Required reading for solar

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tomzleapin
Posts: 485
Joined: Sun Jun 20, 2010 9:15 am

Required reading for solar

Post by tomzleapin »

I just came across this site:

http://handybobsolar.wordpress.com/

Make sure to read "The RV Battery Charging Puzzle". Click the link on the right side of the page.

I have a 125 watt panel that I installed on my coach. It works quite well but after reading this I will definitely make some changes.
Tom
2005 24' RB
Towing 2016 Mini Cooper convertible on tow dolly
New Hope, MN
al1florida

Post by al1florida »

Bob has lots of great info, but does have some very strong opinions.

If you are going to install your own solar, use Bob's advice as some very very good guidelines, but use your own common sense when seting up your system.

If you are having a company install, be sure to follow Bob's advice, especially to wire size and location of components.
bigdipper
Posts: 353
Joined: Thu May 27, 2010 3:13 pm

Post by bigdipper »

My report may be premature, since our new rig has yet to be really tried out from an electrical point of view. Almost a year ago I decided to either retrofit a 2001 23RK or approach the Born Free folks about building a new one with the specified electrical set-up. I got Humboldt OK to install a system provided by AM Solar, an Oregon company specializing in RV solar/electrical systems. AM Solar also specified the installation details. Briefly our 2011 24RB has 3 100W panels on the roof, a high end charge controller, a 1500W pure sine wave inverter, and 440 AH of AGM batteries. Inverter is sized with intent of running nothing else on 120V when microwave is on. All this was accomplished with considerable effort on my part and by the other participants. There is no generator, and the roof layout was dramatically altered. Still there is a Fantastic Fan, a Sat seeking dome, and the regular Winegard antenna, most of which is not in standard location. There will be no parties on the roof! Questions/comments are welcome, but I will be a whole lot wiser after an upcoming 3 week trip that is intended to exercise all systems.
Ralph
Ralph
2011 24RB
Former 2001 23RK
FrankGRUN
Posts: 24
Joined: Tue Jul 06, 2010 9:27 pm

Post by FrankGRUN »

Interesting reading! The comments about wire size between controller and battery, location of the solar controller, voltage levels and the preference for flooded cell batteries all make good sense. This has made me consider adding a second panel and upgrading the solar controller to 10 amps.

In my older coach, there is no outside access to the auxiliary battery, other than the 80 amp hour unit located under the hood. I could fabricate a sliding tray battery mount system to accommodate two additional 6V T-105's for an extra 225 amp hours of capacity.

I was certainly concerned with Bob's comments about 3-stage battery charger systems.
Frank and Paula
1982 BF 24' RB
al1florida

Post by al1florida »

Here are additional links to great information about solar, generators & RV battery usage:

http://www.jackdanmayer.com/rv_electrical_and_solar.htm

This is a great tutorial about RV electrical:
http://www.rv-dreams.com/rv-electrical.html

And here is what they installed in their RV & why they did it the way they did.
http://www.rv-dreams.com/our-rv-electrical.html
al1florida

Post by al1florida »

FrankGRUN wrote:Interesting reading! The comments about wire size between controller and battery, location of the solar controller, voltage levels and the preference for flooded cell batteries all make good sense. This has made me consider adding a second panel and upgrading the solar controller to 10 amps.

In my older coach, there is no outside access to the auxiliary battery, other than the 80 amp hour unit located under the hood. I could fabricate a sliding tray battery mount system to accommodate two additional 6V T-105's for an extra 225 amp hours of capacity.

I was certainly concerned with Bob's comments about 3-stage battery charger systems
.
I'm not sure about your statement about your concern about 3 stage battery chargers, so I thought I would add a link to what the Trojan Battery company says about the proper daily or "bulk mode" charging voltage. They recommend 14.8 volts. Way above what any single stage charger (converter) provides.

http://www.trojanbattery.com/BatteryMai ... rging.aspx

One thing to keep in mind about all this is, if all you do is occasionally dry camp overnight and just run the lights and water pump, you don't really need anything more than the converter which came with your BF. Your alternator on the engine will recharge your house batteries nicely when you drive for several hours the next day. The converter will recharge your batteries when you are connected to shore power.

