Portable Solar panels

[Clayton]

Hi All,

I'm thinking of purchasing a portable 80w solar panel setup to keep the fridge battery (110ah DC) topped up when I head bush every now and then.

The battery is a sealed lead acid deep cycle. Didn't have enough funds for an AGM at the time. The battery lasts around 4 days under cover where possible which I am happy with but there might be the odd occasion where I might need it to last longer.

Rod no doubt you have solar on the homestead.

Lindsay has more solar panels than trees on his property so if needed I could connect the battery up as a last resort.

Looking at the projecta SPP80K (80w) folding solar panel for around $360 with a 20 year warranty.

Look forward to everyone's input.

Cheers,
Clayton.

[Rod Outback]

Clayton,

An 80watt panel is likely to give you around 6.5 amps under full sun, so
plenty to run fridge(1.5 amps average load?) as well as top the battery up.
I wouldnt charge the battery without the fridge connected, though, as 6.5
amps is getting a bit high for anything smaller than around a 140amp/hr
battery.

If the panel is likely to be connected for a long period of
time(weeks/months), you would have to get your charge rate to no more than
the magical figure of 1/21 of the lead/acid battery amp/hr rating(roughly
5.2 amps for a 110amp/hr battery). However, if we are talking for a few
days or even a week, you would be close enough to this figure to not have
any worries, and the fridge will be sucking some of this.

Battery technology is about the biggest limiting factor in making use of
the sun for power; the new battery technologies soon to hit the market seem
to be comfortable with massive charge rates, which opens the door for
oversized panels that can charge the battery in a short period of time.
Unfortunately, the most affordable battery tech (lead/acid) is also about
the slowest to absorb power.

I hope this helps.

Cheers,

Rod.

[Clayton]

Thanks Rod it has helped.

The solar panel would only be connected for a week at the most with someone always in attendance to ensure the beer was still cold ;)

Cheers,
Clayton.

[marko]

you need a charge controller - this will manage the battery charging and
look after the battery. A cheap chinese one is about $20 to $50. If you
want to extract everything the sun has to offer, you need a MPPT (maximum
power point tracker ) which optimises the the panel output and gets you 10
to 20% more power. They are about $80 to $200.

If you are going mppt, then I would suggest you buy a larger charge
controller than you need, then you can add another panel when you need to.

Folding panels are nice, but you can get a 60W panel from jaycar, altronics
etc for about $70 which is much, much cheaper.

Panels hate partial shading, the whole panel works at the efficiency of the
worst cell. If you can mount the panels and turn them at lunch time from
slightly south to slightly north, then you can get an extra 20% power. Also
the panel angle = your lattitude.

Cheers

Marko

[marko]

marko wrote:

>
> worst cell. If you can mount the panels and turn them at lunch time from
> slightly south to slightly north, then you can get an extra 20% power.

That should be slightly east of north in the morning and slightly west of
north in arvo . . .

was in a bit of a hurry!

cheers
Marko

[Rod Outback]

Marko,

The 4 folding panels I have owned or seen, have all had a charge controller
glued to the back of one panel, and wired in to the system.

The two folding panels I have here, have maintained a battery just fine.

Cheers,

Rod.

[marko]

Clayton wrote:

<snip>

>
> Looking at the projecta SPP80K (80w) folding solar panel for around $360
> with a 20 year warranty.
>
> Look forward to everyone's input.
>
> Cheers,
> Clayton.

Long warranties are meaningless as most of them are pro-rata. If your panel
fails in year 19, they will pay you back 1/20th of the cost. Failures
usually occur very early on, then the panels slowly lose output over 20 to
30 years.

I reckon a 1 or 2 year warranty is enough.

Cheers

Marko

[Clayton]

Thanks Marko.