Solar Charging Circuit Breaker(s) - Amp Rating?

[Great Eggstrications]

I apologize for starting a new thread when I maybe really didn't need to, but I already looked through the relevant threads and didn't find a discussion of my bone-headed simple case.

I have the old 160-watt panel that was formerly used by Escape, combined with a Samlex SCC-30-AB 30 amp (PWM) controller - single panel, no portable panel so no combiner, real simple case. I'm finally getting around to doing the low-priority easily-put-off stuff to the trailer and next up on the list is circuit breaker protection for the solar charging circuit and to be able to easily disconnect the panel when needed. Poking around here and on the interwebs, it seems like the hot setup is to install one breaker between the panel and the controller and a second breaker on the output side of the controller.

So the question is: What current ratings should the breakers be? I saw on the web that one could simply match the controller's rating, which would be 30 amps. Is it really that straightforward? I assume for both breakers?

I see these on Amazon:

https://www.amazon.com/Miniature-Cir...85&sr=1-5&th=1

They look pretty good - at least not many bad reviews - and I certainly don't need the fancy-schmancy water-proof ones for $58 each.

Thoughts?

Thanks...

P.S. I'm one of those wishy-washy software guys (not hardware) and I know about V=I*R and W=A*V and all that, but I appeal to the electronical gurus amongst you in hopes of getting reliable information and avoiding flying sparks (or worse).

[Brian B-P]

With no reason at all for overcurrent protection between the panel and the controller, an infinitely high breaker rating is fine. Anything comfortably over the maximum short-circuit current of the panel is high enough, so the breaker will never trip and it will work for the purpose.

The PWM controller is incapable of putting out more current than supplied to the input, so the same sizing logic applies there.

On both sides, an underlying assumption is that the wire size is sufficient to safely carry the panel's short-circuit current (Isc). Breakers exist to prevent excessive current in wires. Isc is only about 15 amps for that panel, and the wiring should be heavier than 14 gauge, so this shouldn't be an issue. On both sides, if wiring is so small that it can't handle Isc, then breakers are actually needed for safe operation, and should be sized to not exceed wire capacity.

[RangerMan]

Originally Posted by Great Eggstrications

I apologize for starting a new thread when I maybe really didn't need to, but I already looked through the relevant threads and didn't find a discussion of my bone-headed simple case.

I have the old 160-watt panel that was formerly used by Escape, combined with a Samlex SCC-30-AB 30 amp (PWM) controller - single panel, no portable panel so no combiner, real simple case. I'm finally getting around to doing the low-priority easily-put-off stuff to the trailer and next up on the list is circuit breaker protection for the solar charging circuit and to be able to easily disconnect the panel when needed. Poking around here and on the interwebs, it seems like the hot setup is to install one breaker between the panel and the controller and a second breaker on the output side of the controller.

So the question is: What current ratings should the breakers be? I saw on the web that one could simply match the controller's rating, which would be 30 amps. Is it really that straightforward? I assume for both breakers?

I see these on Amazon:

https://www.amazon.com/Miniature-Cir...85&sr=1-5&th=1

They look pretty good - at least not many bad reviews - and I certainly don't need the fancy-schmancy water-proof ones for $58 each.

Thoughts?

Thanks...

P.S. I'm one of those wishy-washy software guys (not hardware) and I know about V=I*R and W=A*V and all that, but I appeal to the electronical gurus amongst you in hopes of getting reliable information and avoiding flying sparks (or worse).

I installed a Blue Seas 50amp breaker/on-off switch between the panel and controller. 50amps is large enough. I didn't bother with a switch between the controller and battery. Can't think of why I would want to, but it's very easy to just pull the wire from the controller if I should want to disconnect there.

[Vermilye]

Originally Posted by RangerMan

I installed a Blue Seas 50amp breaker/on-off switch between the panel and controller. 50amps is large enough. I didn't bother with a switch between the controller and battery. Can't think of why I would want to, but it's very easy to just pull the wire from the controller if I should want to disconnect there.

The reason for a fuse or breaker between the controller & the battery is to protect the wiring, and as Brian noted, it should be sized to protect the wire. While unlikely, if you have a fault to ground it would dump the entire batteries capacity through the wire. Since any of our battery systems have the capability of providing 100's of amps, any reasonable sized wire needs protection. Again, unlikely, but not impossible.

