Free Camping

Submitted: Saturday, Sep 29, 2012 at 18:01
ThreadID: 98312 Views:2449 Replies:7 FollowUps:2
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A question regarding power usage when free camping,i have a van with 4x105 deep cycle batteries plus 5x85 watt solar panels on the roof,i will be running a 12 volt fridge and freezer a 12volt tv and led lights,im looking for a ball park answer regarding roughly how long before i would have to run the generator to recharge the batteries
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Reply By: Kris and Kev - Saturday, Sep 29, 2012 at 18:25

Saturday, Sep 29, 2012 at 18:25
This link may assist you.Solar spreedsheet
AnswerID: 495887

Reply By: Notso - Saturday, Sep 29, 2012 at 18:37

Saturday, Sep 29, 2012 at 18:37
Probably about as long as the solar panels last or the batteries die I'd say. Seriously, providing your batteries are getting fully charged whilst driving, I'd say you'd never have to run the Genny unless you get a week of fully overcast days.
AnswerID: 495890

Follow Up By: Ross M - Saturday, Sep 29, 2012 at 19:18

Saturday, Sep 29, 2012 at 19:18
I agree with Not so, If each of the panels only work at 4amp output and run for 6hrs a day this gives around 120ah per day.
If the fridge runs for 18hrs a day, unlikely that much, and the tv and lights will only be used at night time, then the 5 panels output should replace the amount used each day and any extra output will definitely keep the batteries topped up under most conditions. 4x 105ah batteries are a good sized backup.
The only down side is if the conditions require the batteries to be charged then it will take a while unless you have a highamp output 240v charger. Suggest 40amp output to make good use of the generator if it has to be run. A small charger will require the generator to run for a very long time. Don't try to use the 12v charge output of the generator as these are small amps out and the gen again will run forever.

Ross M
FollowupID: 771508

Reply By: member - mazcan - Saturday, Sep 29, 2012 at 19:07

Saturday, Sep 29, 2012 at 19:07
hi humpback
if its sunny every day all day when free camping with 4x deep cycle batts and 5x85w solar panels you shouldnt have a problem providing they are fully charged before you start the camping stint
but if its overcast or very cloudy it will be trial by use and you will be the first to know the answer to the question it really is a crystal ball question
AnswerID: 495895

Reply By: Member - Bruce C (NSW) - Sunday, Sep 30, 2012 at 09:14

Sunday, Sep 30, 2012 at 09:14
Hi Baker,
Without acurate figures on the consumption of each of your devices I have made a small back of the envelope calculation and from what I can see your solar generation in good conditions could be around 1840 watts per day if needed.

Your power requirements, guessing your equipement consumption, is around 1030 watts.

In my rough calcs you have a fair bit of reserve which will carry you through most cloudy periods unless they are extended cloudy periods. If you have mono panels and an MPPT regulator you will still get some power generation even on a cloudy day.
Your biggest asset is 4 batteries which will balance out cloudy weather somewhat..

I have assumed a panel efficiency of 80% and frig consumption of 5 amps for 12 hours but as the frig cycles it will cover the night consumption as well in those figures I think.

TV I have calculated at 3.5 amps for 5 hours and LED lighting at 2 amps for 4 hours, likely to be way over the top for LED lighting requirements for any evening as you usually have minimal lights on unless needed.

Mind you, others are better versed in solar calcs than me but from what I can see you may very likely never need the genny, from these figures.

Cheers, Bruce.

At home and at ease on a track that I know not and
restless and lost on a track that I know. HL.

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Follow Up By: humpback - Sunday, Sep 30, 2012 at 16:17

Sunday, Sep 30, 2012 at 16:17
Thankyou every body who took the time to respond with very valuable feedback much appreciated, see you on the road.
FollowupID: 771551

Reply By: Witi Repartee - Sunday, Sep 30, 2012 at 11:39

Sunday, Sep 30, 2012 at 11:39
That's a huge amount of capacity and weight to drag around. Doesn't it limit where you can get too?
AnswerID: 495932

Reply By: Crackles - Sunday, Sep 30, 2012 at 13:53

Sunday, Sep 30, 2012 at 13:53
Too many variables Baker for anyone to say for sure.
They being.....
* Do you have a separate fridge & freezer or are they combined in one unit?
* What type, size, how often opened, is it well ventilated/insulated, how hot is it?
* What sort of lighting, how many, how long?
* Size of TV, 12 volt or plugged into an inverter, how long used?
* Position of solar panels, mounted flat, cleaned often, parked in the shade?
* Time of year, temperature & location will depend on how much sun the panel receives & their output.
* Will you shift the panels to face the sun or are they mounted permanently?

From similar sized fixed systems I've seen on vans, most have had enough capacity to be self sufficient for all but the worst conditions (very hot with no sun). The simple answer for you is to go out & use it monitoring both input & power consumption with a solar charger/controller. If power use on an overcast day doesn't keep up with that being used then it's a simple matter of recording by how much & subtracting that from the 300ah (You don't want to completely flatten the batteries) to work out when or if a genny would be required.

Cheers Craig................

AnswerID: 495937

Reply By: Cravenhaven - Monday, Oct 01, 2012 at 11:00

Monday, Oct 01, 2012 at 11:00
There are 2 possible problems to resolve here.
Most caravans use 3 way fridges and on 12 volts they use an enormous amount of current. Is yours one of these or is it a 12v only fridge (engel, waeco ...).
Other problem is that most people park in the shade to assist with keeping cool. Unfortunately solar panels dont work well in the shade so you may not get as much output from them as has been guestimated. The other part of this problem is that the panels are fixed on the roof facing straight up, yet the sun moves across the sky from North east to North west so you are unlikely (in fact wont) get full output from them for any significant time.

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