Sy-Revolution
Active member
Would I wire them in series in pairs, just as you would 12v batteries to make 24v?
I guess I know the answer but need reassurance!
C.
I guess I know the answer but need reassurance!
C.
Wiring 12v solar panels into 24v array
- Thread starter Sy-Revolution
- Start date
pappaecho
New member
Depends on which type os panels you have. Theoretically yes. Two nominal 12 volts panels will produce 24 volts.
If you Google solar panels will will find that they are produced in 12, 24 and 36 volt configurations. so if you have a 24 volt system, buy 24 volt panels.
If you have already got the panels, 12 x 10 amp panels when put in series (x2) will produce 24 volts at 10 amps
If you Google solar panels will will find that they are produced in 12, 24 and 36 volt configurations. so if you have a 24 volt system, buy 24 volt panels.
If you have already got the panels, 12 x 10 amp panels when put in series (x2) will produce 24 volts at 10 amps
ukmctc
New member
I don't think it makes any difference to the panels your regulator with adjust settings required automatically, depending on the regulators fitted.
I have 2 x 80 watt pannels in series feeding 12 volt plus a wind jennie its the regulator does the work.
Sy-Revolution
Active member
It's just that there are some cheap 12v panels on ebay at the moment that have come recommended........
pappaecho
New member
I think you will find that 24 volts panels also are on offer because they are used in PV installation on houses, but the recent government debacle over pricing means that some are being dumped because of a change in demand.
I bought a single 12 volt 80 watt panel last year on Ebay - it works very well!
I bought a single 12 volt 80 watt panel last year on Ebay - it works very well!
William_H
Well-known member
PV panels for PV systems on houses tend to describe their panels by the max voltage. The PV inverter using MPPT (max power point tracking) type technology is not so concerned with voltage. My PV system has 8 panels of about 40 volts each in series running then at about 320v DC at about 5 amps max.
When however you are talking solar panels for boat (etc) the language moves to the older technology non MPPT so for a 12v battery you used a 20v max panel. Here the panel can be connected directly to the battery the excess voltage 20 volts of the panel to the 14v of the battery being wasted in heat in the panel. Then panels got bigger and we used a regulator to protect the battery and the excess voltage was wasted in the regulator.
So for the OP. Yes 2 panels designed for 12v battery charging are perfect for charging 24v battery when wired in series. Or if you do find panels cheap that were designed for house hold PV systems then you could use a 40 v panel quite OK. I suspect a 30 v panel might not be high enough voltage. However it might be fine with an MPPT regulator.
Just waffling on about household PV systems (recommend you jump to end)
I have had a 1500w system installed for about 9 months. I love it. At the time the govt offered to pay 47cents per KWH (30 pence) for power fed back into the system.Compared to 25cents per KWH you pay for power.
The system gives about 8KWH per day. I don't know how much is fed into the grid but my bills show about $100 credit over 3 months. Still it will take some years to pay back the cost of the system.
The govt then discovered that too many people were wanting to get in on the 47cKWH sell power back scheme and they could not afford to pay it so that scheme has closed. Prices of a 1500w system are now quoted at $1500 for 1500w compared to the $5000 I paid. I also believe that another incentive rebate is to cease at the end of this month. Government meddling and incentives coming and going are playing havoc with providers but possibly providing cheap panels for boats. They are all pretty big though. 190w per panel.
Now you might have twigged that I don't live in UK. Indeed we have had full sun and high temps in the 35+ mostly since Christmas with records being broken with a week of max over 40 degrees (41 yesterday) and mins at 25degrees. Yes it is too hot to go sailing. Cf eastern seaboard with huge floods.
Regards olewill
AndrewB
Well-known member
Don't know much about this but puzzled by the replies so far. My "12v" solar panel actually delivers anywhere between 18 and 21v depending on the light. It's the "charge controller" (which incorporates the regulator) that converts it to 12v. So does the solar panel itself matter, couldn't you just use a charge controller set to output 24v? And might rigging two solar panels in series just lead to trouble?
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mitiempo
Member
A nominal 12 volt panel has - for example the Kyocera KD135GX which is very popular for marine installation - has a max voltage of 17.7 volts and a max current of 7.63. To charge a 12 volt battery efficiently - a nominal number in itself - you need about 14.4 volts.
