Questions about fusing and grounding my solar.

[BigT]

Yes, I did a search before posting this.  Yes, I did find tons of useful information.  Yes, I'm asking my questions anyway. 

I was going to ask what Amp fuse I needed to run between my Morningstar 15 Amp-MPPT CC and 12V AGM battery, but I found the answer in the manual that came with the unit.  :blush:

My Morningstar SS-MPPT-15L CC manual says to run a 25 Amp fuse between the CC and the battery, but doesn't show a fuse between the panel and CC (a single 190 Watt Mono).  
I'm thinking at the very least, and if something better isn't recommended, I'll install a simple 12V switch on the (+) wire coming from the panel in case I want to disconnect a terminal from the CC without causing sparking/damage.

The manual does show grounding the panel before it reaches the CC.  I'm curious if I need to do this since the entire system is going to be grounded at the battery.  I replaced my OEM, under-hood, battery with a Northstar, Group 24 AGM, so it's connected to the van's electrical/charging/grounding system already. 
Wouldn't this negate the need for a ground in the MC4 wire between the panel and CC?  

My last question is in regards to the remote temp sensor I got for the CC.  Since I've mounted the AGM under the hood next to the engine where it gets very hot, should I connect the temp sensor or leave it out of the system?  I'm concerned the sensor will read very high temps that have little or nothing to do with how hard the battery is working, and more or everything to do with the high-temp environment the battery is living in.  
I'd hate to have the CC limit the amount of power it sends to the battery because it thinks the heat is due to how hard the battery is working.  

 

[BigT]

OK, one more question...

I've heard people say that you should mount your charge controller as close to the battery as possible. Since my battery is under the hood, where should I mount the CC?
I was going to install it inside the van on a rear fender-well, but that would result in over 12' of MC4 cable between the CC and AGM.
I am reluctant to mount the CC under the hood because the unit itself produces heat. I would think it might overheat if I placed it under the hood, near the engine.
I'm not sure if there's a suitable location under the dashboard.
I suppose I could mount it to the frame, under the vehicle, but that would expose it to the elements, and I'm not sure it's waterproof.

 

[K1ngN0thing]

Looks like I need to get myself another breaker...

I thought the temp sensor was supposed to measure the environment?
EDIT: Learned something new today.

 

[Reducto]

I've been running that same controller (or at least one very similar, same brand) for several years now. I do have a fuse between the battery + and controller. No other fuses are needed unless you're worried about a wire getting pinched and shorting something out. No harm in adding more, I suppose, especially if you have a long run of cable.

I haven't grounded anything - I'm only running 2 wires to the battery and 2 to the panel. I guess that's wrong, but I haven't had any problems with it. If you're worried about shorting something when connecting/disconnecting, remove the fuse then unplug the panel at the MC4 connectors if you still have those. Do whatever you need to with the wiring, then plug it all back in the reverse order. It's really not that sensitive though - you can pretty much just plug in the 4 wires and go.

I would definitely not put it close to the engine, but if there's a spot under the hood that is to the side with some airspace around it that should be fine. Under the dash would be great, and in many vehicles there is a ton of room in there. Just make sure it's secured so it doesn't fall down and get in the way of the pedals.

Definitely use the temp sensor if the battery and controller are in different places. Put it on or very close to the battery. It's not detecting how hard the battery is working, just the temp it's at which affects the charge voltage.

A single group 24 battery won't provide a ton of capacity - I hope you aren't planning on running a lot with it.

 

[K1ngN0thing]

The manual for my TS-45 shows a fuse in the diagram between panel and CC, but doesn't mention it in the instructions... opposite of your problem. I'm not sure what amp breaker to go with. I have a 15 between battery and CC. I've only got a single 100w panel.

 

[highdesertranger]

as far as the temp sensor goes, it's supposed to measure battery temp. that is what's important. charge parameters change with the temp of the battery. BigT good question about where to mount the controller, someone else will have to chime in about the engine compartment. if you can't mount it in the engine compartment, I would mount it as close as you can to make the wire run as short as possible. highdesertranger

 

[BigT]

as far as the temp sensor goes,  it's supposed to measure battery temp.  that is what's important.  charge parameters change with the temp of the battery.  BigT  good question about where to mount the controller,  someone else will have to chime in about the engine compartment.  if you can't mount it in the engine compartment, I would mount it as close as you can to make the wire run as short as possible.  highdesertranger

In that case I'll go ahead and install the temp sensor.  Thanks!  

Google searches are showing recommendations of less than 3' between the CC and the battery.  Apparently anything longer than that and you risk "Voltage Drop" that can lead to less than 100% recharge.  They don't specify how much of a drop, but then I figure there are many factors that can effect the numbers.  Given I'd be running 4X the recommended length, I think I'd better start looking into alternative locations.  

Reducto.  I'll only be using the battery to run a CPAP, and then only on occasional weekends.  I don't full-time (heck, I don't even part-time).  I've got a full-time job that pays pretty well, and an apartment that I'm not planning to give up any time soon (even though it's a dump), so my cycles will be shallow and few. 

