From 12V to 24V solar system - what do I have to change?

kjetil · January 2015

I consider changing from 12V to 24V solar system. I know solar panels and batteries have to be in series to get 24V. But can I use all my existing 12V leds? Or do I have to change all the lights in the house to 24V as well?

BB. · January 2015

Re: From 12V to 24V solar system - what do I have to change?

Welcome to the forum Kjetil!

You should not "tap" 12 volts from a 24 volt battery bank. It unbalances the state of charge between the "high" and the "low" batteries.

Either you have to get a 24 to 12 VDC down converter (basically a DC to DC version of the standard DC to AC inverter--And about the same cost)...

Or think about changing to a 24 VDC to 230 VAC inverter and change over to 230 VAC standard home LED lamps... Can be very cost competitive (the AC led lamps are same price or cheaper than many DC LED fixtures).

And it is much easier to send 230 VAC around the place than 12 or 24 VDC (wiring, fuses/breakers, etc.). If you already have an AC inverter--Does not really cost you anything more and only a bit more electricity (10-15% more for inverter losses for AC Lighting vs DC lighting).

If you have a 12 VDC need, such as HAM radio, you may still need to generate some 12 VDC for those.

-Bill

kjetil · January 2015

Re: From 12V to 24V solar system - what do I have to change?

Thank you.

Maybe I don`t need to change the system to 24V anyway? The reason I was thinking of 24V was to save electricity and avoid losses in long 12V cables. But all the lights in the house are 12V, so it`s maybe just more hazzle to change all the lights... I understand I`ll get losses with the inverter as well.

BB. · January 2015

Re: From 12V to 24V solar system - what do I have to change?

If your power needs are not large (less than 800 ah @ 12 volt battery bank),I would think about a smalls 12 volt to AC inverter. And migrate over to AC leds for longer distances/higher power needs.

Move to 24 volts of your DC loads exceed roughly 1,200 watts or 100 amps on your DC battery bus.

-Bill

706jim · January 2015

Re: From 12V to 24V solar system - what do I have to change?

Scrap the 12 volt lights and get some sort of inverter.

Too much line loss over any distance with 12 volts unless you use copper pipes for wires.

kjetil · January 2015

Re: From 12V to 24V solar system - what do I have to change?

We have a small 12V solar panels on the cabin that I am considering to expand. It consists of one 10W and one 30W panel in parallel, one 12 / 24V PWM regulator, and two 70ah lead acid batteries. Considering buying more/larger solar panels and a MPPT regulator that is more efficient. Is it beneficial to make it into a 24V system ? What is the benefits?

Consumption is low since it is a summer cottage that is not in use during the winter. The solarsystem has only been used for some 12V led light that hangs around in the cabin, and charging pc / mobile phones.

I've read that you can use smaller cable sizes at higher voltages with less power loss at 24V than at 12V. Can also have longer cables without equal power loss. Have read that one achieves faster charging on overcast with solar panels in series, because you achieves satisfactory charging voltage earlier. Are there other advantages to 24V ?

If the solarsystem becomes 24V I suppose I have to run the existing 12V lighting via a 24-12 DC-DC converter. Or buy 24V leds. I assume the converter uses some power especially if it must be left on all the time? If I change over to 230 VAC standard home LED lamps I need an inverter. Will the 10-15% inverter losses for AC Lighting be less than line loss over any distance with 12 volts?

I wonder therefore whether we should continue with 12V, or it pays to do it to 24V ?

BB. · January 2015

Re: From 12V to 24V solar system - what do I have to change?

Look for cost/availability of LED Lamps...

12 volt LEDs are common--You can get quite a few from China Direct type companies
24 volt LEDs are less common (heavy trucks, marine)
120/240 VAC LEDs -- Very common and relatively "cheap" in the US (also available from China Direct)

LEDs are all over the map on quality/color temperature/etc...

I would suggest buying one each of several types and see if they will work for your needs before you buy 10 of them.

Note that the "old fashion" White LEDs:

Attachment not found.

Have very poor heat sinking... Many companies try to get as much light out of them as they can--And they may only last 100-500 hours before they turn brown/black.

Whereas those with flat metal heat sinks (such as from Cree):

Attachment not found.
Have very good heat sinking capabilities and are able to run at 1 watt or more for many 10,000's of hours (usually).

