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SSC Load Terminals - To use them or not to use them, this is the question ?

ianganderton

Auckland, NZ
Joined
Nov 8, 2019
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771
Location
Auckland, New Zealand
So I'm planning to use the load connection for my DC loads in my camper vans system but it seems to have folks I've shown the diagram pretty fired up.

I figured it was worth asking the question specifically here and outlining why I think its ok in my use case and then request a reality check from you lot!

First the information

Build thread here

Diagram

1661245321714.png
NB - the SSC - Battery connection will be fused at 60A, not the 100A shown in the diagram. I've found lower than 100A mega sized fuses now!

Here are my thoughts.

The Epever Tracer4210 AN is a 40A SSC and the load terminals are also rated to 40A. The above diagram matches the manual wiring/fuse schematic. The cable sizes in the above diagram match the maximum size for the SCC terminals (both battery and load connections)

In my power audit my peak amp load possible for the 12V DC fusebox off the load terminals is is 25A so I think I've got loads of headroom.

The advantages I see of using the load terminals are primarily to do with control and monitoring.

I have 3 other devices in the mix that factor into my desire to use the Load terminals:

Epever MT75 Remote display & Epever IP-Plus 2000W Inverter
Epever E-Log

So the MT75 Remote connects to the SSC and the Inverter. It has 2 key relevant functions

Monitoring its combines the available display information from both the SCC and the Inverter. This means it will display information including the following
  • PV voltage, current & power
  • Battery voltage, current, capacity & temperature
  • DC load voltage, current & power
  • AC load voltage, current & power
Control It can switch on and off both the inverter and the DC load connection.

Having the DC load information and control neatly with all the other info is definitely a nice to have

Monitoring - E-Log - this device will log all the information available for display by the SCC including data from the load terminals.

Lastly Protection

I can set low battery voltage parameters for load disconnect to help ensure the BMS is only activated as a last resort. This is the same for the inverter too. I can also set a load reconnect parameter so the SCC has a great level of programmable protection functionality that wouldnt be possible if the DC loads were stright to the battery bus bar/victron lynx

So thats the positives. I do have some concerns that I want to pick your brains on

Will the SCC increase the resistance and potentially cause voltage drop? I see lots of folks experience voltage drop problems with fridges and diesel heaters. I'm speccing my cables to minimise that risk but maybe the SCC will cause a problem

Will the additional load going through the SCC cause any problems that will dramatically decrease the life of the device?

So thats where I'm at. Am I completely wrong like some folks have strongly expressed

Relevant device info for reference

Solar Charge Controller – Epever Tracer 4120AN https://www.epever.com/product/tracer-an-10-40a-mppt-charge-controller/
Manual - https://www.epever.com/wp-content/uploads/2021/05/Tracer-AN-SMS-EL-V1.0.pdf

SCC & Inverter Remote Display - MT75 https://www.epever.com/product/accessories-mt75-remote-meter/
Manual - https://www.epever.com/wp-content/uploads/2021/08/MT75-Manual-EN-V2.0.pdf

Data Logging - E-Log https://www.epever.com/product/elog-01-logger/
 
I'm surprised some of the accomplished installers here haven't chimed in...

I don't see why it wouldn't work. Just make sure your fuses are of sufficient capacity for your load items. Seems simple enough. Fuses should be 125% of current draw, or you'll have nuisance tripping.
So that fuse to the SCC should probably be a 70A or so, in lieu of 100A. Wire sizing seems adequate, and seem to meet max gauge for the controller terminals. I like to see some kind of power cut off for the solar controller for service and maintenance without taking the whole system down, and why a switching circuit breaker is popular for this. You have a PV disconnect, so you can re-energize in the proper order: connect to battery, then to PV panels. The problem is you have to take your loads down for any of the other charge components - you could be left in the dark.

I'm not sure I would want to rely on my solar controller to manage the loads, as they can be flakey at times. I've seen them power on loads when they start, but I think you can preset the default mode in the setup.

I would rather connect my load center direct to the bus/battery, with proper fusing for at the connection to protect the wiring. That way it's always on unless you manually turn it off.

Set it up and try it out - let us know how it goes.
 
He didn't like that answer in the other thread. LOL. So he started this one.

The only thing I can think of is to be able to do some kind of logging, but all that really matters is battery state of charge and calculated duration based on current in and out on the meter.

He seems to think that because his load is under the capacity of the SCC it should power it. I've never seen them done that way - DC loads are always run off the battery. [shrug]
 
Stop saying redundant things LOL ?

