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08-18-2019, 02:38 PM
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#15
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Senior Member
Join Date: Feb 2018
Posts: 1,283
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I found this article about building a wind faring for solar panels.
https://www.thefitrv.com/rv-tips/bui...r-the-travato/
__________________
Jeff--
Arctic Fox 22G w/1440 watts solar/GMC2500HD Double Cab with Leer Cap w/740 watts solar
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08-19-2019, 04:24 PM
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#16
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Senior Member
Fleetwood Owners Club
Join Date: Sep 2017
Location: Jefferson, GA
Posts: 147
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The problem with flooded acid or AGM's is this:
For every 1,000 watts of energy expended to recharge them, store that charge and then retrieve that energy, you get about 350 watts in return for your 1,000 watts spent.
The reason? Much like the difference between an incandescent bulb and the LED bulb, where an incandescent uses 90% of its energy producing a frequency (heat) which is well below the threshold of visible light and only 10% manages to produce a frequency that we see as visible light. This means a 60 watt bulb uses 54 of those watts to produce infrared heat and only 6 watts to produce (light), the LED is the opposite. It only needs less than 10 watts to produce the same amount of luminescence, with less than 2 going to to a frequency that we cannot see and the rest going to produce (light).
Flooded acid batteries are resistant to charge. This resistance is turned into heat (a significant loss). The amount of loss can vary, but it is anywhere from 35% to as much as 100% depending on the condition of the battery and the charge rate. Then they lose about 10% per month and when you need to retrieve those electrons from that type of battery it again is resistant to release those electrons and you have yet another heat loss that is anywhere from 20% to as much as 60%. So for your 1,000 watts spent to store and later retrieve that wattage for some other use, you can expect to get about 350 watts for every 1,000 spent.
Lithium batteries also have charge losses (1%-3%) and storage losses (<.1%), as well as supply losses (1%-3%) which means for every 1,000 watts you spend to store energy in them, you get back more than 950 watts in return.
This means you don't need as large of a solar array if you use LIFEPO4 batteries or an equivalent (like a Tesla battery). It also means your batteries charge faster, because they are not as resistant to charge.
So any advice for you to keep your flooded acid or AGM batteries is simply bad advice if money is not an issue for you.
Understand that although your AGM battery might have a 100 amp hour rating, you cannot get 100 amp hours out of it more than once or twice before it'll be too damaged to recharge. The safe and best practices for a flooded acid battery is to never let the State of Charge (SOC) get below 50%. So if you have a dozen AGM batteries, each rated for 100 amps (1200 amp hours), your best expectation is to know that you actually have 600 Ah or less of actual usable power.
Without going into the needed detail to make a subscriber understand that an AGM battery depletes at much less than a sliding scale ratio, the lithium battery is far superior at holding the voltage high and thereby not causing an over amperage condition to develop in the circuitry.
In simple layman's language: Replace your conventional 100 year old battery technology with a much better storage solution and your entire solar question changes drastically.
You might discover that with a LIFEP04 battery storage solution, you'll actually not need solar at all.
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08-19-2019, 04:34 PM
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#17
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Senior Member
Join Date: Feb 2018
Posts: 1,283
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The other advantage to LiFePO4 batteries is that they charge just as fast at the top 5% as they do in the middle state of charge. If you are running an alternator or generator to charge them you can use up to 50% C or 50 charging amps/100 amp-hour battery. Your neighbors are happy because you didn't need to run the generator for hours attempting to get your battery to 100% SOC.
The LiFePO4 batteries will not be harmed if they stay below 100% state of charge for long periods of time.They just need enough charge so the phantom loads don't pull the state of charge down to zero. Solar is a good way to keep this from happening if you store the RV outside.
