New B

Novaz

Hi Just signed up
will be looking for help on installing Solar in my small camper van Dodge Tradesman
currently use a suitcase Solar Kit 90w that is just for keeping battery topped up
would like to set up a system of around 450-500 Watts to see how things work for me
as i am still working but wanting to gain experience while looking for my acreage
ready to set up for full retirement .
My only thoughts so far are that I would like it to be based on 12 Volts
as i will be running propane and have a quiet generator for back up power
Thanks
Roy

niel

Re: New B

hi roy,
you are putting the cart before the horse here. you need to find out what the watt hour requirement per day will be for your loads. sometimes one needs to roughly calculate this from the specs of the loads, but if at all possible it is better to measure it from measuring the currents (amps) for each item and multiply it by the nominal voltage, which in your case is 12v. from there you need to know for how many hours per day (24hrs) it will need to run and multiply the watts times the hours this will operate in the 24hr period for watt hours for that item. each of your loads needs to be figured for this and added together. once that is achieved by you then it can be taken further for working out the other parameters.

BB.

Re: New B

As Niel says, if you can get a good number for your loads--Then it is much easier to design a system that will meet your needs.

And if it does not, all you are out is a bit of paper instead of a few thousand dollars of equipment.

With RVs, generally you are limited to the size of your battery bank (size and weight) and you are also limited in roof space (although, a few folks have made solar "awnings" and can get quite a bit of solar panels deployed).

Also, it matters where and when you will be RV'ing... In the US southwest, you get a lot of summer sun. In the North east in winter--Not so much.

Just to give you some ideas... A 500 Watt array, off grid, for ~9 months of the year will support a minimum of:

500 Watts * 0.52 (120 VAC) system derating * 4 hours minimum (average) sun per day = 1,040 Watt*Hours per day
500 Watts * 1/2 volts * 0.61 (12 VDC) system derating * 4 hours minimum (average) sun per day = 102 Amp*Hours per day (@ 12 volt battery bank)

Working backwards, 5% to 13% rate of charge, with 10% being a nice/healthy array for full time/long term off grid living:

500 Watts * 1/14.5 volts charging * 0.77 panel+controller derating * 1/0.10 Rate of charge = 265 AH @ 12 volt nominal battery bank
500 Watts * 1/14.5 volts charging * 0.77 panel+controller derating * 1/0.05 Rate of charge = 531 AH @ 12 volt maximum recommended battery bank AH rating

Of course, if you are doing a lot of driving every few days, and/or willing to use a small genset when needed--You can go outside the above numbers... These are just a starting point as to what you could expect for a "well balanced" off grid system.

-Bill

Novaz

Re: New B

Thank you for your reply
I am totaly new to this and so am doing as much research as i can before buying
as mentioned i am wanting to outfit my van with a semi part time liveable system before i go full tilt into an every day of the rest of my days system I have a very small energy footprint outside of work and do not require a lot of items to keep me comfortable and happy I have this past year got by with a small solar outfit for weekends 3 days and used my in van propane and generator for extras ,I estimate to have another 4-5 years before i retire and go full time off grid therefore i would like to use this time to gain as much experience with my van system i really appreciate your reply and will spend the weekend thinking and working out my power requirements for medium to long term use i am not afraid to buy more than i need if it means getting a quality system that works
Thanks
Roy

niel wrote: »

hi roy,
you are putting the cart before the horse here. you need to find out what the watt hour requirement per day will be. sometimes one needs to roughly calculate this from the specs of the loads, but if at all possible it is better to measure it from measuring the currents (amps) for each item and multiply it by the nominal voltage, which in your case is 12v. from there you need to know for how many hours per day (24hrs) it will need to run and multiply the watts times the hours this will operate in the 24hr period for watt hours for that item. each of your loads needs to be figured for this and added together. once that is achieved by you then it can be taken further for working out the other parameters.

Novaz

Re: New B

Thanks for your reply Bill
i hope to be Posting and asking a lot of questions hopefully this wont be to tiresome for you guys
Thanks
Roy

BB. wrote: »

As Niel says, if you can get a good number for your loads--Then it is much easier to design a system that will meet your needs.

And if it does not, all you are out is a bit of paper instead of a few thousand dollars of equipment.

