Hello, 1st post guidance needed

[Mike90250]

xxxxx xxxxxx xxxxx xxxxxx xxxxx A 12 volt 50 AH battery is a lot less expensive and takes up a lot less volume and weight.xxxxxx xxxxx xxxxxx

Sunking is is generally right 99.4% of the time. if we could call him on stuff, we would. But, he's a man that tells it like it is, and does not molly coddle about it. This thing called the internet, the vegans want the carnivores banned, the fruitarians want the breathairans censored, and pastafarians want more noodles. So it leaves the moderators few choices, which we still dither about with.

[t5800512]

Just ignore Sunking. There is no place for that kind of talk on this forum. Sunking is knowledgeable and could help you if he wanted. But he would rather talk ****. I for one am getting pretty darn tired of it.

[Griffter]

Trying to get smart which is why Im asking for advice from this forum.
Electric isnt my strong point so please don't beat me up over something I've only just started learning about.

Ok so I can get something like a varta 12v50Ahr for about £65. Don't know if that's a good price but its smaller in size than I thought. Any other recommends?

Assuming I went with this size it would last me the planned week.
If I went for 2 weeks what's the best options for keeping it charged whilst away?
Car / Solar / Mains

Also I'm guessing this will need to live in a battery box, are these ok inside tent or should it be kept outside?

[Sunking]

I realise I can go bigger with batteries but this adds weight and cost both to buy and recharge which is why I was thinking solar.

[...] A 12 volt 50 AH battery is a lot less expensive and takes up a lot less volume and weight. Get smart.

[Griffter]

27led per strip giving a total of 155 lumens each strip.
I have 4 strips but don't think I need all of them connected.

I realise I can go bigger with batteries but this adds weight and cost both to buy and recharge which is why I was thinking solar.
May be cheaper to look at electric hook ups to 240v or disposable battery lights?

[Sunking]

I agree no solar needed. Just get you are 12 volt 50 AH battery and charge it at home with a 5 amp battery charger.

[thastinger]

You don't need a solar panel, just spend that money on an extra battery or two and take those with you when you go. Charge them back up when you get home.

I replaced all the 12V car style bulbs in my RV with these http://www.ebay.com/itm/10x-20-SMD-W...item19e011502c

they are working great but you haven't said how many lumens you are looking for from the lights.

[Griffter]

Sorry Mike90250 I wasn't clear.

100% down would give 20hrs but I know this kills the battery
50% down would give 10hrs
40% down would give 8hrs
30% down would give 6hrs
20% down would give 4hrs


So working this the other way and assuming I will only ever take the batter to 30% down, and that I needed a battery to last 4hrs x 7 days
I would need to be able to run it for a total of 28hrs
Assuming this represents a 30% discharge I would need an additional 65hrs of head room to full discharge giving a total of 93 hrs total capacity
Call it 100hrs total capacity to dead for round numbers and a little more headroom (but I would only use 28 of them).

Required battery size =
100hrs required x 4.2w = 420w
420w / 12v = 35Ah

Does this seem right?

[Mike90250]

Ok I have a decent multi meter but its a long time since I used it.
I know the basic formula is W= VxA

Battery is rated at 12v 7Ah so that gives me 84watt hours
Battery is 12v lets say meter reading I get is 0.35A that would give me (12v x 0.35A) 4.2w

84W/h divided by 4.2w = 20hrs but this would take it to dead - not good so assume 40% of this which would give me 8hrs.


Does this sound correct?

Almost. Discharge to 40% of full (60% down) is pretty severe, and the battery life will be pretty short. Cycle / Depth chart attached Generally, 20 - 30 % discharge is the daily target.BatteryServiceLife.jpg

[Griffter]

you have to look up, or measure, the power (watts or amps) used by the light strip, before you can calculate how long a battery will last.

Ok I have a decent multi meter but its a long time since I used it.
I know the basic formula is W= VxA

Battery is rated at 12v 7Ah so that gives me 84watt hours
Battery is 12v lets say meter reading I get is 0.35A that would give me (12v x 0.35A) 4.2w

84W/h divided by 4.2w = 20hrs but this would take it to dead - not good so assume 40% of this which would give me 8hrs.


Does this sound correct?

[Mike90250]

you have to look up, or measure, the power (watts or amps) used by the light strip, before you can calculate how long a battery will last.

[Griffter]

Hi,
I'm looking to use led lighting for camping.
Ring and others sell led strip lights but they are not cheap (£30 each) and I've discovered today that Ikea sell the same lights for a fraction of the price (£20 for 4)
They come with a 240v to 12v step down transformer which states 0.42A , 0,5 - 5w
Removing the transformer and running off a 12v battery seems to work.
The battery I have is rated at 12v 7Ah

What I can't figure out is:
a) how long the battery would last for if the lights where left on continuous
b) what size/output solar panel I would need to charge the battery back up

Assumption is that camping trips would be at most 7 nights with the lights on say 4hrs per night

Any thoughts?

Thanks