__________________
Jeff--
Arctic Fox 22G w/1440 watts solar/GMC2500HD Double Cab with Leer Cap w/740 watts solar
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08-19-2019, 05:00 PM
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#18
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Senior Member
Fleetwood Owners Club
Join Date: Sep 2017
Location: Jefferson, GA
Posts: 147
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We do have solar panels, residential grade made by Solar World - 300 watt panels installed in series. After much research and many discussions with a number of technical experts in the Yacht world, the go to solution was all Victron Energy (VE) equipment. the VE MPPT controller, VE battery management system, VE LIFEPO4 batteries, VE Multiplus 3000 inverter, and the VE dongle so I can see everything on my phone running down the road.
The engine driven alternator was upgraded from the pathetic 130 amp Delco-Remy 22Si to the Delco-Remy 40Si - 300 amp alternator.
Now the engine driven alternator can recharge the entire house bank in under an hour of driving, or we can recharge the house bank with the 600 watts of solar on the roof if we are boondocking. I can also recharge them with a shore power connection or the Onan 7500 generator.
Folks, you need to know that your inverter needs to be at least 3,000 watts with a surge capacity greater than double that if you intend to operate any A/C appliance with a compressor (or a microwave) off of your inverter/battery bank.
Your battery bank needs to be quite significant as well, with at least a true rating of 400 Ah (minimum) to be able to sustain an overnight quiet sit some place without operating your generator and or being plugged into shore power.
If you are camping someplace here in the SE USA and you want to operate your rooftop HVAC system, you need more than 800 Ah's of true power available.
So imagine having ten AGM's to make this even remotely feasible. In the morning your batteries would be at or near 50% SOC and need a 14VDC charge @ 120 amps (the maximum offered by VE) or 1680 watts. A minimum of 30% of the recharge gets lost to heat, reducing the input charge efficiency to 1,176 watts. That 1,176 watts is trying to recharge 10 AGM's from 50% back to 100%, needing 600 amps overall, with an average charge voltage at or near 13.6 VDC. This equates to 8,160 watts in total, and if you are effectively charging your bank at 1,176 watts, it'll take 6.9 hours to recharge your battery bank.
Gents, that's an unreasonable expectation for what you have in limited space on your roof for solar panels.
When someone sells you a 300 watt panel, that doesn't mean it produces 300 watts at sunrise. It might produce 18 watts at sunrise, 300 watts at noon and 10 watts at sunset. This average comes to a typical solar day. I have 17 residential solar panels on the roof of our residence (not the RV) and each are rated to produce 245 watts of power. They are perfectly mounted facing 191 degrees south and have a 30 degree pitch. It doesn't get any better than that and I still only get about 140 watts in aggregate for each panel. If I needed 1,176 watts for 7 hours, I'd need at least 9 residential sized solar panels to make that even remotely possible. I don't think many RV's have room on the roof for 9 residential sized solar panels.
The two 300 watt panels installed on the top of the RV are not perfectly positioned facing south and they are not pitched to face the sun all day. I estimate they produce about 70 watts per hour (each) over any given solar day, and if the day is 12 hours I get about 1,680 watts of power from them. Thats not enough to fry an egg. It is however, enough to keep my battery bank topped off and provide sufficient energy to the battery warmer mats to bring them up to a temperature that is safe to charge them (when its really cold outside).
In the summer its also enough energy to operate the indoor dehumidifier and keep the battery bank at 100% SOC when the RV is sitting in storage outside.
So having solar panels is indeed a good idea for long term storage and to protect the inside of your RV from the potential hazards of mold growth when its unused, but much more than that requires a serious coverage of your entire roof.
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08-19-2019, 05:22 PM
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#19
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Senior Member
Join Date: Feb 2018
Posts: 1,283
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I get about 3.2 kilowatt hours per day out of my pair of 300 watt solar panels. I live in Nevada and the sun is intense in the summer time. I am getting about 3.0 kilowatt hours per day out of my three 180 watt panels. My 265 watt panels is a poly-crystalline and only gives me about 1 kilowatt-hour per day.
I only see this much out of my panels when I am using my air conditioner to continuously use up the available solar power. Once my batteries see 100% SOC my output from my charge controllers drops of significantly.