With RVs, generally you are limited to the size of your battery bank (size and weight) and you are also limited in roof space (although, a few folks have made solar "awnings" and can get quite a bit of solar panels deployed).

Also, it matters where and when you will be RV'ing... In the US southwest, you get a lot of summer sun. In the North east in winter--Not so much.

Just to give you some ideas... A 500 Watt array, off grid, for ~9 months of the year will support a minimum of:

500 Watts * 0.52 (120 VAC) system derating * 4 hours minimum (average) sun per day = 1,040 Watt*Hours per day
500 Watts * 1/2 volts * 0.61 (12 VDC) system derating * 4 hours minimum (average) sun per day = 102 Amp*Hours per day (@ 12 volt battery bank)

Working backwards, 5% to 13% rate of charge, with 10% being a nice/healthy array for full time/long term off grid living:

500 Watts * 1/14.5 volts charging * 0.77 panel+controller derating * 1/0.10 Rate of charge = 265 AH @ 12 volt nominal battery bank
500 Watts * 1/14.5 volts charging * 0.77 panel+controller derating * 1/0.05 Rate of charge = 531 AH @ 12 volt maximum recommended battery bank AH rating

Of course, if you are doing a lot of driving every few days, and/or willing to use a small genset when needed--You can go outside the above numbers... These are just a starting point as to what you could expect for a "well balanced" off grid system.

-Bill

niel

Re: New B

roy,
i know this sounds cliche, but don't be afraid to do allot of reading. the small system may not be able to be added to by the time you retire either. there is much to consider when designing a system, some of which may not be anticipated by you or us, but hopefully we'll be on target.

Novaz

Re: New B

Thanks Neil
I am reading as much as i can of course knowing what to filter out is difficult being a newB LOL
heading to Idaho and southern Montana in July to check out land for sale parcels but may detour to check out Arizona Wind and Sun
Roy

PNjunction

Re: New B

Novaz wrote: »

.... currently use a suitcase Solar Kit 90w that is just for keeping battery topped up

Quick question - how is that setup configured? Is the controller mounted near the panel, and a long run of cable leads to the battery? How long of a run of cable are you using and do you know the wire gauge?

The reason I ask is that for 12v systems, be it just to keep a battery topped off, or a small RV solar project, voltage drop and losses in thin gauge cabling can rob you of available power, or lead to longer than normal charge times.

Novaz

Re: New B

Hi
well the unit is not installed i just set it up when ever i park for the weekend and just let it do its thing
then pack it away when i head home
Roy

PNjunction wrote: »

Quick question - how is that setup configured? Is the controller mounted near the panel, and a long run of cable leads to the battery? How long of a run of cable are you using and do you know the wire gauge?

The reason I ask is that for 12v systems, be it just to keep a battery topped off, or a small RV solar project, voltage drop and losses in thin gauge cabling can rob you of available power, or lead to longer than normal charge times.

Novaz

Re: New B

Well as was advised i have been doing a bunch of reading and watching videos and that has made me really appreciate what you guys were telling me at the start .
as i wont be actually purchasing this equipment for a whilei would like to post as i research and build a simulated system so that you guys can if you are inclined shoot down my suggestions or offer more viable alternatives.
So firstly i have decided to stick with my original plan of 12 volts my reasoning is that I will be using the 90watt suitcase module i already have for RV Battery charging .
appliances that i will need over and above my 3 burner propane stove and 12v installed furnace are very small power users heating will be taken care of by a propane Mr Buddy heater and the previously mentioned furnace.
As this rv will be my first venture into off grid living I am not concerned that if i do end up back in a house situation it will have been a good learning experience for whats involved with a larger house system.
These are the panels i have been looking at and would probably go for a 4 panel system this panel looks to provide enough VMPP FOR A 12 Volt system through a charge controller
http://www.solar-electric.com/kyocera-kd140gx-lfbs-140-watt-polycrystalline-solar-panel.html
ok guys out with the red line pens and i look forward to your replies
Thanks
Roy

BB.

Re: New B

Are you buying the 140 watt panels because you want to use an "inexpensive" PWM controller? And/or they physically fit the space the best? Easy to setup/take down/store... Or what.

