Solar installation

[dosched]

I have a 210 watt solar panel. Thinking of connecting it to the controller and then going to a buss bar. From there I would connect 2 wires , one for each battery (for some reason the 2 house batteries are on opposite sides of the boat, to be corrected later) and fuse both individual wires. Has anyone done this?

 

[DavidM]

Try to make the wiring distance equal from the controller to each of the two batteries so one doesn't have a lower voltage drop and get all of the charging current. Otherwise, I don't see any problem.

Oh, and the fuses need to be near the batteries, right?

David

 

[koliver]

I have a 210 watt solar panel. Thinking of connecting it to the controller and then going to a buss bar. From there I would connect 2 wires , one for each battery (for some reason the 2 house batteries are on opposite sides of the boat, to be corrected later) and fuse both individual wires. Has anyone done this?

Will this be the interconnection that makes the two separate batteries into a single "house" bank, or is that done somewhere else? If the latter, connect the solar at that connection?

 

[mvweebles]

Try to make the wiring distance equal from the controller to each of the two batteries so one doesn't have a lower voltage drop and get all of the charging current. Otherwise, I don't see any problem.

Oh, and the fuses need to be near the batteries, right?

David

I think prevailing wisdom is circuit protection for the wiring. Fuses should be near controller, not battery.

Rather than run from controller to a bus bar, maybe run to a 25 amp circuit breaker, then run dual leads from that to each battery. Kills two birds with one stone. Anyone see a problem there?

Peter

 

[DavidM]

I think prevailing wisdom is circuit protection for the wiring. Yes, absolutely. Fuses should be near controller, not battery. No, No, No!

Peter

You need to protect the wire from high currents from the battery, not the controller. The current from the controller is absolutely limited by the wattage of the solar panels connected to it. It can never exceed that current. The wire size is such that it is 2 or 3 sizes above what is needed to carry that current.

The batteries OTOH can supply hundreds of amps if that wire is shorted. So you need to put the fuse near the battery. I think ABYC says 6".

Daavid

 

[GoneFarrell]

Check the amps on the 2 wires running to your house batteries when solar charging.

 

[C lectric]

I think prevailing wisdom is circuit protection for the wiring. Fuses should be near controller, not battery.

Rather than run from controller to a bus bar, maybe run to a 25 amp circuit breaker, then run dual leads from that to each battery. Kills two birds with one stone. Anyone see a problem there?

Peter

Sorry but I disagree. THe batteries are the far more dangerous of the two. NOt for long but long enough to cause all kinds of trouble.
Batts. can supply thousands of amps under short circuit conditions. If a short occurs between the charge controller's over current protection [fuse or C.B.]
and the batteries the batteries will fry the wires and maybe cause a fire.
I would expect the wire would disappear. However there is a worse case scenario which includes the wire fry but adds a battery explosion if the short is bad enough.

Best would be protected at both sides for protection for all of it.

 

[SteveK]

Batts. can supply thousands of amps under short circuit conditions.

Can you give an example? I am not getting how a short circuit sends amps upstream past the point of short.

 

[mvweebles]

Hoping an ABYC electrician will chime in. I can see both sides. One being fuse right after the source (low amp solar controller). Can certainly understand the argument for circuit protection nearest largest possible source (battery) even though that would mean a serious reversal of fortunes.

Anyone?

Peter

 

[diver dave]

OCP close to the current source that could supply a high enough current to overheat the wire.

Solar has energy sources at both ends, but only one would need the OCP.

 

[DavidM]

OCP close to the current source that could supply a high enough current to overheat the wire.

Solar has energy sources at both ends, but only one would need the OCP.

Yes, let's take the example of the OP's 210 watt panel to illustrate the point. Assume it is a nominal 12V panel which can produce the most current. It has an Isc value of about 13 amps. That means that it can never ever generate more than 13 amps no matter what the sun, controller or anything is doing. So in this case it may be wired with 10 gauge which is good for 60 amps. So, there is no need to protect that wire.

Some people like a disconnect switch between the controller and the panels so they can work on them and often use a breaker to do that. Fine, but it isn't necessary for over current protection.

Now let's look at the output of the controller. If it is an MPPT controller it will boost the current a bit since the battery voltage during charging is 12-13 volts. So, let's use 12 volts and divide that into 210 watts which gives us about 18 amps. That side will be wired with maybe #8 gauge to limit voltage drop and is good for 80 amps. So, no need for a fuse at its output since the current will never go above the wire's rated current carrying capacity.

Now let's look at the battery. Depending on size and type it can deliver hundreds, maybe thousands of amps of current if it is facing a short to ground. There is no reasonable size wire that can carry that much current, certainly not the #8 gauge it is probably wired with. So, you put a fuse to protect the wire against a short to ground between the fuse and the controller and you mount it within 6" of the battery so there isn't much that can cause a short between it and the battery.

