Noob RV solar Install, looking for input

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jjv

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Joined
Nov 6, 2018
Posts
5
From a lot of lurking and reading, I have come to this proposed system and hoping for some input on configuration and quality of the brand names. Also, does anyone have a generic " System overview" wiring / component diagram of all those parts and connections that don't really come with any of the individual components. ?
I am a Commercial Electrician with experience building control panels, Motor Control , etc. But not much in the 12V world. Also looking for recommendations on the actual panels. I am thinking 800 watts worth of solar. The Install is for a 35' Toyhauler and a lot of Desert Dry-camping

Thanks in advance !


Qty 4 VMAX Xtreme Series 6V AGM Deep Cycle 235Ah 6V
   
Victron BMV-712 Battery Monitor

Victron MultiPlus Compact 12/2000/80-50 120V VE.Bus Inverter Charger

Victron SmartSolar MPPT 100/50 Solar Charge Controller 100V 50A with Bluetooth


 

PJ Stough

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Sep 20, 2009
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2,394
Location
Central Iowa
The amp hours of the batteries and the watts of the solar panels determine how much power you have available to use. With 705 amp hours of batteries you will have 300 to 350 amp hours available if the batteries are fully charged, and you are willing to run them down to about 50% state of charge. 

If you electrical needs are more, then you will need more watts of solar, and more amp hours of batteries.  That is why most people suggest that before you decide on total watts of solar and total amp hours of batteries, get a battery monitor to monitor you actual usage for a while, before deciding on a system.  Another alternative, is look at the power usage of what ever you might run, and multiply the power requirement times the number or hours you expect to use in a day.  This will give you some what of an estimate of your power needs.
 

Isaac-1

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Dec 3, 2016
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5,859
Location
SW Louisiana
Personally I would go with Trojan batteries if going with 6V agm's the cost is not much more, and Trojan is the brand name battery for electric  golf cart use, which is a similar discharge profile as deep cycle RV use.
 

breezie

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Apr 5, 2018
Posts
63
These guys installed a very expensive, but very impressive, super solar system. Strong enough to run their AC (at least in a test situation):

https://www.gonewiththewynns.com/off-grid-solar-rv-air-conditioning


 

jjv

Member
Joined
Nov 6, 2018
Posts
5
breezie said:
These guys installed a very expensive, but very impressive, super solar system. Strong enough to run their AC (at least in a test situation):

https://www.gonewiththewynns.com/off-grid-solar-rv-air-conditioning

I think their system is amazing, but WAAAAAAY over priced for something you can put together yourself, but it is pretty slick.
 

solarman

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Joined
Feb 8, 2018
Posts
618
Location
Texas
jjv said:
From a lot of lurking and reading, I have come to this proposed system and hoping for some input on configuration and quality of the brand names. Also, does anyone have a generic " System overview" wiring / component diagram of all those parts and connections that don't really come with any of the individual components. ?
I am a Commercial Electrician with experience building control panels, Motor Control , etc. But not much in the 12V world. Also looking for recommendations on the actual panels. I am thinking 800 watts worth of solar. The Install is for a 35' Toyhauler and a lot of Desert Dry-camping

Thanks in advance !


Qty 4 VMAX Xtreme Series 6V AGM Deep Cycle 235Ah 6V
   
Victron BMV-712 Battery Monitor

Victron MultiPlus Compact 12/2000/80-50 120V VE.Bus Inverter Charger

Victron SmartSolar MPPT 100/50 Solar Charge Controller 100V 50A with Bluetooth

http://www.rvforum.net/SMF_forum/index.php/topic,113514.0.html

your welcome..
 

solarman

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Feb 8, 2018
Posts
618
Location
Texas
jjv said:
Thank you Solarman, curious Why don't you ever Parallel?  if you had 4 6v Batteries, would you not have to go series-parallel to achieve 12V?


certainly for lead acid, parallel is undesirable due to wiring and internal resistance differences. this causes
uneven charge and discharge currents and will lead to reduced lifespan and capacity issues over time.

in the pro world we are not stuck in a 12 V mindset.. we have choice over battery voltage so 24 or 48 V or higher is normal

the difference for RV is that most people don't want the additional overhead of higher voltage as it requires design practices that they are not willing to accept. so unless you are real serious, 12 V is it.. hence the move to parallel as many 12 V batteries as possible.
some rv'ers ( and you know who you are ..LOL ) have as many as eight in parallel to achieve the required energy store.

I personally, would not recommend more than 2 strings.. so that's 2P2S of 6V. or 2P 12 V or 3S2P of 4 V

another main difference with RV vs off grid solar is the fact that off grid will rely on the solar array as their primary power source. generators are used for backup only. in the RV world there is usually insufficient space to install enough panels to achieve this, so generators are used when solar fails. this is common since most people's electrical load is "bigger than their stomach" .. so to speak. and therefore solar alone is insufficient. having said that, there are a few who have a very frugal energy budget either by lifestyle or by design and can survive on solar alone. my wife and I can usually get by without generator help for 90% of the time, usually weather or other exceptions will require us to fire up the genny..