If you are planning on parking in the shade and planting a portable array 40 feet from the, putting 2 or 4 panels in series and using a higher end MPPT charge controller would be interesting. Lets you keep the extension cord much smaller diameter.

As always, if you have a portable array (vs mounting on the vehicle), you need to stake the array to the ground--To prevent wind damage/falling over. You also have to worry about security (panels having legs).

The higher end MPPT controllers generally have more programability, better logging, and even some computer/networking capabilities--That may be of interest to you, or not. However, that does come at a cost.

I like to focus on your needs/interests/requirements first--Rather than focus on a specific piece of hardware early on (these Kyocera panels are very good).

-Bill

AuricTech

Re: New B

Since you apparently already own the motorhome that you want your PV system to power, here's an idea that might help you determine your RV's total power needs before you spend money on a PV system that will be either too small or too large for your needs (as an advisory notice, please note that I am also a newbie to this forum, albeit one who has tried to read quite a few threads outside my primary interest of building a PV system for my own future Casita AuricTech motorhome):

1. Buy a power meter designed to measure the kWh used by an RV that is plugged into shore power, such as the MeterMaid MC M30-TT 30-amp power meter (this assumes that your motorhome has a 30-amp shore power inlet). Of course, if your favored nearby RV park with available shore power already has pedestal-mounted power meters, you can save the $250 and move to the next step...
2. Spend at least a week or so at an RV park with shore power, with the MeterMaid engaged (or taking daily readings from any pedestal-mounted power meter already provided by the RV park)
3. Make sure to use power-consuming devices exactly as if you were powering them from your planned PV system
4. Keep daily track of your actual power use over several days (or longer, if possible)
5. Look at ways to reduce your power needs (such as replacing 12-volt incandescent bulbs with LED lights, or running an absorption refrigerator on propane, rather than on 120VAC)
6. Design your PV system to provide adequate power for your needs, weighted toward your heavier-use days, with some battery capacity (or generator capacity) to account for low-insolation periods
7. Allow some room for your PV system to grow, without grotesquely oversizing any part of it

That's how I intend to determine the power needs of Casita AuricTech, once I buy my (well-used) motorhome in the (very) near future.

Do any more-experienced forum members see any fundamental flaws in this approach?

BB.

Re: New B

That is certainly a good way to start...

I suggest a Kill-a-Watt type meter... Plug in each appliance for 24 hours (cycling appliances like refrigerators) or for the 2-8 hour daily use + charging (laptop computer), etc.

If you already have a battery system... A Battery Monitor can be used to measure each load.

Or for smaller power measurements, a DC AH/WH meter would be good.

For a smaller off grid/RV system--You are not talking about a lot of power. See the 1,000 WH or 100 AH @ 12 volt available system power from a ~500 Watt array (spring/fall, more possible in summer, sometimes a lot less in winter--central RV heat fans can take a lot of power). A few LED lights, maybe a small fan (hot weather), run the controller for a propane fridge, 8 hours on an energy efficient laptop, a bit of 12 volt power for the water pump, etc...

I am a big believer in knowing the individual loads. For off grid power, you are going to conserve power/husband resources. And you need to review your power usage and look at conservation/alternatives to use a little power as practical.

-Bill

Novaz

Re: New B

BB. wrote: »

Are you buying the 140 watt panels because you want to use an "inexpensive" PWM controller? And/or they physically fit the space the best? Easy to setup/take down/store... Or what.

If you are planning on parking in the shade and planting a portable array 40 feet from the, putting 2 or 4 panels in series and using a higher end MPPT charge controller would be interesting. Lets you keep the extension cord much smaller diameter.

As always, if you have a portable array (vs mounting on the vehicle), you need to stake the array to the ground--To prevent wind damage/falling over. You also have to worry about security (panels having legs).

The higher end MPPT controllers generally have more programability, better logging, and even some computer/networking capabilities--That may be of interest to you, or not. However, that does come at a cost.

I like to focus on your needs/interests/requirements first--Rather than focus on a specific piece of hardware early on (these Kyocera panels are very good).

