Solar panel for charging 2nd battery

[Aquarian51]

Just wondering if there is any advice about solar panels. A friend has some panels, which still work, but his complete array was replaced by his insurance company after some were damaged in last years hail storm. They are Enertech SE-170M panels http://www.solare-power.com/cn/products/detail.php?id=200

I was thinking about fitting it on a slide I'll make to fit under my roof rack, so in normal day-to-day driving it would keep the 2nd battery or possibly even both batteries charged; as there is nothing above it normally. When I go camping and want to park in the shade I can slide the panel out and put it in the sun with an extension cord.

I realise I'd need a regulator and a one way diode, to prevent the solar panel flattening the battery overnight. I have a Redarc isolator to separate the two batteries.

I haven't found anything online about the suitability or not of fitting such a panel on a 4by roof rack. What are you considered opinions, please, along with any advice to make it an even better setup. Thanks in anticipation

[Silver]

I've done the same thing with a toy panel on the dash - autoleccie said it probably kept my old battery going for another 6 months.

I have ne experience with 'real' panels. 16kg per panel would soon add up on a roof rack. Apart from that, I reckon, go for it!

[Bigrig]

Kelvin (Dark1) has a ton of experience with solar panels etc - he should see this, but if not, PM him and I'm sure he will be able to assist!

[Yendor]

Just wondering if there is any advice about solar panels. A friend has some panels, which still work, but his complete array was replaced by his insurance company after some were damaged in last years hail storm. They are Enertech SE-170M panels http://www.solare-power.com/cn/products/detail.php?id=200

I was thinking about fitting it on a slide I'll make to fit under my roof rack, so in normal day-to-day driving it would keep the 2nd battery or possibly even both batteries charged; as there is nothing above it normally. When I go camping and want to park in the shade I can slide the panel out and put it in the sun with an extension cord.

I realise I'd need a regulator and a one way diode, to prevent the solar panel flattening the battery overnight. I have a Redarc isolator to separate the two batteries.

I haven't found anything online about the suitability or not of fitting such a panel on a 4by roof rack. What are you considered opinions, please, along with any advice to make it an even better setup. Thanks in anticipation


Sorry can't help with this.

But I can tell you that, you will not need the diode as the regulator already has this function built in.

[Dark 1]

Mate solar is the only way to go in my book, go for a good quality panel [bp solar or kyocera] & good quality reg [steca, morning star, redarc, xantrex & so on]. Make sure you run decent size cable from panel-reg-battery/batteries. An 80 watt panel & 20amp regulator is all you would normally need for a standard fourby setup.
Good luck & check out my build thread link for some shots of my solar setup, i think it's about page 7 or 8.

[Aquarian51]

Thanks Kelvin.

I was chatting to a guy recently who had two 80 watts panels on his Troopy as he said that he'd found one wasn't sufficient. When my mate was saying he had a 170 watt I thought bonus, but was unsure whether a domestic roof panel would handle the flexing it may get on a roof rack. I don't want to go to the expense and trouble of buying the panel and making the sliding tray only to find the panel can't handle the vibration/flexing/whatever. Although he'd still have another 3 I could buy. :-)

Checked out your rig. Gr8 setup.

[Dark 1]

Thanks Kelvin.

I was chatting to a guy recently who had two 80 watts panels on his Troopy as he said that he'd found one wasn't sufficient. When my mate was saying he had a 170 watt I thought bonus, but was unsure whether a domestic roof panel would handle the flexing it may get on a roof rack. I don't want to go to the expense and trouble of buying the panel and making the sliding tray only to find the panel can't handle the vibration/flexing/whatever. Although he'd still have another 3 I could buy. :-)

Checked out your rig. Gr8 setup.

Domestic panels are the same [solar panels are solar panels] my problem is that size of panel is overdoing it & would probably flex due to physical size. Maybe go to a 120 watt panel but i don't think you need more unless your running multiple batts, fridges, lights, ect. I run 2 fridges, 2 led camplights, led tent light & 12volt tent fan off my 100amp hour agm auxillary battery & camp indefinatly as long as there is sunlight. Note i also do not remove my solar panel & sunchase it stays mounted on the roof permantly.