However if you need to run your furnace for most of the night and only drive for an hour or two the next day, and do this for a couple or three days you will most likely have dead house batteries. Or if you start using an inverter to power your TV & laptops you need more than just the converter.
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bfadmin
Site Admin
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Joined: Thu Aug 11, 2005 10:45 am

Post by bfadmin »

Just a note to say that the above links have been posted in our Technical Library section under the title Solar Charging and other RV Electrical Information and thanks to the above posters for providing the good information.
Born Free Leap'n Lions RV Club Website Forum Administrators
(bfadmin-1) Dave Moffat - Primary Administrator
(bfadmin-3) Sandy Perley - Assistant Administrator
(bfadmin-2) Bill Hemme - Backup Administrator
(bfadmin) Email: bfadmin@bornfreervclub.org
FrankGRUN
Posts: 24
Joined: Tue Jul 06, 2010 9:27 pm

Post by FrankGRUN »

My comment about 3-stage converter/chargers was triggered by the 14.8 bulk charge voltage recommendation. Most 3-stage chargers with which I am familiar are limited to a max of 14.4 volts. Further, this is often in the short pulse desulfanation cycle. I am not yet aware of how to increase the maximum charging voltage in the PD9245. My starting and auxiliary batteries are both flooded wet cell deep cycles.
Frank and Paula
1982 BF 24' RB
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Dallas Baillio
Posts: 1181
Joined: Sun Jul 02, 2006 10:52 pm

Post by Dallas Baillio »

Is this the debate as to how many angels can dance on the head of a pin?
It sure doesn't seem very significant to me. I've had a few beers when I write this and I have a my own quote that "Life's silliness is made plain with beer." So perhaps I am not in full control of my faculties. Still, the more technical an issue, the less likely others will consider it important in the grand scheme of things. Perhaps we should stop and smell the flowers. Aren't you pleased that I come along and offer my opinion?
Dallas Baillio
2001 26RSB
Born Free Leap'n Lions RV Club Member
FrankGRUN
Posts: 24
Joined: Tue Jul 06, 2010 9:27 pm

Post by FrankGRUN »

Well, it seemed to me to be a very useful discussion about the real technical requirements to realize the full potential (no pun intended) of solar panel installs and the lifetime of the wet flooded deep cycle batteries - a critical component of the issue. The cited claim of 14.8V vs. 14.4V charge dynamic suggested potential losses of 20% or more in recovered energy in short term daily dry camping scenarios. The available solar panel real estate in these vehicles is quite limited as is the space available for additional batteries in elder coaches.

To recap, I found it one of the more helpful exchanges on this site in a long while. Sorry to disturb your beer.
Frank and Paula
1982 BF 24' RB
al1florida

Post by al1florida »

In my previous MH, a 40' Diesel Pusher, I installed a TriMetric battery monitor. I had 4-6V golf cart batteries which gave me about 400 +- amp hours (AH) of power. I monitored my usage closely and never used more that 80-100 AH (about 25% of total available) before recharging. I will be installing the TriMetric in my BF before I go on any long trips.

When I ran my generator to recharge the batteries, the TriMetric would show about 85 amps coming from the Xantrex inverter/charger at about 14.5 to 14.6 volts. Since I was measuring the actual amps going into the batteries I pretty much assumed this meant if the reading stayed at 80 amps for at least 30 minutes I actually put 40AH back into the batteries.

Based on these real life measurements, I'm not sure just how important it is or how much difference it makes whether or not the voltage is at 14.8 or 14.4.

The other thing to keep in mind is the 3 stage chargers sense the charge level in the batteries and reduce the amps going into the battery as it get closer to 100% charged.

While my inverter/charger would start off at about 85A, it would drop to about 15A or less within about 1 to 1.5 hours. At this point I turned off the generator. I figured this brought me to about 90% charged. If I would try to charge to 95% or even 100% I would need to run my gen for a lot longer (several hours at 1/4 to 1/3 gallon of diesel per hour). This is where the solar panels would really be useful, to top off the batteries.

