Solar panel - Amps?

[Bazza Senior Member Find all posts View Profile Close Bazza]

I'm looking to purchase a 120w or 140w folding solar panel to keep my auxiliary battery charged while camping. The 105amp battery will mainly be supplying power to my fridge. I understand the regulated voltage requirement but I noticed that the amperage varies greatly on these panels. What would be the minimum amperage required to keep this battery charged at the faster rate?

Bazza

[fridayman Senior Member Find all posts View Profile Close fridayman]

I'm looking to purchase a 120w or 140w folding solar panel to keep my auxiliary battery charged while camping. The 105amp battery will mainly be supplying power to my fridge. I understand the regulated voltage requirement but I noticed that the amperage varies greatly on these panels. What would be the minimum amperage required to keep this battery charged at the faster rate?

Bazza

What do you mean by "charged at the faster rate"? Faster than what?

More amps will mean your battery can be charged faster, but how fast you "need" it to charge will depend on the state of charge of the battery, how long you have to re-charge it, and how much current your fridge/accessories are drawing. You should also factor in whether the battery will be charged by the alternator when you are driving - will you be parked up for long periods of time? Just as important as your panels is having a suitable solar controller that can charge your battery at the correct boost, bulk and float voltages (especially important if you have AGM batteries). Personally I prefer MPPT controllers, but arguments can easily be made for PWM controllers too (they are cheaper).

I went completely overboard with my solar setup (2x185W panels hard mounted on roof with 40A MPPT), but now I can run all the appliances I want for as long as I want no matter what the weather, and I never even think about the batteries.

[vscorsa Member Find all posts View Profile Close vscorsa]

Hi Bazza,

I run a 120W solar panel which delivers in full sunlight about 6.8A per hour, so to put that in perspective a 40L engel will probably average around 2 to 2.5 A/hr when used for chilling not freezing. We bought the solar panel because we run two fridges which starts to put pressure on our 105 A/hr battery if we stay for a few days. With the solar panel it will replenish some of the draw during the day plus cover the draw from the fridges.



Cheers

Dave

[Bazza Senior Member Find all posts View Profile Close Bazza]

Hi Bazza,

I run a 120W solar panel which delivers in full sunlight about 6.8A per hour, so to put that in perspective a 40L engel will probably average around 2 to 2.5 A/hr when used for chilling not freezing. We got the solar panel because we run two fridges so start to put the pressure on our 105 A/hr battery if we stay for a few days. With the solar panel it will replenish some of the draw during the day plus cover the draw from the fridges.



Cheers

Dave

Hi Dave,
I think you've answered part of my question. If you can run two fridges on a 105A battery and a 120W panel, I should be able to run one. I have one 50L Waeco but will be using it as a freezer for 4-5 days. Not knowing anything about solar panels I've likened it to a battery charger..... if a regulated 10amp battery charger charges a battery better that a 5amp battery charger, is that not the same with solar panels? I find many panels supplying around 6.8A per hour and a few supplying 9.8A per hour. Would that not be the better choice?
Bazza

[vscorsa Member Find all posts View Profile Close vscorsa]

Hi Bazza,

I don't completely understand your question, are you talking about a 10 A/hr battery charger charging a battery faster than a 5 A/hr?

If so you are right, if you bought the larger 180W panel which may charge at say 11 A/hr it will charge the battery faster than the smaller 120W at 6.8 A/hr. If you think you are going to be drawing more Amps off your battery then the extra delivery would be required, depending on the ambient temperature we are probably at the limit of the 120W unit running two fridges with one on freeze. If we were going to setup camp some where for a couple of weeks then I think we would end up having to start the car or run a genset.

So to answer your question yes the higher A/hr can be better however it usually comes at a cost of weight and physical size of the unit.

Cheers

Dave

[Guest Close Guest]

Just be careful with the solar panel ratings and using it in your calculations.
The solar panel's output is affected by the ambient temperature, the angle of incidence of the sun and where the sun is in the sky.

[maxjj Senior Member Find all posts View Profile Close maxjj]

I have got a 40ltr waeco fridge freezer and a 60W solar panel. Have done three trips where we have been parked on the beach with a 100ah battery for 5 days with fridge on freeze and solar hooked up. Typically we were taken frozen meat out and putting in fish to freeze. We pre-chilled the fish in the big evacool esky, also had the beer in there, and then put fish into the waeco to freeze. All worked fine even with the odd overcast day in there.
Running as a fridge should be easier, as long as you don`t put too many warm stubbies in all at once.