-Bill

So some information that i missed out is that this first system as envisioned will be in a very small rv actually just a camper van with high top ,I chose those panels as a starting point to get into solar use and they will fit my camper very well actual position of vehicle will be selected based on the acreage i intend purchasing this year in lower Idaho or South western Montana and be semi permanent my intention was to purchase an MPPT charge controller based on the research i have been doing thus far and will continue to do , though make model is not decided yet cost will not be a determining factor ,
as mentioned I dont see me needing a lot of power use for creature comforts my main use would be for computer ,photography batterys,and soldering [ I build slot drag racing cars ]
This forum is proving invaluable to me and i thank all for their time in replying
Roy

Novaz

Re: New B

BB. wrote: »

That is certainly a good way to start...

I suggest a Kill-a-Watt type meter... Plug in each appliance for 24 hours (cycling appliances like refrigerators) or for the 2-8 hour daily use + charging (laptop computer), etc.

If you already have a battery system... A Battery Monitor can be used to measure each load.

Or for smaller power measurements, a DC AH/WH meter would be good.

For a smaller off grid/RV system--You are not talking about a lot of power. See the 1,000 WH or 100 AH @ 12 volt available system power from a ~500 Watt array (spring/fall, more possible in summer, sometimes a lot less in winter--central RV heat fans can take a lot of power). A few LED lights, maybe a small fan (hot weather), run the controller for a propane fridge, 8 hours on an energy efficient laptop, a bit of 12 volt power for the water pump, etc...

I am a big believer in knowing the individual loads. For off grid power, you are going to conserve power/husband resources. And you need to review your power usage and look at conservation/alternatives to use a little power as practical.

-Bill

I have been reviewing appliances that i may purchase for their power requirements and feel that my needs could be met with the panels I am looking at ,I am not opposed to buying higher rated panels if it will give me a higher safety level with regards to power use from the battery bank .
There is no heat fan as such although the furnace does have a small fan which i would need to take into account,currently there is no fridge as i get by on 3-4 days of camping with a cold box and and ice chest .currently i am working on insulating and weatherproofing the van with sound proofing ,reflectix,and an insulated false floor system .
Roy

Novaz

Re: New B

AuricTech wrote: »

Since you apparently already own the motorhome that you want your PV system to power, here's an idea that might help you determine your RV's total power needs before you spend money on a PV system that will be either too small or too large for your needs (as an advisory notice, please note that I am also a newbie to this forum, albeit one who has tried to read quite a few threads outside my primary interest of building a PV system for my own future Casita AuricTech motorhome):

1. Buy a power meter designed to measure the kWh used by an RV that is plugged into shore power, such as the MeterMaid MC M30-TT 30-amp power meter (this assumes that your motorhome has a 30-amp shore power inlet). Of course, if your favored nearby RV park with available shore power already has pedestal-mounted power meters, you can save the $250 and move to the next step...
2. Spend at least a week or so at an RV park with shore power, with the MeterMaid engaged (or taking daily readings from any pedestal-mounted power meter already provided by the RV park)
3. Make sure to use power-consuming devices exactly as if you were powering them from your planned PV system
4. Keep daily track of your actual power use over several days (or longer, if possible)
5. Look at ways to reduce your power needs (such as replacing 12-volt incandescent bulbs with LED lights, or running an absorption refrigerator on propane, rather than on 120VAC)
6. Design your PV system to provide adequate power for your needs, weighted toward your heavier-use days, with some battery capacity (or generator capacity) to account for low-insolation periods
7. Allow some room for your PV system to grow, without grotesquely oversizing any part of it

That's how I intend to determine the power needs of Casita AuricTech, once I buy my (well-used) motorhome in the (very) near future.

Do any more-experienced forum members see any fundamental flaws in this approach?

Thanks for the reply its cool to see someone else going to Solar in a vehicle I do have a 110volt input panel but will not be using any RV parks I usually take my camper off road and park discreetly where there are no roads and little used walking trails i will purchase a kill watt meter so i can log individual items .
I already have the adhesive backed strip LEDS in place they are very good and currently i use them from a 75 watt inverter i have on the main battery which also charges my phone and razor
I today purchased my Yamaha 2000 Watt quiet generator
Roy

BB.