I ran my Mach 1 PS 11,000 BTU air conditioner 7 hours yesterday on the solar output alone. My trailer was kept at 74 degrees and the outside temperature peaked about 3:30PM at 96.5 degrees in the shade. I don't need air conditioning when the sun isn't shining because the dry air temperature drops off rapidly in the evening at altitudes of 5000+ feet. My air conditioner is only pull about 8 amps when running and the unit cycles off enough that my solar can keep the SOC from falling under full sun. My old air conditioner pulled 15+ amps and my solar could not keep up for more than a few hours.
I know if I live at lower altitudes with higher humidity, I would need a generator to run the air conditioner overnight.
__________________
Jeff--
Arctic Fox 22G w/1440 watts solar/GMC2500HD Double Cab with Leer Cap w/740 watts solar
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08-19-2019, 05:37 PM
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#20
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Senior Member
Monaco Owners Club
Join Date: Oct 2009
Location: Tucson, AZ
Posts: 6,575
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Thanks for the great primer on solar, but you almost skipped over the issues LiFePO4 batteries have with temperature extremes, both hot and cold. For those of us that live and travel in the southwest, our everyday temperatures are too much for LiFePO4 batteries. We have to give up precious space inside the coach for a battery pack. I also worry about them when the coach is in storage and the inside temperatures reach 140 degrees.
How many charge/discharge cycles can I expect from a LiFePO4 battery pack?
How much should I expect to pay for a LiFePO4 battery pack equivalent to eight GC2 6V batteries?
Thanks
__________________
97 Monaco Windsor- Sold
07 Monaco Executive McKinley- Sold
04 Monaco Signature Chateau IV
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08-19-2019, 09:49 PM
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#21
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Senior Member
Join Date: Feb 2018
Posts: 1,283
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Quote:
Originally Posted by vito.a
Thanks for the great primer on solar, but you almost skipped over the issues LiFePO4 batteries have with temperature extremes, both hot and cold. For those of us that live and travel in the southwest, our everyday temperatures are too much for LiFePO4 batteries. We have to give up precious space inside the coach for a battery pack. I also worry about them when the coach is in storage and the inside temperatures reach 140 degrees.
How many charge/discharge cycles can I expect from a LiFePO4 battery pack?
How much should I expect to pay for a LiFePO4 battery pack equivalent to eight GC2 6V batteries?
Thanks
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I keep mine inside because they are closer to my inverter and are kept away from the extreme temperatures on a trailer tongue. They are also out of site between my folding sofa and my front pass through storage.
I live in Reno so the overnight cooling prevents the trailer from getting over 100 degrees in the hottest summer sun. I use SensorPush Wireless Thermometer to continuously log temperatures. I can view the recorded history on my phone.
I would contact BattleBornBatteries and ask them about the effects of storing the batteries in temperatures higher than 135 degrees. I would consider shade or ventilation or altitude as a way to mitigate higher storage temperatures.
Here is the info on the BattleBornBatteries:
Below 25F BMS permits discharge only
Between 25F and 135F BMS permits charge and discharge
Above 135F BMS will not permit charge or discharge
My trailer has not been higher than 98 degrees under full sun. I leave a roof vent open and running during hot weather along with my kitchen window which is too small for anyone to crawl through. The vent is under a solar panel and doesn't allow rain in.
I am not sure which GC2 size you are referring to. Going from Trojans T105 specs 8 batteries weigh 496 pounds and provide 900 amp-hours of capacity.
I would consider four 100 amp-hour BattleBornBatteries a better performing solution for these reasons:
total weight LiFePO4 batteries: 124 pounds or 25% of 8 GC2 batteries
volume about 50% less
10 year warrantee and 3000 100% discharge cycles. They expect the batteries to last 15 years in RV applications.
50% C charge rate or 200 amps for four batteries.
Almost all charging energy goes into the battery state of charge vs mostly heat for lead acid so less solar panels and fewer generator hours required to charge them.
100% C discharge rate without reduction in amp-hour capacity which allows battery to support large inverters with 200% C surge capacity. My 2200 watt inverter can surge to 6600 watts and my 4 100 amp hour batteries can surge to 9600 watts for 30 seconds. The surge capacity is great for starting my air conditioner.
