100% Solar ShantyBoat/Houseboat

[syst3m7]

I plan to be 100% Solar, living on my shanty boat I've built. Gas for heat & cooking, and solar for a few necessities. The MAX wattage in use at any given time is well below 100 watts (but usually around 25 watts will be used 24/7). (I haven't factored in the 6k Power Bright inverter's power)I've done so many calculations coming up with mostly different answers. So I figured this was a great place to get some input. I currently have 4 deep cycle 160Ah batteries wired in parallel (have more, but saving weight on the boat), using a 30amp Sunforce Charge controller, with 4x 145watt panels. The panels are just mounted flat on my flat roof, I'm aware that's not efficient, and the inverter is waaaay larger than I need. I'm just curious what you guys think. I've minimized my power consumption as best as I can so far. Do you think my setup is ok to run 25 watts all day/night all the time, with occasionally running it to around 100 watts for maybe 2 hours a day? Thank you in advance! I'm not sure if I'm allow to post images or I would post a few photos of the boat progress.

EDIT: I was just reading the thread called, "Inverter Size vs Battery Size"... Is my 12v 6,000 watt inverter, in combination with 4 to 6 160Ah deep cycle batteries a fire hazard? I have 2 #1 gauge wires on each positive and negative terminals going to the inverter (4 wires total just for the inverter).

[Mike90250]

Any 12V, 6,000w inverter is a hazard. It's not the wires so much, as the inverter itself, is prone to self-ignition from the huge current density when loads are applied. 6kw @ 12V is about 500A. Can traces on a circuit board manage that ? Can wires be crammed into the inverter box, with all the other stuff in there, and still be safe - doubtful.

if your loads are only 25 & 100 watts, get a decent 300W sine inverter and be happy. That 6Kw inverter likely burns 200w just sitting turned on.

Parallel batteries. Generally, a problem, causing shorter battery life. Because of electrical imbalances, the current ping-pongs between the strong battery and the weak battery, not evenly sharing the load, and therefor wearing the batteries out prematurely.
see http://www.smartgauge.co.uk/batt_con.html for the math and the long explanation.

[Sunking]

Reverse engineering tells me this. 25 watts x 24 hours = 600 watt hours. Your panels have 0 degree tilt. Location is unknown but assuming you could get 3 Sun Hours which is doubtful at 0 degree tilt would require a panel wattage of:

300 watts if using MPPT controller.
450 watts if using PWM controller.

12 volt battery capacity requires is 250 AH or a pair of 6 volt golf cart batteries.

Largest inverter a 12 volt 250 AH battery can manage is 400 watts or roughly the panel wattage. a 6000 watt12 volt inverter wil burn your boat down some day or will kill the batteries in a month from abuse. Whichever comes first. I hope for your sake the batteries die first.

There you go.

[jony101]

I do what you do everyday with 1x240 watt panel and a smaller 102ah battery as long as it isnt cloudy. And my panel is also flat on my roof. 25 watts is more or less what my netbook uses when plugged in to my 400 watt inverter. I also run a swamp cooler which uses about 50 watts most of the day. As long as you replenish the power you use at night the following day, you can run your system indefinitely.
As an example I ran a 12 volt fridge 24/7 off a 120 watt panel and 75 ah battery for months at a time. But it can only be done on such a small system if you got good sunlight. Your large battery bank will help you on the cloudy days.

If you decide to increase you loads, highly recommend you get an mppt controller so you can quickly charge your batteries when the sun is out. Myself I would only use the 6000 watt inverter in an emergency. It will be overkill to power a laptop.

[syst3m7]

Thank you guys for your input. I figured I would post a link to the exact inverter I'm using. And from the specs it looks like it's power consumption itself is only .6amps? It says, "No Load Current Draw < 0.6A". That would be 7.2 watts right? That just doesn't sound right to me. Or is that meaning something else? Link to Inverter here


jony101: Glad to know that your setup works fine for that. Other than my boat burning down or dead batteries, I shouldn't have any problems. lol

I've been running this same setup for over a year, but with 6 batteries instead of 4. But when I initially set it up, I planned to use much more power, instead this whole time I've only be running a security system which uses around 15 watts. I know it sounds ridiculous that I've had it for so long and still don't know it's capabilities, but life kinda took me in a different direction right after setting it up.

I do have another question though... My charge controller will only push 30 amps. Since I have 4 panels, each pair produce 25+ amps with peak sun, I realize that the second pair of panels are producing amps that are being unused. But in my mind, I see that allowing 30amps to charge even after peak sunlight.. Is this correct?

