12 volt and 24 volt conversions etc for solar

[DannyB1954]

Electrical Power is called Watts. it is a combination of volts and amps. Watts equals Volts times Amps. So say you have an function that calls for 1,200 watts. If the voltage is 120 volts then the amps will be 10. If the voltage is 12 volts the amperage will be 100. if the voltage is 24 then the amps would be 50. So each one of those will have the same amount of energy. The advantage to using higher voltage is there is less amperage and the wires can be thinner.
With solar panels the voltage the panel actually puts out is higher than the name of the panel. As an example I have 12 volt panels that actually put out 20 volts. The controller then regulates this so that the batteries get charged with 13.8 volts. To charge a battery the voltage needs to be higher than the battery for the electricity to go into the battery.

 

[Low277]

Not sure if I did this right but. What DannyB1954 said!! ?

 

[John61CT]

Except for actual charging Absorb setpoint needs to be much higher.

Follow the batt maker specs. Often 14.7V can be higher.

13.8V is for Float, after 100% Full, no more charging needed, storage or charge source carrying loads.

 

[Oneleggedcowboy]

Good info. So can a 60 cell panel charge a 24 volt bank by using a mppt controller? I see where yall said 60 cell is 20 volts. I have a really great 24 volt inverter and would like to use it. I have a Krieger in the other rig, slide in camper.

 

[John61CT]

If you go back and carefully read the answers above, even just the first few already cover your questions.

If there is something there you don't understand, quote it and ask for clarification.

Just owning a 24V device is not IMO a good enough reason for setting up your whole system on 24V.

Best to avoid using inverters as much as possible anyway.

 

[Oneleggedcowboy]

Just checking my math. So if two 100 watt panels that put out 5 amps each are used.
If I hooked them up as two 12 volt setups I would get 12 volt (whatevery they put out let's say 18 volts) and 10 amps?

If I cross them to make a 24 volt the I would have 24 volt and 10 amp? That seems like less ah would be produced? How does this work?

 

[Trebor English]

Two 100 watt 20 volt 5 amp panels (20×5=100) in series would put out 200 watts.  That would be 40 volts at 5 amps (40×5=200).  

The MPPT controller would chop it up, make AC, transform it to 14.4 volts to charge the 12 volt battery.  200 watts ÷ 14.4 volts = 13.88 amps.  Since there will be actual losses you'll get less than 13.8 amps.

Two 5 amp panels in parallel would give 10 amps, less than 13.88 amps.

 

[highdesertranger]

amps x volts = watts. if you know any 2 you can rearrange this formula and figure out the 3rd. for instance watts ÷ volts = amps

when you wire something in parallel(+ to + and, - to -) the volts remain the same but the amps are doubled.
when you wire something in series(+ to - and, - to +) the volts double and the amps stay the same.

with this basic knowledge you are on your way to understanding solar and batteries. highdesertranger

 

[John61CT]

Only use Amps when the voltage is known and constant.

Otherwise Watts are constant, much better to use them as units to indicate power level.

Once talking about 12V circuits, batteries, loads over time etc, then amps and AH are the norm for apples to apples.