Barn Door for JK factory hardtops

jscherb

Expedition Leader
A few weeks ago I mentioned that I had a growing pile of preproduction samples here from Overland Outfitters, I posted this photo at the time:



Today I packed up pretty much everything in the photo and plus a bunch of other items (preproduction versions of the First Responder Bag, Camp Cabinet (vanity) Bag, Kitchen Keeper Bag and several Compressor Bags, all of which I've posted about here) in a big box - I'm bringing it all to the Bantam show so Overland Outfitters can do a "Sample Sale". I have no idea what the prices will be on the samples, all I know is that I'm very glad to be able to free up the space, move these out of my house and turn these back over to Overland Outfitters. If you'll be at Bantam stop by the Overland Outfitters + MORryde booth and check out their sale (and say hi to me while you're there, I'll be either at the OO end of the space or the MORryde end most of the show :)). You'll know it's the right place because my JKU will be between the two company's tents.
 

jscherb

Expedition Leader
In October I posted this scan from one of the magazines in the Land Rover Ideas thread (https://expeditionportal.com/forum/threads/land-rover-ideas-for-jeeps.218029/page-23#post-2850803); I pointed out the solar panel on the roof:



That inspired me to do this pair of concept images for a panel that stows under the front of the roof rack and pulls out:



I've been thinking about starting a solar project so I've been doing a lot of research. I came across this table in the instructions for a solar panel:



I'm at 42 degrees north, so if I'm reading the table correctly, for optimum output the panel would have to be facing south and be angled at 52 degrees. That would make it something like this:



So if that's correct, a panel that is mounted on the roof or hood, or pulls out from under a roof rack wouldn't put out optimum current. I haven't found any data on how much the output of panels gets reduced when they're not at an optimal angle, so maybe it's not too bad, or maybe it is. A 100 watt panel, of which there are many reasonably priced alternatives, should provide about 8 amps at 12 volts, so more than enough to run a fridge and a few other small things if it's at full output. Even at less than pull output, assuming something like a 50% duty cycle on the fridge, a 100 watt panel could probably keep the fridge battery charged.

I'm thinking that a mount that allows angling and swiveling the panel for maximum output might be a good idea. I haven't found anything like this for Jeeps yet, so maybe I'll build something.

Maybe something that provides an adjustable vertical angle and swivels so it can track the sun from east to west? In this next image it's swiveled a bit east (assuming the Jeep is facing south).



I'm interested in any opinions you might have that would help me finalize a design.
 

justageek

New member
Jeff, I've been to campsites where there was no way to park towards the south. Even with 360 rotation on the swivel your rooftop tent may block the sun. For backpacking I've used the roll-up solar panels that can be laid out on top of the tent, but that doesn't seem like a good idea here.
 

jscherb

Expedition Leader
Jeff, I've been to campsites where there was no way to park towards the south. Even with 360 rotation on the swivel your rooftop tent may block the sun. For backpacking I've used the roll-up solar panels that can be laid out on top of the tent, but that doesn't seem like a good idea here.
I agree - even though my concept images show the Jeep facing south I'm thinking there needs to be a way to mount the panel on the back or sides of the Jeep for times when the Jeep can't be facing south.

Some of the sources I've read say the wrong angle can reduce output by 16% or more, and since output will rarely be 100% due to clouds, haze, etc., a 100w panel that theoretically can put out about 8 amps at 12 volts could be reduced to half that due to those factors so it seems like a solution that doesn't sacrifice 16% due to angle would be a good idea.

I don't think there's a good solution on the market (someone please send me a link if there is a good solution out there), so it seems like this is a good opportunity for some creative design thinking.
 

jscherb

Expedition Leader
Jeep and trailer are in use again this weekend, borrowed by Overland Outfitters.

On the way to the Adirondack Jeep Invasion this morning (I left the trailer at the show last night):



A few shots from the show...



The JKU outfitted with many of their products for display:


 

jscherb

Expedition Leader
Over the weekend I picked up a 100 watt monocrystalline solar panel; it's a new product at Harbor Freight and with a 20% Father's Day coupon it was only $80.



Also picked up their solar charge controller and connection kit, the entire bill was less than $125.



I'm going to experiment with these products and do electrical tests on them to determine optimal ways to wire and connect solar. I see some possible weaknesses in the connection kit (things that will cause electrical losses), so I'll do thorough electrical testing on everything. There are more sophisticated products on the market, but my goal is to develop a design for utilizing these inexpensive components to their maximum possible capability.