David

 

[SteveK]

OCP close to the current source that could supply a high enough current to overheat the wire.

Solar has energy sources at both ends, but only one would need the OCP.

Overheated wire is more likely to occur than a short when a load source that needs more amps than the wire size is rated to supply. The fuse at source blows. Remember the old days when a penny was added to overcome blowing the fuse.
So the wire size needs to meet the need of the load and fused accordingly at source.

 

[C lectric]

If the positive lead running between the solar controller and the batteries is shorted to ground somehow the solar will only supply what it can supply. A few amps although it still needs protection..

However the other end of that wire is connected to the batteries positive and now you have an unintended ground. THat battery does not care about the controller end of things. It is now grounded between the controller OCP and itself.

In this situation you have two energy sources. One at each end of the wire, not just one energy source. Both need to be fused or otherwise protected.

Of course the current from the short depends upon many variables, battery bank size, the quality of the short and the total resistance back to the battery bank ground.

I am not suggesting the battery will always dump thousands of amps due to those other variables, but it could and it is that you are protecting against.

 

[Ang]

For what it's worth, Victron sample circuit arrangements show protective devices before and downstream of the controller. The diagrams are somewhere on their website, just don't remember where.

 

[foggysail]

You need to protect the wire from high currents from the battery, not the controller. The current from the controller is absolutely limited by the wattage of the solar panels connected to it. It can never exceed that current. The wire size is such that it is 2 or 3 sizes above what is needed to carry that current.

The batteries OTOH can supply hundreds of amps if that wire is shorted. So you need to put the fuse near the battery. I think ABYC says 6".

Daavid

Yes Dave, IMHO you are absolutely correct!!! Solar panels are current sources and have zero problems working directly into a short circuit. ABYC states somewhere a fuse should be 18 inches from the battery negative connection. I do not see the importance for not attaching a fuse to the positive connection. Either will provide protection.

 

[Steve DAntonio]

You must have OCP within 7” of the battery (72” if sheathed), period, no exceptions. So the question is, do you need it in both locations?

Re. the solar panel and regulator, ABYC’s language applies…

11.10.1.1.2 In addition to the provisions of E.11.10.1.1.1 the ungrounded conductors to a battery charger, alternator, or another charging source shall be provided with overcurrent protection within the charging source, or within seven inches (178 mm) of the charging source, based on the maximum output of the device.
EXCEPTION: Self-limiting devices.

11.4.30 Self Limiting Device - a device whose maximum output is restricted to a specified value by its magnetic or electrical characteristics.
NOTES:
1. The output remains at a value or will automatically decrease to a value such that it will not damage the battery charger or inverter/charger after application of a short circuit at the output terminals.
2. The output current will not exceed the ampacity of the conductor that is specified for connection to the battery charger or inverter/charger by the manufacturer.

While there is added resistance for every connection, there is no harm in including OCP at the panels, but strictly speaking, if it meets the above exception, it is unnecessary.

 

[foggysail]

Solar panels are current limited eliminating the need over current protection. Now as to ‘’7 inches’’ from battery to an overload protection device, nonsense! ABYC would be better recommending that protection be as close as reasonably possible to batteries instead issuing ridiculous distances

People should NOT get hung up with ABYC’s rules. They have zero enforcement authority. Yes, their recommendations provide value but remember, there are no laws that I know of as dogma pertaining to this topic. It is better to have some protection some where in the wiring than none.

 

[mvweebles]

Solar panels are current limited eliminating the need over current protection. Now as to ‘’7 inches’’ from battery to an overload protection device, nonsense! ABYC would be better recommending that protection be as close as reasonably possible to batteries instead issuing ridiculous distances

People should NOT get hung up with ABYC’s rules. They have zero enforcement authority. Yes, their recommendations provide value but remember, there are no laws that I know of as dogma pertaining to this topic. It is better to have some protection some where in the wiring than none.

I am a decent shade tree mechanic. Additionally, I have done several down-to-stud remodels of homes and apartments. I appreciate codes and ABYC guidance. Even code inspectors will often use common sense.

7-inches tells me much more than as close as possible. As close as possible could mean several feet. 7-inches tells me damn close.

Bottom line is I may decide to set aside ABYC requirements. But I really appreciate knowing exactly what I am setting aside.

BTW - big thanks to Steve D for contributing, and to DavidM for first calling out that OCP should be near batteries. I learned something today.

Peter

 

[SteveK]

You must have OCP within 7” of the battery (72” if sheathed), period, no exceptions. So the question is, do you need it in both locations?

