ask another question? Would it be okay to wire the three different loads, the controller, the monitor, and the inverter as pictured, between the positive terminal of one battery and the negative terminal of the other battery, or would a bus bar work better in this instance? If a busbar would be better, do you have a recommendation for type of busbar that would work best?

    *

    For your use the bolts on the battery bank or a bus bar are fine--a bus bar is just a convenient hunk of metal to tie your electrical connection to> You have already wired your battery bank (if some parallel batteries) for optimum current sharing (batteries each each carry ~1/number of batteries worth of current). So all of your charging sources and loads should "attach to the same point". (don't put your charger in one place and your loads in another--it should not be needed).

    *

    Makes sense. I will hold off on the busbar.

    *

    Can I ask another question? I had a question about your earlier feedback about connecting the pv panels. My idea about having two Kyocera 185s was to connect them in parallel, then connect them to the charge controller. The idea is to convert from 24 volt to 12 volt by connecting them to the Rogue MPPT controller, then go to the battery as 12 volt. Is there a problem with connecting them in parallel?

    *

    Thanks again, seems like i keep saying this, but doesn't hurt to repeat myself on this point it seems. Being able to construct the array seems a lot less problematic, thanks to feedback from this forum and yourself. Best,

    Tom
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: RV Battery System

    Tom,
    So that's why a tower of metal can generate a shock, it could be charged by the ground itself and develop its own voltage potential waiting to discharge. a camper van on the other hand presumably wouldn't be charged because the only contact with the ground is through the tires, which would prevent that from happening.
    The (insulated) tower/object is charged by the static electrical charge in the air "relative" to the Earth/Ground. Connecting the tower/antenna to ground (even through a resistor) bleeds the very small charging currents to ground--so you will not get a static charge.

    The Van tires are rubber and very poor conductors of electricity. So the van can get a charge and shock you if you grab the door handle. When I was a kid, it was not unusual for people to have a couple straps on the bumper that would drag on the ground (and a bridge toll both with a couple of springs that would touch the bottom of the car to ground static charges).

    Most (all?) modern vehicle tires are now compounded with something to make them slightly conductive to bleed off the static charge of a car. Also reduces the chance of a static charge causing a fuel take fire when you touch the gas pump nozzle to your tank when fueling.
    Can I ask another question? I had a question about your earlier feedback about connecting the pv panels. My idea about having two Kyocera 185s was to connect them in parallel, then connect them to the charge controller. The idea is to convert from 24 volt to 12 volt by connecting them to the Rogue MPPT controller, then go to the battery as 12 volt. Is there a problem with connecting them in parallel?
    The Kyocera 185 watt panels have (double check the specifications to make sure this is the rating of your exact model):
    • Voltage at Max Power (Vmpp) 23.6
    • Current at Max Power (Impp) 7.84 Amps
    • Open Circuit Voltage (Voc) 29.
    • Short Circuit Current (Isc) 8.35 Amps
    With these panels, your only option with the Rogue is to place these panels in parallel. Their Voc voltage of 29 volts would, in cold weather, exceed the 60 VDC maximum input voltage of the Rogue controller if you connected the two panels in series.

    With these panels and the Rogue controller, they will work fine for your in parallel. The only limitation I see is that you could not wire these panels in series if you ever wanted to use a 24 volt battery bank with this Panel+Rogue combination.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset