Can you charge a 24V system with a single 12V solar panel?

Is it possible to use 1 solar panel to charge 2 12volt batteries connected in series (24 volt) via 2 seperate 12 volt charge controllers, one linked to each battery? - Richard

Unfortunately, no.

The negative solar and negative battery terminal on most charge controllers are connected together internally - it's only for convenience that they provide you with two seperate terminals to connect the wire.

If you were to try putting two controllers in series, you would be joining the positive battery terminal of the first charge controller to the negative battery terminal of the second. If you then attach the negative solar panel lead to both solar negative terminals you have the following situation:

1) positive battery terminal of first controller is connected to negative battery terminal of second...
2) ... which is connected internally to the negative solar terminal
3) ... which is connected to the negative solar panel lead
4) ... which is connected to the negative solar terminal of the first charge controller
5) ... which is connected internally to the negative battery terminal

In short, you've connected the battery positive to the battery negative. That's called a short circuit, which is a cause of wires melting, fire, grieving next of kin etc etc.

If you must try it, I'd recommend making your will first. I can't see any reason why you couldn't put two 12V controllers in series with seperate solar panels, though don't take my word for it. However, it's more usual to simply wire two 12V panels in series to a single 24V controller. See our handy 24V solar panel wiring diagram.

Multiple regulators on one battery bank

Hello. I have 2 sets of solar panels (200W each) with their own regulator, and a wind generator with its own regulator. However they are not all charging efficiently. Even though the battery bank is fla,t when it is sunny and windy the wind regulator slows the wind gen down and one solar reg beats the other down. So I am getting maximum recharging from only one source not all 3. I think the regulators are sensing the charging voltage of the dominant regulator and thinking the battery is fully charged. Any suggestions? I have been looking for a regulator to manage 3 inputs (and 2 outputs would be good) but can't see any. Could I wire all 3 regulators to a 4th regulator for the bank? Thanks. Stephen.

Hi Stephen. You are right that whenever you are charging a battery, the voltage will increase, and therefore any other charging sources attached to the battery will see a higher voltage and think the batteries are slightly more highly charged than they actually are. That's pretty much unavoidable.

The effect should not be very large, however, and it's not necessarily a bad thing, as it prevents overcharging. PV arrays trickle charge batteries, and with a healthy battery bank and decent sized cables between the battery and regulators, you shouldn't see a massive voltage increase. If you are - if they are cutting out even when you think the batteries are flat - it's suggesting the voltage is rising above 14.4V (the usual cut off), even with a relatively low charging current. That suggests to me that the batteries are on the way out.

Regulators are designed to be used in parallel in the way you have them wired, so I very much doubt you will find any difference if you do change the regulators. Trying new batteries is in my opinion far more likely to give you good results.

Hope that helps.

Connecting solar panel into domestic electrical circuit

If I bought a solar panel to take abroad could I link it up directly to the
house electricity cables after the voltage meter?
Would this draw less power from the grid during the day?
Kindest regards, Saiduz.

Unfortunately it's not that simple! Solar panels produce DC electricity, usually at 12 volts, which is fine for battery charging. But it's not compatible with 240 volt AC mains electricity. You can use an inverter (eg the Silverline Inverters or Steca Inverters on our website)  to produce mains electricity from the battery that you have charged, but even then you can't simply plug that electricity straight into your mains circuit, as the frequencies they are running at will be slightly different and out of phase. Any equipment running off the inverter would have to be on a completely seperate circuit.

It is possible to get a type of inverter which can connect into your mains electricity. However these 'grid-connect' inverters are far more expensive, and only really suited to big arrays of solar panels.

Can I use a solar regulator to regulate a wind turbine?

Just having a look on your website for wind turbines and regulators etc. You suggest that you can connect up to 100W of solar panels into the wind turbine regulator in addition to the turbine itself.

Does this work the other way? ie. Can I plug a wind turbine into the solar regulator I already have?

I'm fairly sure the answer to this is no, from my memory of wind turbines they actually produce AC voltage by induction, is this still the case or do they now produce DC voltage direct?

Yours realising just how long ago it was that I last looked at electronics!!!

Neil

Hi Neil,

You're right that it's not a good idea using a solar regulator for a wind turbine - but it's for slightly more complicated reasons! Yes, turbines do produce AC by induction, although in fact it's normally rectified in the turbine itself so it's usually unsmoothed DC that comes down the wires. The problem is more to do with what happens when a regulator senses a battery is full. Most solar regulators will simply open circuit, which is fine for a solar panel. But an open-circuited wind turbine will spin freely, which is bad news in strong winds. So a turbine regulator is usually designed to short-circuit the turbine, which slows the blades down.

Also, solar regulators might not like the relatively spiky DC from the turbine compared to the very smooth DC from a solar panel.

Having said all that, you might get away with it in places that aren't too windy - but it's not really recommended by the professionals! You are likely to shorten the lifetime of your wind turbine.

Two seperate charging systems

Hello, I have a 50 watt panel and a 130 watt panel, is it possible to wire them both to the same batteries (560 ah)possibly through 2 seperate charge controllers which I have.The 50 watt system is an older system and batteries are suspect where as the 560 ah system is new and could easily take the 2 panels if they can be used together.

cheers, Steve

Yes, it's usually absolutely fine to wire two seperate solar panels to the same battery bank. You could either use two seperate solar regulators, or you could even wire both panels to one solar regulator - as long as it is rated for sufficient current. In your case, that would be 180 watts(130 + 50), divided by the battery voltage (12) - 15 Amps.