Re. the solar panel and regulator, ABYC’s language applies…

11.10.1.1.2 In addition to the provisions of E.11.10.1.1.1 the ungrounded conductors to a battery charger, alternator, or another charging source shall be provided with overcurrent protection within the charging source, or within seven inches (178 mm) of the charging source, based on the maximum output of the device.
EXCEPTION: Self-limiting devices.

11.4.30 Self Limiting Device - a device whose maximum output is restricted to a specified value by its magnetic or electrical characteristics.
NOTES:
1. The output remains at a value or will automatically decrease to a value such that it will not damage the battery charger or inverter/charger after application of a short circuit at the output terminals.
2. The output current will not exceed the ampacity of the conductor that is specified for connection to the battery charger or inverter/charger by the manufacturer.

While there is added resistance for every connection, there is no harm in including OCP at the panels, but strictly speaking, if it meets the above exception, it is unnecessary.

Am I misunderstanding this bolded? The solar panel MPPT is the charging source, not the battery. So why is it said to be within 7 inches of the battery.

 

[diver dave]

How did ABYC allow the term “self limiting device”. I’ve worked on output systems on 1.2GW nuke plants. Even those are “self limiting” [emoji15]
Our battery banks have internal R with a more or less fixed V in series.
Maybe the sun itself is not “self limiting”?

 

[diver dave]

If the positive lead running between the solar controller and the batteries is shorted to ground somehow the solar will only supply what it can supply. A few amps although it still needs protection.,,.

Protection from what?? Are you recommending an OCP at the controller?

 

[RT Firefly]

Greetings,
Mr. dd. Oh my. You can't criticize AYBC they're GOD. No, no. You can't. You just can't!


We were looking at a 33/34 Pursuit OS on the weekend and I asked the broker (David) where the capacity plate was. He pointed to the AYBC compliance sticker on the bulkhead and said that it superseded ANY federal rules and regulations. Didn't matter what the government rules were, as long as it had that AYBC sticker it was good to go. He also said I could load as many people as I wanted to on board as long as I had life preservers for them. Hmmmm.....Gosh, I guess he told me.


Turns out that vessels over 20' didn't need a capacity plate. I didn't know this until I looked it up, afterwards.


Needless to say we won't EVER be dealing with him OR Complete Marine in Pompano Beach again. Hey Dave. It's not bad to say you don't know something.

 

[Steve DAntonio]

Solar panels are current limited eliminating the need over current protection. Now as to ‘’7 inches’’ from battery to an overload protection device, nonsense! ABYC would be better recommending that protection be as close as reasonably possible to batteries instead issuing ridiculous distances

People should NOT get hung up with ABYC’s rules. They have zero enforcement authority. Yes, their recommendations provide value but remember, there are no laws that I know of as dogma pertaining to this topic. It is better to have some protection some where in the wiring than none.

As someone who helps write those dogmatic standards; I'm routinely involved in building vessels that meet them, and inspecting vessels to ensure compliance, I beg to differ. (I spent 4 hours on a Zoom call just today participating in an ABYC Project Technical Committee, refining electrical standards, the committee is made up of some of the most learned and respected members of the professional marine electrical community in the world).

"They have zero enforcement authority." Nonsense. All gasoline powered recreational vessels under 65 feet sold in the US are subject to the CFR for electrical and fuel systems, which mimic ABYC Standards. Perhaps not "dogma" but it is indeed the law.

"It is better to have some protection some where in the wiring than none." That's like saying an aircraft with one wing is better than an aircraft with no wings. To borrow a phrase from the real estate industry, location is everything where OCP is concerned, the closer to the power source the better, every inch between a power source and OCP is unprotected and a short-circuit and fire risk. OCP located at the appliance rather than at the source of power is all but useless.

OCP must be installed no more than 7" from a battery. Having installed or supervised the installation of hundreds of over current protection devices, this is entirely reasonable when one considers the bulk of the average 100-450 amp fuse holder and the space needed to install it. Even off the shelf 15 amp fuse holders come with 7" pigtails.

While I'm not a knee-jerk adherent to every ABYC Standard (even ABYC describes it as the floor, not the ceiling), the standards have undoubtedly been making boat ownership safer, and boats more reliable for nearly seven decades.

 

[Steve DAntonio]

Yes Dave, IMHO you are absolutely correct!!! Solar panels are current sources and have zero problems working directly into a short circuit. ABYC states somewhere a fuse should be 18 inches from the battery negative connection. I do not see the importance for not attaching a fuse to the positive connection. Either will provide protection.

