Off Grid RV System

BB.

Re: Off Grid RV System

You can use the RV frame for your negative lead (heaven knows that pretty much every car/truck out there does that).

However, it would be nice to carry both +/- leads from the controllers (and inverters) directly to the battery bank. Usually a bit more reliable and you 'know" the current capabilities of your wiring. Frame connections for electrical use are a bit hit and miss (i.e., body to frame usually has some sort of jumper wire to get around rubber vibration insulation, frame and body vs uni-body construction, etc.).

Best is to move the Charge controller(s) and AC inverters close to the battery bank (or at least the larger battery in a distrbuted bank). If you have a distributed battery bank--You should run heavy cables between the battery locations to keep voltage drop low.

Ideally, you want ~0.05 to 0.10 volt maximum drop from charge controller to battery bank (12 volt bank)... For AC Inverter, you probably want a maximum of ~0.5 volt drop from battery bank to AC inverter at full load (again 12 volt battery bus system).

If you start running lots of battery cable around the chassis--Make sure cables cannot rub/be cut on sharp metal and I would put some sort of fuse/breaker on each wire where it leaves the battery bank (you don't want 10' of red hot wire buried in your RV's walls).

At a minimum, these BlueSea fuse holders are really small and easy to install (compared to a large circuit breaker+panel):

Attachment not found.

Remember to buy a few extra fuses for spares at the RV.

-Bill

Chris

Re: Off Grid RV System

I calculated having 2% drop with the 6 awg but my real concern was using the frame to carry the neg from the battery, is this acceptable? or are you saying that 15ft is just to far and I should move it closer?

Chris

Re: Off Grid RV System

BB. wrote: »

You can use the RV frame for your negative lead (heaven knows that pretty much every car/truck out there does that).

However, it would be nice to carry both +/- leads from the controllers (and inverters) directly to the battery bank. Usually a bit more reliable and you 'know" the current capabilities of your wiring. Frame connections for electrical use are a bit hit and miss (i.e., body to frame usually has some sort of jumper wire to get around rubber vibration insulation, frame and body vs uni-body construction, etc.).

Best is to move the Charge controller(s) and AC inverters close to the battery bank (or at least the larger battery in a distrbuted bank). If you have a distributed battery bank--You should run heavy cables between the battery locations to keep voltage drop low.

Ideally, you want ~0.05 to 0.10 volt maximum drop from charge controller to battery bank (12 volt bank)... For AC Inverter, you probably want a maximum of ~0.5 volt drop from battery bank to AC inverter at full load (again 12 volt battery bus system).

If you start running lots of battery cable around the chassis--Make sure cables cannot rub/be cut on sharp metal and I would put some sort of fuse/breaker on each wire where it leaves the battery bank (you don't want 10' of red hot wire buried in your RV's walls).

At a minimum, these BlueSea fuse holders are really small and easy to install (compared to a large circuit breaker+panel):

Attachment not found.

Remember to buy a few extra fuses for spares at the RV.

-Bill

Ok thanx Bill,

I have been considering moving the CC closer (aprox 5ft of wire need) into the front cubby where my inverter is located.....but was just dreading having to poke more holes threw my roof and closet to run it all.

BB.

Re: Off Grid RV System

It is hard to know if the "frame" is acceptable or not... If your ground/return wires are attached to the main rails of the vehicle--Then as long as the connections are clean/sealed against weather/water/road salt--Probably OK.

What can happen is that if the current takes paths that you are not expecting (i.e., through door hinges, bearings, u-joints/drive shaft, etc.)--You can end up with things needed repairs because of the electricity flowing in places where it should not--Or if you use a "large" AC inverter--You have much higher current flow vs what the original chassis builder intended (remember those jumper cables between engine block and car chassis, etc.).

Installing your own return cabling, sized to your loads, and there will be less chances for surprises.

-Bill

westbranch

Re: Off Grid RV System

Chris, does your trailer have a vent stack for waste heat from your fridge, if so you can use that for runnning the wires through, rather than drill a new hole in the roof.

The other thing about using the frame for a conducting material is the 'continuing quality' of the connection point to the frame, it can deteriorate with rust or other corrosion buildup. Mechanic friend always says, if you have a poor (high resistance) connection or intermittent connection, ALWAYS start with checking the ground and work back from there.

cheers.

Chris

Re: Off Grid RV System

westbranch wrote: »

Chris, does your trailer have a vent stack for waste heat from your fridge, if so you can use that for runnning the wires through, rather than drill a new hole in the roof.

