Wire Solar Panel and Controller into Accessory Fuse Panel?

SnoViking

Adventurer
Hey Folks, Need some insight here.

I ordered up a 100w solar panel and 20amps solar charge controller for my truck. This one here --> https://www.amazon.com/gp/product/B018ICLC3K/ref=oh_aui_detailpage_o03_s02?ie=UTF8&psc=1 I'll be using this to help offset a future fridge. Eventually I plan to do a separate house battery either by dual battery or ArkPak/National Luna Power Pack/GoalZero. But right now, I only have the chassis battery.

I currently have a separate 10 fuse "accessory" fuse panel which runs directly off of my positive/negative battery which I run my hella lights, CB, USB power outlets, and a few additional small items and eventually a fridge. I prefer to keep all added "accessories" on a separate fuse panel to make sure I don't muck with the factory electronics. And if I have any issues, I just unhook the accessories.

So to my question:

Does it make any sense to wire the solar panel, and controller box into the accessory fuse box (and put a 20-25amp fuse in it's spot). My mindset it to keep all "accessories" isolated from the factory system. I understand that the fuse panel is for accessories drawing power, but would there be any ill effects, or benefits, to running power through the fuse panel into the battery (secondary fuse protection?). (I'm fairly sure the fuse panel doesn't care which way the energy is going)

Anyone have any thoughts on this?


Thanks
 

rossvtaylor

Adventurer
Hi Patrick,

If the wiring is adequately sized, and the connections are sound, the electrons don't care where the connection is made. If the wiring is too small, between the acc panel and the battery (or between the charge controller and the panel, for that matter) the charge controller may not read an accurate battery voltage - this is your only real concern. Better charge controllers have a separate voltage sense wire input, to avoid this. If you're doing temperature compensation, you'll need to run the thermistor to the battery anyway... this may change your plans, if you're running something to them anyway. But, really, what you propose is certainly a good option..

Ross
 

SnoViking

Adventurer
My wire schematic is this:

100w solar panel---12AWG (50ft)--->Solar Controller---10AWG (2ft)--->Accessory Fuse Panel---8AWG(1ft)--->Battery

Right now I have 50 feet of 12AWG wire to connect my solar panel to the controller (I'm using waterproof SAE connectors). I plan to shorten this a bit; I'm just not sure how much. Once I start playing with the setup I'll make the call what to trim.

At 50ft (through 12AWG@12V@8amps) my voltage drop should be approximately 0.6V (5%).
At 25ft the voltage drop should be approximately 0.3V (3%)

I'm not sure is the difference in 0.3V (between 50ft and 25ft) will really make a difference. I'm sure when I'm trying to squeeze every watt out of the sun as I can it'll add up eventually. That's why I went right to a 100w solar panel just to take care of a fridge.
 

SnoViking

Adventurer
As mentioned, provided the conductor sizes are adequate, its a sensible plan.
I assume your 'aux fuseblock is 24hr. That is, not controlled by any switching device ?

One detriment for example,
If you are working on the car and disconnect its battery, If your solar is exposed to light, Its going to be feeding power into your car. You may have systems 'live' when you thought you disconnected.
Perhaps consider a solar disconnect switch of some kind, or simply remember to remove your solar fuse.

That's good insight! I didn't even think of that. Yes, it is direct wire and always hot. It'll def be in the back of my mind now. My plan is to store the solar panel and only use it when camping and setup. I'm not planning on "mounting" in on the truck. It will be positioned, used, then put away. I got a fancy flexible one. Fancy to me atleast.
 

rossvtaylor

Adventurer
I'm sure when I'm trying to squeeze every watt out of the sun as I can it'll add up eventually. That's why I went right to a 100w solar panel just to take care of a fridge.

You're definitely thinking in the right direction, and it's refreshing to see thought put in ahead of time. Too many people just throw together some stuff and then complain later that it doesn't work.

If you don't mind, let me clarify that we're really talking about two different issues here.

The first is the actual loss, mostly in the form of conversion to heat, from resistance in the wires. A symptom of that is voltage drop or rise, but that's a symptom... the "problem" there is wasted energy.

The second issue, and the one I think is more serious to consider, is that the controller may change charge conditions based on inaccurate voltage readings. The .6 or .3 volt differences may not be a big deal by themselves, but if that difference in voltage causes the charge controller to change charge rates (and stop charging prematurely or go into float) that's a much bigger issue. Then you're getting less energy into your batteries not because of the actual line losses, but because the system can't properly interpret the battery's condition.

