Reply
 
Thread Tools Display Modes
Old 09-02-2011, 08:50 PM   #31
Site Team - Lou
 
Herk7769's Avatar
 
Join Date: Oct 2009
Location: South Eastern PA
Posts: 21,169
Quote:
Originally Posted by SoMoney View Post
Okay in order to achieve Nirvana in Solar Boondocking I have a question.

Q. In IDEAL Sun conditions on a nice 70+ degree day;

How many watts total in solar panels are necessary to run:
1. The fridge
2. Water Pump/Heater
3. Run the LPG Detector
4. and Return at least 150Ah of charge back into the house batteries.

All of this in an 8 hour typical day cycle mind you!
Mike,

I am not sure whether this is a real question or a "tounge in cheek" comment. I will try to answer as if you are serious.

Assuming all available output from the panels are used by your items 24/7 I will try to puzzle this out.

First the 150 AH to the batteries. This is a difficult problem since the maximum safe charge varies as the battery takes charge and the charge controller will taper off the charging current as the batteries fill. I have the graphs posted in several posts here. I will assume you have a dead bank of 150AH and need to fill it. Using shore power with an unlimited supply of amps and your 3 stage power converter as the charging source, it will take about 3 days (24/7) to replace your 150AH (The size of my bank at the moment) due to amperage step down as the battery fills.

The Fridge: It matters whether you are running on propane/battery or just battery (3 way units). For simplicity we will use propane/battery with climate control turned off. The Fridge will run on propane until the gas is exhausted or the battery drops to 9.6 VDC (Dead for all intents and purposes). When cooling (average 12/7), the fridge draws 3 amps DC or 3x12=36 watts.

Heater: Depends of course on the BTU size of your furnace. Average is 7 amps DC (12/7) 7x12= 84 watts

Water pump: Amperage depends on where your water pressure is set at. 40PSI pulls 7 amps running (4/7) 7x12=84 watts

LP Detector: 24/7 at .3 amps or 4 watts all the time

You left out the other parasite draws (Concertone instant on - when off; Fridge when not cooling; heater when not running; etc)

BUT if your panels are taking care of all your routine needs your battery most likely won't discharge at all (or very little). To be a frugal power camper you could easily be pretty near independant with 250 -300 watts of panels. If not (inverter use; lots of lights; etc) Generator usage might be limited to a few hours every other day.
__________________

__________________

Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW
Herk7769 is offline   Reply With Quote
Old 09-03-2011, 12:22 AM   #32
Member
 
SoMoney's Avatar
 
Join Date: Mar 2011
Posts: 68
Thanks Lou. Not t&c; I've been shopping solar for a couple years and as panel prices come down my interest rises. I wouldn't call the batteries dead but more like 50% (according to power panel) after a cold night. I did not know the Forest River chargers can take 3 days to charge a drained bank on shore power.

I thought Solar was to run your critical systems and charge up your house battery from the previous nights entertainment and heater use. If I cant do that with 8 hours of sunlight I need to rethink.
__________________

__________________
SoMoney is offline   Reply With Quote
Old 09-03-2011, 07:02 AM   #33
Site Team - Lou
 
Herk7769's Avatar
 
Join Date: Oct 2009
Location: South Eastern PA
Posts: 21,169
Quote:
Originally Posted by SoMoney View Post
I wouldn't call the batteries dead but more like 50% (according to power panel) after a cold night.
Your stipulation for 150AH is two DC-24DP batteries (75AH each) max capacity. That is dead by definition.

The Micro panel does not read in percent when using the battery button.
It reads "C" "G" "F" and "E" (in Volts) using a logic graph in the manual. You only get two voltage readings as "C" is charging and E is any voltage over 6 volts DC. "G" (Good) will stay on till about 50%. When it goes out you MUST charge your battery to keep from damaging it as "F" (Fair) is about 15% when it goes out.

