A few very basic solar questions (12 volt setup - not in house)

Undervalued

I am trying to create a very basic solar setup to keep a 12 volt 120 AHr leisure battery fully charged in a garden workshop. Once a week or so I need to draw c. 20 amps from the battery for one to two hours. The rest of the time it is unused.

I have bought a 100 watt 18 volt panel, which came complete with a basic controller and I already have the battery. Unfortunately the controller's load output is only rated at 10 amps which isn't enough. The instructions are very particular about the connection and disconnection order with dire warnings of damage if it is done in the wrong sequence. Therefore I don't really want to have to disconnect the battery each time I want to use it as sooner or later...!

So, my first question is.....

Can I just not use the controller's load output and draw directly from the battery whilst it is still connected to the controller's charge output?

I realise that won't have the protection of it cutting off the load if the battery voltage falls too low. However I don't have that now with manual charging and it is not really an issue as I don't use more than about a third of the battery's capacity. In any case as it is used in daytime the battery would be getting at least some charge whilst I am drawing from it.

Or, are there problems with this idea and I really need to buy a much better controller with say a 30 amp maximum load?

Alternatively, suppose I had two leisure batteries in parallel. Could I then just disconnect one or other, draw from it for a couple of hours without the controller noticing?

Any other ideas? Preferably without spending money!

A couple of other basic questions.....

Would it be normal / sensible to have a 10 amp fuse between the panel and the controller?

Similarly, between the controller's charge output and the battery?

Finally, the panel has an aluminium frame with just four elongated slots on the underside but no suggestions as to how it should be fixed and no parts supplied! What is normal?

It is going on a sloping corrugated roof.

Many thanks for any advice.

QrizB

Undervalued said:

I have bought a 100 watt 18 volt panel, which came complete with a basic controller and I already have the battery. Unfortunately the controller's load output is only rated at 10 amps which isn't enough.

Is the controller something like this? Basic but functional?

https://www.amazon.co.uk/dp/B08FCQB173/

Can I just not use the controller's load output and draw directly from the battery whilst it is still connected to the controller's charge output?

Yes, you can.

Or, are there problems with this idea and I really need to buy a much better controller with say a 30 amp maximum load?

If you'd rather have a 30 amp one, there's one for £12 at the same Amazon link.

Would it be normal / sensible to have a 10 amp fuse between the panel and the controller?
Similarly, between the controller's charge output and the battery?

I'd put a fuse or breaker at or close to the battery. The only source of stored power is the battery, and all the wiring should be heavy enough to candle the short-circuit current from the panel without damage.

Finally, the panel has an aluminium frame with just four elongated slots on the underside but no suggestions as to how it should be fixed and no parts supplied! What is normal?

It is going on a sloping corrugated roof.

I've mounted mine on "Z brackets" like this, but they're not directly suitable for a corrugated roof:

https://www.amazon.co.uk/dp/B00BR3KFKE

Is the roof corrugated steel, or something flimsier?

What I've seen done occasionally is the panels fixed to the peaks of the corrugations. The idea being that the peaks don't get water running over them, so you won't get any serious leaks. On a steel roof the corrugations are likely to be strong enough to take the weight of the panels, but if it's eg. corrugated plastic you'll need to put some sort of support under the brackets too.

Undervalued

Many thanks QrizB.

Yes, I have exactly the one you linked.

Thanks for the other information too....

One more question, is the similar 30 amp controller really up to providing a steady say 25 amps for an hour or two? The connections don't really look man enough

QrizB

Undervalued said:

One more question, is the similar 30 amp controller really up to providing a steady say 25 amps for an hour or two? The connections don't really look man enough

Having dismantled two examples of a similar model, a 10A one and a 30A, the only difference seems to be that the 10A one has one power transistor and the 30A one has three.

They seem to be using the metal backplate as the heat sink which doesn't fill me with confidence.

For a prolonged 25A drain I'd personally go direct to the battery.

Heedtheadvice

I would do as QrizB suggests: direct off the battery with isolator and fuse in series. You then just use the controller to charge the battery whenever there is sufficient solar in slow time.

To save discharging the battery too much you could add a voltage monitor to the battery output, either one you can keep an eye on when you are using it or one that will give you a warning automatically.

Several available from well known sites such as https://www.amazon.co.uk/Jenny-Watson-Capacity-Indicator-Voltmeter/dp/B09P2SQCB5/ref=mp_s_a_1_18?crid=2651UF5FNKLI3&keywords=usb+voltage+monitor&qid=1660991105&sprefix=usb+voltage+monitor,aps,155&sr=8-18

Something similar might do you or even the cheap cigar lighter style (I have one on my car) if you are handy with wiring. But suggest you also protect the battery/wiring with a fuse in case of short circuits!!

Or just use a multimeter if you have one....

