Output from 2 x solar panels ?

[Colin K]

Hello,
Would like to charge my 24v domestic bank from a couple of solar panels, Spotted one the right size and they are 12v 1.1 A ish output each. I am going to wire them in "series" ?? to get the 24v output but wondered what affect this has on the Ampage output ? Im thinking it wont be 2x1.1A = 2.2 A but 1/2 that as I have wired them in series. Could someone relieve me from my blond moment. Thanks Colin.

 

[AngusMcDoon]

Wire them in series. You will get 1.1A. Or less if it doesn't stop bliddy raining.

 

[VicMallows]

You will be lucky if you actually see much over 0.5A into your batteries for about 4hrs around noon in UK, assuming the panel is more-or-less facing the sun, ...... and it is shining nice and bright!

Solar panels are great, but you have to be realistic about what they will actually achieve.

 

[VicS]

As AngusMcDoon says in theory you will get the same current , at 24V, from two in series as you would have got, at 12 volts, from just one .

To understand what you might get in practice you will have to read the manufacturers specs.

 

[Colin K]

Hi Thanks for that the output that I get will all be a bonus and yes realise that the 1.1 A they say is max etc etc etc I was mainly lost as the chap that Im getting them off said that their Amperage output will be the same whether 12v or 24v if I wire 2 in series but I thought there had to be a sacrifice for upping the voltage ??? Must be someones Law I forget which.
Only go on board once every 3 weeks or so so even 4 hrs a day will be a help ? Will fit a charge controller I think but my battery bank is 400ah+.
Thanks for all your help Colin.

 

[noelex]

Hi Thanks for that the output that I get will all be a bonus and yes realise that the 1.1 A they say is max etc etc etc I was mainly lost as the chap that Im getting them off said that their Amperage output will be the same whether 12v or 24v if I wire 2 in series but I thought there had to be a sacrifice for upping the voltage ??? Must be someones Law I forget which.
Only go on board once every 3 weeks or so so even 4 hrs a day will be a help ? Will fit a charge controller I think but my battery bank is 400ah+.
Thanks for all your help Colin.

I would not bother with a charge controler in the UK with that sized battery bank and solar panel size if they are wet cell batteries.
A simple on off charge controler will reduce the output of the panels and a good PWM controler with sutable battery set points and 2 stage charging will be expensive given the low cost of the panels.

 

[VicMallows]

On that size of bank, the panels will be be about right to maintain fully charged batteries in good condition. Just don't expect the panels to meaningfully recharge the batteries if they have been significantly depleted.

I don't consider that you need a controller with that setup. Usual advice is to check that the panels have a series diode to prevent reverse discharge at night, but I have never encountered this as a problem on any modern panel.

 

[William_H]

Solar panels

I agree with all that has been said. If you have doubts about there being a series diode connect the panels up to the battery then when it is dark check the current with a multimeter. You should have no reverse current. If you have like 10 milliamps or so in reverse you need a diode. NB only one diode in series for 2 panels. Buy a small silicnb diode rated at typically 200 v 2 amps or more. Just a few pence.
As said if you get a half amp for a few hours you will be doing well. But it will be worthwhile. good luck olewill

 

[lw395]

On that size of bank, the panels will be be about right to maintain fully charged batteries in good condition. Just don't expect the panels to meaningfully recharge the batteries if they have been significantly depleted.

I don't consider that you need a controller with that setup. Usual advice is to check that the panels have a series diode to prevent reverse discharge at night, but I have never encountered this as a problem on any modern panel.

Half an amp for several hours a day is a bit more than a decent battery should be self-discharging, but as you say it's not going to overcharge a battery. It's worth having in terms of battery life though IMHO.