# evaluating solar chargers.



## csi-tech (Apr 13, 2013)

I want to buy a solar setup (one or two panels to set on the ground or install on the roof of my RV with a controller). I am new to this and I'm just learning. The Mono panels look to be what are best suited for me but I'm not sure how to size everything. I have two 80 amp hour lead/acid batteries and I have a crappy old converter in the camper. I have installed a 750W inverter in addition to the converter. I am doing the calculations for power usage and the batteries should stay well above 50% for what I expect to use. I replaced all of the bulbs with LEDs and I will be running a 24" TV, a Directv receiver and a blue ray player. Not all at once of course. I live in the South so sun time is usually not an issue.

What I need help with is sizing the solar panels. I can afford as much as two 160 watt panels but is that overkill resulting in wasted energy? Should I look at perhaps two 100 watt panels or maybe even a single 160? I really like the Zamp portable kit but man is that expensive! I have a generator for the heavy lifting (Air conditioner, microwave, hotplate etc.) All I need from my batteries is the receiver, TV, lighting, phone charging, a laptop and a few LED lights at a time.


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## Real Old Man (Aug 17, 2015)

csi-tech said:


> I want to buy a solar setup (one or two panels to set on the ground or install on the roof of my RV with a controller). I am new to this and I'm just learning. The Mono panels look to be what are best suited for me but I'm not sure how to size everything. I have two 80 amp hour lead/acid batteries and I have a crappy old converter in the camper. I have installed a 750W inverter in addition to the converter. I am doing the calculations for power usage and the batteries should stay well above 50% for what I expect to use. I replaced all of the bulbs with LEDs and I will be running a 24" TV, a Directv receiver and a blue ray player. Not all at once of course. I live in the South so sun time is usually not an issue.
> 
> What I need help with is sizing the solar panels. I can afford as much as two 160 watt panels but is that overkill resulting in wasted energy? Should I look at perhaps two 100 watt panels or maybe even a single 160? I really like the Zamp portable kit but man is that expensive! I have a generator for the heavy lifting (Air conditioner, microwave, hotplate etc.) All I need from my batteries is the receiver, TV, lighting, phone charging, a laptop and a few LED lights at a time.


great post. been looking at something similar for the farm, but I'm not quite ready to drop a lot of dough


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## csi-tech (Apr 13, 2013)

I'm probably getting a 120 Watt suitcase style that just clamps to the battery bank. These are supposed to provide a 50% charge over the course of a sunny day. Which beats the crap out of my converter when the generator is on. That seems to provide a 0% charge over the course of a month.


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## 8301 (Nov 29, 2014)

LCD TV with satellite draws about 140 watts, figure another 40 watts for the Blu-ray player. Guessing another 20 watts average for the LED lights with everything running 4 hrs a day so about 800 watt hrs per day. Keep in mind that all of these things (except the lights) including the inverter will draw power when not being used so turning them off when not in use may be the smart choice. Figuring about 80% total charging and storage system efficiency and an inverter that is about 85% efficient so you need about 1000 watt hrs (1 kw/hr) a day. 

Assuming your batteries are strong and healthy your two 12v 80 amp/hr deep cycle batteries hold 1920 watt hrs so you'll drain them to 48% SOC (state of charge) each night. Not the best choice for long battery life but you can always try to slightly reduce your loads or bump up your batteries. 

Keeping in mind the 80% total charging system efficiency and assuming 4 hrs of sunshine per day (less in winter) you can get away with 290 watts in panels. 

The bottom line is it really depends on how many hours per day you run things. Keep in mind that with your 160 amp/hr battery bank you may be watching a game and the TV cuts out because it's been a little cloudy for a few days and you have a small battery setup.


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## MaterielGeneral (Jan 27, 2015)

csi-tech said:


> I'm probably getting a 120 Watt suitcase style that just clamps to the battery bank. These are supposed to provide a 50% charge over the course of a sunny day. Which beats the crap out of my converter when the generator is on. That seems to provide a 0% charge over the course of a month.


