Backyard Aquaponics
A place to discuss aquaponics

What I want to explain here is how to use 3&V for 12V system. The cheap & expensive all can utilize max power as the name MPPT mean but the cheaper one don't have wide input range so we can't use it to convert 37V panel to charge a 12V system.

Link to the cheap http://www.ebay.com.au/itm/20A-solar-re ... 3648wt_907 & expensive: http://www.ebay.com.au/itm/40A-MPPT-Sol ... 242wt_1397

See the note on first link. You can't use 24V to charge 12V system.

Cheers,
Long

Yes you are correct- it says: "Not mean it can transfer 24v current to 12V" which I assume means it wont step down the voltage

I haven't read back to the start of the thread and didn't realise it was for a 12V battery. Those MPPT regulators seem to be of the cheap and nasty variety, makes me wonder if they really are MPPT regulators...

I use Outback FM80s here for my off-grid system, they can accept up to 145V input, and output into 12, 24, 36, 48 or 60V batteries. It is true that you get what you pay for with this sort of gear.

A couple of good brands of low power MPPT regulators that will charge 12V batteries from higher voltage panels are Morningstar/Tristar and BlueSky.

Given the voltage outputs listed I think you have 3 sets of cells in series. Otherwise I would expect about 19v between 1-2 and 3-4.
As such I think you are stuck with 24v.

The auto mode of most controllers relies on the battery voltage. They look at that as they power up. I have seen a 24v system running at 12v once due to this after the system was completely drained due to not using a low voltage cutout. Completely killed the batteries.

Gunagulla is correct quite a few of the cheap units are not a full MPPT. Some are not even MPPT at all.
I add a second vote to the Morningstar controllers.
http://www.morningstarcorp.com/en/sunsavermppt

Regarding the voltage points you're confused on.

Voc - Open circuit voltage- Is what you get when there is no load on the panel. Ie after the regulator has disconnected it due to full battery. The regulator must be able to handle that voltage when it goes to resume charging.

Vmp - Maximum power voltage - Is the optimum point for the solar panel to be at to produce peak output when there is a load.

Thanks for the responce longnt.

So many conflicting reports.

Ok. Thanks.

So what about tapping into the different contacts on the back of the panel to get a voltage under 20v?

Is that doable?



Also what If I ran the system as 24 volt by adding a small motorbike 12v lead acid battery next to the large 120 - perhaps 200amp hour 12 volt deep cycle battery. Is that an option?

Dont I have a 36v panel?

This stuff is crazy.

I got this one. Sorry, I thought I'd linked to it correctly...

http://www.ebay.com.au/itm/350651129040 ... 490wt_1033

That listing clearly shows input voltage range as 12v - 40v/24v - 40v but the documentation that came with it says 12v-20v/24v - 40v.

I'm trying to get some clarification, but I just keep getting cut and past, generic replies that tell me to refer to the manual, have a nice day, and to feel free to contact them if I need any help.

No response yet from visa, paypal, or ebay.

The entire point of the solar panel is to power my aquaponics system from it.

Because I can. Or at least because I should be able to

But as a side adventure, I have 4.3m Sundance catamaran that I converted to an electric trolling motor powered fishing barge by adding a deep cycle battery, plywood deck and two milk creates to sit on.

It serves pretty well and I think from memory had a 6km range or so at walking pace. I think that was 6km there and 6km back. ie 12km range in total distance travelled. It's nice to be all electric. It feels right...like sailing does.

When I bought my 230watt solar panel I figured it should be enough to power the thing. But I have no idea.

If it will make it move for at least a couple of hours a day, I'll add a few NFT tubes along the sides, and pull Murray river water (tests show plenty of nitrates) in the front and dump it behind to grow some salad veggies, and perhaps a tomato to ward off scurvy (ARrrrrr!) and some other stuff.

Maybe get an eye patch.

Then set out on an epic adventure for a few days, weeks, months. The river system in total would provide something like a 5000km round trip, so I guess that's the plan. The first trip with all the gear would just be a weekend to test everything. Then perhaps try to do all of the river in stages.

Or just go and see what happens.

If I try to do all of it, the first half of the trip would be from the mouth up, and plan to turn around when the snows melt and the river starts flowing properly. (I'm guessing spring (September) for the u-turn.

I'm pretty confident I can feed myself with the help of the NFT tubes as there are quite a few fish in the River Murray. And yabbies. And some other stuff like freshwater mussels and glass shrimp that are best avoided. And many more carp than anyone could want. Carp can be harvested from some backwaters by just putting your face in the water and chewing.

