solar

Submitted: Sunday, Mar 10, 2019 at 17:37
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trying to work out what size solar blanket I need I will be useing a 40 litre engel and at night I have camp lights that are 18 watt each and I have 6 of them a bit confused in working out wattage to amps any help would be great
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Reply By: nickb - Sunday, Mar 10, 2019 at 18:32

Sunday, Mar 10, 2019 at 18:32
NOTE: in the interest of keeping the peace, this is an assumed estimate. Actual usage, location, temperature etc etc variations have not been accounted for. It works for me, may or may not work for you. I may have confused A with Ahr, deal with it. Disclaimer done!!!!

As a ballpark your 6 lights will use approx. 9A in an hour. If they are on for 4 hrs that is 36Ahr. Fridge will use approx 30ahr in 24hrs. So a total of ~65Ahr used every day. So you need to to replenish that each day. Approx 6hrs of sunlight a day so 11A every hour. If you chase the sun and try and get every bit of available sunlight you will get away with 200W solar. If it is overcast and you are a set-and-forget person with your solar panels I would go for maybe 300W.

I have 240W of panels mounted flat on the roof on my camper, it supplies my 57L Engel, lights, water pump and various chargers, everything runs off a 120Ahr battery. In full sun I’m fully charged by 9-10am, overcast weather usually early afternoon reaches full charge.
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Follow Up By: Members - Bow & Nan - Monday, Mar 11, 2019 at 08:29

Monday, Mar 11, 2019 at 08:29
Solar blankets are not as efficient as glass panels. If using a solar blanket instead of glass panels a bigger rated panel will be needed.
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Follow Up By: Member - McLaren3030 - Monday, Mar 11, 2019 at 12:43

Monday, Mar 11, 2019 at 12:43
Hi Bow & Nan, I was of the opinion that Solar Blankets were more efficient than Solar Panels. This is one of the advantages of Solar Blankets over Panels.

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Reply By: RMD - Sunday, Mar 10, 2019 at 18:44

Sunday, Mar 10, 2019 at 18:44
G’day John.
If you divide watts, ie, 18 w by 12v , you get 1.5 amps. That is of course nominal numbers as both the voltage and wattage may be slightly different.
If true 18w and system voltage is 12.5, then amps will be a little less.
6 x 1.5amps is therefore 9 amps.
If your lamps are 18 w rating but the lamps are LEDs then the game changes considerably and current draw will be far less. Best to test one with multimeter in the circuit to find what is real.

The blanket size will depend on the total fridge usage for 24hrs and have ability to replace that amp hour use along with the lights use.
All this of course relies on full sun, so any calculations determined as ok will have to be doubled to ensure reasonable charge each day to prevent the battery slowly discharging.
A bit of overkill, sort of.
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Follow Up By: Member - lyndon NT - Sunday, Mar 10, 2019 at 22:02

Sunday, Mar 10, 2019 at 22:02
Hi RMD

"If your lamps are 18 w rating but the lamps are LEDs then the game changes considerably and current draw will be far less"

How so, watts is the rate of power use?

Regards

Lyndon
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Decide now what you will,
Place faith not in tomorrow
For the clock may then be still

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Follow Up By: john m85 - Monday, Mar 11, 2019 at 13:40

Monday, Mar 11, 2019 at 13:40
thanksRMD my lamps are LEDs it is very helpful with your calculations.
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Follow Up By: Member - peter_mcc - Monday, Mar 11, 2019 at 15:45

Monday, Mar 11, 2019 at 15:45
Lyndon - there are "normal watts" and then there are "LED watts". LED Watts are a special unit of measurement aimed at selling lights and bamboozling people. Take a look at LED driving lights & light bars - their claimed "wattage" is often a lot larger than you would expect from the rated voltage x current (ie normal watts). In other words LED watts are often complete rubbish.

It would best to measure how many amps they are using - that's what you need to know for battery life.
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Reply By: Baz - The Landy - Sunday, Mar 10, 2019 at 19:07

Sunday, Mar 10, 2019 at 19:07
I can’t help with the numbers, but similar to Nick’s response in this thread, I run a 60 litre Engel at 0 to +2 degrees and on 24/07 in the back of the canopy, charge anything that needs charging and run lights at night, as well as powering the HF Radio.

To recharge the 160 Amp battery I have 2x120 Watt panels on the roof of the canopy, which is not the most efficient positioning given they lie flat...

For me, this is completely set and forget, I never give it much of a thought.

I guess my point is, when you work out requirements, add some additional capacity so you don’t need to concern yourself with charging needs.