 

[Optimistic Paranoid]

The reason the instructions show grounding the panel is because 99.9% of panels are mounted on buildings and the National Electrical Code REQUIRES that they be grounded to that grounding rod that was driven into the ground near your meter.  Us mobile types are perfectly fine without it.

As far as fusing the panel itself, search on Amazon for "mc4 fuse" and you'll find a number of fuse holders designed to go between the panels mc4 connector and the extension cable you are running to the controller.  A lot of people don't bother.  It's one more thing that can fail and one more thing that you need to troubleshoot when the system has a problem.  And getting access to the fuse holder usually means climbing up on the roof and maybe partially demounting the panel.

The thing is, when a wire hooked up to a battery shorts out, the battery will send SO much current through it that the wire will quickly heat up enough to cause a fire.  A solar panel can't provide that kind of current, even if it's shorted.  Usually it's 5 to 10 amps, not the HUNDREDS of amps a shorted battery will put out.

Should you fuse it?  Probably.  General principles say you should. Is it a problem if you don't fuse it?  Probably not.  At least, not a catastrophic problem.

As far as distance from the controller to the battery, the thicker the wire, the longer the distance you can run without a problematical voltage drop.  Just use a bigger wire and 12 feet will be fine.

Regards
John

 

[BigT]

So given there's just shy of 50 Volts coming from the panel, I probably wouldn't want to run a 25 Amp fuse on that side of the charge controller?  

 

[Optimistic Paranoid]

I think you just demonstrated why most people don't bother fusing them.

The Maximum Power Point Current is 5.25 amps.

The short circuit current is 5.44 amps.

So a 5 amp fuse will probably blow, and you would need something bigger.  I'm not sure they even make 6 amp fuses, I think 7.5 is the next bigger size.  I'm not sure a 6 amp fuse would even blow, and I'm positive that a 7.5 wouldn't.

I'm starting to think those mc4 fuse holders are used when you wire multiple panels together in series.  You for sure don't need them for single panels.  On multiple paralleled panels, you'd have to fuse after the collection point, and you wouldn't use mc4 fuses for that. 

Regards
John

 

[LeeRevell]

50,000 volts is OK so long as it's less than 25 amps.

 

[BigT]

Thanks for all your help, John, I really appreciate it!  Now I just have to find a new place to mount the CC.   :s 

I'll likely install a switch just to have an easy way to cut the power if/when needed.

 

[MikeRuth]

Big T if your counting votes I too did not fuse my panels to CC. I have about a 8 foot run from the roof to the CC but I did add a switch so that if and when I need to temporarily disconnect the panels I can with out having to unscrew a lead from a terminal. 8 feet is total wire length and I choose to use 8 Gauge. I was able to mount my CC close to the batteries so again 8 GA but that is fused.

I agree that you need to find the closest location for the CC to the battery, but hey we have to be practical and if your going to be several feet away just use an appropriate wire size.

My 2 cents, Mike R

 

[SternWake]

The recommendation of putting the Solar controller as close as possible to the batteries, is to minimize voltage drop.


So when the controller is putting out 14.4v, 14.4 v is getting to the battery, not 14.31, or some other lesser number.

 Switches, circuit breakers, and fuses will all cause voltage drop.  Some worse than others, and the quality of these devices can also impact the quality of the circuit, and the voltage drop.

http://www.pbase.com/mainecruising/fuse_voltage_drop

I've got a 20 amp Maxifuse between my 130 watt framed panel and charge controller.  its only purpose is a low resistance disconnect.  My 68 watt unisolar panel has mc3 cables I can just pull apart.

I put a 30 amp lever type  circuit breaker between charge controller and battery, but it is a POS that causes more voltage drop than a good ANL fuse would.  I got sick of removing the fuse to disconnect, the circuit breaker allowed me to push a button to disconnect, and switch a lever to reconnect, but my IR thermometer reveals it gets warmer than surrounding wires when passing solar current.

I have enough solar that this loss is not going to make me cry, but I also dislike inefficiency and this circuit breaker on my solar circuit mocks me.

it looks like this:

http://www.amazon.com/Water-Wood-Ci...014&sr=8-4&keywords=30+amp+dc+circuit+breaker

I have no faith that it will actually open at 30.5 amps either.

I'd urge readers to Not use such a circuit breaker on their solar systems.  If a switch must be used, make sure it is rated for at least 25 amps or more.

Since I now have a Blue seas 6007m switch on my solar, The push button disconnect of this circuit breaker I employ is no longer needed for that purpose.  I also despise the terminals whereby one inserts stranded wire and tightens a set screw over it, crushing the stranding.  A ring terminal properly crimped has less resistance and will not develop more and more resistance with age, like these stranded wiring under set screws will.