[SunEagle]

Thank you guys for your input. I figured I would post a link to the exact inverter I'm using. And from the specs it looks like it's power consumption itself is only .6amps? It says, "No Load Current Draw < 0.6A". That would be 7.2 watts right? That just doesn't sound right to me. Or is that meaning something else? Link to Inverter here


jony101: Glad to know that your setup works fine for that. Other than my boat burning down or dead batteries, I shouldn't have any problems. lol

I've been running this same setup for over a year, but with 6 batteries instead of 4. But when I initially set it up, I planned to use much more power, instead this whole time I've only be running a security system which uses around 15 watts. I know it sounds ridiculous that I've had it for so long and still don't know it's capabilities, but life kinda took me in a different direction right after setting it up.

I do have another question though... My charge controller will only push 30 amps. Since I have 4 panels, each pair produce 25+ amps with peak sun, I realize that the second pair of panels are producing amps that are being unused. But in my mind, I see that allowing 30amps to charge even after peak sunlight.. Is this correct?

Something is not correct with your math or you have some interesting 145watt panels. How can 2 of those panels in series produce 25amps? 2 Panels wired in series would have twice the Vmp of each panel but only generate 1 x the Imp of a panel. That would mean a 145watt / 25 amp = 5.8volts. I think you may have it backwards where the Vmp = 25volts and Imp = 5.8 amps for each panel.

Besides the math issue, I agree with what the others have stated. Get rid of that 6000 watt inverter and go with a nice 400watt pure sine wave one.

[Sunking]

I do have another question though... My charge controller will only push 30 amps. Since I have 4 panels, each pair produce 25+ amps with peak sun, I realize that the second pair of panels are producing amps that are being unused. But in my mind, I see that allowing 30amps to charge even after peak sunlight.. Is this correct?

Where are you coming up with 25 amps from? Are your panels wired in parallel?

[SunEagle]

Where are you coming up with 25 amps from? Are your panels wired in parallel?

That is also my question. Most battery panels in the 145 to 150watt range have a Vmp ~ 18 -19v and Imp ~ 8 amp.

If all 4 panels were wired in parallel he would exceed that 30 amp charge controller which I remember has a maximum input of 450 - 500watts.

And the maximum DC input voltage is 25 so 2 panels in series would exceed that limit as well.

[Amy@altE]

I'm all about the math

Here's some math based on the info you've given.

(25W x 24 hours) + (100W x 2 hours) = 800Wh

Your location says Columbia, SC, worst case sun hours for that location flat is 2.39 hours in Dec.

800Wh / 2.39 hours /.67 system inefficiencies = 500W solar needed / 145W panels = 4 panels. Check!

800Wh / .92 inverter efficiency x 3 days autonomy / .5 (50% DoD) x 1.19 temperature correction / 12V = 517 Ah 12V battery bank / 160Ah batteries = 4 batteries. Check!

145W 12V panels I looked at have a short circuit current of 8.37AIsc x 4 x 1.25 NEC requirement = 42A minimum charge controller needed. Booo. However, at a flat angle, you will not be getting full current out of them. I'd still recommend getting a bigger charge controller to maximize your generation.

I agree 100% with getting a smaller inverter. They are not much $.

[syst3m7]

Well, last night I ran everything but my security monitor and the battery bank was fully charged by 12 noon. (Everything on all night. 23" tablet, phone charging while using hotspot, security dvr with 2 cameras, digital led clock and the inverter). Tonight I'll run the security monitor all night in combination with everything else and a 7 watt led light.

My panels are all in parallel since I have a 12v system. Each panel is rated to produce 8.something amps, and they each actually produse 10 to 12 amps that I've seen using a volt meter. I have another 30 amp charge controller but I don't think I can use it with my setup, or if I can, I don't know how unless I make 2 separate setups.

Thank you for the advice guys and gals. I'm always open to more suggestions. I'll eventually pickup a smaller inverter.

[Amy@altE]

Well, last night I ran everything but my security monitor and the battery bank was fully charged by 12 noon. (Everything on all night. 23" tablet, phone charging while using hotspot, security dvr with 2 cameras, digital led clock and the inverter). Tonight I'll run the security monitor all night in combination with everything else and a 7 watt led light.

My panels are all in parallel since I have a 12v system. Each panel is rated to produce 8.something amps, and they each actually produse 10 to 12 amps that I've seen using a volt meter. I have another 30 amp charge controller but I don't think I can use it with my setup, or if I can, I don't know how unless I make 2 separate setups.