I assume "by the night's entertainment" you are using an inverter to power AC systems as well as the heater and lights. It is totally possible to empty a 150AH bank in one night. Inverted AC watts pull 10 times the power than DC watts from the batteries capacity. The more AH you need from the battery; the LESS AH the battery can deliver.

So say you need 1200 watts from your inverter to power your "entertainment". Watts is Watts no matter AC or DC. So 1200 Watts is 120 Volts times 10 amps. That does not sound like a lot, but to get 10 amps at 120 VAC you must pull 1200 Watts from the battery. 1200 Watts DC is 12 Volts times 100 AMPS! That is about 90 minutes from full to zero; by the math; BUT as you can see from the graph below; pulling 100 amps from the battery will reduce the 150 AH capacity from 150 AH to less than 75AH. (or about 45 minutes to dead from a full battery).

As you can see, in RVs Solar is an additional charge source NOT and "off the grid" system since you would need three to four 250 Watt panels to provide 100% power needs during the day and 4 to 6 6 Volt Trojans to store excess power for after dark coffee making and blender running.
Attached Thumbnails
Click image for larger version

Name:	battery voltage and capacity Curve.jpg
Views:	72
Size:	46.5 KB
ID:	7821   Click image for larger version

Name:	battery Life as a function of charge discharge cycles.jpg
Views:	78
Size:	28.2 KB
ID:	7822   Click image for larger version

Name:	battery voltage and capacity Curve vs Discharge Rate.jpg
Views:	82
Size:	44.9 KB
ID:	7823  
Attached Files
File Type: pdf Micro Monitor Panel Troubleshooting.pdf (149.2 KB, 34 views)
File Type: pdf KIB Monitor Panel M21 Wireing Diagram.pdf (51.2 KB, 25 views)
__________________

Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW
Herk7769 is offline   Reply With Quote
Old 09-03-2011, 12:58 PM   #34
Senior Member
 
ken0042's Avatar
 
Join Date: Sep 2010
Location: Calgary
Posts: 375
Quote:
Originally Posted by herk7769 View Post
Inverted AC watts pull 10 times the power than DC watts from the batteries capacity.
I just want to make sure I am reading that correctly. So if I run a 100 watt 120 volt appliance for 1 hour (using an inverter); I will be using the same amount of power as running a 1000 watt 12 volt appliance for an hour?

I knew inverters were very inefficient; that is why I bought a 12 volt television. I didn't realize it was that bad.
__________________
Wolf Pup T16P owner

"The trouble with quotes on the Internet is that it is nearly impossible to discern if they are genuine." - Abraham Lincoln
ken0042 is offline   Reply With Quote
Old 09-03-2011, 01:33 PM   #35
Member
 
SoMoney's Avatar
 
Join Date: Mar 2011
Posts: 68
Damn you Lou, how did you know I was running a blender?!?!
(Now thats T&C!)

Looks like you answered my question by making me think of immediate needs 1st... I need to look at extending battery capacity (3X), before looking at Solar.

Thanks Lou.
__________________
SoMoney is offline   Reply With Quote
Old 09-03-2011, 01:51 PM   #36
Site Team - Lou
 
Herk7769's Avatar
 
Join Date: Oct 2009
Location: South Eastern PA
Posts: 21,169
Quote:
Originally Posted by ken0042 View Post
I just want to make sure I am reading that correctly. So if I run a 100 watt 120 volt appliance for 1 hour (using an inverter); I will be using the same amount of power as running a 1000 watt 12 volt appliance for an hour?

I knew inverters were very inefficient; that is why I bought a 12 volt television. I didn't realize it was that bad.
Well, Watts is a measure of power. So a 100 watt 120 volt appliance uses 100W/120VAC amps or 0.83 amps

BUT a 1000 Watt 120 VAC appliance draws 8.3 amps from the inverter. But to CREATE that 1000 Watts for the AC side you must draw 1000 watts from your DC grid. To generate that 1000 Watts you need to pull 83 amps from your battery.

