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evrmc1
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# Posted: 8 Apr 2012 13:42
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I f you need only lighting why would you not use these
http://www.ebay.com/itm/RECHARGEABLE-24-LED-LANTERN-W-SOLAR-PANEL-AC-CHARGER-24HR-BAC KUP-LIGHTING-/170821289395?pt=LH_DefaultDomain_0&hash=item27c5be05b3
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timber
Member
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# Posted: 24 Apr 2012 23:49
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thanks, this may work for what im looking for.cheap lighting for sure
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Sarge
Member
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# Posted: 27 Apr 2012 09:28 - Edited by: Sarge
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Some basics if I may.
You always configure your solar array amperage not to exceed 5-10 % of your battery bank amp output. Various battery manufacturers have different bulk/float requirements.
So if I have 42 amps of solar output I would max out my battery bank at roughly 400-500 amps.
Reason for this is you must charge your batteries up to bulk (around 14.8 volts) then float charge of roughly 13.4 volts every cycle period (daily). This prevents your batteries from sulfating and a premature death.
Second rule is you never plan/design for more output than 50% of battery capacity. Batteries bank may have 500 amp hours of capacity. Your usage plan should reflect no more than 250 amp hours. Reason is you never run your batteries below 50% or 12.2 volts. Again....you will significantly shorten the life of your batteries and damage them if you do.
Thirdly...you never use car batteries. Always use deep cycle batteries (marine/golf cart etc.) as they are deigned to be discharged/recharged and car batteries are not.
First post and I sure dont wish to come off as a "know it all" but these are basics I am sharing.
Thank you for the wonderful forum and I have learned a lot here just reading and decided to join.
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timber
Member
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# Posted: 27 Apr 2012 10:38
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hi, I planned to use 6 , 6 volt interstate 225 ah batteries in series and parralel. i need 8 led lights. and able to run a 12 volt pump to circulate water for solar heater. and a lap top and 12 volt small tv.do you think 4 90 watt panels will be enough? another question i have is, is it better to run 12 wire in the cabin for what i need or run 110 and install an inverter ?? whats more efficient. i do have a generator but would only use it in emergency. and i thought id build a solar water heater. and let it circulate through the cabin for radiant heat ,i do have a wood stove also.id like to be as self sufficient as possible. off grid all the way. the cabin is only 320 sq ft right now.thanks for the reply. aaron
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Sarge
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# Posted: 28 Apr 2012 09:30
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Well......
Add up the amp requirements and length of time each draw will run.
then work backwards with the rules mentioned in the post above yours. I use this chart from time to time for planning system design.
Laptop=75 watts
LED lights draw approximately a 1/20th of incandescent bulbs (thumb rule) power.
So lets say a 75w incandescent bulb is our measure so lets use 3.75 watts multiplied times 8= 30 watts
12v TV (again I am just estimating usage...you should refer to the manufacturer material for exacts) lets say 75 watts
12v pump to circulate water....again...I have no idea how many GPM nor diameter of pipe here....but using one of my projects for watering the horses my 5-6gpm pump pulls about 10 watts.
Assuming the lights will run 6 hours a day you have 180 watts.
Pump lets say 18 hours a day= 180 watts
TV 6 hours a day=450 watts
Laptop 4 hours=300 watts
All together=1110 watts=
Convert watts to amps on 12v system=92.5 amps
So size your battery bank to double your requirements (minimum)
you get ~200 amps
1/10 of battery bank size =20 amps required of solar panels.
90watt panel lets say puts out 5amps each (calculate loss etc.)
for 4 hours a day* 4 panels =20 amps
Now granted I made some assumptions here but you get the idea. The most common mistake folks make is huge battery banks and not near enough solar amperage to properly bulk charge the batteries. BIG MISTAKE.
But you get the idea of the exercise one needs to go through to design/configure a clean/reliable solar system.
Hope this helps.
