100w System - Newbie - Diagram Design Review

[Jeepskate]

All, this is my first simple off-grid system, and I had a few questions, and a diagram to reference to help paint a better picture.

1) Solar panel to CC

a) Add circuit breakers at all ?
b) Add to both poles ?
c) Fuse type ?
d) Fuse amperage ?

2) CC to Battery - (dual fuse, on both poles)
a) Fuse type ?
b) Fuse amperage ?

3) Battery to Inverter - (dual fuse, on both poles)
a) Fuse type ?
b) Fuse amperage ?

4) Overall design review, if other things stick-out as a problem

thanks much

[daz]

First off....Welcome To Solar Panel Talk!

All, this is my first simple off-grid system, and I had a few questions, and a diagram to reference to help paint a better picture.

It would be better to post this question in the relevant forum (eg the off-grid section), as you may get a better response to your question. This part of the forum is for new members to introduce themselves, and not everyone looks at this part of the forum.

4) Overall design review, if other things stick-out as a problem

While we are here....
Your battery is a bit on the large side for a 100W panel. What are your power requirements (your daily WH usage) that you need from this setup? Is this just a backup system for outages?

[ILFE]

All, this is my first simple off-grid system, and I had a few questions, and a diagram to reference to help paint a better picture.

1) Solar panel to CC

a) Add circuit breakers at all ?
b) Add to both poles ?
c) Fuse type ?
d) Fuse amperage ?

2) CC to Battery - (dual fuse, on both poles)
a) Fuse type ?
b) Fuse amperage ?

3) Battery to Inverter - (dual fuse, on both poles)
a) Fuse type ?
b) Fuse amperage ?

4) Overall design review, if other things stick-out as a problem

thanks much

1. Your breaker coming from that single panel should be about 1.56 times the rated source amperes. So, you would need a single 9 amp breaker. Wire it on the positive side wire. Although, keep in mind, the real reason for adding a breaker between a single panel and the controller is to use it as a switch to disconnect the panel from the controller.

Personally, I would go with #10 AWG over a 40 feet long run (round trip wiring) from a panel to a controller. I would only run #12 AWG up to 40 feet. Oh, that panel will never generate enough power to overload a #10 AWG wire at that length of a run. You need to keep in mind your voltage drop over the course of the entire run of wire. When running smaller arrays, this is extremely important.


2. The controller will be rated in amperes. They are not rated in watts. So, according to your diagram, you have a 30 ampere rated controller. The breaker protection between your controller and the battery bank should be no larger than 30 amperes, as that is the maximum rated output of the controller. Again, wire circuit protection only on the positive side between the controller and battery. Place the breaker as close to the battery as is reasonably possible.


3. Between the battery and the inverter, #6 AWG will be fine. I am figuring for 800 watts, 70 amperes, at 12vdc here. If you have it already, #4 AWG is certainly fine as well. I would put a Blue Sea fuse rated for 70 amperes on #6 AWG wire, or 80 amperes on #4 AWG wire.

--------------------------

Just my thought here. But, if you were to go with two panels in series and change your PWM controller for an MPPT controller, you will be much better off. Going with an MPPT controller, you can increase the voltage output of the array, by wiring the panels in series, while maintaining only a 12v battery system. Good stuff!

Of course, Jeepskate, if you were to buy a second panel, that is a game changer for some of the information I posted above.

[daz]

A bit on the small side? I was thinking the battery is too large for a single 100 watts panel.

Aaaaaah. Thanks for pointing that out, I just saw that now! It was supposed to say the panel is a bit on the small side for that size battery....see what happens when I try type/think so early in the morning?! haha

I will edit my post now....kudos for spotting!

[ILFE]

No worries. I deleted your quoted text too. No need to leave it afterward.

[Jeepskate]

1. Your breaker coming from that single panel should be about 1.56 times the rated source amperes. So, you would need a single 9 amp breaker. Wire it on the positive side wire. Although, keep in mind, the real reason for adding a breaker between a single panel and the controller is to use it as a switch to disconnect the panel from the controller.

Personally, I would go with #10 AWG over a 40 feet long run (round trip wiring) from a panel to a controller. I would only run #12 AWG up to 40 feet. Oh, that panel will never generate enough power to overload a #10 AWG wire at that length of a run. You need to keep in mind your voltage drop over the course of the entire run of wire. When running smaller arrays, this is extremely important.


2. The controller will be rated in amperes. They are not rated in watts. So, according to your diagram, you have a 30 ampere rated controller. The breaker protection between your controller and the battery bank should be no larger than 30 amperes, as that is the maximum rated output of the controller. Again, wire circuit protection only on the positive side between the controller and battery. Place the breaker as close to the battery as is reasonably possible.


3. Between the battery and the inverter, #6 AWG will be fine. I am figuring for 800 watts, 70 amperes, at 12vdc here. If you have it already, #4 AWG is certainly fine as well. I would put a Blue Sea fuse rated for 70 amperes on #6 AWG wire, or 80 amperes on #4 AWG wire.