Some folks here have had good luck with 12 VDC LED track lighting (without the AC transformer):

http://www.earthled.com/collections/mr16-led-light-bulbs (just a link, do not know anything about vendor)

Of course, there are a huge range of manufacturers out there--Some good, some not so good...

Don't spend a lot of money until you have done the research and planning.

-Bill

westbranch · January 2015

Re: From 12V to 24V solar system - what do I have to change?

Kjetil, if you do not expect to change the use of electricity you are probably fine to stay with the same wiring, unless you want to upgrade old wiring or light fixtures.

From your first post I believe you are thinking of adding more usage of electrical items. Look to places like IKEA for table lamps and desk lamps with LED's that use a plugin to supply 12v for the LED. Discard the plugin supply and connect the light to the 12V wiring. PS you should use at least a 12v < 1 Amp car fuse somewhere in the supply line of each light.

Is this a Hytte or Sommarstuga?

hth

kjetil · January 2015

Re: From 12V to 24V solar system - what do I have to change?

Ok, so I should just continue with 12V... what about cable loss over any distance with 12 volts?

I already use 3W 12V leds from ebay like this one. So I need blade fuse before every led?

We call it hytte here in Norway, but it`s in use just in the summer. It`s too cold in the winter, not so isolated.

CDN_VT · January 2015

Re: From 12V to 24V solar system - what do I have to change?

PYLE PSWNV720 24V DC to 12V DC Power Step Down 720 Watt Converter
Link2 Ebay
I would see if you can work with one of these .
I must have a 12 volt bilge system 24.1 X 7 days working to keep the deep cellar dry .
And now with the weather changing to huge flooding down pours , I run 3 pumps in order.
Normal & spare that is to protect if the normal burns our & a spare for the spare & when we get 10mm of rain in hours .

I upped the 12 to a 24 system plus+++ but still needed 12V just for this & two 12V LEDS for the wood shed , used in case we need wood at night ONLY.
I use inline mini ultra fuses at the 12 v boxes I built & supply the converter with fused maxi fuse .

VT

BB. · January 2015

Re: From 12V to 24V solar system - what do I have to change?

OK, costs are not a big issue here for LEDs.

The fuse/breaker sizing depends on the size of your wire... Sorry, I am not metric--But with US Units...

For example, we have minimum 120/240 VAC house wiring of 14 AWG--Which is good for 15-20 amps with our code (for some reason, even though code says 20 amps is OK, they only allow 15 amps maximum).

And for a 15 amp branch circuit (wire plus fuse/breaker), we are allowed to run at 80% continuous current:

15 amps * 0.80 = 12 amps max.

If you have 3x 4 amp LEDs... Then you can have one 15 amp fuse/breaker if you run 14 AWG wiring to all bulbs/switches. A short at any point in the circuit will draw a maximum of 15 amps through the "correct size" wire and then pop the breaker fuse.

Regarding the automotive fuses you linked too... Wayne (and me) have had problems with them. If you draw anywhere near rated current, they can overheat and fail. Don't know if the connectors to the blades cannot handle the current or what--But Wayne (from Nova Scotia) feared his would have caught fire if they were not in a metal box.

Suggest you use something else (marine fuses/breaker or others). The "simple" automotive fuses should probably not be used.

-Bill

westbranch · January 2015

Re: From 12V to 24V solar system - what do I have to change?

Bill, I agree, that is why I stated 1-1A fuse per light or other outlet. At 3W he will have 1/4 A draw, a short or ? will blow a 1A fuse for sure!
I did that in our Hytte (guest cottage).
Attachment not found.

For safety I used fuse holders like these for 1A,2A and 3A fuses, location dependent:
http://www.ebay.ca/itm/U-S-AMPS-FUSE-BLOCK-WITH-250AMP-FUSE-AND-FREE-GOLD-FUSE-HOLDER-/151541300248?pt=Vintage_Electronics_R2&hash=item234890bc18
http://www.ebay.ca/itm/In-line-Car-Truck-Automotive-Standard-Blade-Fuse-Holder-Fuseholder-/351114573582?pt=LH_DefaultDomain_0&hash=item51c00f370e
http://www.ebay.ca/itm/NEW-8-GANG-FUSE-HOLDER-FOR-ROUND-GLASS-BUSS-FUSES-9626-/161474374264?pt=Motors_Car_Truck_Parts_Accessories&hash=item25989f6a78&vxp=mtr

BB. · January 2015

Re: From 12V to 24V solar system - what do I have to change?

