Simpler side solar with flex panels and one battery (panels on hood)

roving1

Well-known member
At some point I would like to upgrade to a wedge camper top like a Super Pacific or a GFC unit. Until then I really wanted to upgrade to a 12V fridge for longer term travel but also not really mess with a seperate house battery and battery isolation system. I also in the medium term would like to ditch my CVT RTT and get something like a hard/soft shell pop up like a Free Spirit Recreation high country for easier set up. So I wanted to keep the roof clear for either of the above future uses.

So being a small regular cab pickup there are not a lot of options for where to put stuff. I also wanted to keep it simple and cheap and keep most of the components near to and under the hood. I also wanted somewhere between 150-200 watts to get better performance under marginal solar conditions.

So I settled on two Lensun 80 watt panels as they were the perfect size to just barely fit on the somewhat weird hood shape of the Tacoma. Upgrade the battery to 105AH East Penn/Napa group 31 AGM and a Victron 75/15 MPPT solar controller.

One panel would have fit such that I could have just VHB taped it to the hood but no way for two. One could have went on the roof as well but I wanted to leave that open for the above reasons. I also wanted it to be easily removable so I can park in the shade and extend the panels out to the sun or be able to angle the panels toward the sun in winter. So I came up with a system of using 1/4"x1" aluminum flat stock with foam weatherstripping on the bottom with latches riveted to it and the hood. The flat stock is under tension and wants to compress the foam towards the hood making it a very solid system without putting any stress on the panels themselves. The panel is VHB taped to the top of the flat stock in addition to zip ties for a physical connection backup. The panels have the same foam strips every 6 inches or so to have an air gap under the panels for cooling and to keep the panels from fluttering on the hood. So far the system works well and does not move or flutter at 80+ on the freeway.

The first gen Tacoma is known to not have the most robust battery shelf on the fender apron and has been known to sag with dual battery systems added. I am hopeful I can get away with this because I replaced a 40 something pound battery with a 60 something pound battery vs the 100-130 plus most dual battery systems would be in the same location. I thought long and hard about a 2nd Lithium battery but this just makes so much more sense and avoids so much more complicated wiring. My starting battery needed replacing anyways so all in all even though it's AGM it was the lightest simplest solution.

For now the MPPT controller is located in the engine bay "waterproofed" with a silicone reusable food bag zip tied around the wires. We will see how it goes. I really do not want to run 4 10GA wires through the firewall which makes very little sense since this system is all on and under the hood otherwise. Also with not much room in the regular cab it would probably get mounted lower down somewhere where it would be likely to flood out stuck in a mud puddle. Plus its better for the controller to have shorter wires and be the same temp as the battery. The reg cab has really huge temp swings particularly in winter where the cab might be 70 with the sun while its 20 ambient under the hood. At any rate it's a pretty spacious relatively cool engine bay. I am willing to risk the 80 buck controller to try out this setup just for the sake of simplicity for now.

As an aside when I was mocking up the system on sunny days where the car had not been driven for days and the amount of finger searing heat the sun and panels make on the hood even with a 1/2"air gap was amazing. I don't have infrared gun data to back it up but there is no way the engine heat would ever make the panels any hotter than they already get from the sun. Any worry about engine heat affecting the panels is now totally wiped from my mind as hot as these things get on their own.

So far it works great and on even really crappy overcast days it will pull 20-40 watts and 1-3 amps so even in the worst case scenario it will usually get the battery up to absorb and then float charge either every day or every other day with no engine running. As a sort of torture test I filled a cooler full of warm beer and set it to 34F with the battery at 50% charge followed by 3 days of rain and by the third day it had dug itself out of the hole and was float charging with no clear sunny days. So should be fine for normal use.

I have a 12v jump pack plus a manual transmission so I am pretty comfortable with the safety margin of still being able to start the vehicle if something goes wrong with the system.

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roving1

Well-known member
Heat is bad.

Any flexing is bad.

Panels will not last long at all.

We will see.

But the panels are scorching hot whether they are on the roof or the hood so that's a moot point. The only possible way these panels could be hotter would be on top of a rubber insulated roof of an RV or something. Just sitting on top of grass in the sun they are too hot to touch and work with after 15 minutes.