--------------------------

Just my thought here. But, if you were to go with two panels in series and change your PWM controller for an MPPT controller, you will be much better off. Going with an MPPT controller, you can increase the voltage output of the array, by wiring the panels in series, while maintaining only a 12v battery system. Good stuff!

Of course, Jeepskate, if you were to buy a second panel, that is a game changer for some of the information I posted above.

Thanks daz and livingincebu !

livingincebu, let me work on version 2.0 diagram with a 2nd solar panel, and tune based upon your good input, and then get a second review (as the battery is already purchased.)

One clarification though... I see on the forum that it is recommended to fuse both + and - sides with the system is floating and not grounded, thats why I show fuses on both poles...Your thoughts there ?___ is it better to ground one side and have a single poled fuse systems or if not don't I need fuses on both poles ?___

Regards,
Jeepskate

[ILFE]

Thanks daz and livingincebu !One clarification though... I see on the forum that it is recommended to fuse both + and - sides with the system is floating and not grounded, thats why I show fuses on both poles...Your thoughts there ?___ is it better to ground one side and have a single poled fuse systems or if not don't I need fuses on both poles ?___

Why would you not ground the system, though? If mobile, I would ground it to the chassis of the vehicle. If permanent, ground it in accordance with local electric codes.

With that said, as a former amateur radio operator (I gave up my license years ago), I used to buy new equipment that had fuses on both legs, primarily to protect against reverse polarity. In my mind, that would be the only reason to do that. Again, I'm sure someone with more experience can post their opinion here as well. If, for whatever reason(s) you choose to put circuit protection on both legs, do go with the same size fuse on each side.

[Jeepskate]

Why would you not ground the system, though? If mobile, I would ground it to the chassis of the vehicle. If permanent, ground it in accordance with local electric codes.

With that said, as a former amateur radio operator (I gave up my license years ago), I used to buy new equipment that had fuses on both legs, primarily to protect against reverse polarity. In my mind, that would be the only reason to do that. Again, I'm sure someone with more experience can post their opinion here as well. If, for whatever reason(s) you choose to put circuit protection on both legs, do go with the same size fuse on each side.

Makes sense, thanks livingincebu.

[Mike90250]

I used to buy new equipment that had fuses on both legs, primarily to protect against reverse polarity.

Fuses only blow from excess amps. (or age, vibration, thermal shock)

Reverse Protection Diodes force a fuse to blow, if the device gets wired backwards.

[ILFE]

Jeepskate,

Here is my suggested wiring diagram. Of course, an inverter would be connected directly to the battery.
200.watts.gif

NOTE: If you run the breakers through a combiner box, it will have bus bars for grounding.

Fuses only blow from excess amps. (or age, vibration, thermal shock)

Reverse Protection Diodes force a fuse to blow, if the device gets wired backwards.

I'm not sure I follow you, Are you saying that, without RPD, a fuse (on both legs of the circuit) would not help protect a circuit from a reverse polarity connection?

[Jeepskate]

Jeepskate,

Here is my suggested wiring diagram. Of course, an inverter would be connected directly to the battery.
[ATTACH=CONFIG]4615[/ATTACH]

NOTE: If you run the breakers through a combiner box, it will have bus bars for grounding.

Thanks for the diagram livingincebu. One question...since the panels are in series, wouldn't if be at 12 volts and now need a 19am fuse ?

[ILFE]

Thanks for the diagram livingincebu. One question...since the panels are in series, wouldn't if be at 12 volts and now need a 19am fuse ?

No. Voltage will double to 24vdc on the modules, but amperes will remain the same, to the controller.

Like I said though, it has to be an MPPT controller in order to run your panels in series while charging a 12vdc battery. A PWM controller would not work the same way. You would have to run the modules in parallel. Then, it would be 12v and double your amperes.

[Jeepskate]

No. Voltage will double to 24vdc on the modules, but amperes will remain the same, to the controller.

Like I said though, it has to be an MPPT controller in order to run your panels in series while charging a 12vdc battery. A PWM controller would not work the same way. You would have to run the modules in parallel. Then, it would be 12v and double your amperes.

Got it....thanks...... I guess that also means doubling the voltage (versus the current) is a better way to charge the battery ?

[ILFE]

Got it....thanks...... I guess that also means doubling the voltage (versus the current) is a better way to charge the battery ?

An MPPT controller will do more than just charge from a higher voltage. It will turn unused volts into amperes to put into your battery. It will down convert to 12volts for the battery. So, it will still put more amperes into it as well.

In simple terms, it's more efficient than a PWM controller.

[Jeepskate]

An MPPT controller will do more than just charge from a higher voltage. It will turn unused volts into amperes to put into your battery. It will down convert to 12volts for the battery. So, it will still put more amperes into it as well.

In simple terms, it's more efficient than a PWM controller.

Ok...I have weaved all this good info back into my ver 2.0 diagram...for your review

Open questions
1) MPPT controller amperage
2) Fuse amperage battery to Inverter