Correct Power Input (Submersible Pump)

[euca]

We have a submersible pump rated at 700W.  It's been running on two by 300W new, 'mono' solar panels for some months now with no noticeable trouble; that's a little short of correct i/p pwr.  We have just purchased two 2nd-hand 'poly' panels, Bt2000 each, delivering 260W each (don't hold back, opinions, please) to test how they go.  Faen reports they work OK, no problems.  I have a dim but persistent memory that underpowered motors will suffer from slow-down, overheating & fail quicker.  Good Ole Crossy (smashing forum, C, most interesting) wrote supporting my memory that low power i/p should be avoided, but I've just lost the reference, duh.  I am considering a third 260W panel, 3x260= 780W vs 700W requirement.  What damage will that do?

 

I should be most grateful for direct replies concerning the immediate problem, above & also any thoughts of a wider nature regarding the flexibility I could use matching loads to i/ps & about solar powered field pumps.  I also intend to set up solar power to supply daytime domestic use as solar panels flood the market & prices fall, comments, again, please. 

 

Another thought is that I should be able to use clapped out vehicle batteries, increasing the number of batteries to obtain the correct number of working cells, & thus the emf, instead of buying new.  It's a seductive thought...

[northsouthdevide]

Do you run the dc power through an inverter, or a charge controller? 

Is the pump dc? 

Im no expert, and have no solar myself yet, but am planning on an install myself soon. 

I know that your panels won't pull maximum watts until peek time, but should pull at least 4x230=920, so that's more than a 1000w a day. 

How much more depends on amount of sun, and size of battery. 

I think adding panels won't do any harm at all, if your pump pulls 700w from a kw then upping your storage to 1500w+, would give you 2 hours running time. 

Edited June 28, 2020 by northsouthdevide

[northsouthdevide]

For daytime domestic use, I'm considering starting with one of these grid tie inverters pulling from 2x380w panels. 

I read that it's best not to work the inverter too hard and it will last longer. 

I'm going to try 1 setup, and if it's good, I plan to stack them until my bill is low. 

Ive read a bit about them, but would also be interested if anyone has any real experience with this model. 

[northsouthdevide]

[RichCor]

1 hour ago, euca said:

We have a submersible pump rated at 700W.  It's been running on two by 300W new, 'mono' solar panels for some months now with no noticeable trouble; that's a little short of correct i/p pwr.  We have just purchased two 2nd-hand 'poly' panels, Bt2000 each, delivering 260W each (don't hold back, opinions, please) to test how they go.  Faen reports they work OK, no problems.  I have a dim but persistent memory that underpowered motors will suffer from slow-down, overheating & fail quicker. 

Given any thoughts to having the solar charge a set of batteries, then relying on the batteries to give the pump 100% duty power on demand?

[euca]

17 hours ago, northsouthdevide said:

Do you run the dc power through an inverter, or a charge controller? 

Is the pump dc? 

Im no expert, and have no solar myself yet, but am planning on an install myself soon. 

I know that your panels won't pull maximum watts until peek time, but should pull at least 4x230=920, so that's more than a 1000w a day. 

How much more depends on amount of sun, and size of battery. 

I think adding panels won't do any harm at all, if your pump pulls 700w from a kw then upping your storage to 1500w+, would give you 2 hours running time. 

Charge controller, dc.

[euca]

17 hours ago, northsouthdevide said:

For daytime domestic use, I'm considering starting with one of these grid tie inverters pulling from 2x380w panels. 

I read that it's best not to work the inverter too hard and it will last longer. 

I'm going to try 1 setup, and if it's good, I plan to stack them until my bill is low. 

Ive read a bit about them, but would also be interested if anyone has any real experience with this model. 

Thinking similar.  Tks fer tip ref inverters easy load.  I find Crossy's thread helpful & I read round it so slowly increasing knowledge base.  My plan, one test setup is same as yours.  All most interesting.

[euca]

17 hours ago, northsouthdevide said:

Dunno about that one.  Intend study reviews, but not where they review themselves so generously, & get other peoples' opinions.  Did you do that & arrive at that particular unit?

[euca]

16 hours ago, RichCor said:

Given any thoughts to having the solar charge a set of batteries, then relying on the batteries to give the pump 100% duty power on demand?

Yes, indeed, my last para refers to a cheapo idea which I see Thai villagers doing but don't know how effective it is.  Ask & you get a grunt so they don't know either.  Still, it's an enticingly thrifty idea.