The panels are flexed less than what they are rated for.

They have been running like this for 4 months already. So not a ton of exposure yet but not like it exploded on week 2 or anything.

I'll update whatever happens long term. I was trying to avoid rigid panels but that will be the next step if/when these fail.

I am not re-inventing the wheel here on hood mounting or curved panels though.

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john61ct

Adventurer
So called "flexible" panels cannot have **any** flexing movement in use at all once installed, if you want them to last more than say a year or two on average.

The point is to allow them to be fixed permanently to a curved surface.

Ideally that surface being a metal plate heat sink with an air gap below so the heat produced in use is carried away as quickly as possible.

Certainly no heat added to the mix.

That is not just a question of longevity

but also PV conversion efficiency, cooler the better.

A better solution if you cannot accommodate the usual rigid framed panels permanently mounted

is the folding blanket, or "suitcase" style.

Or a small quiet inverter genset and a LFP House bank.
 

roving1

Well-known member
So called "flexible" panels cannot have **any** flexing movement in use at all once installed, if you want them to last more than say a year or two on average.

The point is to allow them to be fixed permanently to a curved surface.

Ideally that surface being a metal plate heat sink with an air gap below so the heat produced in use is carried away as quickly as possible.

Certainly no heat added to the mix.

That is not just a question of longevity

but also PV conversion efficiency, cooler the better.

A better solution if you cannot accommodate the usual rigid framed panels permanently mounted

is the folding blanket, or "suitcase" style.

Or a small quiet inverter genset and a LFP House bank.

Prove the panels are hotter on the hood than on the roof and there would be some validity to the efficiency or heat argument. These are scorching hot mounted on fiberglass too as I had them on a boat briefly just to top up a battery.

Also there are about a zillion panels on boat biminis just on the canvas getting blown around and flexing nominally from their static position.
The panels as mounted don't move any more than the sheet metal they are mounted to.


I think it is strange to have the thought that the same panels sewn to cardboard and covered in nylon are somehow magically OK with the heat in the same location? Why would that be? Or that they are guaranteed to last any longer getting folded and tossed about and beat up. Again why?

Your concerns and best practices make total sense in a perfect world but they are far from absolutes.

As I said I am sort of over the ugly factor if these fail I will mount some rigids but I fail to see why this wasn't worth experimenting with.

For every OMG my panels failed guy there is a guy running around with panels on the hood for 3 years in AZ and Nevada so I don't think there is a preponderance of data either way.
 

chet6.7

Explorer
Using the hood would be a good utilization of space, hope it works out. Please keep up with the thread over time.
 

jadmt

ignore button user
I thought about putting these on my gfc to charge my jackery but worry about the heat on the roof panel. I wonder how much heat transfers to the surface they are mounted to
 

roving1

Well-known member
Coincidence to mention 3 years.
My friend has a sailboat she uses flexible modules. Ends up replacing them every 3-4 years.
Btw,
Sailboat is about the worst place for solar. Being so little room on that boat to mount an array, which on occasion might need to be stepped on, plus there is always shade somewhere on the array. Its surprise their system works as well as it does.
Its just part of the high cost living on a sailboat...

If these things last 2-3 years I would be happy enough. I almost assuredly will crash them into something or have them stolen before then. For 1/4 the price of a premium solar blanket I will give it a try.
 

john61ct

Adventurer
Yes that's fine if you're happy.

Paying less, getting more watts per sq ft and lasting 15+ years is more my jam.

If you pay a top notch yacht panel installer, there are European semiflex panels for over $8/W

but that's before the installation labour.
 

roving1

Well-known member
I thought about putting these on my gfc to charge my jackery but worry about the heat on the roof panel. I wonder how much heat transfers to the surface they are mounted to

I would really like to see how hot a renogy panel gets. These are really hot. I have never been around one of their panels so maybe my fault is just not realizing how hot all these panels all get just sitting there. I am not even talking about being under load or engine heat. Just sitting in the sun doing nothing these things are damn hot. I thought about using aluminium sheet as a heat sink but at that point it's messing with so much metal might as well mount rigids.
 