Oh & thanks for the comment on my ride.

[DX grunt]

I'm watching this thread with interest, too.

[Sir Roofy]

im still running my 80wat solar panel and at the momment it fullfills all our needs theres some pics
under SMOKO ON THE MITCHELL RIVER solar is the way to go

[Ghost]

80 watt panel

110L Waeco, all led lights and electric pump we can camp for 5 days but batteries are loosing charge slowly over that time, the panel is just not quite enough. Once we start charging a laptop via its 12v charger we start to chew into it pretty hard. I did my calcs and arrived at around 120watt minium and 180 to be really safe. Maybe my panel has lost a bit of its output due to its age. I mount it on the camper on a 3m pole that i can rotate and align. I usually move it 3 times a day. I do have a spreadsheet on my home pc that allows you to calculate your useage over a day or week etc. Works extremely well i cna post later tonight.

[the evil twin]

OK... first thing is that the Solar Panel mentioned by the OP is not a great choice for 12 Volt application IE vehicle or camper as it is a 24 Volt (36 Volt open cct) panel. Most domestic installations I am familiar with run on higher voltage Panels and indeed most panels over 160 watts are 24 Volt so not suprised.

You will need a more expensive regulator to reduce the up to 36 Volt Output to 12 volts and then the useable power will only be around 60 watts as the maximum current that panel can produce is around 5 amps. The next option is to regulate to the designed 24 Volts and use a DC DC converter to charge the batteries which will give you about 100 to 120 watss depending on losses. Its all doable but I would price out the costs of a Reg and possibly a DC/DC Converter as the Panel needs to be a bargain to make it worth it

About the only trap with power budgets with Solar Panels is they are rated at the Panel and are current limited IE a 120 Watt Solar panel doesn't deliver 12 Volts at 10 Amps (or 10 amp hours if you like).

Rounded out to make the math a bit easier it works like this. The Solar Panel max voltage output of a 12 Volt panel (depending on technology) is close enough to call it 20 Volts so a 120 watt panel is capable of delivering 6 amps (6 amps X 20 Volts = 120 Watts). They will usually deliver a little more than that but the losses thru the cables and regs etc means its ballpark.

The Regulator will reduce the voltage so it doesn't fry any electronics or overcharge the battery but the Reg doesn't increase the current past the Panel capability. This means a 120 watt Solar Panel in a 12 Volt application will give you approx 75 to maybe 80 watts of useable power under max sunlight and optimum conditions (12 volts X 6 amps = 72 Watts). The rule of thumb is approx 2/3rds the rating IE 60 watt panel 40 watts power 120 watts panel 80 watts power.

[JoeG]

Yes I fully agree, it also gets worse in the tropics as the panel temperature rise causes the rating to fall and the load (if you have a fridge running) gets higher.
We recently (last winter) went through central Aust and up to Darwin we had a 100w system (2 of 50w BP Solar panels) these worked great till we hit the tropics then woefull!
we ended up adding another 100w panel in Darwin (and 20amp regulator) and then bliss, fully charged batteries with 2 hours sunshine!
so what works fine south of the tropics dosn't necessaraly work north of them.
However will never think of not having solar battery chargers as we can stay rough for days and not need to hit town till we run out of water or food
Joe

[Dark 1]

80 watt panel

110L Waeco, all led lights and electric pump we can camp for 5 days but batteries are loosing charge slowly over that time, the panel is just not quite enough. Once we start charging a laptop via its 12v charger we start to chew into it pretty hard. I did my calcs and arrived at around 120watt minium and 180 to be really safe. Maybe my panel has lost a bit of its output due to its age. I mount it on the camper on a 3m pole that i can rotate and align. I usually move it 3 times a day. I do have a spreadsheet on my home pc that allows you to calculate your useage over a day or week etc. Works extremely well i cna post later tonight.

Your 110ltr waeco would be pulling a lot of power, my old 80ltr waeco pulled about 7-8 amps an hour in recirc mode my 2 newish 40 ltr engels pull a max of 5 amps even in cool down mode, a 120-130watt panel would probably siut you better.