10mm Solar Cable

[DShK]

I have removed all of the solar panels from my boat. Soon I will be remounting them in a removeable fashion between the gunwales of the butty boat. The problem is this will, when moored stern to bow, require quite a long run of cabling. I will swap the setup to at least be partially in series, but if possible I'd like to use thicker cables. 10mm^2 solar cable and MC4 connectors are available - but I see no viable way of properly crimping these connections.

 

Does anyone have any thoughts or experience on crimping MC4 connectors of this size? Or perhaps a viable alternative?

 

Thanks!

[MtB]

14 minutes ago, DShK said:

I have removed all of the solar panels from my boat. Soon I will be remounting them in a removeable fashion between the gunwales of the butty boat. The problem is this will, when moored stern to bow, require quite a long run of cabling. I will swap the setup to at least be partially in series, but if possible I'd like to use thicker cables. 10mm^2 solar cable and MC4 connectors are available - but I see no viable way of properly crimping these connections.

 

Does anyone have any thoughts or experience on crimping MC4 connectors of this size? Or perhaps a viable alternative?

 

Thanks!

 

 

Given you are only stepping up to 10mm2 due to the long length, I'd suggest there is no harm in snipping off 40% of the strands for 1/2" or so necessary to fit them into the crimps on the MC4 connectors.

 

Bear in mind also that high voltage drops/losses only occur when the current is high, which will be in sunny weather and this is usually the time you least need high current charging. 

 

 

[Tony Brooks]

10 minutes ago, MtB said:

Bear in mind also that high voltage drops/losses only occur when the current is high, which will be in sunny weather and this is usually the time you least need high current charging. 

 

 

and with well discharged batteries or lithiums in any state of charge, so possibly not as vital as with other circuits.

[matty40s]

58 minutes ago, DShK said:

I have removed all of the solar panels from my boat. Soon I will be remounting them in a removeable fashion between the gunwales of the butty boat. The problem is this will, when moored stern to bow, require quite a long run of cabling. I will swap the setup to at least be partially in series, but if possible I'd like to use thicker cables. 10mm^2 solar cable and MC4 connectors are available - but I see no viable way of properly crimping these connections.

 

Does anyone have any thoughts or experience on crimping MC4 connectors of this size? Or perhaps a viable alternative?

 

Thanks!

MC4 are designed with a maximum 6mm2 cable size in mind, so as MtB says, snip some of the multicore away, or just fit 6mm2.

[TheBiscuits]

I'd just do 6 mm² and not worry too much about it. 

 

Do a voltage drop calculation to see exactly what percentage you'll lose, it may be less than you think.

 

80V, 20A (two house size solar panels in series)

25m one way distance (a boat length away)

 

Voltage drop in 6mm² cable is just over 3V or just under 4% loss.

 

 

You lose more than that when a cloud passes in front of the sun.

[Jen-in-Wellies]

16 minutes ago, TheBiscuits said:

You lose more than that when a cloud passes in front of the sun.

Or if you don't clean the panels regularly.

[MtB]

16 minutes ago, TheBiscuits said:

Voltage drop in 6mm² cable is just over 3V or just under 4% loss.

 

Point of Order...

 

A 4% volt drop will result in a 4% current drop too. So I reckon the power transferred will be 0.96 x0.96 = 92.176%

 

(Well its time somebody started the nit-picking!!  )

[Quattrodave]

Or double up on the number or cables to spread the load, not ideal from an install / maintenance point of view but electrically fine...

[cuthound]

Use reducing pin type crimps.

 

https://www.termtech.co.uk/Catalogue/Crimp-Terminals/Copper-Crimp-Terminals-and-Connectors/Solid-Reducing-Pins, or trim the cable as suggested by @MtB if it won't compromise the current carrying capacity.

Edited May 8 by cuthound
phat phingers

[DShK]

Reducing the cable down to fit in a 6mm crimp sounds like a bodge but a decent one. Nice idea! My only concern is if the 10mm sheath fits in the 6mm mc4 housing. Think I've got some unused connectors I can look at.

 

The solid reducers sounds like a good idea but I'm not sure it will play well with the crimp unfortunately.

 

I didn't calculate potential losses. I believe I was getting quite high volt drop with an old setup with a short run but I was running 4x 375w in parallel - so quite high current. 

 

Thanks for the help, some solid input here 👍

 

 

Edited May 8 by DShK

[Jen-in-Wellies]

Another alternative would be to use a waterproof junction box at the panel end of the run of 10mm2 cables. Connections between the 4, or 6mm² cables from the panels could then go to the 10mm² via ring tube crimps, on to some posts inside the box. Not so quick to disconnect as MC4s, but how often are you going to be doing that? If the junction box is usually hidden underneath a panel, it need only be water resistant, not waterproof.

[MtB]

8 hours ago, DShK said:

Reducing the cable down to fit in a 6mm crimp sounds like a bodge but a decent one.

 

It IS a bodge. A monumental one!

 

But then so is putting the solar panels on a different boat from the batteries....

 

 

 

[blackrose]

20 hours ago, TheBiscuits said:

I'd just do 6 mm² and not worry too much about it. 

 

Do a voltage drop calculation to see exactly what percentage you'll lose, it may be less than you think.

 

 

That's what I was thinking, especially if the panels are connected in series. If they're connected in parallel then voltage drop over the extended cable length may be an issue of course - which is another disadvantage of parallel panel connections.

[Jen-in-Wellies]

I'd be looking at Anderson connectors for the boat to boat connection. MC4 connectors aren't designed for regular making and breaking. Plenty of them happy with 10mm² cable.

 

[DShK]

3 hours ago, Jen-in-Wellies said:

Another alternative would be to use a waterproof junction box at the panel end of the run of 10mm2 cables. Connections between the 4, or 6mm² cables from the panels could then go to the 10mm² via ring tube crimps, on to some posts inside the box. Not so quick to disconnect as MC4s, but how often are you going to be doing that? If the junction box is usually hidden underneath a panel, it need only be water resistant, not waterproof.

I'd certainly not be disconnecting regularly at the panel end. Those posts are only rated for 48V though unfortunately - perhaps there is a viable alternative, I'll have a dig.

 

1 hour ago, Jen-in-Wellies said:

I'd be looking at Anderson connectors for the boat to boat connection. MC4 connectors aren't designed for regular making and breaking. Plenty of them happy with 10mm² cable.

 

That's a great shout - a pain to disconnect mc4 connectors too. Those look much better, thanks. Although no indication they are waterproof - would need to make a little house for them to live in.

[Jen-in-Wellies]

15 minutes ago, DShK said:

That's a great shout - a pain to disconnect mc4 connectors too. Those look much better, thanks. Although no indication they are waterproof - would need to make a little house for them to live in.

There are various cable entry boots and connector covers in the ranges that would give them a degree of waterproofing. How effective these are, I don't know.

[Tracy D'arth]

24 minutes ago, Jen-in-Wellies said:

There are various cable entry boots and connector covers in the ranges that would give them a degree of waterproofing. How effective these are, I don't know.

Fill the boots with grease or Vaseline and they will be very waterproof.