For this holder (2nd link):

Attachment not found.
May want to avoid it... Wayne had said he was not pulling anywhere near rated current when he had the melt down.

1-2 amps is probably not a problem--But you have other choices that are better.

-Bill

CDN_VT · January 2015

Re: From 12V to 24V solar system - what do I have to change?

Maybe Wayne didn't have the ATC fuse plugged in correctly !! OR wire was undersized for the fuse.
I have seen G16 wire on some. I purchase 14 Gauge ones and use 15 amp max for the standard ATC

I use many of these , Mini to Maxi , .5amp to a 60 amp 8 gauge monster !

Yes I know 60 amp is over 8 gauge wire but NOT at 6 / six inches , the fuse is thinner !
Perspective Please . were ASSuming 12Vdc .

And just for jokes & testing I make sure I short & test fuses !!!! Plus I use resetable CB's and with Auto resets on some Inverters to make the cold starts -temps .

You do need to make sure your inserting correctly & the blade receiving is tight .

VT

kjetil · January 2015

Re: From 12V to 24V solar system - what do I have to change?

Thank you guys. I`m using exactly that fuseholder. But my main question is whether I should continue with 12V or not. Is it advisable to change to 24V? What is most common practise?

westbranch · January 2015

Re: From 12V to 24V solar system - what do I have to change?

Kjetil, If you are going to use DC lights and appliances, and the wiring and fixtures are already installed, you probably want to stay with 12VDC. Cheaper and still effective
If you go to 24V you will need a voltage reducer on/at each light and appliance.
However, if you are using > 1000W of power, like electric appliances, or have many very long wire runs (12 m +) then you should possibly consider AC and an inverter.
Eric
hth

kjetil · January 2015

Re: From 12V to 24V solar system - what do I have to change?

Thank you westbranch.

I will probably stay with 12VDC then. Sounds like the easiest and cheapest alternative.

Is there any issue having several 12V batteries in parallel? Like unequal charging?

westbranch · January 2015

Re: From 12V to 24V solar system - what do I have to change?

What battery types were you thinking of? 2V, 6V or 12V? Which chemistry ?
Also you did ask the question about Li batteries in another thread. Those are ~ 3.2V per cell.
It depends on how much storage you are after.
Generally the recommendation is a max of 3 parallel batteries to ensure balanced charging.

CDN_VT · January 2015

Re: From 12V to 24V solar system - what do I have to change?

kjetil wrote: »

We have a small 12V solar panels on the cabin that I am considering to expand. It consists of one 10W and one 30W panel in parallel, one 12 / 24V PWM regulator, and two 70ah lead acid batteries. Considering buying more/larger solar panels and a MPPT regulator that is more efficient. Is it beneficial to make it into a 24V system ? What is the benefits?

Consumption is low since it is a summer cottage that is not in use during the winter. The solarsystem has only been used for some 12V led light that hangs around in the cabin, and charging pc / mobile phones.

I've read that you can use smaller cable sizes at higher voltages with less power loss at 24V than at 12V. Can also have longer cables without equal power loss. Have read that one achieves faster charging on overcast with solar panels in series, because you achieves satisfactory charging voltage earlier. Are there other advantages to 24V ?

If the solarsystem becomes 24V I suppose I have to run the existing 12V lighting via a 24-12 DC-DC converter. Or buy 24V leds. I assume the converter uses some power especially if it must be left on all the time? If I change over to 230 VAC standard home LED lamps I need an inverter. Will the 10-15% inverter losses for AC Lighting be less than line loss over any distance with 12 volts?

I wonder therefore whether we should continue with 12V, or it pays to do it to 24V ?

Seeing you have a 40 watt of panels & run 10 watts of led bulbs , summer use. I would think that you are set with what you have now.

If your thinking of more appliances , lighting ,TV's ,Sound-system, then being 220-50hz Norwegian, I would use a kill-a-watt meter at home to get real numbers . Then work from what your thinking of adding to what it will take to build a system to support the things you want at the summer hytte .

Regardless of voltage , you will be surprised what it will take to run a load .

Kjetil we all love pictures here !! Plz show us the hytte

VT

kjetil · January 2015

Re: From 12V to 24V solar system - what do I have to change?

I`m thinking of three or four 12V lead acid batteries in parallel. Can they have different capacity and brand name?

westbranch · January 2015

Re: From 12V to 24V solar system - what do I have to change?