I was going to suggest the suitcase style but you beat me to it. I have a pop up that I like to take to public land and I was originally looking an Renogy brand but way to much money. I have been eyeballing these ones on eBay.

NEW 100W Folding Solar Panel 12V Portable Kit Camping Caravan Battery Power | eBay

120W Watt 2x60W Complete Folding Solar Kit for 12V Caravan Boat RV Marine Home | eBay

I like how you don't have to do any permanent modifications that could leak. You just place them in the sun and plug in the battery.

As far as your original question about size and how many panels, get as much as you can afford. Its not going to hurt anything as long as the charge controller is strong enough to handle the charge. Its better to have a fully topped off battery than a half charged battery. With having larger solar panels it always leaves open the option that you can add more batteries and that means more energy.


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## csi-tech (Apr 13, 2013)

John Galt said:


> LCD TV with satellite draws about 140 watts, figure another 40 watts for the Blu-ray player. Guessing another 20 watts average for the LED lights with everything running 4 hrs a day so about 800 watt hrs per day. Keep in mind that all of these things (except the lights) including the inverter will draw power when not being used so turning them off when not in use may be the smart choice. Figuring about 80% total charging and storage system efficiency and an inverter that is about 85% efficient so you need about 1000 watt hrs (1 kw/hr) a day.
> 
> Assuming your batteries are strong and healthy your two 12v 80 amp/hr deep cycle batteries hold 1920 watt hrs so you'll drain them to 48% SOC (state of charge) each night. Not the best choice for long battery life but you can always try to slightly reduce your loads or bump up your batteries.
> 
> ...


Very good points. I also run my generator a couple of hours a night too. I guess the overall goal is reducing generator use. Your math is spot on too. These are the same numbers I'm coming up with or very close. I'm not too concerned about battery longevity. These were just 100.00. Everyone says to change to a golf cart battery bank.

Sent from my SAMSUNG-SM-G930A using Tapatalk


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## budgetprepp-n (Apr 7, 2013)

csi-tech said:


> I want to buy a solar setup (one or two panels to set on the ground or install on the roof of my RV with a controller). I am new to this and I'm just learning. The Mono panels look to be what are best suited for me but I'm not sure how to size everything. I have two 80 amp hour lead/acid batteries and I have a crappy old converter in the camper. I have installed a 750W inverter in addition to the converter. I am doing the calculations for power usage and the batteries should stay well above 50% for what I expect to use. I replaced all of the bulbs with LEDs and I will be running a 24" TV, a Directv receiver and a blue ray player. Not all at once of course. I live in the South so sun time is usually not an issue.
> 
> What I need help with is sizing the solar panels. I can afford as much as two 160 watt panels but is that overkill resulting in wasted energy? Should I look at perhaps two 100 watt panels or maybe even a single 160? I really like the Zamp portable kit but man is that expensive! I have a generator for the heavy lifting (Air conditioner, microwave, hotplate etc.) All I need from my batteries is the receiver, TV, lighting, phone charging, a laptop and a few LED lights at a time.


My .02 I don't think there is such a thing as over kill when it comes to panels (within reason) on a sunny day you can use
an appliance and run off the panels more than the batteries if they are full and save that juice for later after dark. 
With a charge controler you don't need to worry about overcharging. And if you ever do have a gloomy day more charging
power is nice to have. So my call would be to go with the bigger panels.


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## csi-tech (Apr 13, 2013)

I went with the 2nd option on Ebay that Meterialgeneral posted. 120 watts. They arrived a few days ago. Poly panels, charge controller, cables and an aluminum support structure that people don't seem to like. The problem is that they went with L shaped aluminum bars. I can get square stock at Lowe's and make it bullet proof if I just can't stand what they came with. It would cost me all of 10.00 and a half hour with a drill and a hacksaw. Other than the weakish legs it looks great and is very portable. It has solid hinges, latches and a handle and the frame is nice and solid. I have no idea how it works yet. I have to go get the camper. I got rained out last week.


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