Help Request: Please back check my wiring diagram

[midlifecrisis]

Good Morning All,
I am electrically competent, but I would really appreciate it if one or two of you super electrically intelligent guys could do a quick back-check on my wiring diagram to make sure I'm not doing anything really stupid.
I am doing a 6Vx2 stand-alone system that is, for the time being, completely isolated from the vehicle electrical system so it's pretty simple. Mainly I want to make sure I'm not off the map on the solar side as that is new to me.



I did the calculations for the fuse size on the solar panel as provided in the instructions and it was 3.5A so I assume 5A is the way to go.
The diagrams I've seen seem to indicate the positive back from the controller with an in-line fuse, going direct to the battery post, but I can't see any difference electrically between that and what I am doing by running it back through a slot on my fuse panel with a 5A fuse, right?

I will probably add in a small inverter later and possibly a powered solenoid setup from the car charging system, but for now this is what I want to go with.

Thank you in advance.

 

[AaronK]

Might put the solar panel + on the other side of the master switch so it'll still charge when everything else is off?

Sent from my OnePlus One using Tapatalk.

 

[CaliMobber]

Might put the solar panel + on the other side of the master switch so it'll still charge when everything else is off?

Sent from my OnePlus One using Tapatalk.

The only thing i saw. don't need a fuse inline with the battery. Hook the positive directly to battery.

 

[AndrewP]

Your power lead from battery + to the panel, needs to be fused. The switch you show is optional. You could use a 100-150 amp breaker from Bussman and it would be both circuit protection and a switch that you will just leave on most of the time. You can open the breaker when working on the rest of the system. Just remember to have it close to the battery.

Your fuses are too small. Fuse according to wire size, not the load in the circuit. Fuses protect wires. With 12ga wire, you could use 20 amp fuses. Nothing really wrong with the small fuses, but there will be more voltage drop with a smaller fuse everything else being equal. Minor problem really, but something to consider.

Where you bring power in from your panel doesn't really matter. Backfeeding through the fuse block works surprisingly well. If you go directly to the battery, which is a more standard approach, you will need an inline fuse right at the battery. Running in through the panel provides that.

One last thing, while technically you need a fuse between the panel and the charge controller, in practice, the maximum voltage (20v) and current (2.5 amps) is low enough that you don't really need to fuse it.

The one glaring problem I see with your plan, is that your solar panel is way too small. To charge those big batteries and run pumps, fridge and charging electronics, you need at least 100 watts and likely more. I'd figure a way to also have the vehicle charge the batteries when you are running. That makes up for a whole lot of "too small solar". But really, 50 watts of solar is going to have a tough time supplying your intended loads. You'll be lucky to get 20 amp-hours per day out of your panel, and the fridge alone will consume all of that and likely more.

 

[midlifecrisis]

Your power lead from battery + to the panel, needs to be fused. The switch you show is optional. You could use a 100-150 amp breaker from Bussman and it would be both circuit protection and a switch that you will just leave on most of the time. You can open the breaker when working on the rest of the system. Just remember to have it close to the battery.

Your fuses are too small. Fuse according to wire size, not the load in the circuit. Fuses protect wires. With 12ga wire, you could use 20 amp fuses. Nothing really wrong with the small fuses, but there will be more voltage drop with a smaller fuse everything else being equal. Minor problem really, but something to consider.

Where you bring power in from your panel doesn't really matter. Backfeeding through the fuse block works surprisingly well. If you go directly to the battery, which is a more standard approach, you will need an inline fuse right at the battery. Running in through the panel provides that.

One last thing, while technically you need a fuse between the panel and the charge controller, in practice, the maximum voltage (20v) and current (2.5 amps) is low enough that you don't really need to fuse it.

The one glaring problem I see with your plan, is that your solar panel is way too small. To charge those big batteries and run pumps, fridge and charging electronics, you need at least 100 watts and likely more. I'd figure a way to also have the vehicle charge the batteries when you are running. That makes up for a whole lot of "too small solar". But really, 50 watts of solar is going to have a tough time supplying your intended loads. You'll be lucky to get 20 amp-hours per day out of your panel, and the fridge alone will consume all of that and likely more.

Thanks Andrew!

Couple of follow-up questions if you don't mind:

1. I understand your point about some sort of large fuse between the battery and the panel (typically a fusible link under the hood, right?), but I was under the impression that was only required when you have a big power producer (aka an alternator) upstream that could go off the reservation and push crazy amounts of amperage into the system if there was no fuse to stop it. I was thinking that since I have no such animal in this system (the panel is the only producer and it's fused) a fusible link or other big fuse wouldn't be necessary?

2. Thanks for the info on the sizing of the fuses. I was under the impression you wanted to size the fuse to just above the downstream load, but I see your point, particularly the choke point that a small fuse would create on a bigger wire. I'm oversizing the wires on purpose to eliminate any heating so no point in choking that. Thanks for that.

3. I was adding the in-line fuse on the solar panel + line between the panel and the controller straight out of the panel installation instructions. Do you think it hurts anything to have it? Once again it's smaller at 5A than the wire capacity at 12awg, but again I was using the formula provided by the panel manufacturer to arrive at that fuse size. Leave it you think?