The other thing about using the frame for a conducting material is the 'continuing quality' of the connection point to the frame, it can deteriorate with rust or other corrosion buildup. Mechanic friend always says, if you have a poor (high resistance) connection or intermittent connection, ALWAYS start with checking the ground and work back from there.

cheers.

Right now I have the wires from the panels routed down the fridge vent and my converter is conveniently mounted directly below the fridge. This made for very easy and quick install as the converter had spare connections to the 12 volt battery line built right in. But my trailer is a 34ft with the fridge apox 1/2 way......batteries are mounted on the tongue aprox 15ft away.

I plan to add another 2 panels and the MPPT in the spring...so 400 watt X .8 = 320 watt 320/14.8 volt = give or take 22-25 amp. Sound bout right?

So....If ran a dedicated neg just for the CC using 6 awg I should be fine then right?

Plan B would be to drill thew the roof at the front of the trailer run the panel feed down threw a closet into a pass threw cubby were my inverter is mounted. could I then wire my CC to the 2/O wires feeding the inverter or would I still need to drill more holes to run separate lines to the batteries?

sorry bout the rambling post LOL

westbranch

Re: Off Grid RV System

re: the MPPT, yes those amps are about right, say 20 A to be conservative ..

Q?: this is a permanent trailer site, right? If so why not move the battery bank to a new home , in its own box nearer the center of the trailer?

Chris

Re: Off Grid RV System

Honestly.......I never even considered that LOL

I think I have about 3ft clearance from the ground to the belly of the trailer (between the frame rails) I could mount them in say a plastic tote sitting on the ground....Hmmmmm

My only hicup would be my super expensive wires to the inverter, I have aprox 3ft of cable running forward from were they drop out....so I would only be able to reverse them buying me 6ft closer making the distance 9ft from batts to CC. Unless I re-located my inverter which I REALLY don't want to do (the wife would shoot me as I had to cut holes in a cabinet to mount the remote and a dedicated plug.

westbranch

Re: Off Grid RV System

Check it out on the voltage drop calculator, every foot adds up.... the less wire in total the better.

Chris

Re: Off Grid RV System

BY my calculations.... moving the batteries back the 6 ft then using #6 between the CC and the batteries, #10 down from the panels at 36 volt..... total system loss should be 1.5%.

westbranch

Re: Off Grid RV System

That is a good number for loss. What happens with #4 wire? and #8 for comparison sake.

Chris

Re: Off Grid RV System

westbranch wrote: »

That is a good number for loss. What happens with #4 wire? and #8 for comparison sake.

#8 would be 1.99% and #4 would be 1.04% and the #6 1.41%

Chris

Re: Off Grid RV System

ok.....I'm a little confused by the info about how to enter your lengths, it says
"When entering wire length use two way length. How long is each wire from the panel to the combiner box both ways? Same for all other wire runs."

does that mean that my 9ft to the batts should be entered as 18?

westbranch

Re: Off Grid RV System

YES! the calculator needs to know the full 'return length' from source back to source, ie if PV panel is 7 feet away from CC then use 14 feet for distance as each segment of wire has losses.
Looks like the losses will be double +- then. you want to be below 3% if possible.

Chris

Re: Off Grid RV System

Well.....I don't feel nearly as warm and fuzzy now LOL

re-entered everything using the #6 2.82% that's getting pretty close to the 3% so, #4 would drop it too 2.09% is that worth the extra expense?

westbranch

Re: Off Grid RV System

It will probably depend on what you can get locally. I found some NOS #2 ga. at a local welding supply shop, that was only a penny a foot more than #4 at another supplier, best to shop around. flea-bay can be good too sometimes... local prices can change daily too, same supplier Fri to Monday price change...

Rybren

Re: Off Grid RV System

Chris,

Is there a Princess Auto near by? They've good decent prices on welding wire.

Chris

Re: Off Grid RV System

Rybren wrote: »

Chris,

Is there a Princess Auto near by? They've good decent prices on welding wire.

No, the closest is about 3 hours away......but I think they have online ordering. I'll have to check them out.

Thanx, Jerry

Chris

Re: Off Grid RV System

Just throwing around some idea's here.

If I were to move my CC into the compartment with my inverter, can I hook it to the terminals on my inverter instead to running another set of wires threw the floor to the batteries? if so....would I just fuse it from that point?

westbranch

Re: Off Grid RV System

close ... but no banana... You can use buss bars as the common connection for all your cables CC, Inverter, battery. Think of the old Peace symbol, the center of all the legs is the buss, one +, one -, the connection can also be a bolt or other method of joining each leg to the others.

CB protection needed between Battery and [ CC and Inverter] so in battery line.

make sense?

BB.

