Getting more power from Solar

[GEOFF.PAULINE]

Oh ! I know Solar again.

Just want some confirmation on parrell Solar panels

Situation is 100 a/h Battery in compartment , cannot go bigger.

Fridge that pulls 4.5 amps and runs for about 16 hrs in 24 hr period

Solar panel 120w , watt meter says on average on sunny day 4.5 amps actually getting to Battery.

In 36 hrs Battery is down to 50 % .

Therefore replacing 4.5 amps for 8 hrs but drawing 4.5 amps for 16 hrs is never going to work.

I want to put 2 120w panels together , in theory producing around 9 amps to the battery to run the Fridge and top up the battery a little as well.

Am I on the right track , Thanks.

[Peterr]

You're on the right track indeed ; however .............. you need to just have one regulator handling both panels..

Separate regs will "fight" each other, as each sees the output voltage of the other and not necessarily the battery voltage.. So , if the panels have inbuilt regs , bypass them , and feed the unregulated parallel connected panels output to a at least 20A regulator, then to the battery ..

I have this setup , one 120W and one 160W panel in parallel , and it works great !

I'm setup so I can use either one or both panels connected to the reg, depending on the load I'm applying ...

[GEOFF.PAULINE]

Thanks Peter

They would be running through the ctek D250s in the camper.

[robcaz]

Hi Geoff,

You need to run your fridge through the watts up meter over a 24 hour period & get the amp hours used figure first. Ah is one of the five data logs that cycle in the bottom left of the panel display. You need to read this before disconnecting the power. http://www.campertrailers.org/watts_up_meter.htm

Using your figures - fridge pulls 4.5 amps and runs for about 16 hrs in 24 hr period - that would be 4.5 x 16 = 72 amp hours, which is a huge power consumption.

The fridge may run 50% of the time to keep the set temperature so it would be more like 2.25 x 16 = 36 amp hours..... presuming you are turning the fridge off for 8 hours over night???

Collyn Rivers recommends the battery should be fully charged after lunchtime, so it may be a case of more solar panel capacity rather than more battery amp hours like you suggested.

But first up get a power consumption of your fridge with the watts up. You can throw the figures into Richards solar spreadsheet http://www.campertrailers.org/solar_spreadsheet.htm

You probably really need another battery too, so you can run the fridge for a few days when there is no sun allowing the battery to discharge to 50% capacity.

By comparison our 40 litre Engel running as a fridge uses.........
- 10 amp hours over a 24 hour period when the ambient temp is 20 during the day & 10 degrees overnight
- 20 amp hours over a 24 hour peroid when the ambient temp is 30 during the day & 20 degrees overnight
http://www.campertrailers.org/fridge_draw.htm

Our fridge did use 40 amp hours in a 24 hour period when the ambient temp reached 40 degrees.

[GEOFF.PAULINE]

Thanks Rob.

As usual caught between the devil & the deep blue sea.

Fridge is a 60 ltr no name Chinese that came with the trailer and I believe it's thermostat from new has never known when to cut off at the set temperature.

But it is what we have at the moment , I hope that when we get a " Brand " fridge it will be more efficient.

Cheers Geoff.

[jw2170]

Hi Rob,

presuming you are turning the fridge off for 8 hours over night???

Is this a general practice. Does the fridge maintain low temp for that long overnight?

We have a Waeco CFX40.....

Going down to Merry Beach at end of month, so interested.

PS.. will also post this question on the FB page for a general consensus...

[armbrup]

My 120Watt cheapo folding solar panel output is approximately 6.5 amps even with battery at 12.5 volts or above and I have seen 7 amps.
I have replaced the thin 5 metre wires with 8 gauge 10metre wires and fitted a GSL MPPT 10 amp controller at the end near the battery.
I also run the panels in series rather than parallel which reduces "pumping" losses which is possible with a REAL MPPT controller ( as opposed to some controllers marked as MPPT but not in fact MPPT)

So some of your problem appears to be an inefficient setup with your solar. Before buying more panels in your position I would try to get better performance from your existing panels.

While my old Engel uses a bit of power I doubt that it would use an average of 4 amps and this is confirmed by the fact that the batteries go into float by about 9-10 AM. My dual battery controller cuts at 12.4 volts and I run a 120AH AGM and Optima Blue top 55AH in the car.
I have not measured my Engel demand over 24 hours but measure solar input with a amp logging meter from ABR.
Regards Philip A

[robcaz]

Hi James,

As in the reply to Geoff, our Engel uses little power overnight so we leave the the fridge running all the time.

[Ern_Reeders]

In mild weather if turned off at 4C overnight my Waeco CF40 will hit 8 degrees plus by morning. That with an insulating cover. Not a good idea.

[Rowley]

Hi Folks,
Well after much procrastinating I have commenced my attempts to have 12v system in my camper. With mixed results.
I had a 4 day camping trip at my local Gumball Music Festival just out of Branxton NSW. Thursday to Sunday ANZAC weekend.
I have a 80lt Waeco Fridge/freezer.(it can hold 108 cans of drink, baked beans, stag stew etc ) This fridge has been running for a few weeks on the back deck. So it was well and truly at its best temp. I decided this is it...start building and take the fridge. I asked my local auto electrician to source me a 100aH battery...that turned out to be an error in judgement.
$280 E-Nex Dual purpose 12v/90aH(20hr) arrived. When I asked WTF? I was assured there is not much difference between 90-100aH. okkaaay says I and start getting other bibs and bobs for the job.
So a quick build of battery, 1200w (pure sine) inverter, 100amp fuse, Anderson plug connector.
I will add 6 pin fuse box for accessories later. I already had some 100w mono crystal solar panels.
Using the Redarc Solar calculator it tells me I need 120w panels..Opps. Nothing for it but try anyway.

Results?
It rained on the Friday afternoon, 1st time in 6yrs at the Festival.
So the solar panels not working that well. 3am Friday night/Saturday morning I am awoken to the inverter alarm screaming its tits off. So 48hrs maybe out of the battery. So I turn off inverter and hope for sun in the morning...no luck sporadic rain and sun throughout the day. Call a friend Esky and ice please...save the beers. Waeco still cool but not for long opening and closing lid etc.

So as I now wonder what to do next before finishing up the wiring of the accessories fuse box, cigarette lighter & USB connectors. Buy 2nd battery? Buy a bigger battery 120aH? Buy new 120 W Solar Panels?