ABYC calls for OCP to be installed 7" from the battery, or 72" if sheathed, and no more than 7" (40" if sheathed) from a battery, switch, starter post or similar distribution point. ABYC also mandates that OCP be installed in ungrounded, i.e. positive, conductors. OCP can be installed in both conductors, but never in just the negative conductor.

Here's the exact verbiage...

11.10.1.1.1 Overcurrent Protection Device Location - Ungrounded conductors shall be provided with overcurrent protection device(s) within a distance of seven inches (178 mm) of the point at which the conductor is connected to the source of power measured along the conductor (see FIGURE 8).
EXCEPTIONS:
1. Cranking motor conductors.
2. If the conductor is connected directly to the battery terminal and is contained throughout its entire distance in a sheath or enclosure such as a conduit, junction box, control box, or enclosed panel, the overcurrent protection shall be placed as close as practicable to the battery, but not to exceed 72 in (183 cm).
3. If the conductor is connected to a source of power other than a battery terminal and is contained throughout its entire distance in a sheath or enclosure such as a conduit, junction box, control box, or enclosed panel, the overcurrent protection shall be placed as close as practicable to the point of connection to the source of power, but not to exceed 40 in (102 cm).
4. Overcurrent protection is not required in conductors from self-limiting alternators with integral regulators if the conductor is less than 40 in (102 cm), is connected to a source of power other than the battery, and is contained throughout its entire distance in a sheath or enclosure.
5. Overcurrent protection is not required at an alternator if the ampacity of the conductor is equal to or greater than the rated output of the alternator.
6. Pigtails less than seven inches (178 mm) are exempt from overcurrent protection requirements.
NOTES:
1. Multiple main overcurrent protection devices may be connected to a common busbar connected directly to the source of power.
2. If the DC electrical distribution system is not connected as a grounded system per E-11.5.2.3, then both the positive and the negative DC conductors are ungrounded conductors.

 

[SteveK]

You must have OCP within 7” of the battery (72” if sheathed), period, no exceptions. So the question is, do you need it in both locations?

Re. the solar panel and regulator, ABYC’s language applies…

11.10.1.1.2 In addition to the provisions of E.11.10.1.1.1 the ungrounded conductors to a battery charger, alternator, or another charging source shall be provided with overcurrent protection within the charging source, or within seven inches (178 mm) of the charging source, based on the maximum output of the device.
EXCEPTION: Self-limiting devices.
......

Am I misunderstanding this bolded? The solar panel MPPT is the charging source, not the battery. So why is it said to be within 7 inches of the battery.

.
................

OCP must be installed no more than 7" from a battery. Having installed or supervised the installation of hundreds of over current protection devices, this is entirely reasonable when one considers the bulk of the average 100-450 amp fuse holder and the space needed to install it. Even off the shelf 15 amp fuse holders come with 7" pigtails.

......

I will ask again for clarification.
The source of charge is not the battery for the purposes of this thread. The ABYC suggestion you quoted says 7" from charger, you are saying 7" from battery.

 

[mvweebles]

I will ask again for clarification.

The source of charge is not the battery for the purposes of this thread. The ABYC suggestion you quoted says 7" from charger, you are saying 7" from battery.

My read is 7-inch from battery is absolute (unless shielded). Nothing needed in MPPT as it is internally limited.

At risk of another thread detour, what is shielded battery cable? Provides 10x distance protection.

Peter

 

[catalinajack]

Another divergence but an important question in my mind. Steve D said:

"5. Overcurrent protection is not required at an alternator if the ampacity of the conductor is equal to or greater than the rated output of the alternator."

My alternator feed is fused at the battery. The alternators are rated at 100 amps. How large should the fuse be? Can the fuse be eliminated if the ampacity of the wire is large enough. I am interpreting this provsion as so.

 

[DavidM]

#6 gauge wire has an ampacity of 120 amps. So if the alternator is wired with #6 or greater then you don't need a fuse at the battery. Also you may need bigger than #6 wire to limit voltage drop if it is a long run to the battery.

FWIW many swap out the OEM alternator for a high output one and forget to increase the wire gauge to handle the increased current that it can deliver.

David

David

 

[Steve DAntonio]

I will ask again for clarification.
The source of charge is not the battery for the purposes of this thread. The ABYC suggestion you quoted says 7" from charger, you are saying 7" from battery.

Only necessary if it does not meet the exception...

 

[Steve DAntonio]

My read is 7-inch from battery is absolute (unless shielded). Nothing needed in MPPT as it is internally limited.

At risk of another thread detour, what is shielded battery cable? Provides 10x distance protection.

Peter

Sheathed, not shielded. Sheathing can be almost anything that protects the wire, including electrical tape (not a detail within the standard with which I agree) but in most cases is flame retardant split loom, or a conduit.