I you are going to be doing a lot of boondocking or dry camping it really pays to have a battery monitor like TriMetric to tell you just what the charge state is, how many amp hours you have used, how much charge you have put back in, etc.

On the other hand if you just dry camp overnight once in a while and run the lights & water pump and furnace for a hour two in the morning, then this discussion means nothing to you and your engine alternator and existing converter will work just fine for you.
tomzleapin
Posts: 485
Joined: Sun Jun 20, 2010 9:15 am

Post by tomzleapin »

Last winter I spent 3 months in south Florida, all dry camping. One campground I stayed for one month. My 125 watt panel with two Interstate 12 volt batteries performed well. I think I had to run my generator twice. My solar system is hooked up with #10 gauge wiring. The articles mentioned previously claims that this is inadequate. I was getting a consistent 5 to 7 amp charge but doubt if I was fully charging the batteries. I think worst case is that this would shorten the life of my batteries.
Tom
2005 24' RB
Towing 2016 Mini Cooper convertible on tow dolly
New Hope, MN
al1florida

Post by al1florida »

tomzleapin wrote:Last winter I spent 3 months in south Florida, all dry camping. One campground I stayed for one month. My 125 watt panel with two Interstate 12 volt batteries performed well. I think I had to run my generator twice. My solar system is hooked up with #10 gauge wiring. The articles mentioned previously claims that this is inadequate. I was getting a consistent 5 to 7 amp charge but doubt if I was fully charging the batteries. I think worst case is that this would shorten the life of my batteries.
I think you would find that for one 125 watt panel the #10 gauge wiring would work. I think a lot of the articles talk about 2 or 4 or even 6 large 125 watt panels. The more amperage you are trying to push down the wire the larger the wire needed.
I think a good rule of thumb is one 125 watt panel for each 100-125AH of 12V battery.
As you most likely know if you only use about 40AH of battery per day, the 5-7 amps are probably doing a good job of recharging your batteries. As long as you don't have a run of cloudy days.
In our diesel pusher, running 2 laptops 2-5 hours a day, old picture tube type TV and satellite TV receiver/dvr for 2-4 hours a day, plus lights & water pump, but no microwave, coffee maker or furnace we would use about 70-110AH a day.
bigdipper
Posts: 353
Joined: Thu May 27, 2010 3:13 pm

Post by bigdipper »

I am a rather technically oriented person and find all the detailed info interesting.

Still my battery/solar/charging experiences have been quite adequate with me simply considering batteries full at 12.6-12.7 V RESTING and in need of recharge if/when they get to 12.1-12.2V. I simply assume 10% of my battery AH capacity is equivalent to .1 volt. Most dry camping experience has been in the generally sunny west where the solar can do it's job well.

While I have moved from flooded golf cart batteries to AGMs, IMO ordinary golf cart batteries can take a lot of abuse, including pulling them way down. My last set was still doing well after 6+ years and a lot of cycles. They are designed for that kind of use/abuse. Just don't let them go dry and do not leave them in discharged state. Not to knock Trojans, but any 6V battery designed for golf cart use is a tough cookie. Lots of brand names, but very few manufacturers.

Just a nod toward keeping it simple from one who is inclined to complicate issues.
Ralph
Ralph
2011 24RB
Former 2001 23RK
FrankGRUN
Posts: 24
Joined: Tue Jul 06, 2010 9:27 pm

Post by FrankGRUN »

After due consideration, I'm going to up the ante by mounting 2-100 watt panels, running 10 gauge wire with MC4 connectors from panels to controller, with a Sunsaver PWM controller, 4 gauge wire to an 12V 8D battery in a vented poly case. This should give an auxiliary level of 290 A-H and an inadequate level of solar recharge, but supplementable with generator and/or engine as needed. Using a Voltminder Battery Monitor and Alarm. No room upstairs for three panels. Calculations show voltage loss of less than 1%. To be seen.

Thanks for the help.
Frank and Paula
1982 BF 24' RB
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