Power usage?

[DiploStrat]

Getting Amped Up

There are lots of converters to go from watts to amps at either 12v or 220v. (The fun comes translating x watts at 220v into y amps at 12v.)

Basically:

-- You want to know your load in amps at 12v times the number of hours you want to draw it. (Why Ampere Hours [Ah]? Because that is how batteries are sold.)

-- Multiply this times the number of hours you need it without recharging. 24 hours a day? overnight, two days, a week etc. This tells you how much battery you need.

-- With those numbers in hand, figure out how you will recharge. Shore power between trips? Alternator while driving? Solar? I vote for all of the above.

 

[Scoutn79]

As mentioned in one of the first replies is to see how many amps YOUR equipment uses.
I have 2 ea 36watt LED lights on my ATV and together they only draw 1.5A so unless you are using a large area light your LED draw should be much less than 2 amps.
FWIW in my pop up camper I run and Engel 43 fridge plugged in 24/7 a water pump and interior florescent lights maybe 30 minutes a day my 40W solar panel keeps everything topped off.

Darrell

 

[pyemaster]

Thanks fellas, yeah these are the lights I'll be using http://www.amazon.com/Eyourlife-Waterproof-Driving-Lights-Spotlight/dp/B00Q81D1Q0, so I'll try and work out their draw in amps.

You've inspired me to look into a small fridge now! By the sounds of things I could with your Colorado sun!

Owen

 

[Scoutn79]

Just curious, the lights you linked to are spot not flood lights. Flood lights would give better camp lighting...If this is your intent look into lights that put light out in all directions, even floods, designed for vehicle use, only have a 60 deg beam. I do not know your exact intended use so these lights may be perfect, I am thinking more area lighting than a focused beam.
Unless you are a night owl, or camping in winter you probably won't run the lights for 6 hours a day. So your watt usage may drop considerably. My 36w LED lights "should" draw 3 amps if you do the math(36w/12V=3A) each but only draw .75A each so you really need to measure your exact equipment not just take the manufacturers specs.

Darrell

 

[pyemaster]

Very fair point on the beam angle Darrell! Might get one of these instead then I think - http://www.amazon.co.uk/Discoball®-Flood-Truck-Off-road-Light/dp/B00JOWQPMC

If the lighting can save some draw in reality, then that'll free up a little more for a fridge too...

Owen

 

[rayra]

The bluetooth speakers likely draw at 1A at 5VDC. Likewise, the iPad won't draw more than a couple amps, same voltage. A little inverter loss, your few hours of use / recharge is only a small portion of your 'house' (what you are calling leisure) battery. As long as yoru battery recharge method / cycle is sufficient to cover that usage, you could go effectively indefinitely. (yeah yeah, 12v battery life, fuel, etc etc take it as given, pedants)

 

[pyemaster]

Okay fellas, so this is what I'll be aiming for:

Power calculations...


Smartphone

2600mAh battery, 5v charge = 13wh

Tablet

4450mAh, 5v charge = 22wh

Bluetooth speaker

2200mAh, 3.6v charge = 8wh

LED light

18w (for four hours of use) = 72wh

So...

Scenario a) Total charging phone / light / speaker = 93wh

Scenario b) Total charging tablet / light / speaker = 102wh

Scenario c) Total charging phone / tablet / light / speaker = 115wh

Considering I'll probably be using the solar panel for camping mainly in three seasons (March - October) and mainly in West Wales, the irradiance figures for Swansea (for a 100w solar panel operating at 75% efficiency to account for losses in the system and capture process) are:

February - 100kWh/Sq m
March - 166
April - 264
May - 342
June - 356
July - 353
August - 298
September - 203
October - 116

With these as an average then, a 100w panel should be able to provide enough power for all my items in 8 of 9 months, and enough for lighting, speaker and phone or tablet for February.

November, December and January provide 67, 44 and 54kWh/Sq m respectively, which is still enough for a couple of hours of lighting and a fully charged phone.

The above is also calculated for 'worst case', i.e. in powering each item to full charge each day. Realistically the only thing needing daily charge would be the light, the other items could be charged every other day, as they are each supposed to last at least 10 hours once charged.

I've also measured the roof space behind my roofrack, which is 100cm x 80cm. A 100W panel fits perfectly in this space, and I'll fit it on a hinge and catch to angle it perpendicularly to the sun ray angle when in camp.

So, this is my plan, with an MPPT controller. Thanks so much to everyone in this thread for their help and advice. Very much appreciated.

Owen

 

[DiploStrat]

"Free" Power

Sunlight in Wales? You jest!

But seriously, do spend some time to be sure that you harvest all you can from the vehicle's alternator - then adjust your usage to charge while you are driving, not while you are camped. Likewise, charge your phones, etc. during the day when you have sunlight. Break the old habit of putting stuff on charge before you go to bed.