How much does this need from batteries?

[DeanS]

Hi all.

 

100 LED lamps.

3Watts each.

240V

 

I work that out needing approx 1-2Amps ...to supply them all...

 

but how much current is drawn from the 12V batteries.

Will it be...

 

300Watts divided by 12V = roughly..25Amps........and over 12 hours....300Amps....

 

 

So would you really need to have 6 batteries recharged daily with a 30Amp charger...charging for 10hours each night.....to cope.

 

 

 

Is this right, or have I made some terrible error?

 

 

 

[MtB]

Hi all.

 

100 LED lamps.

3Watts each.

240V

 

I work that out needing approx 1-2Amps ...to supply them all...

 

but how much current is drawn from the 12V batteries.

Will it be...

 

300Watts divided by 12V = roughly..25Amps........

 

 

Yes, but you say tey are 240v lamps so you'll need to add on a bit for inverter inefficiency. Not much though, probably draw 27 or 28 Amps.

300Watts divided by 12V = roughly..25Amps........and over 12 hours....300Amps....

 

 

Here you've gone a bit wrong. An Amp is the speed at which electricity is used. So over 12 hours, the current is still 25 Amps (plus an allowance for inverter losses).

[MtB]

But to take into account the time over which the current is being drawn, multiply by time. Time is measured in hours so you get AmpHours as the unit of energy sucked out of the batteries aver your chosen period of time.

 

25 Amps x 12 hours = 300 AmpHours.

 

Or to give another example 25 Amps drawn for 24 hours would use 25A x 24hr = 600Amphours.

[Sir Nibble]

Your figures do seem to assume these lights burning 12h a day. Is that really the intention?

Edited May 26, 2016 by Sir Nibble

[MtB]

Your figures do seem to assume these lights burning 12h a day. Is that really the intention?

 

 

I was imagining it would be 12 hours at night!

So would you really need to have 6 batteries recharged daily with a 30Amp charger...charging for 10hours each night.....to cope.

 

 

Is this right, or have I made some terrible error?

 

 

 

This is broadly right, but it would take longer than 10 hours with a 30A charger, as a 30A charger only starts off at 30A, then drops off after a while. I'd suggest a 60A charger to replace 300Ahrs in just ten hours.

[Boat&Bikes]

That seems a lot of light output! Are you warning other boats away from rocks? Our boat has 30 leds at 2 or 3 watts each.. Not often that they are all on as in different rooms.

[KenK]

Also why 240V LED's, 12 v versions don't need the more complex electronics of the 240 V versions.

Your going from 12V DC to 240V AC and then converting inside the LED bulb back to 12 V DC to run the LED.

 

Ken

[by'eck]

Hi all.

 

100 LED lamps.

3Watts each.

240V

 

I work that out needing approx 1-2Amps ...to supply them all...

 

but how much current is drawn from the 12V batteries.

Will it be...

 

300Watts divided by 12V = roughly..25Amps........and over 12 hours....300Amps....

 

 

So would you really need to have 6 batteries recharged daily with a 30Amp charger...charging for 10hours each night.....to cope.

 

 

 

Is this right, or have I made some terrible error?

 

 

 

 

Since they will be inverter driven, allow say an extra 15% = 345 watts.

 

345/12 = 29 amps drawn from batteries whilst they are all on = 348 amp hours over 12 hour period.

 

Conclusion is that from a practical point of view you will need a larger battery bank say circa 800 amp hour to offset inevitable loss of capacity and so provide adequate reserve, plus certainly a larger charger say 100 amp. Remember that a 30 amp charger will not put 300 amp hours into batteries over a 10 hour period. It will take at least 10-20% longer and maybe more dependant on battery discharge and sulphation state.

 

You could of course consider managing with less than a 100 lamps

[Cheshire cat]

100 3 watt leds is nearly enough for Blackpool tower. I wonder what Dean is planning

[Dalslandia]

Solarium? 300 watt le(a)ds to tan skins, or if they are red led it might be massage ...

[cuthound]

100 3 watt leds is nearly enough for Blackpool tower. I wonder what Dean is planning

My house is now pretty much exc,usively lit by LED's and with them all on theye amount to around 200 watts!

[ditchcrawler]

Hydroponics run under lots of LEDs these days.

[Delta9]

Is this for a grow room?

 

ETA: ditchcrawler beat me to it

Edited May 26, 2016 by Delta9

[Arthur Brown]

The only likely error is considering 300w of LED light! That would be incredibly bright, By current thinking 30w of LED should be good for a reasonably long boat.

 

Say 6 x 3w lamps on the living space and something in the bathroom and engine room for occasional use and perhaps a table lamp.

 

I'm thinking that 70 ft by 6 ft would house 400 plants. It's been done in an ISO refer container before, one of the 40 footers on the road wasn't hauling freight!

[Horace42]

3 watts sounds like an awful lot of watts for an LED. They run for hours on a torch battery.

Double check your figures first.

Maybe multi-cluster ones - but a 100 of them?

 

Something odd here.

Mind you, if you are right, and it is 3 watts each, then most of watt's (yuk!) been said is correct.

 

[cuthound]

As a rough rule of thumb, LED's Co some 10% of the power of incandescent or halogen bulbs, so 100 x 3 watt lights = 300 watts, the equivalent of 3000 watts of conventional lighting!

 

If he goes through a tunnel and turns on the interior lights, it will light up the tunnel, not only for him but for everyone else in it!

[DeanS]

Thanks all...

 

The 100 bulbs are for a land building.

The guy has free elec at night, and wants to capture it by charging batteries, and then during the day, use the stored power to keep indoor lights on for 12hours...

[cuthound]

Thanks all...

 

The 100 bulbs are for a land building.

The guy has free elec at night, and wants to capture it by charging batteries, and then during the day, use the stored power to keep indoor lights on for 12hours...

Doesn't he have any windows?

[Richard10002]

It might be cheaper/more efficient, to pay for the electricity from the grid than to buy, charge, and maintain the batteries needed to run this exercise?

[Arthur Brown]

How many boaters get two years use from an installed house battery? the battery capital cost per cycle will be the dominant factor in evaluating the project. IMO with lead technology the batteries will probably cost more than the electricity saved. Using Lithium technology probably will be better but the charger will cost more!

[MtB]

Thanks all...

 

The 100 bulbs are for a land building.

The guy has free elec at night, and wants to capture it by charging batteries, and then during the day, use the stored power to keep indoor lights on for 12hours...

 

 

So it IS a hydroponics project!

 

And it is your 'friend' eh?

[ditchcrawler]

I have just realised I have a 3 Watt 230 volt LED fitting on the corner of my garage to light the pathway. 100 of them and I could have a football match on the lawn.

[Arthur Brown]

 

The guy has free elec at night, and

 

free elec when the streetlights come on??? That's so old hat for a full house grow!

 

 

Dean a sensible answer to this question will give the property user the answer they don't want, drop it before it gives you a bad reputation. Even if the storage of night electricity for day use happens on day one, then battery life and charge rate issues will afflict the profitability of the scheme.

[Steilsteven]

Cheapest option then would be night work