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Dave1013

Solar maintained battery power supply

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Hi all.

I am experimenting with low power timed led lighting sets at around £4 each from eBay. These use the micro leds and a small battery control box. When activated they stay on for 6 hrs and off for 18.  They give a bright light for their size, but batteries only last a few weeks. 

I thought about solar power, prompted by the outbreak of summer. I had a 12v 1.7Ah lead acid battery so I needed a solar battery charger and a charge regulator. 

My first solar panel was a 1.5watt panel from Maplins. This didn't keep up with the load of three light sets coming on for 6hrs. I got two 3watt panels and wired them all in parallel giving a possible output of 7.5watts.

So far this has kept up with demand even under overcast conditions.

Has anyone played with this type of thing? I am not sure if I'm using the correct components. 

Any thoughts guys

Dave

 

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i've considered this as a supply for a battery supported power unit for my garden railway... but i've not done anything about that yet.

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l have used a battery, inverter, solar panel set up for the past two years without a problem.

I am an idiot at electrics so this is a simple setup.

A car battery will work but l opted for a leisure/caravan type battery. I do not run my controllers directly off the battery. The battery is connected to a 300 watt inverter that gives me a 240 volt power supply and that then powers controllers etc. The battery is trickle charged by a cheap solar panel. The panel is in the shed window and does get direct sunshine for a couple of hours a day. I have never had to charge the battery as yet.

I should point out that l do not use lighting in the shed (yet) but l think it would power them ok. I have used a mains electic saw in short bursts and although a bit slow worked ok but would'nt trust in the long term.

Whole set up in UK cost about £100 when new much cheaper than getting the shed wired to the mains.

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Hi guys

Well this is encouraging. Jimbob I think I will follow your lead and invest in a bigger battery. All my electrics are 12volts or 5volts and dcc track power comes from inside the house, so I don't need an inverter. I do fancy one though. 

I will tidy up my (embarrassing) wiring and post some photos.

Dave.

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I used an inverter to give me 240 volts in a catering trailer that I had. No good for fridges or anything that heated. The leisure battery is the one to have because it will take long low dischsrges, where a car battery is designed more to give a powerful discharge to fire the starter motor. I'm sure that Q will be along to give us the technical whys and wherefores surrounding batteries.

 

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I'm no expert on the construction of batteries themselves, however from what I know leisure batteries use thicker heavier plates that are of a more active compound.  Starters use more surface area to give that higher short period current. Generally I'd agree with Roddy's assessment of the two main types of batteries as to their use.

Going via an inverter to control a model railway is an electrically expensive way of doing it as there are losses, converting 12v to 230v and back down again.

However using a Car battery doesn't give you 100% of a mains supplied system

first they are charged at up to 15.6 volts, although a floating voltage of about 13.5 V for long term charging is required.

Although called 12V power supplies, oo gauge controllers actually put out up to 16v, so if you want to run flat out you'll find your top speed limited unless you use more electronics to up the battery voltage.

I could quite easily see a battery supplied, solar charged, model railway system, working quite well. Say allowing for losses you need 3 Amps 12v supplied to the controller an extreme 10 hour running session ( single loco) would use 30Amp hours 

A 150 amp hour leisure battery has about 120AH available to use so you'd only use 25% of its capacity.

How often you could do that would depend on your charging capacity, the more full discharges of any type of battery the shorter its life.

Jimbob, Putting a jig saw on a 300w inverter is pushing it somewhat, most jigsaws are 500W or more you could easily blow your inverter.

Personally I always would over rate inverters by at least 50%. For the boat below I will eventually get a 5kW continuously rated inverter to run a 3kW kettle!!!

I have about 600w of nominally 12v solar panels, charging 24, 2v batteries of 500AH. This will power my 27ft motor boat for about 4 to 5 hours on the Norfolk Broads. However If I'm going that far I'll wind up the 4kW generator, batteries are expensive so I don't want too many cycles taken out of them. Short trips the solar panels can look after..

 

 

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Well roddy you were dead right about Q's fascinating comments. 

About 40 + years ago I was an apprentice auto electrical engineer and learnt about lead acid battery construction. Absolutely right about surface area for short term, high amp demand, about 200+ amps for a starter. Just shows how technology has moved on there were no leisure batteries or sealed gel batteries then. I didn't realize the different makeup of leisure batteries, makes sense though.

As I am only running some LED lighting and some signals I was thinking that a modest sized deep cycle battery of around 15 to 20 amp hrs would suffice.  I had best measure the current drain and work it out properly though.

Dave

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Right I've measured the consumption of my three sets of timed led lights. They draw 2.5 watt hours for 6 hours, which amounts to 15 Wh per day. Allowing for a 50% over calculation, the on line solar calculator I used suggests a 4  to 5 Ah battery and 5 watts of solar power. So I'm close, just need to upgrade the battery. Looks like I have enough power to run my led signals as well.

Cheers

Dave

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I have ordered a 12 Amp hour battery. Meanwhile here are some pictures of my little solar system.

The white connector box is for 5v out for the three lighting sets.

 

DSC_0019.JPG

DSC_0017.JPG

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