BMS protects the batteries from dead shorts, low voltage, high voltage, high current. The only requirement before storage is to charge the batteries to at least 50% The BMS will turn off the battery at the low voltage cutoff but the cells will eventually drop to a voltage level that is harmful.
BattleBornBatteries 100 amp-hour price is $949 each or $3796 for 4.
__________________
Jeff--
Arctic Fox 22G w/1440 watts solar/GMC2500HD Double Cab with Leer Cap w/740 watts solar
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08-19-2019, 09:49 PM
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#22
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Senior Member
Fleetwood Owners Club
Join Date: Sep 2017
Location: Jefferson, GA
Posts: 147
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Our residential system is a 17 panel, 245 watt per panel system with individual microinverters that output 240 VAC. It was installed and became operational on the 13th of July, 2013, and today’s date is the 19th of August 2019, 2229 days have elapsed in the interim.
If the system has produced 36.26 MWh in those 2229 days, that’s 36,260 KWh with an average daily production is (36260/2229) = 16.27 kilowatts, or 16,270 watts. Divide that by the number of solar hours each day (on average) of 12 and we have the average hourly production of solar power: 16270/12 = 1356 watts/hr, or 1.36 KWh.
Our system was sold to us and pitched as a 4.1 KWh system, when in reality it is a 1.36 KWh system. It has the potential to produce 0-4100 watts, and it averages 1356 watts per hour as seen over the 6 years, 1 month and 7 days since its installation.
Here in Georgia we are getting 1/3 the power production that was originally ascribed. As an engineer I knew the actual performance depended on too many factors for a salesman to guarantee, and although the sales pitch came across as if it was going to practically eliminate our power bill every month, reality and some simple math proved otherwise in my head. I just wanted enough power production to offset the pool pump.
If you install 1000 watts of solar on top of your RV you can and should expect a bit less than similar performance. Expect about 250 watts per solar production hour on average for every 1,000 watts of paneling on your roof. If you have a couple of those 100 watt Renogy panels, you’ll have the same proportional outcome.
We have 600 watts of potential solar power generation on the roof of the RV and I expect to get 200 watts/hr on average out of them, or 2400 watts of usable power stored in our LIFEP04 battery bank. As soon as we upgrade the refrigerator to a JC Refrigeration 88 watt (50% duty cycle) DC refrigerant compressor system, the projected 1056 watts of power consumed (in a given 24 hours) by the upgraded refrigerator compressor can be sustained by the expected 2400 watts of power produced by the solar array. The added wattage being consumed by the other gadgetry and things running on DC power with the Inverter off.
My whole point here: Don’t plan on being able to go off grid in complete silence in your RV, never need to operate your generator or be connected to shore power with the limited space you have on your roof for a solar array.
I think the most I’ve ever heard of someone packing onto an RV roof was something just shy of 2400 watts. Using the 1/3 power performance expectation that we have 6 years, 1 month and 7 days of proof to show, that 2400 watts will produce about 800 watts on average over a 12 hour period. That’s 9,600 watts.
A 13.5k BTU airconditioner with a 50% duty cycle on the compressor and an 80 % duty cycle on the blower fan will consume 2,000 watts to start both the fan and compressor, 1,200 watts to sustain run both the blower fan and the compressor (50% duty cycle) and 300 watts to operate the fan only for the remaining 30% duty cycle of the blower. The start energy demand makes up for any savings that might have manifested from being off-duty-cycle, meaning that there is no realized savings potential when a compressor motor has to start against a non-equalized pressure condition. All of this means the average power consumption of the 13.5k airconditioner in any given hour of operation is over 1,000 watts. The power efficiency losses to convert DC into AC power is typically 20%, making the 9,600 watts of stored power more likened to 7680 watts of available power.
At 1,000 watts an hour of consumption, and having a battery bank with an effective capacity of 7680 watts, you can safely operate one roof mounted 13.5k AC unit for 7 hours without need of starting a generator or having shore power available.