If you were connecting a 100 Watt AC appliance to the Inverter it would draw only 0.83 AC amps but on the DC side of the inverter you would need 100W/12VDC (8.3 amps) from the battery,
__________________

Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW
Herk7769 is offline   Reply With Quote
Old 09-03-2011, 01:56 PM   #37
Site Team - Lou
 
Herk7769's Avatar
 
Join Date: Oct 2009
Location: South Eastern PA
Posts: 21,169
Quote:
Originally Posted by SoMoney View Post
Damn you Lou, how did you know I was running a blender?!?!
(Now thats T&C!)

Looks like you answered my question by making me think of immediate needs 1st... I need to look at extending battery capacity (3X), before looking at Solar.

Thanks Lou.
My next major upgrade will not be panels, but a larger 12VDC bank. Since you MUST recharge your batteries at the 50% discharge level, the larger the bank the less strain on your batteries and the longer they last.

I will be adding panels one day, but I feel a 500AH bank is worth the investment. Think of the panels as a trickle charger for the batteres.
__________________

Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW
Herk7769 is offline   Reply With Quote
Old 09-03-2011, 02:16 PM   #38
Senior Member
 
ken0042's Avatar
 
Join Date: Sep 2010
Location: Calgary
Posts: 375
Quote:
Originally Posted by herk7769 View Post
If you were connecting a 100 Watt AC appliance to the Inverter it would draw only 0.83 AC amps but on the DC side of the inverter you would need 100W/12VDC (8.3 amps) from the battery,
OK, I thought that you were saying is would draw 83 12VDC amps; not 8.3

I was a little concerned; most of our stuff that we use is 12 volt- but I do have an inverter with me in case we need it.
__________________
Wolf Pup T16P owner

"The trouble with quotes on the Internet is that it is nearly impossible to discern if they are genuine." - Abraham Lincoln
ken0042 is offline   Reply With Quote
Old 09-03-2011, 03:34 PM   #39
Site Team - Lou
 
Herk7769's Avatar
 
Join Date: Oct 2009
Location: South Eastern PA
Posts: 21,169
Quote:
Originally Posted by ken0042 View Post
OK, I thought that you were saying is would draw 83 12VDC amps; not 8.3

I was a little concerned; most of our stuff that we use is 12 volt- but I do have an inverter with me in case we need it.
Check your post. You were trying to compare a 1000 watt item to a 100 watt item. Remember AC Watts are are equal to DC Watts in an inverter. To get watts OUT you need the same number of watts IN. It just takes 10 times more DC amps at 12 volts to get it than it does at 120 volts. (less a very small factor used by the inverter - noramlly neglidgible)

To generate 1000 watts 120 AC you need 83 amps of 12VDC
To generate 100 watts 120 AC you need 8.3 amps of 12VDC

So, running a 1000 watt 120VAC TV for an hour will draw 83 amps from your battery powered inverter. HOWEVER, plugging a 1000 watt 12 VOLT DC TV directly into the battery will ALSO draw 83 amps over the course of an hour.
__________________

Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW
Herk7769 is offline   Reply With Quote
Old 09-03-2011, 03:47 PM   #40
Senior Member
 
ken0042's Avatar
 
Join Date: Sep 2010
Location: Calgary
Posts: 375
It was more of a case of me reading the post I quoted from you wrong.

I read it as "in order for an inverter to produce 100 watts of 120VAC, you need to supply it with 1000 watts of 12VDC." However I understand now that what you were saying was "in order for an inverter to produce .83 amps 120VAC, you need to supply it with 8.3 amps 12VDC."

__________________

__________________
Wolf Pup T16P owner

"The trouble with quotes on the Internet is that it is nearly impossible to discern if they are genuine." - Abraham Lincoln
ken0042 is offline   Reply With Quote
Reply

Tags
led pad, solar

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



» Virginia Campgrounds

Reviews provided by




ForestRiverForums.com is not in any way associated with Forest River, Inc. or its associated RV manufacturing divisions.


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 06:03 PM.