the big panel the better? volt vs Amps

[ilovehoby]

Hello I'm trying to DIY solar panel. I have about 150 .5v 3.6amp cells.

1. Should I make a bigger panel with high volt and the amps stay the same? or anybody have a good idea!
2. is it true the higher volt the better panel, and will charge the batteries faster?
3. I want to use this to run my pond pump about 2 amp 115v about 230w for 24hrs with this panel. I have 3 12v 160ah batteries.
4. is there a such a auto switch setup to run the pump only at night or when the batteries bank became low.

thanks for the help advance.

Mike

[Mike90250]

Welcome. Take a breath before you jump too fast and trip.

Home built panels, while a fun project, rarely last more than a couple years, and need constant maintainance.

> 2. is it true the higher volt the better panel, and will charge the batteries faster?

False and False. Is a faster car better then another car ? A panel's voltage will be
"pulled" down to the battery voltage, about 15V (for a 12V battery) This is true for a 18V panel, or a 45V panel, hook both to a battery, and they both would read the voltage. It's pretty certain the 18V panel will charge the battery faster, because it is delivering it's watts
very close to it's power curve. A 45V panel has higher voltage, but lower amps. Amps are what charge a battery.

So, you calculated your wattage to be 230W. for 24 hours, that's 230 x 24 =
5520 watt hours

If we only count sunny days, and ignore cloud losses, you generally have 5 GOOD solar charging hours in a day, centered around noon. That's when you to replenish the battery, and still keep the pump running.
a battery can safely deliver only 50% of it's charge, before damage begins to occur.
160 x 3 / 2 = 240AH x 12V = 2880 watts
So, in the summer, this amount of battery may just barely be able to keep the pump running all night before it goes dead at sunrise.

To recharge it all, 5520 /5 = 1104 watts per hour, for 5 hours, to recharge.

And the fly in the ointment, to account for losses in the PV, charge controller, inverter, and battery efficiency, al the losses add up to about 50%.

You would need about 2,000 watts of solar panels, to run the pump 24/7 and recharge the battery, in the summer (long days, short nights), with no clouds or rain.

So, now looking at conservation and efficiency to improve the situation, is the next step. Can you use a smaller pump? Run less hours ?

[ilovehoby]

Hello Mike, I still don't understand, a 18v 3.6 amp will charger the batterie faster then a 45v 3.6 amps and you state that amps is what charging the batteries.

If I make 2 panels 18v 3.6amp connect it in palalell make it 18v 7.2amps, 130 watts will it charge the batteries any faster, since amps is what it need to charge the batteries.

even 3 panels 18v 3.6amps, that make 18v 10amps, 180 watts, will it need bigger wire to carry the amps, this will cost a lots.

thanks in advance

[Mike90250]

Hello Mike, I still don't understand, a 18v 3.6 amp will charger the batterie faster then a 45v 3.6 amps and you state that amps is what charging the batteries.

If I make 2 panels 18v 3.6amp connect it in palalell make it 18v 7.2amps, 130 watts will it charge the batteries any faster, since amps is what it need to charge the batteries.

even 3 panels 18v 3.6amps, that make 18v 10amps, 180 watts, will it need bigger wire to carry the amps, this will cost a lots.

thanks in advance

Right, the 18V panel is closely matched to your battery voltage, the 45V panel will not operate near it MaxPower voltage, and you LOOSE efficiency.

And panels in parallel, need fat copper wires. Or you can buy a special type of charge controller called a MPPT controller. That will convert high volts, to amps, and run panels at their max power. But They cost a lot too.
MPPT info : http://www.windsun.com/ChargeControls/MPPT.htm

Confused yet? It's a lot of new information to absorb at once.