67cj5

Man On a Mission
It's crazy adding panels to the Hood, The Heat from the Motor would speed up the rate the panels heat up, Panels need an Air Gap, If this is not the case then why are all Domestic and Government panels mounted either free standing or with a 3 or 4" gap between the back of the Panel and the Roof ??.

There is always some smarta$$ who thinks they know better who claim they have some new wonder Panel and then charge 8 to 10X the price for this new wonder panel that performs less than Average at best,, It's a fact that the cooler a panel is the more efficient they will perform, So regardless if someone has had them for 2 or 3 years means nothing, Where as proper panels will perform well for 20/25 years and then drop to about 80% after that which is why they come with such a long warranty.

Just because we want the sales blurb to be true the performance and long livity of flexible panels are at best equal to the cheap "B" Grade panels from China and the "A" Grade panels from China will out perform flexible panels by 10 to 1, Where even the cheap panels from Tandy's or Walmart will out perform flexible panels. I still have the first Solar Panel I bought from Tandy's 22+ years ago and it still works,
 

roving1

Well-known member
It's crazy adding panels to the Hood, The Heat from the Motor would speed up the rate the panels heat up,

Yet another one that repeats the motor heats the hood up substantially more than being in direct sunlight does anyways with nothing to support it.

The panels have a 1/2" gap underneath. I can look through them underneath. When the engine is running the panels won't be charging anything. When the engine is running I will be driving and moving through air 98% of the time.

Here is a link that shows a black Corvette that has been sitting with the engine off at 166F and a Black BMW that just parked after driving with a temp of 172F.

OMG THATS CRAZY!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


I'm not saying it's the best idea since sliced bread or that it's the cheapest longest lasting form of PV power but I definitely don't think it's crazy.
 
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67cj5

Man On a Mission
Yet another one that repeats the motor heats the hood up substantially more than being in direct sunlight does anyways with nothing to support it.

The panels have a 1/2" gap underneath. I can look through them underneath. When the engine is running the panels won't be charging anything. When the engine is running I will be driving and moving through air 98% of the time.

Here is a link that shows a black Corvette that has been sitting with the engine off at 166F and a Black BMW that just parked after driving with a temp of 172F.

OMG THATS CRAZY!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!


I'm not saying it's the best idea since sliced bread or that it's the cheapest longest lasting form of PV power but I definitely don't think it's crazy.
A flexible panel is going to cost 2 or 3 times as much as a ridgid panel and it will have a very limited life span, You've already made your mind up so do what ever suits your needs,

Mounting a panel on the Bonnet/hood puts it at risk of being damaged by people/passersby or stolen, I don't see any practical reason to mount it there and would rather go with a foldout panel,
 

john61ct

Adventurer
Yes, because ANZ have relatively strong and enforced mandatory warranty Consumer Protection laws

vendors have I believe stopped selling the semi-flex type completely.

For mobile use with little available roof mounting space, the folding "blanket" style seems to have emerged there as pretty widely used.

Not yet sold much in NA, and yes pricey per watt

but apparently lasts pretty well.
 

roving1

Well-known member
Well 5 months in and maybe 5K of driving. 100 degree AZ heat. 1st 2nd gear 4LO sand running. Bunch of stuff in between. Bombing up mountain passes WOT in 4th gear then pulling off the freeway to get gas with a super heat soaked engine. So far so good.

Have not touched anything in the system. Been running the cooler all the time minus a couple of weeks.

Currently on an open ended trip. Living out of the truck. Charging lithium power packs, laptops, running fans, recharging chainsaw batteries as needed. About to cross into Baja tomorrow.

Most days depending on use position etc it's topped up and floating by 9am-noon. So far any efficiency loss is really moot because it tends to do most of its charging with low weird oblique light angles before I have even fired up the engine for the day. A few times I have stopped in a heat soaked condition and ran the HVAC blower while parked with the engine off and had it still push 120-130 watts.

22KWH charged in total and no issues so far other then everyone and their brother bombs me with questions every time I gas up.


The experiment continues...

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