[alanmalk]

Originally Posted by Vermilye

...
Again, unlikely, but not impossible.

Unlikely, yes. Improbable, not so much. Catastrophic, absolutely.


For example, you load up your compartment with tuna (or worse, Van Camp Pork & Beans). You drive down a washboard road and a can rubs against a wire connecting "X" to the battery. The can breaks the insulation and you have a short circuit with the battery dumping 100's of amps and the wire glows red hot. That is precisely when you wish you had installed a proper size circuit breaker on that wire as close to the battery as reasonably possible.


As mentioned above, proper size is small enough to protect the wire but big enough to not to have "nuisance" trips. For a 30 amp controller, a 30 amp breaker is probably just right.

[RangerMan]

Originally Posted by Vermilye

The reason for a fuse or breaker between the controller & the battery is to protect the wiring, and as Brian noted, it should be sized to protect the wire. While unlikely, if you have a fault to ground it would dump the entire batteries capacity through the wire. Since any of our battery systems have the capability of providing 100's of amps, any reasonable sized wire needs protection. Again, unlikely, but not impossible.

Now I can think of a reason I would want to do that. I had switch on the brain as opposed to a breaker or fuse.

Ground fault protection didn't occur to me. I'll stick a fuse in there. Probably 50a.

[Brian B-P]

Originally Posted by Vermilye

The reason for a fuse or breaker between the controller & the battery is to protect the wiring, and as Brian noted, it should be sized to protect the wire. While unlikely, if you have a fault to ground it would dump the entire batteries capacity through the wire. Since any of our battery systems have the capability of providing 100's of amps, any reasonable sized wire needs protection. Again, unlikely, but not impossible.

That brings up a good point: overcurrent protection should be provided for each source of current, and between the solar charge controller and battery both ends are potential sources. The charge controller is unable to drive more current than any reasonable wiring can handle, so the source of concern to me is the other end of the wire.

Originally Posted by alanmalk

For example, you load up your compartment with tuna (or worse, Van Camp Pork & Beans). You drive down a washboard road and a can rubs against a wire connecting "X" to the battery. The can breaks the insulation and you have a short circuit with the battery dumping 100's of amps and the wire glows red hot.

That's an excellent argument for properly constructed equipment and storage compartments, not storage tossed in with unprotected equipment. Reality includes these unfortunately setups.

The pork & beans are better, in a way, because they should be heated up to eat, unlike the tuna.

Originally Posted by alanmalk

That is precisely when you wish you had installed a proper size circuit breaker on that wire as close to the battery as reasonably possible.

That brings up another good point: overcurrent protection should be close to each source of current, and between the solar charge controller and battery both ends are potential sources so that's two possible locations... with only the battery end being required in my opinion.

Originally Posted by RangerMan

Now I can think of a reason I would want to do that. I had switch on the brain as opposed to a breaker or fuse.

I think that I would stay with a switch as the disconnect, and separately a fuse at the battery, unless I found solar charging disconnects physically located adjacent to the battery to be convenient.

[Brian B-P]

I'm not at all sure why most people insist on switching and even overcurrent protecting both polarities of the solar charging system, but only the positive side of everything else. It could be argued that the panel to controller connection is - as it should be - floating (neither side connected to chassis "ground"), but even that doesn't apply to the controller to battery connection.

Electric vehicles do switch and fuse both polarities of the high voltage battery, but those batteries are floating and we're not talking about hundreds of volts in the solar system.

[Great Eggstrications]

A hearty "Thanks" to everyone that chimed in with their considered thoughts.

I got a couple of 40 amp breakers/switches and some 8 gauge wire (it looks substantially bigger gauge than the original Escape-installed wires although maybe the multitude of strands bloat it up somewhat?) from Amazon

https://www.amazon.com/dp/B09BQP924P...roduct_details

https://www.amazon.com/dp/B01A45YFME...t_details&th=1

but note that the wires are apparently made up of many many (1650!) very very small tinned copper strands - not the usual maybe 8 or 10 or 12 larger strands - so a couple of final questions...