One thing to watch with this set up is when you have been running it as a fridge and then want to change it to run as a freezer, it will run flat out for a long time, otherwise I found the 60w to handle it no probs.
Its just about managing it what you have got, I have used 2ltr bottles with drinking water and frozen them to give the waeco a bit of thermal mass.

The 60W solar panel is good for around 4A max, which is about what the waeco uses when it runs. If it runs 20 minutes in an hour ( once its cold it runs less than that ) that is about 32ah. Given a conservative 8 hours of daylight and you have got a minimum of 32ah going into the battery. As long as you get too many heavily overcast days, it works out.

[vk2ss55 Senior Member Find all posts View Profile Close vk2ss55]

Have you guys noticed the big price difference between 12/24 V panels and grid connect panels ? You can get 190W grid connect panels now for $190 . Ok their O/C voltage is higher than 12/24 V panels but will run and charge batt's with MPPT controllers ok . My mate lives in the bush with no grid power and runs totally on solar with an occasional generator run . He and his neighbours use conventional grid connect panels and MPPT controllers runnning 12 or 24V systems in conjunction with quality sine wave inverters . Sure the grid connect panels are large but hey they're 1/3rd the price of 12/24V panels !
Cheers Ross

[craigm Addicted PP Member Find all posts View Profile Close craigm]

Grid connect panels are Mass produced on a ridiculous scale in proportion to the 12/24v panels that we are interested in on this forum and I dare say this is the main factor for price difference. Still I agree that it doesn't justify the size of the price difference...

[fridayman Senior Member Find all posts View Profile Close fridayman]

I run 2x Sharp grid panels which put upto 30V into my 40A mppt controller. They deliver charge with only a hint of light. Very happy with them.

[Chris220220 Senior Member Find all posts View Profile Close Chris220220]

Imagine a set of folding 190's for camping :-). You could go to town as long as you had a good controller and battery.
Size is a bit of an issue. I know you can run the fridges on 24v might be worth looking at if they get to give away prices.

BTW. Having panels capable of dragging in 10amps doesn't mean the battery will pull that unless real flat. You battery will draw less and less till charged, you cannnot force feed it.
When the fridge/freezer, laptop charger, phones and ipod charges are all plugged in my set up draws about 9amps from the 3 50W panels and trickles the battery if not full. Once that load drops the setup just trickle charges the battery with a fe hundred mAmps. I went for a charger with a digital display its great tells me real time what the panels are putting into the charger and what load is being drawn. Well worth it.

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

What the battery will absorb also depends on what voltage it is being fed. If you have an MPPT controller in a DC charger then it will vary the voltage to suit. However Chris is 100% correct that the solar panel will only supply what the battery will absorb.

My 80W panel pretty much keeps up with the fridge demand with only a small deficit which is made up driving every few days. I will keep that panel to charge a 2nd auxiliary in the trailer (lights and the demand from iThing chargers) and run a larger panel through the BCDC1225. I will also charge the pads and phones in the car off the main auxiliary (not that just sounds wrong). Panel is still arriving from Neptune but that is ok because the roofrack isn't ready to fit yet either and the new panel is too long for the old rack.

[Bazza Senior Member Find all posts View Profile Close Bazza]

Solar panels

Guys,

I'm looking at the options available to keep my two CF50 fridges powered for about five days without the need to run the vehicle too often. I'll have one fridge as a freezer and the other as a fridge. I have a new 130A marine battery under the bonnet as the accessory battery. If the weather was good, would a 120w solar panel produce enough power to keep these fridges going? I'll also have a 1K Honda generator available if absolutely necessary.

Bazza

[slimf Senior Member Find all posts View Profile Close slimf]

Hi

I have 200ah and two fridges - same setup as you. With 200ah you can easily go 5 days providing you get some sun on the panels. With 130ah you would be cutting it fine - but if it's only 5 days you would probably be ok. I would recommend bigger panels - another 120w if you want to be sure or go longer.

[vk2ss55 Senior Member Find all posts View Profile Close vk2ss55]

Hey Fridayman which MPPT are you using ? Your panels are 30V , is that O/C or loaded ? Mine run around 38V O/C and around 33V loaded . I get around 5A short circuit current . The price has come down recently , now $126 for 190w , a whole lot cheaper than the 12/24v panels that's for sure !
Cheers Ross