Wiring Lighting w/ Series or Not?

[cvick]

Thanks for all the responses guys. The longest run would be roughly 25-30 feet from actual battery to the actual fixture. The price of each bulb would not be a factor but the efficiency/safety and quality of the system would be. If I went with converting to AC, say I had 12 total 8.5w lights (as shown in the link from Butch Deal) using half of them 6 hours a day this equals 357 total watts. I know there are losses etc. I am looking at using 2 x 100w panels that would at minimum get 3.5 hours direct sun per day. This would equate to gains of 700w (give or take minimum a day) This is also a weekend use cabin (6-8 days a month usage) separated by 5-10 days each visit.

It sounds as if the question comes down to if I am ever planning to ramp up things going beyond lights, ie. add a refrigerator, TV, computer etc. down the road. If this was a possibility, then It would make the most sense to set up the entire system on a 120v system and convert my power from the get go to avoid going back and rewiring anything later. Could I not set up the system (as attached) and start with the dc system with lights only and a small 12v water pump ( for toilets, sinks) then should I wish to add 120v later (for a refrigerator) add the inverter on another wiring setup at this point as shown. Again, not trying to complicate anything, just want to make sure I am not going to making additional work or create issues down the road. Cost is not a factor as it is a small system that will make more power than I need with 2 panels and a max of 3 panels 100w each.

Thanks,

VICK

[AzRoute66]

When looking at expansion, especially any refrig, going back to my notion of treating it as an RV, you would want to consider a propane refrig - minimal DC control amps. Now, to chew on my own point, when considering a propane furnace, be aware that the furnace fan takes much more power than you might think if you have never dealt with one before.

[Sunking]

First thing is you should do forget low voltage lighting and wiring. Extremely expensive and horrible efficiency. Example a 20 amp 12 volt DC circuit with a 1-way cable run of 30 feet requires 6 AWG wire and that cost you some $0.90/ft x 60 feet = $55. 12 volts @ 20 amps is only 240 watts max of power. Need more power. Need more fuses and more wire. Say you need to run it 40 feet, now you need larger more expensive 4 AWG.

At 120 volts 20 amp circuit only requires inexpensive 12 AWG wire that cost $0.14/ft and you can run it up to 60-feet 1-way. A 120 VAC circuit at 20 amps can carry up to 2400 watts or 10 times more than 12 volt DC. That means up to a 2000 watt Inverter and every circuit you have daisy chained on one circuit. Not 10 extremely expensive circuit. With an Inverrter no fuses except fot the ones on the battery. . Do not confuse daisy chained with Series.

So forget 12 volts, that is for toys like RV's with short runs and expensive poor quality lights and equipment made to run on 12 volts.I just saved you a few thousand dollars.

[cvick]

Sunking- Fantastic! Thanks so much - this was the exact clarification I was looking for and what I highly suspected all along. I will put my research hat on and attack this going forward with an inverter in the mix converting everything to 120v. This makes more sense overall and will certainly make things much easier. I am sure I will have more questions in the future.

Thanks for now.

VICK

[Sunking]

Sunking- Thanks for now.

VICK

You are welcome Vick

[Mike90250]

MorningStar makes a very nice, solid 300w inverter (10 minute surge to 600W) that is quite efficient and would be a good candidate for a small install. Called Suresine.

[AzRoute66]

Did Sunking just turn this little cabin project into a 240W 30' extravaganza? Don't get me wrong, I have no problem with the inverter solution, I like it. But not needed at this time and maybe never. Wire the project with Romex and standard 120V switches, when the 260 mA LED light won't wake up the inverter, put it back into the box until such time as you are ready for the fridge. At that point, install the inverter and switch to 120V bulbs. Now, if you use the interim DC option, and you get to where you turn on one of the lights and the others dim - I will deeply apologize for wasting your time and for ever bucking people who can hack up more solar knowledge in a spitball than I will probably ever have.

Honestly, I have no problem with the inverter solution - it is just that Sunking has never seen a 12V system that actually works and it breaks my heart that there are so many of them out there.

(And no, I don't know for a fact that the inverter cvick selects will go into standby.)

