12v without solar - ideas please

[Delicatedave]

So I'm renovating our home while living it in and on a very strict budget, we currently have no income. I want to get on and do as much as I can while I have the time. One thing we want to do is reduce the electric bill to a minimum long term so I was thinking eventually to run things like lights & chargers of 12v via solar but the catch is I need to replace the ceilings & do repairs to the roof. I can do some work myself now. So when I do the ceilings I want to install the lighting 12v so I need a way to do that without using lots of transformers. I think running all the cables to a fusebox > battery which is charged via the main perhaps? but I don't know. Our cottage has small windows so we use the light a fair bit, right now the lights on in the living room it's that dark with the rain.

[Jeremy Harris]

No problem with running ELV cabling around, just needs to be sized to take the higher current that 12 V stuff will draw for any given power, so that the losses aren't too great.  The running cost of such a system will be higher than that for normal mains lighting, until you get the solar system and battery installed, though.  A single 230 VAC to 12 VDC switched mode power supply, as a temporary measure until you get the solar system and batteries installed, will have a vampire power consumption 24/7 from the mains, so increasing the energy usage.  Hard to know for sure how big this may be, but it would be a bit lower than using a transformer, rectifier and smoothing approach, I think, as transformers generally have a higher no-load power consumption.

 

The main issue I ran into when looking at installing 12 VDC lighting is that normal light switches cannot reliably switch DC - their contacts are very slow to open, so they will arc if used to switch DC.  I couldn't find any decent looking 12 VDC rated wall switches, there seemed to be none available that were suitably approved.  The best I could do was find switches intended for use in boats and caravans, but these didn't easily fit standard wall boxes.  The way around this may be to buy some standard blanking plates and then cut holes in them to allow 12 VDC switches to fit.

[Delicatedave]

Yes switches do seem a problem, I had thought wifi switches were a solution but they run of battery and I don't want go around chasing for them every 3 months. I had wondered if I could hack those to run a lead in to replace the battery but then my mind does tend to wonder. Some places I could use movement sensors.  We won't be selling the house so anything I do is fine, might even make some out of wood ?

[Delicatedave]

I suppose I could just use a computer power supply.

[ProDave]

Be careful the cost of the battery and periodic replacement of it does not end up making your "free" electricity cost more than from the grid.

 

Look at NiFe cells. Very long life and very forgiving. I might experiment with a small battery system based on those eventually.

[Jeremy Harris]

1 minute ago, Delicatedave said:

I suppose I could just use a computer power supply.

 

 

You could, but it would have a high vampire drain, and wouldn't be able to deliver much current at 12 VDC.  PC supplies tend to have high current outputs at 3.3 VDC, and may be 5 VDC, but can't usually deliver much current at 12 VDC.  This means that the unused outputs will cause the front end of the power supply to draw power from the mains, even though they aren't used, adding to the losses.

 

You can buy high power 12 VDC switched mode power supplies fairly cheaply.  I have a fairly small 15 VDC one (turned down to 13.5 VDC)  that keeps a bank of 12 V batteries charged up, to run all our house network stuff (modem, router, switch, etc) and that cost around £15.  One to run a few rooms of LED lighting would probably only cost around £20 to £25.

[Delicatedave]

15 minutes ago, Jeremy Harris said:

 

 

You could, but it would have a high vampire drain, and wouldn't be able to deliver much current at 12 VDC.  PC supplies tend to have high current outputs at 3.3 VDC, and may be 5 VDC, but can't usually deliver much current at 12 VDC.  This means that the unused outputs will cause the front end of the power supply to draw power from the mains, even though they aren't used, adding to the losses.

 

You can buy high power 12 VDC switched mode power supplies fairly cheaply.  I have a fairly small 15 VDC one (turned down to 13.5 VDC)  that keeps a bank of 12 V batteries charged up, to run all our house network stuff (modem, router, switch, etc) and that cost around £15.  One to run a few rooms of LED lighting would probably only cost around £20 to £25.

What do you think of something like this, caught my eye for the ruse protection https://www.amazon.co.uk/HAILI-Monitoring-Equipment-Accessories-Security/dp/B07R1YNG8Y/ref=pd_sbs_147_5/261-3696974-7025443?_encoding=UTF8&pd_rd_i=B07R1YNG8Y&pd_rd_r=de42ad9c-ce87-4713-9db2-3615cf297f8e&pd_rd_w=BnYs4&pd_rd_wg=nBa0G&pf_rd_p=96cae456-8d7a-4bc1-91c7-9b20b4dfd7c9&pf_rd_r=9BQPNF9D56V6CG6Y7X93&psc=1&refRID=9BQPNF9D56V6CG6Y7X93

[Jeremy Harris]

1 hour ago, Delicatedave said:

What do you think of something like this, caught my eye for the ruse protection https://www.amazon.co.uk/HAILI-Monitoring-Equipment-Accessories-Security/dp/B07R1YNG8Y/ref=pd_sbs_147_5/261-3696974-7025443?_encoding=UTF8&pd_rd_i=B07R1YNG8Y&pd_rd_r=de42ad9c-ce87-4713-9db2-3615cf297f8e&pd_rd_w=BnYs4&pd_rd_wg=nBa0G&pf_rd_p=96cae456-8d7a-4bc1-91c7-9b20b4dfd7c9&pf_rd_r=9BQPNF9D56V6CG6Y7X93&psc=1&refRID=9BQPNF9D56V6CG6Y7X93

 

 

OK for just a single room, perhaps.  However, you wouldn't really need all those fuses for just a single room.  We have a lot of 12 VDC LED lighting, and the power supplies needed tend to be around that size per room.  The small study I'm in at the moment is a fair example.  It's a bit under 3m square, and the 12 VDC LED lighting draws about 4 A.  Our kitchen is bigger, and has two sets of 12 VDC LED lights, and each has a 5 A power supply, so 10 A in total (the lighting only draws about 7.5 A, though). 

 

It depends a great deal on the power of the LEDs that you plan to install.   I have some LED strip lights in the garage/workshop, and they are roughly the same light output as a traditional daylight fluorescent tube, but a bit over half the power consumption.  This is a fairly good indicator of the power you may need, as a single 5ft fluorescent tube may be rated at around 60 W, and you could probably get away with using about 35 W to 40 W of LED lighting to replace it (roughly 3 A to 3.5 A at 12 VDC).  I had four 5ft long fluorescent tubes lighting my old garage/workshop, plus a couple of lights over the workbenches, and in the new garage/workshop I have 6 LED strip lights, cutting the power needed by about 40%.  That's still a total of well over 100 W, though, around 9 A at 12 VDC.

 

Some of our 12 V LED lighting is powered with supplies like these, that aren't too expensive and are fairly easy to use: https://www.ebay.co.uk/itm/Universal-12V-5-10-15-20-25-30-50A-Switching-Power-Supply-Driver-for-LED-Strip/263824483495?hash=item3d6d2a24a7:m:m_qbFJUVUpO1n2ghbSBEEuw  They need protection over the terminal block area, though.  I 3D printed covers for a couple of ours, to make them a bit safer when installed.