Starting small

[juperwort]

I have been meaning to give Solar electric a go for a while. Recently, I received a Maplin mailout which had a 12w 12v solar panel on offer. I sent off for the panel, plus a charge controller.

I salvaged four 7ah 12v UPS batteries from work that were due to be taken away, but still showed 12v.

I attached panel to south facing wall, inside our conservatory, built a small wooden box to house the batteries & the works. I dug about in shed & found an old car battery meter plus a switch & a lighter socket. I can now charge the household mobile phones, plus the kids Nintendo's. Hopefully, soon, I will get hold of a 12v CFL bulb & use the kit at the conservatory light too.

All in, its cost less than £45 to get this all set up. Was only meant to be fun, but we all know, that only the start of it :)

J

[Islay]

Congratulations!

Have you any idea (I haven't, I'm just interested), how long it will take to harvest £45 worth of leccy from it?

[Big Al]

Congratulations!

Have you any idea (I haven't, I'm just interested), how long it will take to harvest £45 worth of leccy from it?

£45 worth of leccy will be on average taking a price of 12pence per Kwh will 375 kwh for the £45.00. So as an example I use around 9 Kwh per day in the house so this would take me just under 42 days to recoup £45.

I wouldn't be able to run the house off this set up obviously but that's an example.
I don't know the power useage of the phones and nintendo but taking a 12v CFL of say 20w if JW is only using this then the total time would be massivly longer, around 18750 hours of light to pay back the £45 BUT if he was to use 4 lights then the time would come down quicker.

However as JW says it's only the start.

I'm doing a lot of research and at the same time saving up for a couple of 300w panels and 4 12v 110Amphr batteries then I should be able to run a lot more from the start but then again that set up will be costing 20 times JW's so no comparison really... I'll go and make a cuppa...
My aim is to run the lights in the kitchen and bathroom off the solar to start with then add room by room to the circuit.

[juperwort]

The main aim for this wasn't to get any sort of payback, but a personal proof on concept. I am pleased that it seems to be working. I dont have much money for anything larger yet. I do have another bank of four 7ah batteries, which I may add to the system. Need to do the maths though as the panel needs to be able to charge them up quicker or as quick as them being run down.
The light bulb addition should be OK, and If it looks like its bright enough, then the whole kit may be moved upstairs so that I can use the light in the small toilet..........then Its rainwater harvesting time. Eco toilet!

[Big Al]

The main aim for this wasn't to get any sort of payback, but a personal proof on concept. I am pleased that it seems to be working. I dont have much money for anything larger yet. I do have another bank of four 7ah batteries, which I may add to the system. Need to do the maths though as the panel needs to be able to charge them up quicker or as quick as them being run down.
The light bulb addition should be OK, and If it looks like its bright enough, then the whole kit may be moved upstairs so that I can use the light in the small toilet..........then Its rainwater harvesting time. Eco toilet!

Regarding the re charging times. Obviously this depends on the state of discharge but I read somewhere that if you run the batteries down to 20% of their capacity they will only last about 100 charges ( estimate IIRC) where as if you only discharge them to 20% of their capacity then they will recharge thousands of times so it might be better to have larger capacity either in size or number of batteries and discharge less.

Just a bit of info that's stuck in my head somewher, hope it's useful.

[KathyLauren]

if you run the batteries down to 20% of their capacity they will only last about 100 charges ( estimate IIRC) where as if you only discharge them to 20% of their capacity then they will recharge thousands of times

Something not quite right about the percentages, methinks.

It depends on the type of battery. A regular car battery is designed for momentary use only and cannot handle a deep discharge, whereas a marine battery of the same capacity is designed to run equipment for a long time and can handle a much deeper discharge without damage. For solar applications, marine or deep-discharge batteries are preferable.

[Big Al]

if you run the batteries down to 20% of their capacity they will only last about 100 charges ( estimate IIRC) where as if you only discharge them to 20% of their capacity then they will recharge thousands of times

Something not quite right about the percentages, methinks.

It depends on the type of battery. A regular car battery is designed for momentary use only and cannot handle a deep discharge, whereas a marine battery of the same capacity is designed to run equipment for a long time and can handle a much deeper discharge without damage. For solar applications, marine or deep-discharge batteries are preferable.

I always get these things mixed up. If you discharge it deeply in that you use 80% of it's power the battery will generally only last a 100 charges etc. Where as if you discharge the battery by 20% in that leaving 80% of it's power in the battery it will recharge 1000's of times.

I was aluding to the use of leisure batteries and not car batteries. I have the test papers somewhere that backs up this info but I will need to dig them out for absolute proof.

[KathyLauren]

I always get these things mixed up. If you discharge it deeply in that you use 80% of it's power the battery will generally only last a 100 charges etc. Where as if you discharge the battery by 20% in that leaving 80% of it's power in the battery it will recharge 1000's of times.

That's what I thought you meant.

