victron 75/15 solar controller

[SoulRaven]

Since I read so many threads about using large gauge wire for solar / battery usage, I'm a little confused about what people have done who use this controller. 

The inputs are on the bottom of this controller and are really tiny.   Basically what I've used are a method to "step down" the gauge from what comes from my solar panel , for example, to a 12 gauge wire .  This wire is usually about 6 inches or so.  Same thing for my battery cable , which is 8 gauge. 

For those who use this controller, what have you done?  

For those who haven't , is this a really bad idea?  If so, what would you think the proper way to connect to a very small input "port"?

Thanks,

Pat

 

[tx2sturgis]

The inputs are on the bottom of this controller and are really tiny. 

{snip}

For those who use this controller, what have you done?  

I ran into this issue with mine.

I fully tinned the wire ends, lots of solder, then with a small grinder, shaped the tinned ends into a small square shape, (square cross section) which fit very nicely into the terminal openings.

As the solder will compress, you may need to re-tighten the clamp screws once or twice.

 

[John61CT]

These MPPTs are designed to work with high-voltage inputs, so the ability to use light gauge cabling is a nice side benefit.
Thus sizing of wiring from the panels does not have to be at the chart's heavier side to eliminate voltage drop, just enough for thermal safety.

Using them with input at nominal 12V, say under 22V would prevent you from getting much increased performance compared to using a PWM SC.


But yes, in the end, there is no problem stepping down at the end if needed.

 

[tripper]

The Victron MPPT 75/15 has  6 mm² / AWG10 power terminals. See Victron Datasheet        
AWG10 wires can push 15 amps up to 20 feet with only a 3% voltage drop BlueSea AMP/Volt drop chart

Typical MC4 wires will be 12 AWG, the power coming from, the solar panels will be less amperage & higher voltage than the power output from the controller, so 12 AWG MC4 cables of 20 feet long or so should be no problem/minimal loss. The 10 AWG wire running from the controller to the battery should be as short as possible, typically 2-3 feet. Since 10 AWG can be up to 20 feet long with only the 3% loss you can see 10 AWG is plenty large enough to handle the output current. The wire terminals on the controller are plenty large enough for the application it is designed for.

You can get 10 and 8 AWG MC4 cables but they are not needed in this application, the MC4 connector itself is only rated for the 10 AWG max size (30Amps I believe).

There is no need for 8 AWG wire to the battery as 10 AWG is plenty and the controller accepts 10 AWG IN/OUT. BTW it should be the very fine thin multi stranded copper wire that is very flexible, not the solid stiff single or couple of core type wire. The fine strand wire is better to get a solid connection with the clamping mechanism on the controller (more surface area contact) and can handle the vibrations of a mobile platform much better than solid core.

 

[UptownSport]

It's simply a poor design.
Mine have loosened several x's.
Ended up tightening more, has worked for last two weeks so i think that's it.
Contemplated cutting tinned ends and using 3/4" of solid, but looks like it won't be necessary.

 

[John61CT]

Could just terminate with square ferrules.

I've looked for a reasonably priced MC4 die set for the Rennsteig crimper that goes up to #8, no luck at all.

Standard ones (under $300) cover

2.5mm2 (#14), 4mm2 (#12), with the biggest 6mm2 (#10)

 

[John61CT]

You can get 10 and 8 AWG MC4 cables but they are not needed in this application, the MC4 connector itself is only rated for the 10 AWG max size (30Amps I believe).

The #10 connector itself is rated for 43A

#8 at 50A but never used one, maybe genuinedealz.com can terminate them

 

[John61CT]

MaineSail sells a great value MC4 crimper

http://www.pbase.com/mainecruising/mc4_cimp_tool

Lots cheaper than the Rennsteig, but fine for occasional use.

See also the HowTo linked from there.

 

[SoulRaven]

Could just terminate with square ferrules.

I'm going to guess this is an online item.   I've been to HD and Lowe's looking for stuff like that.

 

[John61CT]

I'm going to guess this is an online item.   I've been to HD and Lowe's looking for stuff like that.

I use aviation/marine grade stuff so dunno.

Here's a cheapie example just for illustration, not a reco

https://www.amazon.com/gp/aw/d/B00H950AK4/

 

[SoulRaven]

I use aviation/marine grade stuff so dunno.

Here's a cheapie example just for illustration,  not a reco

https://www.amazon.com/gp/aw/d/B00H950AK4/

Yeah, that's the kind of stuff I've looked for. 

I'm looking in the wrong places. 

Thanks, 

Pat

 

[tripper]

It's simply a poor design.
Mine have loosened several x's.
Ended up tightening more, has worked for last two weeks so i think that's it.
Contemplated cutting tinned ends and using 3/4" of solid, but looks like it won't be necessary.

I have three of these Victrons, no loosening up on mine, I use fine multi strand copper, I suspect it doesn't get a good bite on the tinned end or on a solid end. I'm sure a dot of Loctite on the threads would work if you kep on having that problem.

 

[tripper]

The #10 connector itself is rated for 43A

#8 at 50A but never used one,  maybe genuinedealz.com can terminate them

Interesting, didn't realize there were different MC4 amp ratings, from Alt-E site:
17A (1,5mm²)
22,5A (2,5mm²; 14AWG)
30A (4mm², 6mm²; 10AWG)
43A (10mm²)

MC4 ratings

 

[UptownSport]

You cant really access the threads. I should use ferrules, as suggested, or a jut a bit of solid copper. I've reefed the little screws well past all good judgement, and it seems to work.

Just had to move the fridge from the controller 'output' (load terminals) direct to battery. There was enough voltage drop at 0 dark thirty that the fridge's electronics would shut compressor down. The fridge would go into some type of cycle where the fan ran for an extended period, then compressor would run for about 5 seconds, then shut down, then repeat.

I *think* someone said to direct connect in he first place, but do i listen?

 

[SoulRaven]

You cant really access the threads. I should use ferrules, as suggested, or a jut a bit of solid copper. I've reefed the little screws well past all good judgement, and it seems to work.

I *think* someone said to direct connect in he first place, but do i listen?

What I chose to do UptownSport, is the following: 

I got a piece of 2x8 wood, cut 4 short pieces, or leads,  of the PV panel cable and inserted them into the holes and cranked it down.
Then added a terminal block to make my battery and PV connections to.  My hypothesis is that will reduce any downward stress on the leads if I have to manipulate connections.  

If it doesn't work out, I'll bother to report that.  Otherwise, silence is golden. 

Pat 

 

[John61CT]

Excellent approach, any voltage drop should be miniscule.

But I'd check, just in case