Off grid Design- water pump and extra power

[pda1]

That's over $1/watt for PV.

Check out SanTan Solar.
Shipping a pallet by truck gets expensive if you only want a couple.
I got many (several pallets) and drove my pickup to freight terminal to save on last mile delivery.
For small quantity, you can find local sellers with similar price.
PV panels can be ha for $0.15 to $0.50/W

DIY LiFePO4 can be smaller cash outlay than lead-acid. But it is a project in and of itself.
It will give longer cycle life (maybe up to 3500 cycles)
AGM can give 200 to 700 cycles depending on quality and DoD.
FLA is cheaper and can give 2x cycles of AGM if quality. Requires maintenance.

Which battery meets your needs depends on how often you plan to cycle.
Mine is only backup during grid failure. I chose AGM, expecting < 200 cycles in a decade. I sized it for 70% DoD.

If you avoid nighttime drain so battery is only a buffer during the day, then demand on battery is minimal. Even a used car starting battery would work fine if never cycled, only providing a surge to start motors.

Batteries are expensive and wear out. PV is cheap and lasts forever. So I try to over-panel and minimize batteries.

Thanks for the mentioning SanTan....it's the shipping that's going to be expensive but it's reasonable. You can get a lot of power fairly inexpensively. Should the fact that the panels are used be a major concern?

Peter

 

[Hedges]

"Used" means infant mortality has been weeded out, and he gives a 1 year warranty.
He also sells some new. Limited quantities, I think they are excess left over after a contractor purchased many for a large job.

When you can buy for 25% the price of new and they've been used maybe 5 years out of 25 to 40 year life, it is a bargain.
Try to research reputation of brand/model. Don't let anyone tell you they're all the same. Some degrade rapidly.
SanTan says they test the panels. But I don't know the details. Isc and Voc don't show what Vmp & Imp do, actual power output. So ask him (and tell us what you learn.)

 

[pda1]

Say, take a look at this panel-

SanTan 250w

Now, I'm curious. If I want a 24v panel, these panels are Voc= 37.6v

Now what charge controller would accept 37 input and give me a 12vdc for battery etc?

Thanks fellas,

Peter

 

[Hedges]

Any MPPT charge controller that can take at least 44V input. Two panels in series, at least 88V input.
(37.6V x 1.16 for cold weather = 44V)

This one, for instance (there are cheaper options)

Victron 30A Solar Charge Controller | SanTan Solar

store.santansolar.com

 

[lupo]

Now I'm pursuing the 24v panel system. But I'm inclined towards a high wattage array, for me, of about 800w as mentioned before. What's the cheapest and most practical way to go about panel selection? It would nice to get everything off of ebay and it looks like a more reasonable single panel wattage is 200 (24v) and then connect them in parallel. Like this one-
Concerning batteries- Are you recommending a 24vdc LiFePO4 battery?

I always try to design a system open for extension, therefore, I recommend to start with a MPTT controller. You can start with two or even one panel (second hand) and a cheap lead acid battery. Later you can still upgrade the panels or the battery to LiFePO4 without changing everything and all cables. LiFePO4 is a good choice on long term but 24V on LiFePO4 is also expensive. So a cheaper solution would be to start with two cheap lead acid batteries and test if it is sufficient for your use case. Changing the battery later is not a huge deal. If you have the money, go for LiFePO4, otherwise build a system that you can upgrade in the future.