I would suggest you pay careful analysis to your energy budget and then decide if solar is suitable, you may end up short due to space and/or cost constraints. i'm not trying to dissuade you, but solar isn't a good solution for a lot of cases and you might be better off with a generator or a partial solar array to help charge during the day and then a generator for a/c etc overnight..


 

AStravelers

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Joined
Nov 14, 2016
Posts
1,590
Location
San Antonio, TX
PJ Stough said:
The amp hours of the batteries and the watts of the solar panels determine how much power you have available to use. With 705 amp hours of batteries you will have 300 to 350 amp hours available if the batteries are fully charged, and you are willing to run them down to about 50% state of charge. 

If you electrical needs are more, then you will need more watts of solar, and more amp hours of batteries.  That is why most people suggest that before you decide on total watts of solar and total amp hours of batteries, get a battery monitor to monitor you actual usage for a while, before deciding on a system.  Another alternative, is look at the power usage of what ever you might run, and multiply the power requirement times the number or hours you expect to use in a day.  This will give you some what of an estimate of your power needs.
He doesn't have 705AH of battery! Two sets of 6V (235AH) batteries, each set wired in series for 12V provides 470AH of capacity, of which 235AH is usable.

Batteries wired in series, the voltage is added, however the AH stays the same.  With batteries wired in parallel (i.e. two 12V batteries) the AH is added, but the voltage stays the same.



 

PJ Stough

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Posts
2,394
Location
Central Iowa
AStravelers said:
He doesn't have 705AH of battery! Two sets of 6V (235AH) batteries, each set wired in series for 12V provides 470AH of capacity, of which 235AH is usable.

Batteries wired in series, the voltage is added, however the AH stays the same.  With batteries wired in parallel (i.e. two 12V batteries) the AH is added, but the voltage stays the same.

Thanks for the correction.  I misread the original post.  I read it as he had six batteries in series/parallel.  I know I should never post on a forum until I have had at least two cups of coffee.
 

jjv

Member
Joined
Nov 6, 2018
Posts
5
AStravelers said:
He doesn't have 705AH of battery! Two sets of 6V (235AH) batteries, each set wired in series for 12V provides 470AH of capacity, of which 235AH is usable.

Batteries wired in series, the voltage is added, however the AH stays the same.  With batteries wired in parallel (i.e. two 12V batteries) the AH is added, but the voltage stays the same.

To be technical, I (HE) Doesnt have anything yet, I am posting what I think would work and looking for suggestions. I have been told to stick with Trojan or Rolls due to their warranty's. Thanks in advance for any input, critique and the like !
 

wmtired

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Oct 27, 2018
Posts
73
As a rule that I've used for over 10 years with 3 separate solar installs on my RV and 2-3 installs on RVs each summer to generate spending cash, I prefer about 1 amp of battery capacity for every 1 watt of solar power.

If you have 800 watts of solar, you should consider adding at least another battery bank of 6 volt golf cart batteries.

All batteries I have installed are installed in parallel but are SEPARATELY switched.  I also installed my converter (A progressive dynamics one) within 3 feet of the batteries so I don't have a .4 voltage drop which is significant if you wish to fast charge or equalize your batteries when you are not on solar.

The less you discharge your batteries during the day/night the longer your batteries will last.  My system typically only uses 10% of battery capacity overnight and that is with a lot of use which includes microwave for popping popcorn, coffee maker, and lots of movie watching via our entertainment system.  Our propane forced air furnace runs almost every night during the summer months as we camp at high altitudes where temps are  in the high 30's to low 40's overnight.  This uses a lot of electricity and we no longer worry about waking up with dead batteries.  Our batteries are fully charged by mid-morning and I don't have to worry about the wife using her hair dryer first thing in the morning as there is tons of residual battery capacity in the early morning.  No need to fire up the generator in the morning to use microwave or coffee maker!  We've even used one of our 1500 watt forced air heaters for about 30 minutes each morning to warm up our living area a bit to save propane.

Solar panel wiring:  MPPT controllers are the most efficient but to take advantage of them you must wire solar panels in series for higher voltages.  However, series solar panels can be wiped out with just the smallest amount of shading of one panel.  A compromise was to wire 2 pairs of solar paries in series for 22 volts with max sun exposure and then run the pairs in parallel.  This gives a good compromose for utilizing our MPPT controller at higher more efficient voltages and minimizes losing all solar output with partial shading panel issues.

Don't forget to run high amperage fuses next to the batteries to prevent a fire if a wire gets loose and shorts!
 

wmtired

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Joined
Oct 27, 2018
Posts
73
I saved $$$ and use the EGC2 batteries are Sam's Club. They are awesome and priced more then their cheaper GC2 golf cart batteries and are heavier, i.e. thicker heavier lead plates.  My only battery regret is not getting AGM golf cart batteries but adding water once a year is done with a remote filling system and not that difficult.  Since my batteries are used very little in capacity, I don't boil off much water then they are recharged by my solar system.

