Can I run my inverter off my charge controller?

[BigT]

I just noticed there's an extra set of terminals on my Mornigstar MPPT charge controller that are labeled as "Load".  
These terminals are on the 12 Volt side of the controller.  

Since I'm able to safely run my 400W inverter off of my 15A fused, Acc / cigarette outlet, would it be possible to hook the controller up to these "Load" terminals instead of hardwiring the inverter straight off the battery?  Seeing as the 8 AWG wires from the CC go straight to the battery and have a 25A fuse and all..  
(I'd be happy to install an extra blade fuse at the inverter too).  

I should mention that the only thing I'm going to charge with the controller, is my MacBook Air laptop (85W - 100W), and maybe (maybe) my beard trimmer, which I'm told uses next to no Watts at all.  

It would be a GIGANTIC help if this is doable (safe), as there's precious little room inside my tiny Transit Connect to mount things.  
Being able to wire the inverter at the back of the van, under my folding table where the CC is located, would simplify my life considerably.  

If necessary, or safer, I can return the 400W and get the 200W model instead.

 

[Weight]

Inverters pull a lot of amps and need consistent current. While the panels may have enough, they may not exactly when the inverter needs it. The battery will work as a buffer to keep the current steady.

 

[BigT]

Does it make any difference that the battery in question is the unit under the hood of the van that's connected to the alternator?  

It's a Northstar AGM and the inverter will only be used while the engine is running, and even then, only used to charge a laptop and maybe a cordless razor.

 

[B and C]

I just noticed there's an extra set of terminals on my Mornigstar MPPT charge controller that are labeled as "Load".  
These terminals are on the 12 Volt side of the controller.  

I should mention that the only thing I'm going to charge with the controller, is my MacBook Air laptop (85W - 100W), and maybe (maybe) my beard trimmer, which I'm told uses next to no Watts at all.  

It would be a GIGANTIC help if this is doable (safe), as there's precious little room inside my tiny Transit Connect to mount things.  
Being able to wire the inverter at the back of the van, under my folding table where the CC is located, would simplify my life considerably.  

Yes, you can connect your inverter to the load terminals.  It will still be connected to the battery.  This is kind of what the load terminals are for, streetlights, signs, etc.  Use the biggest wire that will fit and put a fuse close to the CC to protect the wire going to your inverter in case of a short.  IDK if the Morningstar has a schedule to turn the load on/off though.  You may want to check.  There should also be a low voltage disconnect setpoint which will disconnect the load (inverter in your case) if the battery voltage drops below the setpoint voltage.

 

[jimindenver]

The load terminals will have a output amp limit. Make sure you will not pull more than that limit or you may pop a fuse inside the controller. Personally I would not put any undue stress on the controller as it can create heat. You could just connect it to the lines running to the battery for the same affect.

 

[Trebor English]

The charge controller is connected to the battery.  You can use that fat wire to power the inverter.  When the sun is shining those solar amps can go to the from the controller directly to the inverter.  The fat wire to the battery doesn't know that you wanted it to charge the battery.  It will work both ways.  

The load terminals let the charge controller turn off the load.  That transistor has resistance.

 

[BigT]

Yes, you can connect your inverter to the load terminals.  It will still be connected to the battery.  This is kind of what the load terminals are for, streetlights, signs, etc.  Use the biggest wire that will fit and put a fuse close to the CC to protect the wire going to your inverter in case of a short.  IDK if the Morningstar has a schedule to turn the load on/off though.  You may want to check.  There should also be a low voltage disconnect setpoint which will disconnect the load (inverter in your case) if the battery voltage drops below the setpoint voltage.

Darn.  I just found this in the owners manual for the Morningstar SunSaver SS-MPPT-15L..

"CAUTION: Do not wire any AC inverter or other inductive load such as a motor, pump, compressor or generator to the load terminals of the SunSaver MPPT."
"Damage to the load control circuit may result.  Wire the inductive loads directly to the battery or battery bank."  

I wonder if I could just splice the inverter into the 8 gauge wires leading out of the CC instead, and leave the load terminals alone?  
Or maybe just clamp the wires from the inverter under the wires on the CC that run to the battery...   Or maybe install a BusBar...   :s

Edit: Oops, I think this was just answered in the above post from Jim and Trebor English.  


CAUTION: Do not wire any AC inverter or other inductive load such as a motor, pump, compressor or generator to the load terminals of the SunSaver MPPT. Damage to the load control circuit may result. Wire inductive loads directly to the battery or battery bank. 

 

[Trebor English]

I wonder if I could just splice the inverter into the 8 gauge wires leading out of the CC instead, and leave the load terminals alone?  
Or maybe just clamp the wires from the inverter under the wires on the CC that run to the battery...   Or maybe install a BusBar...   :s . 

Yes.  Any of those will work.  All are better choices than using the load output.

 

[BigT]

Thanks, guys, this has been a huge help!

I'm just gong to clamp the wires to the inverter underneath the wires leading from the CC to the battery.   Maybe toss in a 25 or 30 Amp fuse while I'm at it...
Though I'm told the inverter has an internal 25A fuse.  

If I'm able to safely plug the inverter into my cigarette outlet and charge my laptop without blowing the 15A fuse, I might not need a fuse at all.  Though it's always a good idea.  

Thanks again!  

 

[willprowse]

Not smart. Many recommend not to connect large loads to the load terminals because they have a limit on the load terminals, but its always best to wire the inverter close the battery with short and large wires.

I avoid the load terminals. Much better to wire directly to battery.