Thank you for the advice guys and gals. I'm always open to more suggestions. I'll eventually pickup a smaller inverter.

I calculated figuring wired in parallel. You are measuring something wrong, there is no way each 145W panel is producing 10-12A. Was the multimeter set to amps, and in line with the negative line?

If you wanted to use the 2nd charge controller, you can break it into 2 circuits, with 2 parallel panels going into each charge controller. It would be interesting if you can charge up your battery bank faster by using all of the available current, rather than clipping due to a too small charge controller. But again, I'm not sure what losses you are getting by having them flat, you may not actually gain anything.Maybe take out one of the panels and see if there is any difference in charging rate, and if the 4th one is actually making a difference.

[SunEagle]

Well, last night I ran everything but my security monitor and the battery bank was fully charged by 12 noon. (Everything on all night. 23" tablet, phone charging while using hotspot, security dvr with 2 cameras, digital led clock and the inverter). Tonight I'll run the security monitor all night in combination with everything else and a 7 watt led light.

My panels are all in parallel since I have a 12v system. Each panel is rated to produce 8.something amps, and they each actually produse 10 to 12 amps that I've seen using a volt meter. I have another 30 amp charge controller but I don't think I can use it with my setup, or if I can, I don't know how unless I make 2 separate setups.

Thank you for the advice guys and gals. I'm always open to more suggestions. I'll eventually pickup a smaller inverter.

8.x amps per panel and all of them wired in parallel makes more sense then what you were describing in post #5 ... "Since I have 4 panels, each pair produce 25+ amps with peak sun" ...

As for not over loading your 30Amp CC it is most likely due to the flat angle of the panel mounting and less than perfect weather conditions. They probably will not produce their full Imp except for a few minutes when the Sun is directly overhead. Just be aware that those 4 panels have the potential to overload your CC under certain conditions.

So based on Amy's "math" you have been lucky not to have hurt that 30amp CC. You should look into getting at least a 40amp rated CC because under the right conditions you will push that Sunforce beyond it's overload capacity.

Also replace that over sized 6000 watt inverter with a pure sine wave type around 400 watts.

[SunEagle]

I calculated figuring wired in parallel. You are measuring something wrong, there is no way each 145W panel is producing 10-12A. Was the multimeter set to amps, and in line with the negative line?

If you wanted to use the 2nd charge controller, you can break it into 2 circuits, with 2 parallel panels going into each charge controller. It would be interesting if you can charge up your battery bank faster by using all of the available current, rather than clipping due to a too small charge controller. But again, I'm not sure what losses you are getting by having them flat, you may not actually gain anything.Maybe take out one of the panels and see if there is any difference in charging rate, and if the 4th one is actually making a difference.

It is possible that the 10 -12amps he measured is a false reading based on the multimeter he was using and if it is calibrated correctly.

My Sunforce CC has a digital readout showing the amount of amps it is charging the batteries and since it is a PWM CC that means Amps out = Amps in. Attached is a picture when mine was charging around 14.0 amps.

PV Charge controller 1.jpg

[Sunking]

His controller is PWM and thus he has to use 12 volt battery panels wired in parallel. Assuming he has standard 140 watt 12 volt batteries panels because grid tied panels are not that low of a wattage, means Imp is of each panel is roughly 7.8 amps or a total of 31 amps possible. OP FWIW that means your controller turns your 560 watt panel array into 12 x 31 amps = 370 watts. Just the nature of how PWM works. If you want that missing 190 watts get a 40 or 60 amp MPPT controller and rewire the panels in 2 x 2 configuration.

It is impossible for you to see 10 to 12 amps from any one panel as Isc should be around 8.5 amps. What I suspect you have done is measure voltage, and mistaken it for amps. On the other hand if you are measuring current at the input of the controller seeing 10 to 12 amps from all 4 panels is very possible as it can be as high as 31 amps.

[Sunking]

Your location says Columbia, SC, worst case sun hours for that location flat is 2.39 hours in Dec.

800Wh / 2.39 hours /.67 system inefficiencies = 500W solar needed / 145W panels = 4 panels. Check!

Amy my protein computer says you made wrong assumptions and might be leading you to the wrong conclusions. He is using PWM controller, not MPPT which drops system efficiency to 50% rather than the 67%. I have not checked the table for 0 degree tilt, but 2.39 hours sounds a bit high in December.