4. I completely understand your point on the panel, but I am balancing a lot of issues there. What I didn't tell you is that this system is going into a 2015 Subaru Outback expedition setup so I have to balance space/size/weight, etc. against output. I see my usage as 95% the refrigerator at 5.5A and very little water pump and other to be honest. I've had several RV's over the years with battery setups that were not even this good, and even with full "RV usage" I could go quite a while without going bingo by just being reasonable with usage. Granted the frig in the RV's was typically propane, so maybe that will blow up in my face, but I want to get some real-world data based on my system and usage before I go to any next step.

Like I said previously, I can certainly see going to alternator support as well, but there are issues to dig into on that (not the least of which is a 110 Amp alternator) and I would rather limp into this thing and gather some date before I do everything.

Thanks for the input and the conversation, it's MUCH appreciated!

 

[LeishaShannon]

1. I like the blue sea MRBF fuses for this purpose as they're directly on the battery terminal.
3. No need for a fuse in the panel ->controller run , the cable the panel is supplied with will be able to handle a dead short.
4. You can't have too much solar

 

[DiploStrat]

Some Thoughts

... I see my usage as 95% the refrigerator at 5.5A and very little water pump and other to be honest. !

FWIW, a 5A refrigerator (about what mine draws) comes out to 120Ah per day. Granted, you will probably only have about a 30% duty cycle, but that is still on the order of 30 - 50A for that load alone.

You can guesstimate about 5 - 6A from a good 100w solar panel under good conditions.

With properly large wiring and an intelligent relay you will be able to harvest a lot of amps from a 100A alternator. If you are really going to limit yourself to a 50w solar panel, then I would really tie into the alternator; it is an excellent way to get a 50A - 75A bulk charge, assuming that you drive for an hour or three.

This calculator will help you size your wiring: http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=0.3224&voltage=14&phase=dc&noofconductor=1&distance=15&distanceunit=feet&amperes=100&x=38&y=6

 

[AndrewP]

Thanks Andrew!

Couple of follow-up questions if you don't mind:

1. I understand your point about some sort of large fuse between the battery and the panel (typically a fusible link under the hood, right?), but I was under the impression that was only required when you have a big power producer (aka an alternator) upstream that could go off the reservation and push crazy amounts of amperage into the system if there was no fuse to stop it. I was thinking that since I have no such animal in this system (the panel is the only producer and it's fused) a fusible link or other big fuse wouldn't be necessary?

2. Thanks for the info on the sizing of the fuses. I was under the impression you wanted to size the fuse to just above the downstream load, but I see your point, particularly the choke point that a small fuse would create on a bigger wire. I'm oversizing the wires on purpose to eliminate any heating so no point in choking that. Thanks for that.

3. I was adding the in-line fuse on the solar panel + line between the panel and the controller straight out of the panel installation instructions. Do you think it hurts anything to have it? Once again it's smaller at 5A than the wire capacity at 12awg, but again I was using the formula provided by the panel manufacturer to arrive at that fuse size. Leave it you think?

4. I completely understand your point on the panel, but I am balancing a lot of issues there. What I didn't tell you is that this system is going into a 2015 Subaru Outback expedition setup so I have to balance space/size/weight, etc. against output. I see my usage as 95% the refrigerator at 5.5A and very little water pump and other to be honest. I've had several RV's over the years with battery setups that were not even this good, and even with full "RV usage" I could go quite a while without going bingo by just being reasonable with usage. Granted the frig in the RV's was typically propane, so maybe that will blow up in my face, but I want to get some real-world data based on my system and usage before I go to any next step.

Like I said previously, I can certainly see going to alternator support as well, but there are issues to dig into on that (not the least of which is a 110 Amp alternator) and I would rather limp into this thing and gather some date before I do everything.

Thanks for the input and the conversation, it's MUCH appreciated!

1-Well your impression was incorrect. The battery is capable of supplying way more amperage then your alternator, and it can easily burn down your truck if shorted. Hence, the suggestion to fuse that 2 ga wire at the battery. This is a very standard recommendation and it makes common sense too.

2-This fusing to the load thing seems to be a common misconception, but in reality, you fuse to protect the wire. Besides, later, you may want to use one of those circuits for something else and you'll be prepared and not limited by a fuse that is undersized. Plus, since all your wires are the same size, you can use fuses all the same size and that simplifies spares you need to carry.

3-The fuse between the panel and the charge controller won't hurt anything. Just not needed, but if you've already done it, call it good and take credit!

4-You're going to be undercharging your batteries. Just the way it is. It's very helpful to get a watt meter and measure your refrigerator's 24 hour consumption of power. They can be had for $20 on Amazon and work great. That will tell you what kind of power consumption to plan for in a 24 hour day. 5.5 amps is a hefty draw when you're only putting 2.5 or so back in, and that 's only for 6-7 hours per day on a good day.