 

[Trebor English]

You said in the original post that you have a 25 amp fuse at the battery.  The battery is the high power source that can start a fire.  The charge controller isn't blowing the 25 amp fuse so it cannot put out 40 amps.  If it could, your 25 amp fuse would blow.  AWG 8 can carry 40 to 55 amps, depening on insulation temperature rating.  You don't need another 25 amp fuse going to the inverter because you already have one, at the battery.  

The inverter's internal fuse will not protect the wire from the battery.  It will only protect the inverter itself.

 

[BigT]

You said in the original post that you have a 25 amp fuse at the battery.  The battery is the high power source that can start a fire.  The charge controller isn't blowing the 25 amp fuse so it cannot put out 40 amps.  If it could, your 25 amp fuse would blow.  AWG 8 can carry 40 to 55 amps, depening on insulation temperature rating.  You don't need another 25 amp fuse going to the inverter because you already have one, at the battery.  

I just meant that I could install a fuse in the wire going to the inverter, not the wire that already has a 25A fuse and goes to the battery.  
I wasn't sure if that was necessary or not.  Just being careful.

The wire with the 25A fuse is the one that connects to the 12V side of the CC and runs to the battery.  The 25A fuse is inches from the + battery terminal.  
Since the inverter would be attached to the same posts on the CC, I thought it might require its own fuse.

If not, great, I'll go toss it together right now. 

 

[Trebor English]

If the wire from the battery to the inverter chafes against a sharp edge and shorts to ground the fuse at the battery will blow.  An additional fuse in series will make for more resistance between the battery and the inverter.  That's not helpful.  An additional fuse means several additional connections, wire to fuse holder, fuse holder to fuse, other side of fuse to other side of fuse holder, etc.  More connections make it all less reliable and higher resistance.  The first fuse at the battery limits the current all the way to the inverter.  

Since the AWG 8 wire can handle 40 amps you could replace the 25 amp fuse at the battery with a higher current fuse.  That will have slightly lower resistance and allow higher wattage inverter load.

 

[tx2sturgis]

BigT, I have a question about the picture you posted.

Is that charge controller mounted on a horizontal surface?

Or is it vertical with lighting that makes it look horizontal?

The prefered position is mounting on a vertical surface for better airflow over the heatsink.

 

[BigT]

BigT, I have a question about the picture you posted.

Is that charge controller mounted on a horizontal surface?

Or is it vertical with lighting that makes it look horizontal?

I just took another look a the photo.  You're right, it is a confusing angle..  I was laying on my back, below it, when I took the shot.  

The CC is mounted to the wall, just above the left-rear fender well.  I put some coupling nuts behind it to space it off the wall a little.  

I'm going to mount the inverter to the top of the fender well, below and a little to the left of the CC.

(I'm not sure why that thumbnail is sideways until you click on it)..   :s

 

[B and C]

Darn.  I just found this in the owners manual for the Morningstar SunSaver SS-MPPT-15L..

"CAUTION: Do not wire any AC inverter or other inductive load such as a motor, pump, compressor or generator to the load terminals of the SunSaver MPPT."
"Damage to the load control circuit may result.  Wire the inductive loads directly to the battery or battery bank."  

I guess I shouldn't have made my statement a blanket statement.  I have a Midnite Kid and don't remember anything about a warning such as you posted.  I am glad you read the manual.

 

[Weight]

My inverter will draw more current than my controller charges. I have 2/0 awg battery to inverter. 4 awg controller to battery. Fuses are at the battery positive for all connections. I have no need to run inverter sized cables to the controller. I did use a buss bar, and treat that as the positive battery terminal. Controller to fuse at the buss bar. Inverter from fuse at the buss bar. Buss bar to fuse at the battery. My inverter will not shut down at the higher voltages from my solar charger. Some inverters shut down at the common solar charge voltage. Your equipment will be different than mine and you have to determine the wire sizes you will need. Start by reading the manuals, the whole thing.

 

[frater secessus]

I would consider running a relay off the LOAD output and the inverter through the relay.  This allows the controller to switch the load but the actual current is offloaded to a cheap part (relay).   A relay is cheap, usually allows much more current, and saves strain (if any) on the controller.

This would allow you to be much more aggressive with the Low Voltage Disconnect than most inverters are internally.  I've seen inverter specs thay say they cut off as low as 10.5v.  Rekt!!!

A downside to using a relay is the controller won't be able to see how big the load is, assuming you wanted to watch that metric on the display.  It will only see the load of the relay, which will be a fraction of an amp.

 

[BigT]

If the wire from the battery to the inverter chafes against a sharp edge and shorts to ground the fuse at the battery will blow.  An additional fuse in series will make for more resistance between the battery and the inverter.  That's not helpful.  An additional fuse means several additional connections.  
More connections make it all less reliable and higher resistance.  The first fuse at the battery limits the current all the way to the inverter.  

Thanks, I hadn't thought about it that way.  I was under the impression that having a fuse at each and every component was considered a good idea.  

As I've said before, though, if it's safe to run it off my Acc. outlet and it's 15A fuse, or the Alligator clips off the battery, which has no fuse at all, I imagine this planned setup will work fine for charging tiny loads, like my laptop or razor.  Especially since my engine will be running 100% of the time I'm charging things. 

Right when I got the inverter, I plugged it into my cigarette outlet, connected my laptop, making sure to open the laptop so it wasn't "hibernating", and it worked fine.

 

[tx2sturgis]

Connecting a relay to the load terminals creates an issue because a relay is an inductive load, albeit a small one. 

Relays provide some inductive kickback to the controlling device, especially when the relay coil is de-energized, although sometimes a suppression diode is used.

I wonder if the controller is rated for a relay at the load output?