Re: Off Grid RV System

I would highly suggest that you "home run" the wires from major current sources/loads back to the battery... I would avoid "sharing" runs.

I can go into all of the possible issues--But to sum it up, the equipment usually runs better (or at least just as good) and there are better understood answers to safety questions.

-Bill

Chris

Re: Off Grid RV System

I think I'm getting what you mean.......so if I were to mount a piece of plywood in the cubby with 2 bolts in threw it....attach my existing inverter feed wires (2/O) add new say 1ft wires to the inverter and separate ones to the CC stacked on top? or do they make a screw clamp type busbar that will except 2/O? the only ones I found said 1/O..........and not trying to a pain....but what is the difference if it's on the inverter?

Chris

Re: Off Grid RV System

BB. wrote: »

I would highly suggest that you "home run" the wires from major current sources/loads back to the battery... I would avoid "sharing" runs.

I can go into all of the possible issues--But to sum it up, the equipment usually runs better (or at least just as good) and there are better understood answers to safety questions.

-Bill

So....are you saying not to use a busbar and to run separate lines all to the battery? the terminals would have a hole mess of connections on them

Chris

Re: Off Grid RV System

Dreaming of summer today, I shared these in a different thread but thought I'd post them here as well




Our flush outhouse under constrution

BB.

Re: Off Grid RV System

Chris wrote: »

So....are you saying not to use a busbar and to run separate lines all to the battery? the terminals would have a hole mess of connections on them

Not really... Yes, bus bars can be used to send power longer distances--But most people use insulated cable instead.

Bus bars around here are typically just chunks of copper or brass with drilled and tapped holes so a person can terminate all the cables in once, easy to attach, location.

Here are some examples of cable termination type bus bars that poster "2manytoyz" made:

http://2manytoyz.com/battbank.html

-Bill

Chris

Re: Off Grid RV System

BB. wrote: »

Not really... Yes, bus bars can be used to send power longer distances--But most people use insulated cable instead.

Bus bars around here are typically just chunks of copper or brass with drilled and tapped holes so a person can terminate all the cables in once, easy to attach, location.

Here are some examples of cable termination type bus bars that poster "2manytoyz" made:

http://2manytoyz.com/battbank.html

-Bill

So...this is what I'm contemplating

2/O wire from the batteries 5ft terminating in a cubby hole at the front of the trail using somthing like this
http://www.solar-electric.com/mnsbbn.html

well the neg side would go threw a shunt first, but all the electrical would be routed threw 2 of these.......are you saying this is a bad idea?

BB.

Re: Off Grid RV System

No--That is fine too... Note the shunt connection would be: Battery Negative, Shunt terminal A, Shunt Terminal B, Battery negative bus bar, negative leads to loads+chassis ground.

You want all the battery current to flow through the shunt (for battery monitor to account for all battery current).

What I am saying is to "avoid" battery cable to Inverter to Charge Controller A to charge controller B, etc. (daisy change connections of power leads between loads). The "noise" from the various heavy current devices (PWM current from charge controllers and AC inverter inputs) can sometimes confuse each other (i.e., battery charger may not quickly/fully charge battery bank because of shared noise from the AC inverter).

-Bill

Chris

Re: Off Grid RV System

It's been a wile, but just wanted to show some of the additions this year.

Finally got some new batteries!!
This are mounted under the trailer about 4" off the ground to keep them cool in the summer.

Just making cables up here


New SW Cotec inverter, Bussbars, shunt and WBjr. The big MS inverter is going to be removed this fall so the new inverter can be mounted in place.
Batteries are directly below this cubby so 2/0 wire coming up is only about 4ft long.


2 more panels on the roof so 4X100, and new aluminum angle iron adjustable racking.


Re-claimed pallet wood skirting.....had I know what a pain in the arse taking them apart was....not sure I would have gone the same rout......but all in all I think it turned out not bad.....kinda rustic looking

ILFE

Re: Off Grid RV System

Chris wrote: »

New SW Cotec inverter, Bussbars, shunt and WBjr. The big MS inverter is going to be removed this fall so the new inverter can be mounted in place.
Batteries are directly below this cubby so 2/0 wire coming up is only about 4ft long.

You run most all appliances and electronics off the inverters?

Will you be adding more panels any time soon?

Great photos. Thanks for sharing them.

Chris

Re: Off Grid RV System

well being an RV most most the appliances are either 12 volt or propane. So the inverters are for everything else.

I do plan to add another 2 panels.....but at the moment, my batteries are pretty much floating by noon daily........other then of course on cloudy days.
But comming into fall when we will be spending more eavnings inside watching TV we'll see how consumption goes.