I'll do my electrical testing with the Trail Kitchen in mind, so looking at keeping a kitchen battery fully charged even in hot weather when the duty cycle of the fridge is very high. Theoretically a 100 watt panel can do that, but probably that will require careful attention to eliminating losses in the wiring and proper aiming of the panel to maximize sunlight utilization.

I'll also work on integration with the MORryde Trail Kitchen power panel and the upcoming MORryde charging kit which charges the kitchen battery when the Jeep is running; seems to me that an ideal system would utilize both charging from the vehicle alternator and solar charging so the kitchen battery can be maintained in any situation.

As I posted before, instructions for most solar panels prescribe angling the panel for maximum sun exposure so I'm also working on ideas for mounting and aiming the panel (including just setting it on the ground with its adjustable angle legs). I'd like to mount it on the Jeep and provide angle adjustment, so I've been researching various methods for adjustable mounting. These include:



I'll report on all of my electrical testing and mounting ideas as I make progress.
 

jscherb

Expedition Leader
This will be interesting to watch!
Ways to mount and adjust solar panels on a Jeep.
The first thing I'll do is electrical testing to understand the panel's operating characteristics - like to what degree (pun intended) the angle of the panel affects both voltage and current output. Once I understand that, I'll work up a mount that's the minimum required to meet the performance goals (keeping a fridge battery charged).
 

Alloy

Well-known member
I made a panel swivel with a pcs of 1/2" plywood with 1/4" bolt in the middle. It sat on a pcs of 3/16" alum with a hole in the middle that was bolted to my roof rack. It failed right away because I didn't want to park my truck in the sun. These days I use 50' (tinned wire) extension cords and I set my panels on the ground up with adjustable poles. In some places I may move the panel 30' from morning to afternoon.
 

jscherb

Expedition Leader
I made a panel swivel with a pcs of 1/2" plywood with 1/4" bolt in the middle. It sat on a pcs of 3/16" alum with a hole in the middle that was bolted to my roof rack. It failed right away because I didn't want to park my truck in the sun. These days I use 50' (tinned wire) extension cords and I set my panels on the ground up with adjustable poles. In some places I may move the panel 30' from morning to afternoon.
Length and gauge of wire is something else I plan to analyze in this project.

This table is in the instructions that come with the HF solar panel:



Most of the table is useless BTW, since the a 100w panel is unlikely to ever produce more than 7 or 8 amps.

But going by the table, you would think 16' of 18-gauge copper wire would be fine for an extension to put the panel away from the vehicle. The problem is that at 5 amps, that wire will cause about 1v drop, which is almost 8.5%. There are a number of voltage drop calculators online, here's one I often use:



Increasing the wire gauge to 14 results in only a 0.4v/3.5% drop.

The HF solar panel connection kit I bought includes a 16' extension. The gauge of the wire isn't specified, but it looks to me to be 18 gauge. I'll be doing some testing with both that extension and with 14-gauge and I'll report on the difference between the two.
 

Alloy

Well-known member
Length and gauge of wire is something else I plan to analyze in this project.

This table is in the instructions that come with the HF solar panel:



Most of the table is useless BTW, since the a 100w panel is unlikely to ever produce more than 7 or 8 amps.

But going by the table, you would think 16' of 18-gauge copper wire would be fine for an extension to put the panel away from the vehicle. The problem is that at 5 amps, that wire will cause about 1v drop, which is almost 8.5%. There are a number of voltage drop calculators online, here's one I often use:



Increasing the wire gauge to 14 results in only a 0.4v/3.5% drop.

The HF solar panel connection kit I bought includes a 16' extension. The gauge of the wire isn't specified, but it looks to me to be 18 gauge. I'll be doing some testing with both that extension and with 14-gauge and I'll report on the difference between the two.
I boosted the wire size up. Voltage drop on the input is more significant to the overall output as well as getting the controller to start. I'll also connect (Anderson plugs) two 50' for 100'.
 

jscherb

Expedition Leader
The instructions that came with the solar panel list the rated output at 18 volts, 5.56 amps, 100 watts. 18 x 5.56 ~= 100, so the math works, but it doesn't say which is the limiting rating. For example, at 12 volts, 100 watts would be 8.3 amps but I'm guessing that in lower sunlight conditions the output still won't exceed 5.5 amps, which would be 66 watts. I'm planning to do some testing to see if voltage output or current output varies most with differing sunlight conditions.

The instructions go on to say
Performance will vary depending on temperature, brightness and time of sun exposure. Summer production will be higher than in the winter. Bright sunny days will generate higher output than cloudy days.
That's what I think we'd all expect, but I plan to do testing to quantify the differences in output due to conditions.

