Off Grid Living / Camping > Off Grid Living / Alternative Housing

12v or 24 v solar

(1/2) > >>

roty:
I have recently purchased and installed an off grid system. 3x100 watt panels 12 V system. they work great my issue is that I was not aware of the benefits of having a 24v system.
I am using this in our cottage for several light bulbs as well as a small fridge that will be only used on weekends and on a timer so it pulses on for only about 20 minutes per hour to conserve battery power.
I currently have 2 12v marine batteries that I will swap out in a few years (after the marine batteries die) for 6v golf cart batteries.
I am new to solar and would like to know if I should look at adding another panel so I can get a 24 v system ? if I do go for the 24 system can I add a 225 watt panel to my set of 3 100 watt panels? not sure if I can mix and match different wattages?

Thanks in advance for any assistance.
yes I am new so patience with me please :) :o

MadScientist267:
Roty -

Welcome to the board, first things first. ;)

In a nutshell, yes and no. Can it be connected that way? Yes. Should it? No.

The 100W panels will only pass what they are rated. A larger panel in series with a smaller one will derate to the capabilities of the smaller panel. The "extra" 125W will simply be lost.

It's always best to match panels as closely as possible. *To a point*, no damage will occur to the smaller panel, it will simply go to waste. Someone else may be able to chime in with an experience that draws that line, but they'll all say the same thing beyond that - match.

If you haven't bought the panel yet, don't waste your money. Go for another 100W to complete the second 200W 24V pair (to give you a total of 400W), then add any additional pairs in parallel with the existing panels.

Hope this helped,

Steve

 

Wolvenar:
At this point unless your going for a large increase of power use, or generation capacity it is maybe not worth the change to 24 volt.

Many things are available in 12 volt for vehicles that can be used, and the added benefit that in a pinch your car could act as a generator.  The car stuff may not be the most efficient but they are sure plentiful.

I miss the ability and options of a 12 volt system, but we outgrew what 12volt systems can supply with reasonable wire sizes or loss.

Rover:

--- Quote from: roty on July 20, 2014, 12:51:44 am ---I have recently purchased and installed an off grid system. 3x100 watt panels 12 V system. they work great my issue is that I was not aware of the benefits of having a 24v system.
I am using this in our cottage for several light bulbs as well as a small fridge that will be only used on weekends and on a timer so it pulses on for only about 20 minutes per hour to conserve battery power.
I currently have 2 12v marine batteries that I will swap out in a few years (after the marine batteries die) for 6v golf cart batteries.
I am new to solar and would like to know if I should look at adding another panel so I can get a 24 v system ? if I do go for the 24 system can I add a 225 watt panel to my set of 3 100 watt panels? not sure if I can mix and match different wattages?

Thanks in advance for any assistance.
yes I am new so patience with me please :) :o

--- End quote ---

Hi Roty,

Now is the time to plan out future growth, actually you are a little late on the planning stage, but none the less. A lot of us started out the same way you are, adding panels, one at time, getting excited, wanting to grow the system, etc. It is the most expensive way to do it, you end up replacing stuff that is working simply because it can't handle the growth or change in voltage etc.

I was 12V and went 24V last year, it was not a cheap endeavor. In your case, I would not think of combining the current 100W panels with 24V (yes it can be done, best way is probably to series the 100s and parallel to the 24V and use an MPPT controller, however, it will be inefficient). I would probably create 2 arrays with 2 separate controllers (Actually how my system is, I have 3 100W  12V panels, and 5 235W 24V panels) you would still series the 3 100s into an MPPT controller, then let the new 24V panel be the first panel on your new array with its own controller. You can use the output from both controllers to charge your batteries. Either case you would need controllers that can charge at 24V, most good controllers have models or the capability to do so, they will cost you as much as a panel, and if MPPT, a couple times more (each).

As far as running 12V stuff off the bank, there are (and I use them) lots of 24 to 12V converters , I use some that are in the 240W range, which is usually more than needed for 12V stuff. But you need to work out your usage. Consider the possible inverter down the road and what it requires, etc.

Rover

A of J:
Solar panels are DC beasts and as such it is voltage that takes precedent.

You can use different wattage panels, maybe at the loss of some efficiency as opposed to using banks of the same panels through a MPPT.

You could use 2 x 12v x 100W panels in series (12+12=24V) and parallel that with 1 x 24v x 275w panel, it will work just fine. Both strings will work at the same voltage and output amps consistent with their rating at that voltage. Theoretically the 12v string would give 4.1A @ 24v (100 /24) and the single 24v panel 11.4 A (275/24).

Allan

Navigation

[0] Message Index

[#] Next page