One's charge controller might say to use only such and such a rated fuse, and one must abide by that recommendation while still in warranty, but that does not mean one needs to introduce any extra resistance to the circuit.  Use as short  as possible of wiring between controller and battery.  Use a fuse holder of minimal added resistance, and use wiring as thick as one can fit into the charge controller.

Do not put charge controller in engine compartment, or anywhere it will get hotter than it would on its own.  They need air circulation.

Everything is a compromise.

 

[BigT]

SternWake, thank you for responding to my thread.  I know we've had less than stellar times in our recent past, but I greatly appreciate and value your input and suggestions.  They and you are always welcome in my threads.  

As for mounting the CC:  My van is driving me crazy!  The Transit Connect is the very model of space efficiency.  There is no unused space anywhere! 

I've come up with only two possible locations to mount the charge controller that will allow less than 3' of the MC4 to run between the cc and battery.  
These locations depend heavily on the amount of heat a charge controller normally puts out.  The manual says to mount it with at least 6" of space above and below the unit.  

The first location is very cramped and would make getting at the connectors quite difficult.  It would however put the cc within easy reach of the battery.  
Those two rubber plugs to the left of the cc pop out and access the engine compartment, right behind the battery tray.  
I'd probably have to make some kind of bracket.  That or use self-tapping sheet metal screws and a little sealant and fasten it directly to the firewall.  
I would of course remove the insulation from the mounting location first. 

There's actually pretty decent air flow there due to the AC vents under the dash.  



The second location would allow much easier access to the terminals, but I worry how hot a charge controller gets, esp when mounted to plastic (or near my foot). 
Again, I could make a bracket to keep it off the plastic.  

Just how hot do these things get??   :huh:  Again, ventilation would be quite good as I always have the AC/heater fan running.  



The idea is to run the MC4 wires under the car, fastened to the frame via conduit clamps, and in through one of the rubber plugs to the cc.  
The wires from the cc to the battery would simply go through the other rubber plug to the AGM under the hood, with a 25A fuse right next to the (+) battery terminal.

 

[akrvbob]

Why are you using MC4s for the run from the controller to the battery? You have to cut off both ends anyway. Get an 8 gauge wire and run it as far as you need to find a safe place for it. Use a spade connector and if you have to, bend them together a little to fit inside the controller. Get 8 gauge spade connectors from amazon here:
http://amzn.to/1LmfEga

Bob

 

[BigT]

I thought that's what I was supposed to do. :blush:   I've already cut the MC4 in half (I hope I don't end up regretting that), so I thought chopping off a little at the ends to make the cc-to-battery run seemed like a good idea.  

If I run 8 Gauge, will it be thick enough to mount the cc in the back of the van and run 12'+ of wire to the battery without suffering Voltage-Drop?  

I'd be happy, thrilled in fact, to run thicker wire to the battery so that I could mount the cc in a more reachable location (if I knew what size to run), but my concern was just what you mentioned: The connectors being too large to fit on the cc terminals.  

There's not a lot of room...            If I keep the run short enough, is there any reason why I couldn't use the MC4?  (just curious and to keep my options open). 

 

[SternWake]

If you can't physically position the Charge controller close to the battery for a shorter circuit, then increase the wire gauge size to make up for the increased resistance with increased circuit length.

How big a wire can you stuff into that charge controller output? The fatter the better. If it has to be 6 feet away, or 10 feet away, then so be it, just increase the wire size.

There are also methods for getting wire which will not physically fit into the terminals. It is not like plumbing where a 1/2 inch pipe forever restricts any 3/4 pipe after it.
6 or 8 awg should fit and I'd say to use that thickness even if it was 12 inches away from the battery.

Don't paralyse yourself by putting this somewhere where getting to it requires one stick their head where their feet usually go.

How long is the battery temp sensor?

I dislike the insert stranded wire, crush under screw type of terminals. The copper oxidizes and develops higher resistance, and the screw always needs to be retightened. Here was my solution which also allowed 4awg from controller to battery.

 

[BigT]

How big a wire can you stuff into that charge controller output?  I dislike the insert stranded wire, crush under screw type of terminals.

6 or 8 awg should fit

How long is the battery temp sensor?   

I didn't realize the connectors on the CC were designed to wrap the wire around.  I assumed I was supposed to use crimp-on spade/fork connectors.  

So are you saying 8AWG wire will work on a 12 - 14' run?  

The temp sensor wire is 33', so it looks like it will reach fine from just about anywhere.  

Lowe's carries the wire, but not connectors that fit anything larger than 10AWG.  :dodgy:

 

[Reducto]

You can use a connector made for 10ga on 8ga wire - just snip off enough strands so it will fit.

Do not put the controller anywhere you're likely to kick it when getting in or out of the vehicle! I'd rule out location 2 for this reason. Up higher, right underneath that connector harness thing, looks great to me. There's a bracket there you could use and you could zip tie the wires to the harness. Should be a little easier to reach than location 1.

The controller really doesn't put out a ton of heat - those warning are just to keep people from mounting them inside tiny air tight boxes. As long as it has some airspace around it you'll be fine.