The fine stranded wires are tinned, which according to what I'm seeing on the interwebs is largely done to forestall surface corrosion, and is reputed to have no deleterious effect on conductivity. Does this sound correct to you guys? I'd always thought that tin was an alloy of some sort - turns out it's actually a chemical element itself.

I know that some people advocate using crimp- or solder-on ferrules for compressive clampy-screwy connections. Would it be a good idea to use them here, especially considering the very fine strands? Or maybe just solder the exposed strands together before clamping? Any ideas?

Thanks...

And hopefully alanmalk will be a responsible Escape trailer owner and keep his wayward canned comestibles far away from our wiring and plumbing systems!

[MVA]

Originally Posted by Great Eggstrications

A hearty "Thanks" to everyone that chimed in with their considered thoughts.

I got a couple of 40 amp breakers/switches and some 8 gauge wire (it looks substantially bigger gauge than the original Escape-installed wires although maybe the multitude of strands bloat it up somewhat?) from Amazon

https://www.amazon.com/dp/B09BQP924P...roduct_details

https://www.amazon.com/dp/B01A45YFME...t_details&th=1

but note that the wires are apparently made up of many many (1650!) very very small tinned copper strands - not the usual maybe 8 or 10 or 12 larger strands - so a couple of final questions...

The fine stranded wires are tinned, which according to what I'm seeing on the interwebs is largely done to forestall surface corrosion, and is reputed to have no deleterious effect on conductivity. Does this sound correct to you guys? I'd always thought that tin was an alloy of some sort - turns out it's actually a chemical element itself.

I know that some people advocate using crimp- or solder-on ferrules for compressive clampy-screwy connections. Would it be a good idea to use them here, especially considering the very fine strands? Or maybe just solder the exposed strands together before clamping? Any ideas?

Thanks...

And hopefully alanmalk will be a responsible Escape trailer owner and keep his wayward canned comestibles far away from our wiring and plumbing systems!

For cables with greater than 10 awg thickness (i.e., 8 awg and lower) I decided not to bother with getting my own hydraulic crimper, lugs in multiple ring sizes, heat shrink tubing, red/black cables in multiple sizes, etc. I was able to purchase for a very fair price professional custom built cables with the end lug sizes and cable awg sizes I needed. There are a number of vendors that will make cables to your spec; I have been happy with Battery Cables USA. They offer cables for both marine environment and not. I usually get them within 3 days after placing an order. Rarely am I this satisfied with a vender.

For 10 awg and smaller sized wire, I use a ratcheting crimper.

BTW - your confusion on tin being an alloy may be from what some call tin solder, which is an alloy of tin and lead elements, or sometimes tin, silver, copper.

2 cents

[Brian B-P]

Originally Posted by Great Eggstrications

... some 8 gauge wire (it looks substantially bigger gauge than the original Escape-installed wires although maybe the multitude of strands bloat it up somewhat?)

The number of strands shouldn't affect the bulk significantly - round strands still pack together the same regardless of scale.

Originally Posted by Great Eggstrications

The fine stranded wires are tinned, which according to what I'm seeing on the interwebs is largely done to forestall surface corrosion, and is reputed to have no deleterious effect on conductivity. Does this sound correct to you guys?

Yes, that's right.

Note that ferrules and crimp-on terminals are normally tin-plated copper, for the same reason.

Originally Posted by Great Eggstrications

I know that some people advocate using crimp- or solder-on ferrules for compressive clampy-screwy connections. Would it be a good idea to use them here, especially considering the very fine strands? Or maybe just solder the exposed strands together before clamping? Any ideas?

I've never seen ferrules used in this sort of application before Charles showed them today, but they seem like a good idea. More commonly stranded wires are capped with a spade, ring, or pin terminal which serves the same purpose (of keeping strands together) for different styles of connections.
This seems like a good and clear discussion of the use of ferrules to me (from a somewhat strange source for trailer wiring information):
Hackaday: To Ferrule Or Not To Ferrule

Soldering is the usual alternative for the same purpose, and (just to confuse things a bit more ) is often called "tinning" (just because tin is the major element in the composition of solder). Don't overdo the solder - it's not as good as direct contact of copper strands to the terminal, and it can flow over time causing the connection to loosen. Just coating the strands and sticking them together is all you want, not making a big glob.