Re: New B

OK--We have something we can start with... Using PV Watts for Rock Springs Wyoming. Fixed array mounted flat to roof:

Month    Solar Radiation (kWh/m 2/day)
1      2.09     
2      3.03     
3      4.32     
4      5.71     
5      6.57     
6      7.22     
7      7.23     
8      6.49     
9      5.23     
10      3.75     
11      2.28     
12      1.84     
Year      4.66      

and if you tilt the array to ~42 degrees from horizontal:

Month    Solar Radiation (kWh/m 2/day)
1      3.96     
2      4.95     
3      5.67     
4      6.33     
5      6.27     
6      6.47     
7      6.69     
8      6.76     
9      6.51     
10      5.66     
11      4.03     
12      3.69     
Year      5.59      

You can see that tilting the panel will give you about 2x more sun (energy) in deep winter, and a bit less power in the middle of summer.

So--When will you be in the area (winter/summer/9 months/12 moths, etc.).

With 4x 140 Watt panels (560 watts) using 4 hours (for now) of sun, and 5-13% rate of charge (20 Hour battery AH rating):

• 560 Watts * 1/14.5 volts charging * 0.77 panel+controller derate * 1/0.05 rate of charge = 594 AH @ 12 volt maximum battery bank
• 560 Watts * 1/14.5 volts charging * 0.77 panel+controller derate * 1/0.10 rate of charge = 297 AH @ 12 volt nominal battery bank
• 560 Watts * 1/14.5 volts charging * 0.77 panel+controller derate * 1/0.13 rate of charge = 229 AH @ 12 volt minimum "cost effective" battery

If you discharge the battery bank by 25% per day (2 days of storage and 50% maximum discharge):

• 297 AH * 12 volt battery * 0.85 inverter eff * 0.25 discharge = 757 Watt*Hours of 120 VAC power per day (storage)

A 560 Watt array and 4 hours of sun will produce:

• 560 Watts * 0.52 AC off grid system eff * 4 hours of sun = 1,165 Watt*Hours per day (AC power from solar array)

So, you can look at how big of battery bank you want to fit in your RV--One pair of 6 volt golf cart batteries (2* 6 volt * ~220 AH = 12 volts at 220 AH) would be a good starting point (not too much money/not too large-heavy battery bank). Good if you are using some power during daytime (running computer editing and such).

If you work mostly at night--You could look at the larger battery bank (more stored power for over night use).

For an RV and if you are going to use 4x 140 Watt panels with Vmp~17.5 volts (vs, for example, 2*250 Watt panels with Vmp~30 volts)--You do not have much need to go with more than a "simple" PWM controller--Unless you want the "higher tech" MPPT controller (and/or want to look at using 2* 250-280 Watt panels--Larger panels are usually much cheaper, but the MPPT controller cost a lot more money--Do paper design of several options and see what works best for you).

As you can see, you have choices to make (tilt of panels, size of battery bank, etc.)... But, in general, a 12 volt battery bank with a 300 Watt MorningStar TSW inverter (or similar) would be a sweet setup (the MorningStar has a remote on/off control and "search mode" to reduce DC power usage/waste).

A 560 Watt array may be a bit large for a 30 Amp PWM charge controller (your array may be ~32 amps). For MPPT charge controller, a 30 amp controller would be fine (Midnite, Rogue, Morningstar make nice mid-range MPPT controllers).

-Bill

Novaz

Re: New B

So--When will you be in the area (winter/summer/9 months/12 moths, etc.).
Bill
Thank you for the great reply
********************************************************************************************************************
I intend being at the location full time and will look into building an adjustable mounting system that will enable me to tilt the system when I am
on site but let it lay flat when away from the site

With 4x 140 Watt panels (560 watts) using 4 hours (for now) of sun, and 5-13% rate of charge (20 Hour battery AH rating):

• 560 Watts * 1/14.5 volts charging * 0.77 panel+controller derate * 1/0.05 rate of charge = 594 AH @ 12 volt maximum battery bank
• 560 Watts * 1/14.5 volts charging * 0.77 panel+controller derate * 1/0.10 rate of charge = 297 AH @ 12 volt nominal battery bank
• 560 Watts * 1/14.5 volts charging * 0.77 panel+controller derate * 1/0.13 rate of charge = 229 AH @ 12 volt minimum "cost effective" battery

-Bill[/QUOTE]
**********************************************************************************************************************
I am not totally understanding this part are you reffering to the amp/hour capacity of the battery bank
Thanks
Roy

BB.