I totally agree that it would be easy to add alternator charging capability and with a 100 amp alternator, you have plenty of juice. I also agree that the way to control that charging is with a voltage sensing relay like the Blue Sea 7610. Inexpensive, easy install, very reliable. $70 right now on Amazon-that's $40 off list.

At least add an inexpensive volt meter to your set up so you can see at a glance the voltage of your battery bank. That will give you a reasonable approximation of state of charge.

 

[4x4junkie]

Not only will more panel better keep up with your fridge, it'll also keep your batteries much healthier.
Lead-acid batteries not periodically brought to a full 100% charge eventually die due to sulfation. A 50W panel is unlikely to complete charging by the end of the day with a fridge running off it (yes, a compressor-based fridge consumes far more energy than the DC side of a propane fridge operating on propane).

One of these panels weighs 4 pounds:
http://www.amazon.com/Renogy®-Monocrystalline-Bendable-Solar-Panel/dp/B00IK19VF6

I'd go with two of those panels myself... That would allow much faster recovery of your battery should you encounter a couple cloudy days (set it up as a portable bi-folding setup, this would allow you to follow the sun with it as it moves throughout the day, then fold it up and store it in the vehicle (or strapped to the roof) when you don't need it).

 

[midlifecrisis]

At least add an inexpensive volt meter to your set up so you can see at a glance the voltage of your battery bank. That will give you a reasonable approximation of state of charge.

I had picked up a voltmeter to install, but if I am reading the documentation for the solar controller correctly, I believe it already provides that information on its readout.

 

[IdaSHO]

FYI, most fridge MFG recommend connecting directly the battery, as apposed to going through a fuse panel.

I did this, with an inline fuse as well as an inline switch just for the fridge.

 

[midlifecrisis]

I totally agree that it would be easy to add alternator charging capability and with a 100 amp alternator, you have plenty of juice. I also agree that the way to control that charging is with a voltage sensing relay like the Blue Sea 7610. Inexpensive, easy install, very reliable. $70 right now on Amazon-that's $40 off list.

I went back and looked up the specs and I actually have a 130 amp alternator (6 cylinder as opposed to the 4 I must have pulled the numbers for when I looked previously).

That Blue Sea SI-ACR looks like a great piece of gear, but it only comes in the one size with a continuous rating of 120A (intermittent of 210 amp). So, for another in a long line of stupid questions, does my 130 amp alternator mean I would need a different relay? Or does the alternator only put out that kind of amperage in certain dire circumstances? I apologize if that is ignorant.

A related question, I pulled the wire sizing and fuse sizing numbers on that relay and it is all determined by the charging amps, so back to the question above, how do I make that determination? I've seen threads that simply say "run an 8 awg wire"....

Assuming a wire run distance of <10' from my engine compartment to my aux batteries, what would you think?
Also, the schematic at Blue Sea has big fuses on both + lines between the ACR and each battery and even has a fuse on the ground wire.



So the setup with the alternator charging would look like this?

 

[AndrewP]

The 130 amp alternator would be fine with that ACR. Your Subaru I'm sure takes a minimum of 10 amps to run the car's electronics so you don't need to worry about the relay passing too much current. Besides that, the current flows won't be anywhere near that. Even charging a deeply discharged battery you're maybe looking at 50 amps and that would even be just transient.

I would assume max of 60 amps and while 8 gauge could carry it, you'd be safer with 6 ga or even 4 ga to minimize voltage drop and increase the speed of charging. I'd use 4 ga in your set up and used 2 in mine.

I always figure that any wire attached to a battery (+) needs to be fused in some way. Fuse, breaker, fusible link, all good. You want a safe system when you add on to what is already a safe system.

 

[DiploStrat]

...
A related question, I pulled the wire sizing and fuse sizing numbers on that relay and it is all determined by the charging amps, so back to the question above, how do I make that determination? I've seen threads that simply say "run an 8 awg wire"....

Assuming a wire run distance of <10' from my engine compartment to my aux batteries, what would you think?

What would I think? I think I would use the link I gave you. Using your numbers, 130A alternator, 15 foot run, less than 0.5v drop, you get something like: 15 feet 1/0 AWG wire giving a 0.5v drop at 130A at 14v. The drop will be less as the batteries charge and the amp flow decreases.

See: http://www.calculator.net/voltage-d...nce=15&distanceunit=feet&amperes=130&x=64&y=8

Use these for fuses: https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A Fuse at each end to protect your wire.

You have a lot of folks with real world experience offering to help, but you have to do your bit.

 

[midlifecrisis]

You have a lot of folks with real world experience offering to help, but you have to do your bit.

You know, I really appreciate all of the information and help, but I think this statement is a little uncalled for.

I went to the link you gave me and entered in the information, but without knowing what an "acceptable" voltage drop is, you really can't come to a definitive answer. It's an open ended equation to some degree where a 4 awg wire "works" and so does an 8 awg, depending again on what voltage drop is deemed acceptable. Unless I am reading it wrong, which is probably another good reason to continue asking questions I would think.

Which is why I asked.

If providing answers is a burden please don't waste your time. Believe me, my SOP is to figure things out for myself and I generally do just fine, but I'm also smart enough to know what I don't know.