[alanmalk]

Originally Posted by Great Eggstrications

...
And hopefully alanmalk will be a responsible Escape trailer owner and keep his wayward canned comestibles far away from our wiring and plumbing systems!

I promise to keep the beer far away. No promises regarding tuna fish.

And since you asked, I use solder to merge the strands into one piece. Primarily because I'm cheap and never have the correct connectors nor a proper crimper. But I do have a butane soldering iron for field work.

[John in Santa Cruz]

I tried a hydraulic crimper, and found it somewhat annoying to use.

instead, I'm using this mechanical crimper which does 8 up to 1/0. so far I've just used it on 4,6, 8, and its worked great for those.
https://www.amazon.com/gp/product/B00MVE48Z6

I can hold the wire with one hand firmly in the crimp, lean one handle against my lap or belly, then compress the other handle with my other hand, and get solid crimps in all sorts of positions.



I also got this kit of crimp on ring terminals, for 8,6,4,2 ga, with 1/4, 5/16, and 3/8" holes in each size.
https://www.amazon.com/gp/product/B083QBQKC5/

I found I've used a lot of specific sizes, so I've restocked those sizes from these, https://www.amazon.com/gp/product/B07J2WQ4B1 (and the various other sizes there)

[Great Eggstrications]

Originally Posted by alanmalk

I promise to keep the beer far away. No promises regarding tuna fish.

Thanks, but you'll notice that I specifically and deliberately addressed canned comestibles - not a word about adult beverages. The latter would certainly constitute an acceptable risk:benefit ratio.

Originally Posted by Brian B-P

I've never seen ferrules used in this sort of application before Charles showed them today, but they seem like a good idea. More commonly stranded wires are capped with a spade, ring, or pin terminal which serves the same purpose (of keeping strands together) for different styles of connections.
This seems like a good and clear discussion of the use of ferrules to me (from a somewhat strange source for trailer wiring information): Hackaday: To Ferrule Or Not To Ferrule

I ordered this from Amazon

https://www.amazon.com/dp/B09724DCJH...roduct_details

Haven't used it yet, but it looks like good quality. No bad reviews anyhow.

Thanks for the Hackaday link - a nice in-depth discussion of ferrule usage. I was somewhat concerned about just using bare stranded wire, even if soldered into a nice firm bundle, given the possibility of damage to the extremely fine strands of the tinned copper wire that I ended up with. The tinned copped wire and the solder would still be pretty soft and mushy, and likely be easily messed up.

And some interesting Arduino stuff.

And - be still my heart!!! - a link to a modern Pi-based 2:3 scale PDP-8 look-alike/work-alike

https://hackaday.com/2015/03/26/hack...-raspberry-pi/

bringing back some fond memories of my first foray into assembly language programming - running a PDP-8 assembler simulator on a CDC-6400 Super-(for-its-time)-Computer in the late 1970's - punch card input using an IBM 029 card punch machine. Making a smart CPU act dumb again. Breaks my heart to remember seeing working PDP-8's at the Boeing Surplus store in the 1980's for dirt cheap prices. Spouse said "That's not coming into the house - not even the garage".

[HarleyD]

Ahhh yes!
SLDL was my fav. Also the whole realm of AND/OR.
Got my 'green card' right here.

[DGLP]

Originally Posted by Brian B-P

The number of strands shouldn't affect the bulk significantly - round strands still pack together the same regardless of scale.


Yes, that's right.

Note that ferrules and crimp-on terminals are normally tin-plated copper, for the same reason.


I've never seen ferrules used in this sort of application before Charles showed them today, but they seem like a good idea. More commonly stranded wires are capped with a spade, ring, or pin terminal which serves the same purpose (of keeping strands together) for different styles of connections.
This seems like a good and clear discussion of the use of ferrules to me (from a somewhat strange source for trailer wiring information):
Hackaday: To Ferrule Or Not To Ferrule

Soldering is the usual alternative for the same purpose, and (just to confuse things a bit more ) is often called "tinning" (just because tin is the major element in the composition of solder). Don't overdo the solder - it's not as good as direct contact of copper strands to the terminal, and it can flow over time causing the connection to loosen. Just coating the strands and sticking them together is all you want, not making a big glob.