I'll pre-grow the plants to varying ages so I can start harvesting straight away, and I'll take a few tins of something to eat just in case, and probably a still to clean up all the drinking water I'll need. There are towns every 100km or so if I need them. With a CB and an aquaponics powered boat, hopefully a visiting woman's hockey team, on a team building houseboat trip will take pity on me and I'll just fake the entire trip on my blog while actually living in luxury (sorry Mrs Bullwinkle, but you have to have a dream)

A big trip like that would need the solar panel to be able to drive the trolling motor without using any battery for half the daylight hours at least. I also have a 3.5 hp twostroke. but it will kill the ambience, and make the trip a bit of a chore. It might be ok for a couple of hours a day just to put away some miles. (the outboard will get Bullwinkle II (yeah I stole the name of the boat for my user name) to 17kph (displacement only. My hull shape is deep Vs, and doesn't plane) I'm guessing the trolling motor will get to perhaps 6kph at the fastest speed, but I'd probably aim for 4-5kph (I had gps for the twostroke run but not when I would take it out fishing on electric only power so the electric speed is just a guess) The drain on the battery at higher speeds is high compared to 3/4 speed.

I should really invent some kind of passive solar still because I wont want to lug 10 kg of water around. It would be better If I could make it on the boat as needed throughout the day. I'd rather save the 10kg for other junk. I even decided to loose some weight so I could take my swag (achieved as of today - next (and final) target is 4 more kg for essential single malt emergency fluids). (weight is quite an issue on a racing cat built for one, and carrying a stinking great battery, a trolling motor, a 12kg solar panel, and everything else needed to take on an epic adventure.

Anyway. That's the plan.

And sorry to those people who posted in this thread in January. For some reason I only just read the posts today. Maybe January was when BYAP changed servers. I lost some of my subscriptions then. Who knows.

But I appreciate the reply as always, even if it seemed like I ignored them. I need all the help I can get with making this particular "thing" pan out properly.

This stuff is so confusing. I cant help thinking there is some small fundamental thing that escapes me, and will let me in on the the secret that will allow me to get past this block I have with electronics. I'm trying




try·ing
/ˈtrī-iNG/
Adjective
Difficult or annoying; hard to endure: "it had been a very trying day".

What it actually says is:"Input current range: 12V - 40V/24V - 40V"

so clearly they dont have much understanding of what they are selling... volts, amps, who cares, its all electricity!

I'd be returning it and buying a recognised brand that is going to last, and do the job you require.

That size panel has traditionally been used to charge 24V batteries, the older "12V" panels had Vmp~16-18V for for 12V batteries. You need a higher voltage source than the battery in order to get a current flow, even under cloudy conditions. A 24V battery can require up to ~31V for equalisation charging, which is for cell balancing, de-sulphation etc, so ~35-37Vmp is ideal.
As I mentioned in a previous posting, most panels nowadays come in 60, 72 or 96 cell varieties, the 60 cell ones can be used to charge (some, but not all) 24V batteries with PWM type controllers without too much wasted energy, but proper a MPPT charge controller is the way to go if you want all energy the panel can produce.



[quote="BullwinkleII"]

When I bought my 230watt solar panel I figured it should be enough to power the thing. But I have no idea.
[quote]

Probably not, a 230W panel will deliver about 185W under typical conditions, when it is pointed directly at the sun, less at other times, mainly because the cell temp will be much higher than the 25C used for the standard test conditions under which panels are rated. If you throw a bucket of water over it every few minutes while floating down the river, you should get closer to the rated 230W though
Will you have paddles for cloudy days


I'd be investing in a Lithium battery instead of carting a bloody heavy inefficient Lead-acid around!
That way you will be able to use about 95% of the energy from the panel, if you use a proper MPPT charge controller, vs only about 85% with the Lead-acid, because they are so inefficient. Have a read of this discussion about Lithium vs Lead-acid batteries:
http://forums.energymatters.com.au/sola ... c5108.html

quote Gunagulla - Will you have paddles for cloudy days:?:


I'll have a swag and single malt scotch for cloudy days


I might just have to take the two stroke outboard I have. But that would mean I'd have to lose 12.6 kg from either my body, or by dumping some other gear. I dont think my body has 12.6 kg to spare.

If I can power the motor almost directly from the panel rather than charging a battery all day, and running the motor for two hours, perhaps I could just add a very small 24v battery.

Money is a major issue here. Everything gets funded directly from ad revenue on my blog, so buying a decent sized battery would kill the project.

It looks like even a 10 amp LiFePO4 24v battery would cost around $220. Too much.

A reply at last via paypal

"Dear [Edit - Bullwinkle], thanks for your message. Regarding to this item, it will work with 36v 230watt solar panel, please try again. Sorry for any inconvenience caused."

I've replied with something alone the lines of ...

"So you are saying the documentation that came with the device is in error. Please send me the correct documentation."



But t guess I'm protected now because the messages went through paypal's site, so it's on the record.

It will work!

No because of the way they are series wired short of completely re-wiring the cells its not possible.
What you have is panel that would normally be used for a grid connect system or with a MPPT suited for 40v.

The small battery would be very quickly cooked unfortunately.

I know of the controller you have linked to and the manual is correct. 20v max when charging a 12v battery, 40v max for a 24v battery.

What you want for running the motor directly from the panel is a device called a maximiser- it is basically an MPPT device designed to get the most from a solar panel when running an electric motor.

Presumably you will want at least some battery storage for a bit of light at night?