Re: New B

For our rules of thumb, we use the 20 Hour Discharge Rate for determining battery capacity.

Basically a 100 AH @ 12 volt battery from full charged to dead as door nail discharged over 20 hours would look like:

100 AH / 20 hours = 5 amp discharge (for 20 Hours).

If you discharge a battery slower, it has higher "apparent capacity". If you discharge a battery faster (8 hours, 5 hours, etc.) its apparent capacity is less. For example a 6 volt golf cart battery from Trojan:

http://www.solar-electric.com/lib/wind-sun/Trojan-specifications-guide.pdf

5 hour rate 185 AH
20 hour rate 225 AH
100 hour rate 250 AH

So, when we say 5% to 13% recommended rate of charge, based on the 20 hour rate (numbers are approximate--~+10% is about "the same" in solar calculations):

225 AH * 0.05 = 11.25 amps minimum
225 AH * 0.10 = 22.5 amp nominal
225 AH * 0.13 = 29.25 amp maximum "cost effect" rate of charge for solar array

Take a number like 22.5 amp rate of charge:

22.5 amps * 14.5 volts charging * 1/0.77 panel+controller derating = ~424 Watt solar array

The formulas I gave you above, are sort of side ways--Given a 560 Watt solar array, what would be the Amp*Hour capacity recommend that such an array can support.

With 4x 140 Watt panels (560 watts) using 4 hours (for now) of sun, and 5-13% rate of charge (20 Hour battery AH rating):

• 560 Watts * 1/14.5 volts charging * 0.77 panel+controller derate * 1/0.05 rate of charge = 594 AH @ 12 volt maximum battery bank
• 560 Watts * 1/14.5 volts charging * 0.77 panel+controller derate * 1/0.10 rate of charge = 297 AH @ 12 volt nominal battery bank
• 560 Watts * 1/14.5 volts charging * 0.77 panel+controller derate * 1/0.13 rate of charge = 229 AH @ 12 volt minimum "cost effective" battery

Batteries need a range of current to recharge quickly/optimally. 5% is the minimum recommended charging current (for several reasons). 10-13% is a great charging range--High enough to charge quickly, better mixing of electrolytes, and you can draw some power during the day and not go below the 5% minimum rate of charge recommended (some battery mfg. will even recommend 10% as the minimum rate of charge).

Does this help?

-Bill

Novaz

Re: New B

BB. wrote: »

For our rules of thumb, we use the 20 Hour Discharge Rate for determining battery capacity.

Basically a 100 AH @ 12 volt battery from full charged to dead as door nail discharged over 20 hours would look like:

100 AH / 20 hours = 5 amp discharge (for 20 Hours).

If you discharge a battery slower, it has higher "apparent capacity". If you discharge a battery faster (8 hours, 5 hours, etc.) its apparent capacity is less. For example a 6 volt golf cart battery from Trojan:

http://www.solar-electric.com/lib/wind-sun/Trojan-specifications-guide.pdf

5 hour rate 185 AH
20 hour rate 225 AH
100 hour rate 250 AH

So, when we say 5% to 13% recommended rate of charge, based on the 20 hour rate (numbers are approximate--~+10% is about "the same" in solar calculations):

225 AH * 0.05 = 11.25 amps minimum
225 AH * 0.10 = 22.5 amp nominal
225 AH * 0.13 = 29.25 amp maximum "cost effect" rate of charge for solar array

Take a number like 22.5 amp rate of charge:

22.5 amps * 14.5 volts charging * 1/0.77 panel+controller derating = ~424 Watt solar array

The formulas I gave you above, are sort of side ways--Given a 560 Watt solar array, what would be the Amp*Hour capacity recommend that such an array can support.

With 4x 140 Watt panels (560 watts) using 4 hours (for now) of sun, and 5-13% rate of charge (20 Hour battery AH rating):

• 560 Watts * 1/14.5 volts charging * 0.77 panel+controller derate * 1/0.05 rate of charge = 594 AH @ 12 volt maximum battery bank
• 560 Watts * 1/14.5 volts charging * 0.77 panel+controller derate * 1/0.10 rate of charge = 297 AH @ 12 volt nominal battery bank
• 560 Watts * 1/14.5 volts charging * 0.77 panel+controller derate * 1/0.13 rate of charge = 229 AH @ 12 volt minimum "cost effective" battery

Batteries need a range of current to recharge quickly/optimally. 5% is the minimum recommended charging current (for several reasons). 10-13% is a great charging range--High enough to charge quickly, better mixing of electrolytes, and you can draw some power during the day and not go below the 5% minimum rate of charge recommended (some battery mfg. will even recommend 10% as the minimum rate of charge).