These types of calculations are used on boats that are parked in slips or anchored in bays where generators are unwelcome from 10pm through 7am. They apply to RV’s the same way, and as you can see you need at least a 2400 watt solar array to make this possible and only again if you use highly charge efficient LIFEPO4 batteries – something only achievable with at least eight 90-100 Ah LIFEPO4 batteries and at least 8 full sized 300 watt residential grade solar panels.
In the morning, when your batteries are drained from running the AC unit all night, you can’t plugin your coffee pot or microwave a breakfast burrito without needing power from another source – your generator. So you start the generator and depending on its capacity you run it for an hour to give you fresh coffee and a burrito, with the added initial charge going back into those highly efficient LIFEPO4 batteries. As the sun rises you again might need to operate that 13.5k AC unit, which means you’ll either have to start the generator or risk having dead batteries by sundown.
So for those boondockers living in high temperature and high humidity environments, needing to operate an air conditioner, you need a really large array and a big bank of batteries or you can forget being comfortable in a quiet environment. Your generator or a shoreline is the only solution to anything less than 900 Ah of LIFEPO4 battery storage and at least 8 full sized residential solar panels rated at 300 watts each.
Expect to pay $1200 for a 100Ah LIFEPO4 battery. If you buy enough of them at the same time, that price drops. You can also get them in larger sizes from Victron Energy.
A LIFEPO4 battery made by VE will not accept a charge if the temperature conditions are outside of the parameters of the built in BMS. Temperatures below 35 F and above 110 (I think) are the limits. Consult with them online to see the specifics. Warmin them is a cinch with a dog bowl heating mat that automatically activates at 35 degrees and turns off at 45. Its a gadget made by ThermoCube and its dirt cheap. It works perfectly with low wattage planter starter heaters or dog bowl mats.
I relocated our battery bank under our bed, because three 90Ah VE batteries (270Ah) actually have more than double the power longevity of 6 AGM or GC2 type batteries and they are indoors. They never get too hot even here in Georgia and I've already addressed the cold issue. They are perfectly safe, have no off-gassing or fluids to leak and they weigh about 1/2 that of a comparable sized lead battery.
Hope this helps. I know its long winded and detailed, but this type of information is what people actually need when it comes to understanding the reasons why they should have realistic expectations on the performance of their system.
Obviously if you live in the Desert, where there are few clouds to diffuse or obscure your solar day, your performance numbers will be much better than what we see here in Georgia.
Good Luck!
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08-19-2019, 10:04 PM
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#23
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Senior Member
Join Date: Jul 2018
Posts: 2,812
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"Expect to pay $1200 for a 100Ah LIFEPO4 battery. If you buy enough of them at the same time, that price drops. You can also get them in larger sizes from Victron Energy"
Actually Battle Born 100 a/h batteries have been going for $949, no tax, no shipping, list for several years, and if you catch them on sale or do a bulk buy can get them for a little as $850.
I also use the thermo cube and a little 200 watt space heater and it works fine in 0 f weather. Never stay where ambient temps in battery compartment goes over 135 f, but have thermostatic vent fans to vent compartment if necessary.
__________________
Foretravel tag axle 40 ft. 500 hp/1550 ft/lbs ism 1455 watts on the roof. 600 a/h's lithium down below.
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08-19-2019, 10:08 PM
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#24
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Senior Member
Join Date: Aug 2017
Location: Syracuse Ut.
Posts: 692
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Can't determine best without knowing what your specific needs, and camping conditions are. How much energy do you need the system to provide, and for what time duration. Can you generally park with the sun on a certain side of the vehicle, or will directional orientation of the rig vary a great deal? Seasons you'll be camping, and geographic locations pretty much fixed, or will they vary greatly? Will you be mostly in areas with a clear view of the sky, or do you need the system to handle shade on all, most, or part of the vehicle? Another thing that makes a difference is how many days in a row will you likely be running on solar, and how many days a year?
Finally, be cautious of what you read and learn on the forums. You get what you pay for, and so far you haven't even offered up a brew....