I personally do not like using load terminals due to heat contribution. I think it was $15 to buy an inductive watthour accumulator.

But I can’t put up an argument regarding control. However, even that is overcome with a properly rated DC relay triggered by the load terminals.

Finally, I suggest a blue sea fuse box with negative bus connections. That’s what I use with a 8ga feed wire with 30A fuse, wired directly. All my lights and heater, pump, phone chargers, range hood run on 12V.
 
We would almost always use the load terminals in our setups - but our cases are specific;
1 or 2 panels, into a victron controller, 24v LiFePO4 battery, with the load terms powering a passive POE injector into waterproof (carrier grade) ethernet up a pole to power radios, cameras, APs, lights etc.
All gear runs off the POE, and by using the load terms you ensure that the radios/cameras etc turn off before the battery bms gets upset.
If you have a really important radio(s) (say, bouncing signal to other parts of the network and it must NOT go down) then the cameras/APs go on the load terminals, and the criticals go on the battery terminals (and you have to run 2 ethernet cables up the pole, 1 for non-criticals, 1 for criticals. Its a way to provide 2 or more levels of load shedding.
If we had a super-critical load, or wanted 3 layers of shedding, we would run 2 victron controllers, with panel(s) on each so there is your redundant solar source (and redundant controller), then have the super criticals on the battery, the not-so-criticals on victron#1 with the load terminals set to go off just above the BMS cutoff, and the non-criticals on victron#2 with the load terminals set to go off early (usually cameras and IR floodlights on this controller). Our systems are sometimes buried ~400mm deep (for constant battery temperature where night temps might be below zero) so the system has to be rock solid.
The difference between this and @ianganderton setup is that our loads are usually about 7w per device (camera, radio, IR flood etc) so we are talking small but constant (24h/day, 365d/year) draws.
Having said all this, i have seen one motorhome owner have a problem with a victron turning off the load terminals which required a reboot to clear - this happened to him twice in the space of 5 years.
 
I'm in the camp of not using the load terminals. Not to say that one can't, but I just prefer to have all loads connected to the battery. If nothing else, it means those loads are not dead if you need to remove the CC for some reason.
 
I'm in the camp of not using the load terminals. Not to say that one can't, but I just prefer to have all loads connected to the battery. If nothing else, it means those loads are not dead if you need to remove the CC for some reason.
As in the above application where physical setting and device-specific power is required as well as other applications I can see the load terminals having useful benefits.
In a ‘residential’ installation, I too would want a battery connection to a DC fuse and distribution box like the bluesea product.
 
I think it might help to understand where all the push back seems to come from.

Back in "The Day" most SCC's were PWM and the load ports were only rated for 1-5a so people would put their inverter on the load ports and then wonder why it tasted like burning. Only after the higher end (and yes, in the grand scheme of things I would consider EPEver to be in the Higher End category) MPPT controllers became more readily available were the load ports capable of handling the amperage loads of the SCC rating. Because of this the concept of load ports became ingrained in everyone's mind as pretty much useless outside of a few specific low draw cases like the afore mentioned POE injector or using it to tend a battery.

Nowadays more and more controllers are capable of handling their rated capacities on their load ports so in theory it should work, but take it with a grain of salt as many of the clones out there SAY they can do 40a of load, but start smelling really spicy at 20a. Think of the load port rating as more of a Surge rating and treat it as such.

As to your original question, it should work in theory, the only concern I have being that if your SCC goes down so does your 12v bus which would really suck if all your lighting and heat are off while you're waiting a couple days for a replacement to show up in the mail. It becomes a major Point-Of-Failure risk. If you're willing to take that risk then the numbers say you can do it.

In other news, your diesel heater will need a 15a fuse and at least 14AWG wire to feed it. On startup between the fan, fuel pump, and glow plug it's not uncommon for those to draw 14a when getting up to temp.
 
So to summarise everyone's comments;
  • - you can have Power (directly from the battery terminals)
  • - you can have Control (via load terminals)
  • - can you have both?
  • - On some controllers, with modest loads, YES!!!
  • - On older controllers, maybe not
I do wonder why the Victron controllers only have load terminals on a limited number of products - ie the 75/10, 75/15, 100/15 & 100/20, but not the 100/30 and 100/50. That feature seems to be based on the switching / controlling gear required for the higher (ie 30A, 50A) loads.
 
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