Nebbian's solar upgrade

nebbian

Thought I'd start a new thread instead of hijacking Rod's lovely build notes

So I'm going to convert my IBC system to solar power.

Here's what I'm going to use:

1 x 120W solar panel with MPPT regulator (Ebay) ~ $180
1 x 60 Ah wet cell battery ~$160
1 x 20 W Johnson L450 bilge pump ~$40
1 x 5 W air pump ~$100
1 x home made timer/voltmeter ~$100

Back of the envelope calcs suggest that this should all work well, and give me 4 days of running time even if there is no sunlight. So we'll see...

nebbian

Solar panel arrived on Friday, I picked up the battery on Saturday, and the pump arrived today.

I tried it out and it seems to be quite powerful for its size, it's tiny! I've heard others say that these bilge pumps don't last, while others say that the Johnson ones are OK.

Perhaps I should build in some PWM to my timer so that the pump isn't quite so vigorous... But then perhaps that might stress it out even more.

Hmmm...

Also I managed to get some 2A solid state relays instead of 5A ones, so I'll have to go back to Jaycar to get the better ones. Forgot that the pump will draw 2.5 A (at least that's what it says on the packet, I'm not sure how 2.5 A times 12V gives 20W, but there you go.)

solarmon

Hi Nebbian,

I found this calculator. Not sure how accurate it is:

http://lib.store.yahoo.net/lib/sports-i ... nCalc.html

According to this, you will get 12 hours continuous use with your setup. For a timed setup then that will depend on your cycle period. If you use the 50% rule (don't drain your batteries below 50%) then this figure will be halved (your charge controller may cut the load to prevent the battery from going below a certain voltage - i.e. from over-discharging).

Cheers,

Mon

nebbian

Thanks Solarmon, I think that site takes the 50% already into consideration. It suggests I'll get 2 days of running time, before the batteries get to 50%.

That's good enough for me :-)

We'll see how it works in the real world.

Rodm

Hi Nebbian,
I am wrapped you are posting about your solar adventure. Good luck with your system and lots of photos please.

If you want any panels made yell out as I have a CNC machine and a reasonable supply of acrylic and ally sheeting - recycled stuff but isn't that the best type.

solarmon

nebbian wrote:

Thanks Solarmon, I think that site takes the 50% already into consideration. It suggests I'll get 2 days of running time, before the batteries get to 50%.

That's good enough for me :-)

We'll see how it works in the real world.

I think it takes more than 50% in to consideration - since if you supply the calculator with:

Battery Voltage: 12V
Battery Capacity: 12 AH
Watts: 12 (=1A)

It calculates it as 5 hours. With the 50% rule I would expect it to return 6 hours. So it must be factoring something else in, and/or using another Depth of Discharge percentage figure.

I've also found another calculator:

http://www.batterystuff.com/kb/tools/so ... lator.html

It is a bit more complex but there is a tutorial page for it:

http://www.batterystuff.com/kb/tools/so ... orial.html

This Battery Stuff site is actually quite a good source of battery information and there is useful Battery Basics page at:

http://www.batterystuff.com/kb/articles ... asics.html

Cheers,

Mon

nebbian

Wow thanks for the links, they are very informative. I learnt something today :-)

nebbian

Air pump arrived today, so it's time to start testing things out...

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nebbian

Pump amps...

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Box for the electrickery with goodies inside...

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solarmon

Nebbian,

Is that 2.58 Amps for the air pump?

Wouldn't that make it 2.58A x 12V = 30.96W

You mentioned in your first post that it should be a 5W air pump?

Or is that for the water pump, but even with that you stated it should be 20W?

Cheers,

Mon

nebbian

2.58 amps is for the water pump.
0.24 amps is for the air pump.

My stated values were what the manufacturer posted on their website, before I had the chance to get my hot little hands on the bits and pieces.

No matter, I still calculate 2 days runtime if the sun goes on holiday :-)

Rodm

Hi nebbian
Where did you get your air pump? The one I have is not suitable so looking for an alternative.

nebbian

Heya Rod, yes good luck finding an air pump with just the right specs...

This is where I got mine from:
http://www.boatstoreusa.com/outriggers- ... air-stone/

This one would work well for your systems I think, you might get away with only one air pump as it has two outlets.

The flow isn't huge but it should do the job.