Solar Panels -- questions for the experts --

Submitted: Monday, Jun 16, 2008 at 08:16
ThreadID: 58836 Views:6764 Replies:10 FollowUps:4
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Greetings guys --- I am just gearing up for this summer and times when i am away for a week at a time

i currently have a Primus 80 watt solar pannel ( 2 x 40 w in a neat frame with regulator/ folds out) i now know this is not enough for what i need but was desperate for anything when i went away last year

My current configuration is as follows

In my car - 1 truck battery for start - second battery - deep cycle 100 AH - Isolated via Redark isolator

In the Jayco - 2 x Deep cycle batteries 100 AH each 1 used at a time the other not connected until needed

I use a Waco 80 litre fridge in the car on the secondary battery - and in summer time the thing virtually runs 18 hours a day - especially when on the beach ( misses loves the novelty of ice cream at any time whilst camping on the beach )

The lighting is just 12 v standard globes(in the Jayco) only usually run 1 light at a time inside and maybe the outside light when the kids are asleep and we sit outside - occasionally play the dvd player for the kids near bed time ( 12 v portable from car )

So in the past what i have been doing is to hook up the solar panel during the day to the second battery on the car to help trickle charge it - but when the error light would turn on ( the fridge ) i would then just swap batteries around from van to car- and by the end of the week - i have 1/2 flat batteries x 3 and a fridge that goes into low power use mode and will not cool past about -10 ( Its not actually -10 if your measure - just there scale- barely enough to keep meat frozen )

NOW - i am thinking of buying 2 additional 80 w solar panels ( 160watt in total ) with a 20 AMP regulator would i be able to use my other smaller 80 watt panel ( 2 x 40 watt ) with the smaller regulator all in line on the same battery --- Or should i just use the new 80 watt x 2 ( with 20amp regulators) on one battery and use the smaller panel on a separate battery , or even just sell the smaller 80 watt panel ?

and would the 2 x 80 watt panels with 20 amp regulator be enough to recharge the batteries during the day whilst charging the 80 Litre waco fridge --- Or should i go maybe 3x ?

Boc


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Reply By: Ozboc - Monday, Jun 16, 2008 at 08:19

Monday, Jun 16, 2008 at 08:19
Last line "and would the 2 x 80 watt panels with 20 amp regulator be enough to recharge the batteries during the day whilst charging the 80 Litre waco fridge --- Or should i go maybe 3x ?" above should read


"whilst charging battery/ Running the 80 Litre waco fridge --- "
AnswerID: 310261

Reply By: Simmo67 - Monday, Jun 16, 2008 at 08:40

Monday, Jun 16, 2008 at 08:40
I'm watching this thread with interest.

I know little about auto electrics and want to get some solar panels to keep my Waeco Coolpower unit trickle charged when I'm out for days at a time.
Would also like to get a proper dual battery set up one day of course.


AnswerID: 310270

Reply By: MEMBER - Darian (SA) - Monday, Jun 16, 2008 at 08:57

Monday, Jun 16, 2008 at 08:57
To add to any expert advice you might pick up here, consider getting the book "Solar that really works" by Collyn Rivers isbn 0957896557- your library may have it too (mine got it in from the State Lib for perusal - I then bought one direct from the author). From my techno-klutz point of view, it seems to cover everything in fine detail - its all about mobile solar !
AnswerID: 310275

Reply By: Simmo67 - Monday, Jun 16, 2008 at 09:09

Monday, Jun 16, 2008 at 09:09
Tx Darian,
I'll drop into the library later today....
AnswerID: 310278

Reply By: Best Off Road - Monday, Jun 16, 2008 at 11:54

Monday, Jun 16, 2008 at 11:54
Boc,

I'm no expert but can offer some practical experience.

I do have a CF 80 and did have a Jayco Van.

I use solar to run my 80.

My suggestion to you is use the new 2 x 80 panels just to run the fridge. They are a big fridge and when running as a fridge and freezer in hot weather they use a lot of power.

Do you have a bag for the fridge? They save considerable power.

The 80 watt folder should be more than enough to keep the van charged.

Jim.

AnswerID: 310305

Follow Up By: Member - Tony B (QLD) - Monday, Jun 16, 2008 at 16:02

Monday, Jun 16, 2008 at 16:02
Yes that will be close to the mark. I have the CF80 and when getting my solar panels the experts summed it up to 2 x 80w needed for the fridge. I went with one because of costs and as long as I am mobile every 3rd day I seem to get away with it. Regards Tony
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Follow Up By: Steve - Monday, Jun 16, 2008 at 22:31

Monday, Jun 16, 2008 at 22:31
Boc: that should give you plenty of power

I have a set-up more or less the same as Jim describes with a 40w + 2 x 80s and there's more than ample power - (as long as that big yellow light is shining on us, that is)
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FollowupID: 576440

Reply By: Rod - Monday, Jun 16, 2008 at 17:36

Monday, Jun 16, 2008 at 17:36
Here's what I've found from my experiences...