I did some quick voltage testing in the morning. The sun was still low in the sky (it was 7am) and with the panel pointed directly at the sun the output was just over 22 volts. Laying the panel flat on the ground had almost no effect on the voltage output. The analog meter I was using isn't graduated to accurately determine the difference in output but the difference was probably less than 1/4 volt. That surprised me, I expected to see the needle vary more as I varied the angle of the panel.



The 22 volt output is above the rated 18 volts listed in the instructions, but there's no load on the panel; I expect the voltage may be lower under load and I plan to do some load testing.

This was just a quick initial test, lots more testing to be done. I've got some travel coming up so work on this project will resume when I get back.
 
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oldnslow

Observer
A solar panel is a current source so with no load the voltage will be nearly constant. The 18V spec is the max power point (at 5.56A). When the panel is connected directly to a battery the voltage is brought down to the charging voltage of about 14.4V and the current will go up slightly above the 5.56A spec'd if the battery is down on charge.

The charge controller will switch the solar panel on and off rapidly to limit the charging voltage when the battery is nearly full. You will need an oscilloscope to see this. A meter will show the charging voltage and lower current which leads some to think the panel is bad.

You need a battery at low charge or a controlled load to fully test a solar panel and charge controller. Then you will see the charge current vary when you tilt the panel towards or away from the sun. Also bear in mind the current will vary with the sine of the angle of the sun to the panel, a 10 degree angle away from perpendicular will result in 98% of full current. For this reason a panel mounted flat on the roof of your Jeep will work quite well during the middle of the day without the complexity of an angled mount. Of course the further north you are the less well it will work. At 43 north lattitude you will have about 20 degrees to the panel at noon at the summer solstice, which will give 94% of full current.

The clarity of the air comes into play also. Thin clouds, pollution, or even moisture in the air reduce the power available. Dirt on the panel is another reducer. High panel temperature is another factor. All these things together mean you can expect around 70-80% of rated power at best in the real world. That 100W rating is for perfect conditions only attainable in the laboratory.
 

jscherb

Expedition Leader
A solar panel is a current source so with no load the voltage will be nearly constant. The 18V spec is the max power point (at 5.56A). When the panel is connected directly to a battery the voltage is brought down to the charging voltage of about 14.4V and the current will go up slightly above the 5.56A spec'd if the battery is down on charge.

The charge controller will switch the solar panel on and off rapidly to limit the charging voltage when the battery is nearly full. You will need an oscilloscope to see this. A meter will show the charging voltage and lower current which leads some to think the panel is bad.

You need a battery at low charge or a controlled load to fully test a solar panel and charge controller. Then you will see the charge current vary when you tilt the panel towards or away from the sun. Also bear in mind the current will vary with the sine of the angle of the sun to the panel, a 10 degree angle away from perpendicular will result in 98% of full current. For this reason a panel mounted flat on the roof of your Jeep will work quite well during the middle of the day without the complexity of an angled mount. Of course the further north you are the less well it will work. At 43 north lattitude you will have about 20 degrees to the panel at noon at the summer solstice, which will give 94% of full current.

The clarity of the air comes into play also. Thin clouds, pollution, or even moisture in the air reduce the power available. Dirt on the panel is another reducer. High panel temperature is another factor. All these things together mean you can expect around 70-80% of rated power at best in the real world. That 100W rating is for perfect conditions only attainable in the laboratory.
Thank you for all that. Most of it I knew but you added a few details I wasn't aware of.

I do plan to test with a controlled load (not the fridge) so that I can accurately monitor the change in current due to differing angles and sunlight conditions. I had planned to do most of my testing by measuring current and monitoring how long it takes for the battery to return to full charge but I do have an oscilloscope and based on your comments I may include monitoring the waveform.
 

jscherb

Expedition Leader
From time to time companies ask me to test and review products. For example, recently MORryde sent me a hitch stabilizer that's a new product in their RV line and asked me to test it for stabilizing Jeeps with roof top tents: https://expeditionportal.com/forum/...factory-hardtops.127687/page-313#post-2906304

Another example: the synthetic winch line I'm using in this video is a product another company sent me:


Two years ago a lighting company sent me a switch panel to review: https://expeditionportal.com/forum/...factory-hardtops.127687/page-264#post-2640857. The other day that company contacted me again asking if I would be interested in testing some of their new products. On the list was a new 6-gang switch panel:



Since I had already tested their previous product I thought it would be interesting to see this new version, so I agreed.

They also had several new LED lighting products on the list, and while I'm not much of a "light guy", I found these interesting - they're 9" diameter and 12,000 lumens (a stock JK low beam headlight which is about 1100 lumens). Something that bright sounded very interesting so I said I would be interested in testing those too. An image from their web site:



When the products arrive I'll test them and post the results.
 
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