If you are using a basic PWM controller it will output the proper voltage for charging and waste the excess as heat. A MPPT controller will convert the 7.63 amps @17.7 volts to a higher amperage at the proper (14.4) voltage.
If you are using a basic PWM controller it will output the proper voltage for charging and waste the excess as heat. A MPPT controller will convert the 7.63 amps @17.7 volts to a higher amperage at the proper (14.4) voltage.
VicS
Well-known member
A little puzzled.
I understand, I think, the principle of MPPT regulators but surely a PWM regulator is a switching regulator. The output is controlled by varying the percentage of the "ON" time not by dumping the excess energy as heat ?
It's not like the shunt type regulators used for wind turbines in which the excess power is diverted to a shunt and dissipated as heat ?
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ccscott49
Active member
Yes, with a regulator, thats exactly what I have done, I have four, two in series each bank. Mine work fine.
ghostlymoron
Well-known member
Not an expert but I would have thought that if the panel is still producing volts when the regulator has switched off feed to the battery, those volts must go somewhere and therefore be dissipated as heat?
noelex
Well-known member
Solar regulators briefly disconnect the solar panels to regulate. They are open circuit during this time so the "power" does not go anywhere.
VicS
Well-known member
The volts dont "go" anywhere
When you switch a torch off the battery volts don't go anywhere.
You only get heat or power produced when a current flows Ie when you switch the torch on and the filament in the bulb becomes white hot.
When no current flows no heat is produced!
William_H
Well-known member
Charge controller??? What sort is it? If it is an MPPT type then yes possibly it could take the 19 odd volts of the panel and convert to the 28 volts needed to charge the 24v battery. However quite possibly even thhe MPPT controller needs more volts in than it gives out. (even if it can give out more current.
A solar panel connected directly to the battery will while providing 19v without a load will happily drop the difference in itself to charge a 12v battery. Unfortunately having a starting voltage of 19v means that as the battery reaches full charge the solar panel still has excess volts so can still push its full current in. This means if the solar panel can provide enough amps compared to the battery size it can cook the battery.
So the majority of regulators will simply limit the voltage by a series pass transistor or bypass some current to reduce voltage (shunt type) or switch it off and on at a proportion appropriate to the required current. No a solar panel has no problems without a load.
Only the MPPT regulator works differently by taking whatever the panel gives usually about 17 or 18 volts sucks as much current as possible out of the panel then converts by switching and transformer rectifier to produce the ideal voltage for the battery. This transforming gives the effect of more current at less voltage. In dim light the MPPT controller can actually raise the voltage of a meagre amount from a panel to produce enough voltage to charge a battery albeit at small current.
The MPPT is max power point tracking which effectively decides the compromise between sucking too much current and so reducing the voltage or reducing the voltage to increase current. It finds the best compromise for the sunlight arriving so tracking best power (voltage current combination)
I hope this explains olewill
Dave_Seager
Member
I imigine that a solar panel, exposed to sunlight, must either deliver electrical power or heat.
If the circuit is broken I think that it will heat up like any other black object in the sunshine. As it gets hotter than its surroundings, it will also lose heat by convection, conduction or radiation. Any electrical power taken from the panel will be offset by a reduction in the heating effect.
noelex
Well-known member
Very few MPPT regulators will do this.
ghostlymoron
Well-known member
I think I see now - isn't pv complicated?
VicMallows
New member
Agree. But when I first came across the 'MPPT concept' in relation to solar panels that's how I instinctively assumed they would work: A DC-DC voltage converter with a variable input dynamically optimised for the panel output, and an output optimised for battery charging. I now realise the typical implementation is a lot less sophisticated
Vic
SHUG
Active member
SVB sell 24V panels which make for a neat installation:
http://www.svb24.com/electric+lighting/solar+panels+wind+generators/?lang=1
http://www.svb24.com/electric+lighting/solar+panels+wind+generators/?lang=1
mitiempo
Member
Whether the excess voltage from a panel is dissipated as heat at the panel or the controller (with PWM controllers) really makes no difference. The main issue is you are not getting the maximum current to the battery which is the goal - MPPT controllers do this.
MPPT controllers also allow a series connection of the panels - many will accept 45 volts or so.
MPPT controllers also allow a series connection of the panels - many will accept 45 volts or so.