Does this help?

-Bill

Hi Bill
Thank you that explains it
I guess I was looking forward not sideways ,
I see why a lot of people choose the T 105 and why a pair would be
good in my 12 Volt System
Roy

AuricTech

Re: New B

A battery bank consisting of two Trojan T-145 batteries, with a C/20 rating of 260 Amp-hours, would be a bit closer to the "nominal" battery bank for the panel array you're considering. The extra capacity might be worth the extra cost ($203 each, compared to $151 per T-105).

ETA: See how easy it is for me to spend your money?

Novaz

Re: New B

AuricTech wrote: »

A battery bank consisting of two Trojan T-145 batteries, with a C/20 rating of 260 Amp-hours, would be a bit closer to the "nominal" battery bank for the panel array you're considering. The extra capacity might be worth the extra cost ($203 each, compared to $151 per T-105).

ETA: See how easy it is for me to spend your money?

Thanks for the input I was looking at the link Bill had sent me and could see that the 105s would work well in my system which i plan to continue to look at specs on
I frequent an off grid cheaper living
forum and see that a lot of people with van and RV systems use the 105s
Thanks
Roy

Novaz

Re: New B

Still doing my research and a question I have concerns the number of panels per the amount of total watts I will need
is it preferred to have less panels with a higher per panel output if space is not an issue.
I can see that less panels would leave you exposed to a decrease in power should one panel fail but the higher output of maybe 2* 320watt panels would be capable of charging a battery bank quicker than 4* 140 watt panels
Thanks
Roy

solar_dave

Re: New B

Novaz wrote: »

Still doing my research and a question I have concerns the number of panels per the amount of total watts I will need
is it preferred to have less panels with a higher per panel output if space is not an issue.
I can see that less panels would leave you exposed to a decrease in power should one panel fail but the higher output of maybe 2* 320watt panels would be capable of charging a battery bank quicker than 4* 140 watt panels
Thanks
Roy

640 watts vs 560 watts, the big panels will do better if you are using a MPPT controller. And the big panels will be cheaper per watt.

Novaz

Re: New B

solar_dave wrote: »

640 watts vs 560 watts, the big panels will do better if you are using a MPPT controller. And the big panels will be cheaper per watt.

Thanks for the reply
I have decided to go with the 2*320 watt panels this is the charge controller i have looked at
Morningstar TS-MPPT-60 TriStar 60 Amp MPPT Solar Charge Controller with digital meter
would this be too much for the system i plan on
instead of a 45 amp variant for the expected panel out put which will be in parralel
Roy

BB.

Re: New B

For an MPPT type charge controller, the largest "cost effective array" will be around (these are very round numbers--but a good starting point);

• 640 Watt array * 1/14.5 volts charging * 0.77 panel+controller deratings = 34 amps typical peak current on a good day

If you deeply cycle your battery bank and charge a lower voltage quite often (finish charging in afternoon), the peak current could be:

• 640 Watt array * 1/13.5 volts charging * 0.77 panel+controller deratings = 37 amps typical peak current on a good day

A 45 amp controller is a "good match" for this array on a 12 volt battery bank...

If you ever think you will add a third panel--You might look at the 60 amp controller (or larger)... But if this is all you need/all the room you have, then there is really no good reason to go higher.

As always, look at the cost of optional equipment (MorningStar tends to charge for LCD display and remote temperature sensor options--Both usually good things to have, as well as something to interface to a computer for detailed programming/logging). These can affect the overall pricing by a goodly amount.