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timber
Member
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# Posted: 28 Apr 2012 09:54
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thanks again, ill do some more research on the amount of amp draw that i need and go from there. would you wire the cabin with 14/2 wire and run an inverter, or run all 12 volt wiring ? i ask cause i have 14/2 and 12/2 wire left over from a job along with boxes and receptacles, thankyou again for your time
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MtnDon
Member
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# Posted: 28 Apr 2012 10:32
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If I was only going to run a couple of lights a 12 VDC system would be okay. If I was wanting to use several devices that required 129 VAC I would pretty much forget the DC and go strictly 120 VAC from the inverter. That's my opinion. When you get into higher amounts of 12 VDC being used, and longer wire runs for items you have to be careful of wire sizes or you run into voltage drop issues. Also note that common house switches burn out quickly when used with DC.
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MtnDon
Member
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# Posted: 28 Apr 2012 10:35
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And I sort of agree with Sartge on the most common problem people have..... it is with batteries, but usually that they don't have enough battery capacity and they run them down too low all the time. . Followed by insufficient PV capacity for recharging. Be honest in the power requirement estimate, then add20% to allow for expanding use. That always happens.
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timber
Member
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# Posted: 28 Apr 2012 10:49
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yes it makes sense to go with 110 ac. voltage loss and wire size can be a problem. running 14/2 wire is simple and i have a 400 watt inverter, will start looking for a larger inverter ,thanks for your help.the picture is starting to get clear now. the reason i thought of going all 12 volt was i found interior camper lights at princess auto, and they sold the led bulbs that replaces the existing high amp bulbs. the light fixtures would have cost 120. plus tax .thought that would be cheap enough.
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timber
Member
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# Posted: 28 Apr 2012 10:51
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and i thought the inverter itself would consume some amps also
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MtnDon
Member
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# Posted: 28 Apr 2012 11:15
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There will be some inverter loss. Nothing is perfect.
Our system is a bit high end I guess, you'd say. We run a 3500 watt Outback inverter. It has a search or standby function. When nothing AC is turned on the inverter sits there using only milliwatts. When an item is turned on the inverter switches on. It's adjustable for sensitivity. Ours will come on with just a few watts of demand the way it is set.
Search or standby will not be found on inexpensive inverters but if you are looking to expand someday it's something to keep in mind.
Some of the less expensive inverters do have a remote on-off switch feature though. That coyld be handy, place the remote switch someplace handy and turn the inverter off when it is not needed.
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Anonymous
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# Posted: 17 Oct 2012 23:32
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In regards to the last post if you are considering buying a 50amp mppt regulator to allow for future upgrades I would consider moving to a 24v system, much more efficient and these days plenty of 24v stuff out there and if you decide to run a 110v/240v inverter you will have substantially less issues. In regards to a simple lighting system check out Sundaya. Their T lights are great - direct connection to a 12v solar panel - no regulator, batteries etc required, its all built into the light (replacement parts are reasonable in price should they fail). I run these in conjunction with a 24v system running an inverter a 40w panel keeps 4 lights fully charged (not sure how many more you could put in that string) and even during times of rain they hold enough power to have nil input (I disconnected them from the solar to see how long they would run) and last 5 days.
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MtnDon
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# Posted: 17 Oct 2012 23:51
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Quoting: Anonymous In regards to the last post if you are considering buying a 50amp mppt regulator
That has me confused. Mine is the "last post", previous to the one above. I can't see any reference to a MPPT controller. ???
For the record we do have a 24 VDC system; the only way to go for any system with more than a 4 or so golf cart batteries, IMO. And we have a 60 amp MPPT controller. If I was wanting or needing to enlarge the system I would add a second controller for new PV modules and probably replace the golf cart batteries with L16's, maybe twelve of the 2 volt battery version in a single string. .
