solar panel

[jvs]

I have a dc waterpump i use for irrigation,rated 100volt,10 amp.

I use 3 solar panels to run it,two panels 30.6 volt 250 watt and one panel 30.6 volt 300watt.

I want to take one panel away and use for another set up.

I have choices,40 volt 380 watt or 30 volt 350 watt.

Which panel is going to help increase the performance of the pump?

30 plus ,30 plus 40 gives me 100 volts but does not much to increase amps

30 plus 30 plus 30 gives me 90 volts but it will increase the amperage?

Wisdom please?

[ArranP]

•  

I have a dc waterpump i use for irrigation,rated 100volt x 10 amp = 1,000 watts. 

30.6 volt x 250 watt = 8.17 amps

30.6 volt x 300watt = 9.80 amps

 

I want to take one panel away and use for another set up.

I have choices,

40 volt 380 watt = 9.50 amps

30 volt 350 watt = 11.66 amps

 

ummm......

 

you could test it, time for 1 minute measure how much water it pumps into a container.

Edited February 28, 2020 by ArranP

[jvs]

2 hours ago, ArranP said:

•  

I have a dc waterpump i use for irrigation,rated 100volt x 10 amp = 1,000 watts. 

30.6 volt x 250 watt = 8.17 amps

30.6 volt x 300watt = 9.80 amps

 

I want to take one panel away and use for another set up.

I have choices,

40 volt 380 watt = 9.50 amps

30 volt 350 watt = 11.66 amps

 

ummm......

 

you could test it, time for 1 minute measure how much water it pumps into a container.

Problem is i do not have a panel yet,only need one but trying to figure out what

i should get.

 

[ArranP]

21 minutes ago, jvs said:

Problem is i do not have a panel yet,only need one but trying to figure out what

i should get.

 

 

This may shed some light, I'm no expert....   at first glance it leans towards having the correct voltage and the appliance will draw as many amps as it needs.

 

https://electronics.stackexchange.com/questions/34745/choosing-power-supply-how-to-get-the-voltage-and-current-ratings

 

[Crossy]

Since your system is working why not use the new panel for the new project?

 

[jvs]

4 hours ago, Crossy said:

Since your system is working why not use the new panel for the new project?

 

Yes i could do that but the new system does not need to produce a lot of pressure,

it is for a waterfall.The irrigation system can be upgraded by using a new panel that way  it

can produce a little more

water.Either way i do not think it will make a lot of difference,i just thought i would ask a professional for their opinion.

Thanks for responding and i think i will go to the shop tomorrow and see what panel i come home with.

[tjo o tjim]

Might be overkill, but if you want to maximize flow then you add a battery, charge controller, and a voltage converter to the system; the battery and voltage converter stay as close to the pump as possible. 

 

Unregulated DV voltage will reduce performance.  Voltage output is a function of several variables, so easiest to externalize those things if system performance matters.  

[jvs]

1 hour ago, tjo o tjim said:

Might be overkill, but if you want to maximize flow then you add a battery, charge controller, and a voltage converter to the system; the battery and voltage converter stay as close to the pump as possible. 

 

Unregulated DV voltage will reduce performance.  Voltage output is a function of several variables, so easiest to externalize those things if system performance matters.  

I used to have all that but it was not working properly,when there was a cloud the whole

system shut down amd it would take minutes for everything to run again.

Now i run dc current directly and when there is a cloud it just slows down but it will keep running.What i have now works a lot better imo.

 

[Metropolitian]

Amazed that there is not an good reply given to the OP.

Even pointing to some mistakes made at some comments.

I will jump in right away. ????

 

On 2/28/2020 at 4:30 PM, ArranP said:

30.6 volt x 250 watt = 8.17 amps

That's just an small typo but the answer is still right.

It is 250 W : 30.6 V = 8.17 A

 

P=U*I , so I = P/U

(Not all countries use the same units, but the formula we all share.)

 

On 2/28/2020 at 9:37 AM, jvs said:

I have a dc waterpump i use for irrigation,rated 100volt,10 amp.

I use 3 solar panels to run it,two panels 30.6 volt 250 watt and one panel 30.6 volt 300watt.

I want to take one panel away and use for another set up.

I have choices,40 volt 380 watt or 30 volt 350 watt.

Which panel is going to help increase the performance of the pump?

30 plus ,30 plus 40 gives me 100 volts but does not much to increase amps

30 plus 30 plus 30 gives me 90 volts but it will increase the amperage?

Wisdom please?

Ok:

3 panels. All of them are 30.6 volts And two of them are 250 watt and one is 300 watt.

You have these in series, which get you theoretically to 91.8 volts.

The watt doesn't really ad. In series the current is the same everywhere and 'dominated' with the weakest link, the 250 watt panel(s).

250/30.6 = 8.17 Amp.  at 91.8 volt your setup with the 3 panels in series gives you 750 watt of power.

 

The volt is 10% below the rating of the pump, and the amperage 20% under. The pump is working below its rating.

 

You want to take away one, and put another in place.

380 watt (40v) or 350 watt (30v).

 

But if you really want and the you want to get the volt up, then choose the 380 watt version.

My answer should be: none of these two, the amperage will still be the same.

Unless you get more panels, to connect them in parallel.

 

In series the volt adds, current isn't.

In parallel the currents adds, volt isn't.

A combination of both, both volts and currents adds.

 

I just draw a sketch, if in this sketch all panels are the 250 watt (30.6) volt version at figure 2 you will have double the amp compared as in figure 1.

This will make the pump work better well for its rating , especially with shade.

^{The two links (thin gray lines) are not needed per s'e for this to work.}

 

The best: Get the same kind of panels to connect in series.

For example buy three of

 

[Metropolitian]

If I was you, I would get 3 x 380 watt (40 volt) panels and connect them to an controller for pumps.

This way I can control the flow and the pump will get the right voltage even when a big cloud pass by.

 

[jvs]

Thank you all for the replies.Metropolitan,i want to use what i already have without

investing too much.

What you are proposing would probably be ideal but if i would go that big i would be better off with an AC pump?I already have an AC pump as back up and it puts out a

lot of water ,too much actually.

Anyway i went to the store today and bought a 37.4 volt panel rated 330 Watt.

Not totally ideal but the price was right,the first 250 Watt panels i bought were

over 7000 baht each.This new one was 3750 baht.

I will take one 250 Watt panel and connect it to the small pump,i will have

plenty of water as it will just run a waterfall.

I will end up with a little higher voltage for the bigger pump and will see how things go.

[Metropolitian]

22 hours ago, Metropolitian said:

The best: Get the same kind of panels to connect in series.

For example buy three of

...

It looks like the TVF is cutting some parts when posting.

Happened twice now, the page is flashing continuously trying to reload from assets.thaivisa.com and google ads.

 

Anyway, it should say:

 

For example buy three of the 350 watt panels (30 volt) then you get 90 volt and 11.6 amp for the pump.