Solarchaser

I'd agree with both comments, for the price of an inline fuse, why not really?

The charging circuit is like running your car (alternator charges the battery) but also using the lights, so drawing from the battery too, so shouldn't be an issue.

In regards to attaching the panels, as a diy, i used small amgle brackets and TEC screws. you could use TEC screws, they are specifically made for attaching things to corrugated rooves, and put a base of CT1 or other decent silicone down on the contact point before you screw it down and that should provide a water proof seal.
The frame of the panel is there for structure rather than electrical, so you should be fine to drill through it and secure your angle brackets with more TEC screws,  that's how I did mine 3 years ago, and they have been fine.
Just make sure you are drilling into the part that's further away from the panel and glass.

Pile_o_stone

I have pretty much this setup in my potting shed. We have a stream that runs through our property and pump water from the stream into a water butt, powered by the 100w panel and battery. I bought it in a kit from Bimble solar. They don't seem to have the exact kit anymore, but this 90w version seems similar. The charge controller is the same as the one I have. 

https://www.bimblesolar.com/offgrid/complete-packages/12v-90w-pwm-sealed-complete-kit

We have had the battery connected for about a year and a half and have never had to disconnect it. Bimble offer the full kit, but I believe you can just buy individual parts, such as the controller.

Please note, I'm not connected with Bimble Solar, I'm just a satisfied customer.

70sbudgie

Pile_o_stone said:

I have pretty much this setup in my potting shed. We have a stream that runs through our property and pump water from the stream into a water butt, powered by the 100w panel and battery. I bought it in a kit from Bimble solar. They don't seem to have the exact kit anymore, but this 90w version seems similar. The charge controller is the same as the one I have. 

https://www.bimblesolar.com/offgrid/complete-packages/12v-90w-pwm-sealed-complete-kit

We have had the battery connected for about a year and a half and have never had to disconnect it. Bimble offer the full kit, but I believe you can just buy individual parts, such as the controller.

Please note, I'm not connected with Bimble Solar, I'm just a satisfied customer.

With a stream, have you ever looked into micro hydro?

Undervalued

Pile_o_stone said:

I have pretty much this setup in my potting shed. We have a stream that runs through our property and pump water from the stream into a water butt, powered by the 100w panel and battery. I bought it in a kit from Bimble solar. They don't seem to have the exact kit anymore, but this 90w version seems similar. The charge controller is the same as the one I have. 

https://www.bimblesolar.com/offgrid/complete-packages/12v-90w-pwm-sealed-complete-kit

We have had the battery connected for about a year and a half and have never had to disconnect it. Bimble offer the full kit, but I believe you can just buy individual parts, such as the controller.

Please note, I'm not connected with Bimble Solar, I'm just a satisfied customer.

Interesting, thanks.

That is certainly a complete kit, unlike my "kit" which was literally just a panel and a very basic controller and nothing else!

That said, by shopping around mine will probably end up nearly a hundred pounds cheaper even if I needed to buy a battery. My panel and controller were an Amazon special offer @ £82 for the pair. Say another £25 for the bits which should be in a kit but weren't making £107 excluding battery.

Relative quality is difficult to judge. Panel seems nicely made but how long it will last, who knows? Controller seems very bottom end of the market but would, say, a £25 one be twice as good or last twice as long?

Time will tell.....

Pile_o_stone

70sbudgie said:

With a stream, have you ever looked into micro hydro?

Yes, I did a bit of research but found that I didn't have enough flow or head to generate anything and I wouldn't be able to dam it or anything to try and improve its generation potential as I only own the land to centre of the stream. It's unfortunate because even 40wh of generation would be 24hrs a day and net me 960wh a day, which is a nice trickle charge into a battery. However in the recent heatwaves, the stream has been a godsend in helping us keep the garden and allotment watered.

Note: Under UK Riparian rights, we are allowed to extract 20 cubic meters of water per day without a license. We're nowhere near that sort of limit

Solarchaser

I wonder if you could pump that water up to a height, creating your own small hydro dam, and then use that water to water your plants..... after running through a small bore hose it would have to travel very quickly through the hose, and perhaps a small turbine?
Venturi effect to good use.

I mean logically you cant make more energy than you expend, (which makes heat pumps witch craft 😉)but in this case you are already going to be using the energy to water your land, you are just also capturing its energy in a turbine. Plus you will have inherent energy in your running stream which would help with pumping it to a height.

I dunno, but I'd definitely be messing about with it to see if I could make something work if I had a stream running through my property. 

Like if the stream was 1meter wide, id be directing it through a 300mm pipe for say 10 meters in the middle of the property and put a turbine in the middle of the pipe.

20 tons of water has to be able to generate some decent power.

Meh I'm just letting my mind wander

Edit. Missed a zero