-Bill

Novaz

Re: New B

BB. wrote: »

For an MPPT type charge controller, the largest "cost effective array" will be around (these are very round numbers--but a good starting point);

• 640 Watt array * 1/14.5 volts charging * 0.77 panel+controller deratings = 34 amps typical peak current on a good day

If you deeply cycle your battery bank and charge a lower voltage quite often (finish charging in afternoon), the peak current could be:

• 640 Watt array * 1/13.5 volts charging * 0.77 panel+controller deratings = 37 amps typical peak current on a good day

A 45 amp controller is a "good match" for this array on a 12 volt battery bank...

If you ever think you will add a third panel--You might look at the 60 amp controller (or larger)... But if this is all you need/all the room you have, then there is really no good reason to go higher.

As always, look at the cost of optional equipment (MorningStar tends to charge for LCD display and remote temperature sensor options--Both usually good things to have, as well as something to interface to a computer for detailed programming/logging). These can affect the overall pricing by a goodly amount.

-Bill

Thanks Bill
Most all my life i have tended to go with slightly more than i needed at the time for my hobbies,photography and see this venture to possibly need the same approach
its highly likely that this system will be moved from my Camper and placed in an off grid dwelling so purchasing my main equipment now and having spare capacity in the charge controller
is inline with my usual thought process
Thanks again
Roy

BB.

Re: New B

In general, it is difficult to "cost effectively" expand a system... I would just build out your small system now and enjoy. Down the road, figure out your power needs for the next system and design/build out the system from there.

If you are planning on running a full size refrigerator and more in your off grid dwelling--You probably will be looking at a 24 or 48 volt battery bank (new inverter/backup AC charger, batteries, etc.)... And possibly a larger than 60 amp charge controller.

-Bill

Novaz

Re: New B

Apart from deciding on an Inverter for my proposed system as I am still deciding what appliances I am likely to use on 110v
I have decided that I will use the 640 watt PV array with a 12 volt system my question is which would be the most effective way to wire this system my initial thoughts are to wire the panels in Parallel and to wire the batteries 4*105s in Series/Parallel.
as usual all suggestions are welcome and I thank every one who has helped me with advice and recommendations since I joined the forum.
Roy

Photowhit

Re: New B

What appliances do you need?

I'd suggest going with cheaper golf cart batteries to start, If you have access to Sams club or Costco you can likely purchase generic 6v golf cart batteries for around $80 each, Often they aren't picky about the batteries you bring in for a core charge, car batteries or even lawn mower batteries! My local battery store charges $26 for a golf cart core and $7 for a lawn mower core... I suggest this since it isn't uncommon for people, new to solar, to underestimate their loads or make mistakes that ruin batteries, call this a starter set.

There isn't a huge cost difference between the TS60 and TS45 MPPT charge controllers, a bit less than $100 if you think you might add panels later this would give you a little expansion, though switching to a 24 or 48 volt system would also give you room, with 4 batteries you could switch to a 24volt system and add a panel or 2 with out swapping out batteries, only needing a new inverter.

We haven't discussed inverters, Xantrex has a couple inexpensive 1800(XM1800) and 2000(Prosine 2000) watt pure sine from 12 volt inverters, ExelTech 1100 might be all you need, it can be hard wired which might be nice.

Novaz

Re: New B

Photowhit wrote: »

What appliances do you need?

I'd suggest going with cheaper golf cart batteries to start, If you have access to Sams club or Costco you can likely purchase generic 6v golf cart batteries for around $80 each, Often they aren't picky about the batteries you bring in for a core charge, car batteries or even lawn mower batteries! My local battery store charges $26 for a golf cart core and $7 for a lawn mower core... I suggest this since it isn't uncommon for people, new to solar, to underestimate their loads or make mistakes that ruin batteries, call this a starter set.

There isn't a huge cost difference between the TS60 and TS45 MPPT charge controllers, a bit less than $100 if you think you might add panels later this would give you a little expansion, though switching to a 24 or 48 volt system would also give you room, with 4 batteries you could switch to a 24volt system and add a panel or 2 with out swapping out batteries, only needing a new inverter.

We haven't discussed inverters, Xantrex has a couple inexpensive 1800(XM1800) and 2000(Prosine 2000) watt pure sine from 12 volt inverters, ExelTech 1100 might be all you need, it can be hard wired which might be nice.

Thanks for the reply
mostly I will be wanting to be able to charge 110v power tools and running a high output amp for my shortwave radio
would still appreciate any input on my plans for wiring both the panels and battery system
Roy