I was aluding to the use of leisure batteries and not car batteries. I have the test papers somewhere that backs up this info but I will need to dig them out for absolute proof.

No need for proof; I don't doubt you. I was merely pointing out a common gotcha when people design their own solar systems.

[Big Al]

I always get these things mixed up. If you discharge it deeply in that you use 80% of it's power the battery will generally only last a 100 charges etc. Where as if you discharge the battery by 20% in that leaving 80% of it's power in the battery it will recharge 1000's of times.

That's what I thought you meant.

I was aluding to the use of leisure batteries and not car batteries. I have the test papers somewhere that backs up this info but I will need to dig them out for absolute proof.

No need for proof; I don't doubt you. I was merely pointing out a common gotcha when people design their own solar systems.

Did that link for the LED lights in Canada work for you ?

[KathyLauren]

Did that link for the LED lights in Canada work for you ?

Yes, it did, thanks. Being able to order them is nice, but what I discovered that is even more interesting is that WalMart ( ) has them. Not that I am a big fan of WalMart, but it appears to be the first retail store that carries LEDs here. Now, all I need is for them to come in more than 40W equivalent.

[snapdragon]

.......I salvaged four 7ah 12v UPS batteries from work that were due to be taken away, but still showed 12v.....
.....Hopefully, soon, I will get hold of a 12v CFL bulb & use the kit at the conservatory light too....

Well done :) - so how do I do this? no work, no pay, no electrical knowledge, no shed with components, and nowhere to 'liberate' batteries from. (luckily no nintendos either)

[Big Al]

.......I salvaged four 7ah 12v UPS batteries from work that were due to be taken away, but still showed 12v.....
.....Hopefully, soon, I will get hold of a 12v CFL bulb & use the kit at the conservatory light too....

Well done :) - so how do I do this? no work, no pay, no electrical knowledge, no shed with components, and nowhere to 'liberate' batteries from. (luckily no nintendos either)

I like this sitehttp://www.midsummerenergy.co.uk as there is a lot of info on there that even I can understand and I'm as thick as s% two short planks. Mind you every time I post this link someone comes on and says "you can get help from the navitron board" but i don't know the linky for that one.

Edited to add the linky link here http://www.navitron.org.uk/

[juperwort]

.......I salvaged four 7ah 12v UPS batteries from work that were due to be taken away, but still showed 12v.....
.....Hopefully, soon, I will get hold of a 12v CFL bulb & use the kit at the conservatory light too....

Well done :) - so how do I do this? no work, no pay, no electrical knowledge, no shed with components, and nowhere to 'liberate' batteries from. (luckily no nintendos either)

Best get reading then. There is loads of info out there, with simple circuit diagrams. To be quite honest, once you have a panel, controller & batteries, there isn't much more to get started. You dont need to get the whole lot mounted up neatly to start.
I read somewhere that old forklift batteries are good for this application, not sure what the voltage is, but may be worth hunting out forklift maintainers local to you & have a chat. Since they have to pay for the batteries to be taken away, you may get a nice surprise.

I have finally got a 12v CFL bulb attatched. I got two from ebay from Hong Kong delivered for about £8. You get a bright white light.

[dave45]

I know those 7AH batteries and have a load myself (I started small, just like you). Be aware that they do fail, and if you strap them together permanently in parallel, you may not notice. What will happen is that a failing battery will consume energy from the others and just get warm, wasting your energy. Best to disconnect them every now and then and check their individual voltages hold for several hours. Or feel them to see if one is getting warmer than others. I'd be even more suspicious if they were being chucked out (er - why?)

At least there isn't much chance of you overcharging them with a small system :-)

And by the by (not a lot of people know this) you can reverse-charge a lead-acid battery. By mistake I connected my small solar panel the wrong way round to a large 110Ah leisure battery (these batteries are the next step!). The result was a fully-charged battery with the positive terminal becoming negative.... And I didn't notice. I blew up several things with the reversed polarity before I figured out what had happened. I subsequently charged it the correct way round, but it was never the same and it died (sucking power from its mates as described above). Expensive mistakes.

In my experience all batteries self-discharge over time, so part of the game with RE is to use the battery energy ASAP. If/when you get into battery charge controllers, you will note that you waste energy trying to charge a nearly-charged or fully-charged battery (the charge controller will throw it away). Best to use it quick. But then wet lead-acids need an occasional controlled "burn-up" or overcharge to recondition them (gas bubbles to stir up the electrolyte). Fascinating topic !

[juperwort]

The 7Ah batteries were part of a large array of about 50. When the bloke came to change them, as they have to every 2 to 3 years, I hung around and claimed the 8 that were still at 12v.
I managed to get them to below 12v at the weekend by leaving the lamp on. Now the next test will be to see how many days charging to get back to 12v. I will take your advice on checking individual voltages through.
The charge controller I have should handle the over charging issue I assume.
Still only have the four batteries running, as believe it or not, cannot find my crimp connectors !