[SunEagle]

Did Sunking just turn this little cabin project into a 240W 30' extravaganza? Don't get me wrong, I have no problem with the inverter solution, I like it. But not needed at this time and maybe never. Wire the project with Romex and standard 120V switches, when the 260 mA LED light won't wake up the inverter, put it back into the box until such time as you are ready for the fridge. At that point, install the inverter and switch to 120V bulbs. Now, if you use the interim DC option, and you get to where you turn on one of the lights and the others dim - I will deeply apologize for wasting your time and for ever bucking people who can hack up more solar knowledge in a spitball than I will probably ever have.

Honestly, I have no problem with the inverter solution - it is just that Sunking has never seen a 12V system that actually works and it breaks my heart that there are so many of them out there.

(And no, I don't know for a fact that the inverter cvick selects will go into standby.)

12 volt systems will work just fine in an RV but for homes it can be more of an issue due to running the correct wire size and making the proper connections to the DC terminals. Bigger wire requires different termination points and with DC those need to be a little different then the AC terminal connection.

What SK is trying to get people to understand is that using 12V limits you to the size of the system ("stuck inside the 12v box"). It can also cost more then people think. Adding loads will start to make the cost jump up a lot and if you haven't done a good estimating job of what you need in the beginning most people end up throwing away their equipment and wire due to not being sized correctly. Which is the waste that SK is trying to make sure people do not do.

[max2k]

... that Sunking has never seen a 12V system that actually works

doubt it; and it sounds he did much better- he seen many that don't .

and it breaks my heart that there are so many of them out there.

it would help if you could list specs for some here to clarify applicability. SK comes from classic engineering point of view- once things get properly designed and implemented they tend to be headache free. There's another popular approach to 'just try it' and depending on the voltage / power involved this might end up quite differently. All I'm saying what you might consider acceptable many ppl on this board won't so it helps if you clarify what exactly 'working 12V system' means.

[AzRoute66]

Not saying anything specifically. Just wondering why the RV, camper, marine etc. industries haven't all just gone to an inverter right off the DC source, buy stock in Romex, and call it a day. Seems like that would please a certain segment of the population.

[max2k]

Not saying anything specifically. Just wondering why the RV, camper, marine etc. industries haven't all just gone to an inverter right off the DC source, buy stock in Romex, and call it a day. Seems like that would please a certain segment of the population.

few reasons:
- many of the applications you listed have 12V generator as part of the system
- when saying 'marine' you prob mean small private boats as I have no idea how big ones are wired and I don't think it's 12V due to losses involved along their lengths
- they also have relatively small total wattage and if you want more you'd supplement with auxiliary generator and pay $$ for 12V consumer devices. It's good business.

[Sunking]

Not saying anything specifically. Just wondering why the RV, camper, marine etc. industries haven't all just gone to an inverter right off the DC source, buy stock in Romex, and call it a day. Seems like that would please a certain segment of the population.

You are missing some important facts. RV's and small boats use 12 volt electrical systems and use the Engine Alternator as the prime charge source. Solar charging is mostly show and tell. Second fact is things like a fridge, fans, microwave, coffee pots are high power items. 12 volt is very inefficient and very expensive because at lower voltages requires higher current for a given power level. Great example just to run say a toy sized 600 watt RV Microwave at 12 volts takes a dedicated 60 amp circuit. Nothing else can be on that circuit. a 60 amp circuit requires at least a #6 AWG copper wire with a max distance of 10 feet. Go price #6 AWG wire and lok at the tols required to terminate it properly. The tool alone will cost you a few hundred dollars. Romex is 14 and 12 AWG my friend and cannot handle that current.

OTOH what if I just had say a 1000 watt Inverter sitting right next to the battery. All I need is a single 100 Amp circuit of about 4 feet of #4 AWG. I can then run all the circuits I want without any fuses using that 14 AWG Romex. I can run the microwave, lights, fridge and anything else you got. 120 VAC at 1000 watts is only 9 amps.

As for marine, small boats use 12 volts for the same reason an RV does. However larger boats use 24 volts because they use more power. Move up to Ships and Battery voltages goes as high as 480 Vdc on civilian craft and up to 600 volts on USN subs. Now here are some batteries on a boat. This guy uses SM batteries to make Ball Lightning.