I believe a rough rule of thumb is that for a 40-50l danfoss based fridge/freezer, 100-120W of solar is usually sufficient. I know my existing 2x40W cannot keep up with my 50l fridge.

Just bought a 3rd panel (65W) from Jaycar on Sat for $150 off. They have a sale on solar at the moment.

I'd guess that 160W for an 80L should be fine.

I'd also consider getting a BurnBrite or sumilar CFL based flourescent light instead of the incandescent globes in the Jayco. They draw around 1 amp (or less) and put out a lot more light.

Not sure what sort of redarc you have. If it is a true isolating type (does not charge the starter whilst charging the aux) you will get a faster recharge time on the aux battery than the types that charge both batteries in parallel.

When you drive, an AGM battery will also be able to take higher currents from your alternator (compared to your non AGM deep cycle or even starting batteries) - reducing battery top-up times.
AnswerID: 310360

Reply By: MartyB - Monday, Jun 16, 2008 at 18:16

Monday, Jun 16, 2008 at 18:16
Hi Boc,
I prefer cheaper options. If you only want to camp for a week at a time try this idea.
I assume you have an Anderson pole out the back of your vehicle to charge the van batteries while you are driving to site. If not get this installed so you start with fully charged batteries.
While stationery have all 3 batteries connected together running the fridge, this will save all the stuffing around changing batteries. I use a pair 10m 16sqmm cables made into an anderson pole extension lead to easily connect all together while camping.
When you go for a drive the second battery will recharge and the other two batteries will recieve some charge from your panels, when you get back to camp leave the vehicle idle when you reconnect the batteries. Leave it idle for about 15 min so the two batteries in the van get a bit of a boost.
Between the panels you have & your alternator you should be able to last a week ok without hot beer. I would try this before spending heaps on more panels.
from Marty.
AnswerID: 310369

Reply By: Member - bungarra (WA) - Monday, Jun 16, 2008 at 20:09

Monday, Jun 16, 2008 at 20:09
Gidday...it is difficult for anyone to give you an answer as the whole system needs to be in balance and well designed before you can be certain of anyone giving specific advice that is correct

by that I mean..the area you are using the panels in (north or south) and therefore the number of charging hours available......the fridge amp draw........the number of hours it runs / 24 hour period...all relevant to ambient and the temperature you are running it at.........the type of panel (eg the "glass" type panel are less effeceint in the heat when compared to the unisolar type)...but the unisolar type are shade tolerant to a degree (little patches of shade wont stop the charge)....... the cable size both to the device (fridge) and from the panels to the battery etc.

we have just had 5 weeks in the Kimberley (all of May with miid 30's temp)...ran 2 x 100 ah deep cycle running two engels one as a fridge and one as a freezer.......total draw 7 ah when both running...plus camp lights...........4 x 64 w BP panels (3 would have been suffice this trip, but other trips with bad sun days the 4th has been useful)......and the batteries never got below 67% SOC..........worst current usage was 83 ah in a 24 hour period

its all about knowing the intended usage (now and the guessing the future), and the environment you intend to use it in....... and a well designed system...

its just like planning a water / sprinkler system.....water = volts.....reservoir = battery.........amps = pressure..........hose pipe = cable size.

dont rush into any purchase as there are many ignorant salesman out there
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AnswerID: 310387

Follow Up By: Ianw - Monday, Jun 16, 2008 at 20:38

Monday, Jun 16, 2008 at 20:38
Volts are the measure of electrical pressure. Amps are the flow rate.
Ian
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Follow Up By: Member - bungarra (WA) - Monday, Jun 16, 2008 at 21:38

Monday, Jun 16, 2008 at 21:38
thanks Ian.....I should type slower and proof read my post...
Life is a journey, it is not how we fall down, it is how we get up.
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Reply By: Mainey (wa) - Monday, Jun 16, 2008 at 21:04

Monday, Jun 16, 2008 at 21:04
Boc,
First, you have to know your 'total' power consumption to work out what has to be replaced by the Solar system, multiply your total usage by (about) 3 and you will have a reasonably sized Solar system.
Example; a 15 Amp power requirement requires 3 x 80 watt panels JUST to replace what power has been used, IF the weather is perfect every day.

With the batteries you ½ discharge and then switch them around, connect them ALL in parallel and run everything from them as just one huge battery and also charge them all as only one huge battery.
That way you only partially use each battery and have them recharged before any of them get too low and they become slow to recharge, assuming they are ALL the same type of battery.
If not then re-organise them into two different systems.
(Hint: AGM batteries WILL charge much faster than any other battery!!)

Mainey . . .
AnswerID: 310399

Reply By: Ozboc - Tuesday, Jun 17, 2008 at 16:12

Tuesday, Jun 17, 2008 at 16:12
Thanks to all that have replied so far - it has been a great help - some very good suggestions there .. i am in no rush so will digest all the replies and work on a solution that works best for our situation

thanks again :)

Boc
AnswerID: 310544

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