Cheers, Baz - The Landy
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Reply By: Gazza70 - Sunday, Mar 10, 2019 at 20:31

Sunday, Mar 10, 2019 at 20:31
Hi John,

What is your battery capacity?
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Follow Up By: john m85 - Monday, Mar 11, 2019 at 13:43

Monday, Mar 11, 2019 at 13:43
hi Gazza my battery is 105 ah
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Reply By: swampy - Sunday, Mar 10, 2019 at 21:21

Sunday, Mar 10, 2019 at 21:21
Hi
Consumption
Fridge 20--40 ah upto 50ah if used as freezer in hot weather .
Allow 40Ah
lights
18w x qty=6 =108watts divide by volts 12.oov = amperage consumption per hr
9amp/hr x 4 hrs =
36Ah
Solar production
160watt approx 38 Ah production in 24hrs
200watt approx. 48Ah "" ""
300watt approx. 72ah "" ""
Solar panels never produced claimed output over the whole day ,why
panel fixed position
wires under size
controller type Pwm // Mppt and other specification s
**Not included is MPPT production
**Sun light outside of peak sun hrs ==PSH. Its unreliable
***Calculated on 5.5hrs average mainland ozzy summer spring autumn

250watts plus should do it with mppt controller . Minimum
Battery =150-160ah minimum [usable capacity 50%=80Ah]
AnswerID: 624357

Reply By: Member - lyndon NT - Sunday, Mar 10, 2019 at 22:13

Sunday, Mar 10, 2019 at 22:13
Hi John

It will depend on model of fridge, yep, model. There have been several different versions of the Engels over the years. Each more efficient as the years rolled by.
For my 13 year old 40 ltr, in the tropic's. It's 2.5 a/h 24/7
Beers going in are at 33 + degrees, same for water.
As someone else said. 40 a/h a day would be a fair estimate.
If your camping down south in winter and it's sunny then 1 large solar panel may cut it.

I purchased a 150w Kickass panel a few years back. I'm wondering why I did.
It's big and HEAVY. It doesn't have a hope in hell of supplying our camp power needs of around,mmm, say 150 a/h per day and then maybe some.
I'd need to take at least 5 of the suckers, an extra trailer and spend half the day moving them around.
I'm all for solar, but unless I want to spend a fortune on blankets it's not cutting it yet for us.

Cheers

Lyndon
Now is the only time you own
Decide now what you will,
Place faith not in tomorrow
For the clock may then be still

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Reply By: bellony - Sunday, Mar 10, 2019 at 23:55

Sunday, Mar 10, 2019 at 23:55
John
Consumption figures have been done numerous times for you, but I would be rethinking your lights as the current system is using way too much power for off grid camping.
A 1m LED strip will use about 1Ah and provide plenty of light for an outdoor awning. Then a couple of short 25-50 cm strips for above the stove or in the tent/trailer so say another 1Ah. That's 8A for a 4 hr night, and about 3 or 4 hours less work for the solar panels the next day.
That's how our camp runs anyway.
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Follow Up By: Member - lyndon NT - Monday, Mar 11, 2019 at 08:01

Monday, Mar 11, 2019 at 08:01
Hi John

Bellony is correct. Go for lower wattage lights. How old is the Engel?
Now is the only time you own
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Follow Up By: john m85 - Monday, Mar 11, 2019 at 13:51

Monday, Mar 11, 2019 at 13:51
hi Bellony you are right about the lights they have small 6 leds in each light and are 3 watt each I am going to rethink my light set up.
cheers.
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Follow Up By: Allan B (Sunshine Coast) - Monday, Mar 11, 2019 at 14:09

Monday, Mar 11, 2019 at 14:09
.
John, do you really have six LED lamps, each of 18 watts?

That's a lot of lumens!
If you use them all at once you would be "visible from space".

If you only use one or two at a time then the calculations done above are excessive. How do you run the tights?
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Allan

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Follow Up By: john m85 - Monday, Mar 11, 2019 at 15:27

Monday, Mar 11, 2019 at 15:27
Allan I have a roof rack on my hj60 and 2 lamps on each side also 2 at the back they are rectangle about 5 inches long about 1 inch high and has 6 small leds in each one at 3 watt each all run off the spair battery
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Follow Up By: Allan B (Sunshine Coast) - Monday, Mar 11, 2019 at 19:49

Monday, Mar 11, 2019 at 19:49
.
But John, you don't have them all turned on for 4 hours each night, do you?
Cheers
Allan

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Follow Up By: john m85 - Tuesday, Mar 12, 2019 at 17:45

Tuesday, Mar 12, 2019 at 17:45
Allan they might only be on for a hour
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Reply By: Bob Y. - Qld - Monday, Mar 11, 2019 at 18:48

Monday, Mar 11, 2019 at 18:48
John,

I’ve found these LEDs from Jaycar to be excellent for camping, with good light output. They have a rocker switch fitted as well as a plug-in power lead that you connect power too.



There is also a shorter version, about 300mm long, that’s good for narrow rear doors.

Bob

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Can't remember most of it.

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Follow Up By: john m85 - Monday, Mar 11, 2019 at 18:57

Monday, Mar 11, 2019 at 18:57
thanksBob I will drop in and have a look next week still can/t make my mind up of what type of solar blanket will be looking at around the 150 watt
cheers
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Follow Up By: nickb - Monday, Mar 11, 2019 at 20:20

Monday, Mar 11, 2019 at 20:20
If you can reduce your lighting power consumption substantially the 150W will probably suit your needs, provided the sun treats you nicely!!!
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Follow Up By: john m85 - Tuesday, Mar 12, 2019 at 17:48

Tuesday, Mar 12, 2019 at 17:48
Thanks Nick I have been thinking about the 150
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