__________________
2016 Bighorn 3270RS, 2015 Ram 3500 CTD/ASIN
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08-19-2019, 10:11 PM
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#25
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Senior Member
Join Date: Feb 2018
Posts: 1,283
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I don't disagree about your solar production in Georgia. If you need air condoning in hot muggy environments camp with full hookups or run a generator constantly.
In Nevada the solar power performance is outstanding. Very dry weather and 35 degree overnight cooling means you only need air conditioning from about 10-11 AM until about 6PM. I am getting 75-82% of my panels rating production in the peak 10-3 period. I get significant additional solar production between 8am and 6pm in the summer months. I am getting about 7 Kilowatt/hours daily when parked at home. My trailer gets shaded significantly after 3:30PM. When camping in open spaces I continue to get good solar to about 6PM.
My air conditioner pulls 8 amps when cooling and I let run it in 'cool low auto' so the fan stops when the compressor cooling cycle is over. 1400 watts of solar is enough to keep my batteries charged while run the Mach 1 PS air conditioner under full sun. My Mach 3 Plus drew too much power for my solar system to keep up.
Here is a graph showing my battery state of charge and wattage for two hours while running air conditioner in a 96 degree max outside temperature with a 74 degree inside thermostat setting. This was part of a 7 hour test of running air conditioning using solar only. I was also using a laptop and watching tv during the test.
__________________
Jeff--
Arctic Fox 22G w/1440 watts solar/GMC2500HD Double Cab with Leer Cap w/740 watts solar
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08-20-2019, 07:56 AM
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#26
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Senior Member
Fleetwood Owners Club
Join Date: Sep 2017
Location: Jefferson, GA
Posts: 147
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Astrocamper,
Those are some impressive numbers. We don't see that kind of performance here in the SouthEast because the sun is diffused almost every day and as you'll see on the chart provided (attached) that the sun and clouds do indeed negatively affect the performance.
The bottom Line: Solar performance varies greatly and depends on where you are located geographically and if you have any trees or shading that might obstruct your panels line of sight to the sun.
Heat, humidity and environmental conditions greatly affect your power consumption needs, and you need to consider these factors before installing a solar system. Its easy to have one thats too small, and its practically impossible to have one thats too large.
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08-20-2019, 10:19 AM
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#27
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Registered User
Monaco Owners Club
Join Date: Mar 2018
Location: Blairsville, GA & WPB, FL
Posts: 3,993
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Ret60sp, how about the source of your battery charging efficiency % numbers. Would help to have the bulk %, absorption %, and float %.
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08-20-2019, 03:01 PM
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#28
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Senior Member
Join Date: Aug 2017
Location: Syracuse Ut.
Posts: 692
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Quote:
Originally Posted by Ivylog
Ret60sp, how about the source of your battery charging efficiency % numbers. Would help to have the bulk %, absorption %, and float %.
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Based on 40 years of work in mobile power generation and storage systems, and of course my personal toys, round trip energy loss on a flooded cell battery is approximately 20 percent max. For my personal RV, I have my charging system set to hit the normal voltage current setpoints prior to going into float, then continuing with a mini equalization of sorts until I hit 120 percent of what was drawn from the batteries. This is the recommended overcharge by Deka for the EGC2 batts I'm using. Last I checked, Trojan recommends a max overcharge of 115 percent with their GC type batts.
AGM batteries not only don't benefit from overcharging to any extent, and they can be damaged if you do overcharge them. With AGM, you're generally fully charged at somewhere around the 112 percent level of what was drawn. Of course comparing total energy required to return to a fully charged state against what was removed from the initially fully charged battery will give you the energy loss or battery efficiency for the full cycle. To figure out whether the efficiency loss is in the discharge or charge portion of usage gets somewhat complicated, and isn't measurable with simple equipment like my trimetric.
Lead acid batteries have been around for an awful long time, and their characteristics are well understood and documented, yet there still seems to be a lot of misinformation floating around about them.
__________________
2016 Bighorn 3270RS, 2015 Ram 3500 CTD/ASIN
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