Hope this helps a bit!

By the way, all of this only applies if you are using recycled electrons. If you're using new ones, then that's out of my area of expertise.
 

4x4junkie

Explorer
My wire schematic is this:

100w solar panel---12AWG (50ft)--->Solar Controller---10AWG (2ft)--->Accessory Fuse Panel---8AWG(1ft)--->Battery

Right now I have 50 feet of 12AWG wire to connect my solar panel to the controller (I'm using waterproof SAE connectors). I plan to shorten this a bit; I'm just not sure how much. Once I start playing with the setup I'll make the call what to trim.

At 50ft (through 12AWG@12V@8amps) my voltage drop should be approximately 0.6V (5%).
At 25ft the voltage drop should be approximately 0.3V (3%)

I'm not sure is the difference in 0.3V (between 50ft and 25ft) will really make a difference. I'm sure when I'm trying to squeeze every watt out of the sun as I can it'll add up eventually. That's why I went right to a 100w solar panel just to take care of a fridge.

One concern I had with hooking the solar controller to the fuse panel is the controller potentially causing noise in any audio gear you have hooked to the panel (this also includes a CB or other two-way radio). The pulsations (ripple) in the controller's output while it regulates the charge current might find it's way into the equipment's speaker circuit similar to how an alternator ripple can (makes a whine or whistle sound in the speaker). However your post stating you have only one foot of 8 AWG between the panel and the battery lowers this concern somewhat.
(f it still becomes an issue, a 10,000µF filter capacitor connected right on the fuse panel can smooth out the ripple)



As for the wire length to your panel, I very highly doubt you will be able to notice a 0.3V difference on the solar side of things, especially with a PWM-type controller that already operates the panels below their Vmp. The much more limited flexibility where you can place the panel in the sun due to the shorter cable is more likely to affect your ability to harvest the sun's energy.

If you really want to maximize your solar harvest (w/o going to a bigger/more panel), get a MPPT charge controller. MPPT won't make a huge difference mid-day when the sun is directly on the panel (maybe 5% better), but early morning and late afternoon (and when it's cloudy) the difference can be 15-20% or even more current going into your battery vs with PWM. This is because the panel is cooler during these times, which increases it's output voltage (but not output current). MPPT takes advantage of this extra voltage where a PWM cannot. Decent MPPT units have begun to reach below 3-figures, so they are becoming a better value.
 

SnoViking

Adventurer
By the way, all of this only applies if you are using recycled electrons. If you're using new ones, then that's out of my area of expertise.

Maybe that's why my calculations are off a little bit. I was calculating using only new electrons. But I'm probably not taking into account the depreciation once I drive them off the orbital lot. :smiley_drive:


The controller isn't anything super fancy but it got pretty good reviews, fit my budget, plus it is capable of charging up to 13.7V (vs 12.6V on similar models). I have a voltmeter which I can see whilst I drive and under normal driving conditions I'll see anywhere from 13.2-13.9V on the readout. I was speculating that the 13.7 float mode would definitely be an improvement over the 12.6V. Especially if I'm siphoning off power for the fridge.

My ultimate goal is to end up with either a National Luna, ArkPak, or GoalZero setup. It will really come down to what fits in the allotted space I have left in the back of the 4Runner. I think I can just squeeze the National Luna or ArkPak in the space I have. It will be tight. I want something separate from my chassis battery, But I can still charge that system from my chassis battery.
 

dwh

Tail-End Charlie
Most charge controllers have to have the battery connected or they won't work.

Same sort of thing with grid-tie inverters...if the grid goes down, they've got nothing to sync to so they shut down. They don't backfeed the grid and electrocute hapless linemen.
 

SnoViking

Adventurer
If you really want to maximize your solar harvest (w/o going to a bigger/more panel), get a MPPT charge controller.


I did consider these, and eventually will upgrade to one. Right not my budget didn't allow for it. I think the cheapest (one that still got good reviews though) was still around $100. I figured for $22 to get me started it wasn't a terrible lose... Plus I figure when I'm ready to upgrade the prices on the MPPTs will probably drop the $22.

I spent a little more and went with a "better, more efficient" solar panel. Plus I wanted the flexible, thin style for easier storage in the truck. (https://www.amazon.com/gp/product/B01DXYNGA0/ref=oh_aui_detailpage_o03_s01?ie=UTF8&psc=1)
 

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