I considered DC lighting, however because I also wanted 120 VAC outlets for things like a microwave, toaster, blender, a fan on the propane heater, regular flat screen TV and DVD player, sound system plus AC around the outside, in the shed and the barn and gazebo for power tools and a BBQ rotisserie. To use both AC and DC for appliances and lights began to grow more costly. Add to that the extra complexity if anyone other than myself was to become responsible for maintenance and it did not seem a wise move. (My wife is very intelligent, more than me in some matters, but when it comes to electricity all she wants is to plug in whatever she wants from home or a regular department store. Statistically she will outlive me and I want to leave things as neat and tidy as can be. Hopefully that will be of no consequence for another 20 years or so. However my conservative nature makes me think about that now.)
As the price of LED's continue to fall I may substitute some LED for the present CFL, but in 120 VAC.
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Jadeenvironment al
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# Posted: 6 Nov 2012 19:48
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My powerbox manual says to connect the solar panels to the AC adaptor input then the built in charger (i.e. charge controller) charges the battery properly. Just like the AC adaptor, always leave it plugged in. No need for a separate charge controller plugged directly into the battery.
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MtnDon
Member
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# Posted: 6 Nov 2012 21:07
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Quoting: Jadeenvironment al manual says to connect the solar panels to the AC adaptor input
?? PV panels put out DC. Connecting them to an AC adapter is incorrect; maybe a typo was made?
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razmichael
Member
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# Posted: 6 Nov 2012 22:20
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Quoting: MtnDon ?? PV panels put out DC. Connecting them to an AC adapter is incorrect; maybe a typo was made?
MtnDon, assuming it is the same as one I used to have - not a typo - suspect you just read it too quickly (not something I have ever done  . The input socket is 12V for the output of the AC to DC adapter (120 to 12V). You need to wire the matching type DC barrel connector type to the panel and plug it in to provide 12 volts for limited charging
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Donkeydave
Member
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# Posted: 25 Oct 2015 12:02
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I know I'm coming into this awfully late since the last post is three years old but it's all quite new to me. We're still in the early planning stages for our cabin.
I have one question so far. I saw that someone mentioned that ordinary switches don't hold up well to D/C current. At this point our A/C needs will be quite small. The only thing I can think of that will require A/C is the charger for our walkie-talkies which can be accomplished with a little inverter that can be plugged into a "Cigarette lighter" socket. For entertainment I plan to use a car radio and a portable DVD player so the only tricky issue I see would be the light switches. The lighting would be all LED's. What kind of switches should I use?
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NorthRick
Member
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# Posted: 25 Oct 2015 12:27
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From what I've read, a regular AC wall switch will burn out the contacts if used with DC, even at fairly low voltage. There are switches for RVs and boats that are designed for DC. I've also found DC switches that fit a standard electrical box but those were spendy - over $30 a switch.
I'd love to know where to get a more reasonably priced DC rated switch that looks like a normal household one.
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razmichael
Member
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# Posted: 25 Oct 2015 14:28
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Assuming LED lights and not a lot per circuit/switch there should be no problem with AC toggle switches. I have maximum two 8 watt LEDs on standard but 20amp rated AC toggle switches with no issues and no sign of arcing - took one apart this year to check. I went with 20 amp rated. Even if after 5-10 years you lose a switch or two, still a lot cheaper than DC switches. If however you plan to load up a circuit with a lot of lights you will need to be much more careful.
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MtnDon
Member
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# Posted: 25 Oct 2015 18:06
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I used rocker switches from Carling, similar to these. I would start with a blank switch plate and cut out the rectangular shape hole that the switch snaps into. There are usually many to be found on ebay. Many marine dealers handle them as the Contura series are sealed.
Somewhere in all the pages of Carling tech info I think I read that a switch rated for 125VAC 10 amps (for example) can usually be used safely for the same DC amp rating but with a voltage limit of 24 VDC. Or something like that. Which goes against many other advice I have read where it is suggested to keep the DC amps low. But they were talking about their own switches, which normally have an AC and a DC rating. The above "rule of thumb" was to be applied when the Carling switch had no published DC rating.
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