Hi,

I am new to the forum. We have purchased an Escape 21 NE and plan to have it delivered to Oregon in early May for pick-up. The trailer has the full solar package. Given my limited understanding of all things electrical, I have followed numerous threads in the forum on matters pertaining to electrical systems and solar, in particular, with the hope of compiling and organizing the many useful tips I’ve found. The comments and recommendations made by a number of senior members are much appreciated. However, I’ve found some of the material to be rather esoteric. In an effort to develop a knowledge base that extends beyond my 11th grade physics, I’ve gone through “RV Electrical Systems” by Bill and Jan Moeller (which is dated), “Off Grid Solar” by O’Connor and “Mobile Solar Power Made Easy” by Prowse. Do you have any recommendations for other references? I’m thinking in terms of “nuts and bolts” information regarding wiring, fuses, breakers, converters and such for trailers and solar, in particular.

Given the shortcomings (pardon the pun) of the electrical components I’ve checked in our home, including the ceiling fan speed controls (photo attached), I want to become well versed in understanding electrical systems and troubleshooting electrical issues. I’ve replaced three of the fan speed controls, which were installed by a professional/licensed electrician. I’ve also replaced many of the outlets and light switches with push-in wire connectors, also installed by the same electrician. A few of the outlets and switches had cracked on the connector side, leaving bare wires exposed. In other outlets and switches, wires had loosened to the point where the connectors no longer provided any grip at all and the wires slipped out with no effort.

I’ve recently purchased a Fluke 115 multimeter for the home and trailer, which I hope will prove useful. It replaces an old Heathkit multimeter that has been gathering dust in the basement for some time. For the trailer specifically, I’ve purchased a Victron MPPT solar charge controller and a BMV-712 battery monitor based recommendations made in numerous threads on this forum.

Thank you again for your advice.

Darrell

[Centex]

Originally Posted by DGLP

Do you have any recommendations for other references?

Darrell - a resource you may find of interest: Wiring Unlimited - Victron Energy (<link is to Victron PDF document download url)

Welcome to ‘Wiring unlimited’, a book about electrical wiring of systems containing batteries, inverters, charger and inverter/chargers. With this book we aim to explain wiring basics of electrical systems. We will explain the importance of ‘getting it right’ and the issues that might result if a system has inferior wiring.

Other somewhat more esoteric but often interesting reading is found at this Victron Technical Information Downloads webpage.

Have Fun!

[DGLP]

Excellent, thanks Alan!

[tdf-texas]

Originally Posted by Centex

Darrell - a resource you may find of interest: Wiring Unlimited - Victron Energy (<link is to Victron PDF document download url)

Welcome to ‘Wiring unlimited’, a book about electrical wiring of systems containing batteries, inverters, charger and inverter/chargers. With this book we aim to explain wiring basics of electrical systems. We will explain the importance of ‘getting it right’ and the issues that might result if a system has inferior wiring.

Other somewhat more esoteric but often interesting reading is found at this Victron Technical Information Downloads webpage.

Have Fun!

Thanks Allen! The "Wiring Unlimited - Victron Energy" pdf covers almost all of the stuff I was taught in first year EE classes but better organized and written.

I saved a copy for reference.

[John in Santa Cruz]

Originally Posted by Vermilye

The reason for a fuse or breaker between the controller & the battery is to protect the wiring, and as Brian noted, it should be sized to protect the wire. While unlikely, if you have a fault to ground it would dump the entire batteries capacity through the wire. Since any of our battery systems have the capability of providing 100's of amps, any reasonable sized wire needs protection. Again, unlikely, but not impossible.

my BATTERIES have 100A ANL fuses inline, this will protect against shorts. I wired each battery with AWG 4 welding cable to its own 100A fuse, then paralleled those at my main positive bus bar. the two batteries ground wires are tied together at the SmartShunt battery monitor, and that smartshunt goes to the main negative bus bar. crude schematic, not quite final as I ended up using one fuse for each battery (and in this schematic, I used the 2nd fuse as a 'placeholder' for the smartshunt)



my solar panels have a 250A rated (overkill) disconnect switch on the positive wire between them and the solar controller, this is purely so I can shut off the solar if I'm working on the battery wiring, OR if I want to disable solar charging for whatever reasons.