Another reason for each bank being switched is one bank goes bad due to internal fault, I can remove it electrically from the system and continue my camping trip.
 

jjv

Member
Joined
Nov 6, 2018
Posts
5
wmtired said:
As a rule that I've used for over 10 years with 3 separate solar installs on my RV and 2-3 installs on RVs each summer to generate spending cash, I prefer about 1 amp of battery capacity for every 1 watt of solar power.

If you have 800 watts of solar, you should consider adding at least another battery bank of 6 volt golf cart batteries.

All batteries I have installed are installed in parallel but are SEPARATELY switched.  I also installed my converter (A progressive dynamics one) within 3 feet of the batteries so I don't have a .4 voltage drop which is significant if you wish to fast charge or equalize your batteries when you are not on solar.

The less you discharge your batteries during the day/night the longer your batteries will last.  My system typically only uses 10% of battery capacity overnight and that is with a lot of use which includes microwave for popping popcorn, coffee maker, and lots of movie watching via our entertainment system.  Our propane forced air furnace runs almost every night during the summer months as we camp at high altitudes where temps are  in the high 30's to low 40's overnight.  This uses a lot of electricity and we no longer worry about waking up with dead batteries.  Our batteries are fully charged by mid-morning and I don't have to worry about the wife using her hair dryer first thing in the morning as there is tons of residual battery capacity in the early morning.  No need to fire up the generator in the morning to use microwave or coffee maker!  We've even used one of our 1500 watt forced air heaters for about 30 minutes each morning to warm up our living area a bit to save propane.

Solar panel wiring:  MPPT controllers are the most efficient but to take advantage of them you must wire solar panels in series for higher voltages.  However, series solar panels can be wiped out with just the smallest amount of shading of one panel.  A compromise was to wire 2 pairs of solar paries in series for 22 volts with max sun exposure and then run the pairs in parallel.  This gives a good compromose for utilizing our MPPT controller at higher more efficient voltages and minimizes losing all solar output with partial shading panel issues.

Don't forget to run high amperage fuses next to the batteries to prevent a fire if a wire gets loose and shorts!
 

Interesting, could you please elaborate on the Second bank of Batteries, is this a backup ? and how do they coexist with the primary bank ?

"All batteries I have installed are installed in parallel but are SEPARATELY switched."  Like a A/B switch ? never used at the same time ?

Thanks!
 

wmtired

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Oct 27, 2018
Posts
73
Each bank I have are 6 volt batteries wired in series for 12 volts output.

Each bank of two 6 volt batteries have an inline on/off switch.  I use the following switches  https://www.westmarine.com/buy/blue-sea-systems--e-series-compact-battery-switch-off-1-both-2-no-alt-field-disc--3831393?mrkgcl=481&mrkgadid=3202694843&cm_mmc=PS-_-Google-_-GSC%3ENonB%3EProduct%2520Type-_-3831393&product_id=3831393&adpos=1o4&creative=108421552324&device=c&matchtype=&network=g&gclid=EAIaIQobChMIrM798NLG3gIVmoKzCh2JKgYDEAQYBCABEgJPOPD_BwE

I typically run all batteries on all of the time when I'm dry camping.  The advantage of having switches is the ability to disconnect a battery bank if a battery fails thus not ruining your camping trip.  Also, individually switched batteries allow me to individually condition the batteries with desulfation charge when I'm at home hooked up to shore power and to individually do a top off charge, if needed, so all batteries (all built on same date and same brand) are fairly equal in charge and condition.

If you have spare capacity, you can easily disconnect (switch off) a battery bank and keep it in reserve for times when the sun refuses to shine for several days.  Since I live in a state with 300 plus days of sunshine a year, I don't have to worry about needing a backup battery bank. Although I'm solar, I do carry a backup generator because I prefer to be prepared for the worst case.  I have 2 generators, a 3kw generator which is capable of running the airconditioner on the rare times we anticipate  high temps and want to stay cool or keep our dogs cool when we are riding ATVs during the day and a smaller 1kw generator that we carry when we don't anticipate air conditioner use and want a backup to recharge batteries if a volcano blows and hides the sun for a week.


 

Frank B

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Apr 23, 2005
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Calgary, Alberta
Wmtired:

Solar panel wiring:  MPPT controllers are the most efficient but to take advantage of them you must wire solar panels in series for higher voltages.  However, series solar panels can be wiped out with just the smallest amount of shading of one panel.  A compromise was to wire 2 pairs of solar paries in series for 22 volts with max sun exposure and then run the pairs in parallel.  This gives a good compromose for utilizing our MPPT controller at higher more efficient voltages and minimizes losing all solar output with partial shading panel issues.


Or use 72 cell residential solar panels that generate near 40v. No need to series those, and price per watt is very attractive.  If you pick a panel with bypass diodes, partial shading issues are mitigated.

http://www.rvforum.net/SMF_forum/index.php/topic,106669.0.html
 
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