You do not want to mix Ahr size, manufacturer, manufacture date, commissioning date, the batteries need to be as identical as possible. 4 batteries in series is not a good option.

One of the best ways to get the ampacity up above 225Ah in a 12 V configuration is to use 4 - 6V Golf Cart GC batteries, 2 in series and 2 parallel strings. that way you would have 450Ahr at 12V or 2 would be 225Ahr
For example :
http://www.batterystuff.com/batteries/golf-cart-products/6-volt-deep-cycle/t-105-6-volt-trojan-golf-cart-batteries.html
Because of their intended use they are better suited to Solar applications than car (starter) batteries, they are more robust for discharge over time (all day).

BB. · January 2015

Re: From 12V to 24V solar system - what do I have to change?

In general, best to have identical battery/model/size/type so that they share the charging/discharging current.

Check this link out for how to best parallel batteries.

-Bill

kjetil · January 2015

Re: From 12V to 24V solar system - what do I have to change?

Here is the hytte:

Attachment not found.

westbranch · January 2015

Re: From 12V to 24V solar system - what do I have to change?

How much shade do you get in the winter where you will mount your panels?

Several other Norsk members have posted and summer time solar insolation is right off the chart so that does not need to be planed for as far as location goes. IIRC one had a pole mount that he could manually adjusted for the seasons and time of day.

kjetil · January 2015

Re: From 12V to 24V solar system - what do I have to change?

Thank you. Can I use my three 12V lead acid batteries with different capacity and brand name in parallel? Or do I have to buy new ones?

We are not using it in the winter. But in the summer it is not much shade when solar panels are on the roof.

westbranch · January 2015

Re: From 12V to 24V solar system - what do I have to change?

I would use them till you replace them with a matched of batteries that will supply all your planned needs (loads) plus some reserve (10%?) but be cautious, they could start to fail anytime. they will need to be monitored. In the mean time lets do up a good plan for the improved system... What other loads do you plan other than lights?

BB. · January 2015

Re: From 12V to 24V solar system - what do I have to change?

If you have three different batteries of the same type (all flooded cell, all AGM, etc.), go ahead and use them.

If they are mixed type (flooded cell, AGM, GEL mixed/matched)--It is not as good of an idea. GEL and AGM have lower charging voltage requirements. If you charge them at higher voltages intended for flooded cell, AGM and GEL batteries can vent gasses/electrolyte--Will pretty quickly kill a sealed battery.

If their sizes are a huge difference (i.e., 100 AH and 10 AH), I would not even bother paralleling them. Or, if you do, you should fuse each battery separately. You don't want a fault in one small battery to be feed by a good larger AH battery (smoke, etc.).

-Bill

kjetil · January 2015

Re: From 12V to 24V solar system - what do I have to change?

Thanks, thats very helpful!

It`s 3 flooded cell batteries and they are have different capacity but inside the range of 60-75ah. I`ll parallel them.

I also have a new AGM 90ah battery, can I use that one as well in a way? My regulator is not for AGM batteries thoug...

The load will be lights, pc/mobil charging, drill battery charging...

BB. · January 2015

Re: From 12V to 24V solar system - what do I have to change?

"Boiling batteries dry" does run the risk of fumes, hydrogen explosion, and fire when overcharging any lead acid battery.

Do this in a box outside in the back yard. Not much risk.

Do this in your home or cabin, the risk is higher.

Will the battery "explode"? Not very likely. Don't know your risk tolerance.

-Bill

CDN_VT · January 2015

Re: From 12V to 24V solar system - what do I have to change?

Nice hytte
Looks almost to be a Hyatt Regency. (& I mean that in a good comfy way)
So we are seeing a solar panel in the window .
Are you going to need to put away the panels in the winter , Like remove them off the outside & store for winter . Two small panels now, ive read .
I can see 12 v lights , charge Nokia , but how is charging a drill with a 12 volt supply . I use Buck voltage controllers for my 18V -20V stuff from 12Vdc in my car while running . I was wondering why we started the thread with 24 V .
12 Vdc has more accessories items than 24vdc , but 24v dc /48V dc is better when inverters are used , IF your thinking that way.
It really depends on what you want to power & how your going to mount panels .

You have alot of battery size for what you have in panels right now.
Summer your like our Arctic , I wear my sunglasses @ night .

VT

I think the Avatar was taken @ either 04:00 or 22:00 spring Candle

From 12V to 24V solar system - what do I have to change?

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