Cable/fuse sizing.....

[mistericeman]

Getting to a point of planning fitting of new solar panel...
One of these,

Product not found!

www.bimblesolar.com

Connected to a Ctek 250sa.

Anyone point me in the right direction of cable sizes/fuses (ideally trips)

Please.

 

[wildebus]

this is for Solar to CTEK?

Solar Cable is twin-insulated (outer layer UV-Resistant) and comes typically in 2.5mm2, 4mm2, and 6mm2.
For your panel, all of the above options have the required ampacity (current carrying ability) to safely work. So you can use whichever of the above you may happen to have. If you are buying cable for the job, or want the best solution possible, I would suggest the 6mm2 cable as it will also minimize the voltage drop from Panel to Controller, so will give you better efficiency (it is a very small difference admittedly, but all these bits add up over time, long past when the extra minimal cost of the thicker cable has been forgotten).
Fuse wise, a 15A or 20A Fuse is more then enough for the panel whilst still being under the current rating of any of those cables.

Not used one of these myself, but if you want a trip, I would probably go for one of these for PV-Controller cable protection:

https://amzn.to/2V2yJ2l

 

[mistericeman]

Perfect.... Many thanks I'd not spotted the in line trips.

 

[wildebus]

Dropped you a PM, but if it is not too late, DOWN TOOLS!

I was only looking at the question about cable sizing suitable for that panel. But the bigger issue is that panel and the CTEK 250SA are incompatible, sorry to say.

When I read this thread again I remembered about the CTEKs limitations.
The CTEK will only work with "12V" Panels - e.g. panels that have a Voc (Max Voltage) of about 20-22V. Your panel has the specs of a 24V panel, with a Voc of 40V - the CTEK 250SA has a maximum input voltage of just 23V.

Generally speaking, just about every B2B/MPPT combo device has a similar limitation with the PV panel Voltage limit. Some examples - the CTEK is the lowest at 23V, the Ablemail is either 32 or 35V (can't recall which) and the Redarc BCDC is in the upper 20V.
The effect is no "24V" panel will work with them (which also means no 12V panels in series either). I don't know what happens with the CTEK if you try? The Ablemail will I think do a protection and disable whilst overvoltage but the Redarc goes "boom"! and you have an expensive doorstop (I have one of those from someone else who fitted the same panel as you have, as it happens).

 

[mistericeman]

Ahhhhh that's a bit of a bugger.... Teach me not to thoroughly read specs I guess.

Thanks for the heads up though... I never like smoke escaping out of stuff.

 

[wildebus]

Ahhhhh that's a bit of a bugger.... Teach me not to thoroughly read specs I guess.

Thanks for the heads up though... I never like smoke escaping out of stuff.

Glad I am not too late! I was focussed on the current side of the panel and the voltage bit for the CTEK didn't click until this morning.
If you are committed to that panel, The Victron 100/20 SmartSolar (330W max) would be a good match for the basic 315W, but if you think it will be delivering upto 400W with this bifacial feature, the Victron 100/30 (440W max) would be the one to go for.
PS. the 100/20 is 330W but if you go above, nothing is damaged, the power just gets capped.

 

[mistericeman]

Thanks for that....
I'll have a look around (I bought the ctek at a good price so should be able to recover cost)
I went the ctek route so I had one unit managing both solar and alternator input....
But not the end of the world.

 

[mistericeman]

What about the ring rscdc30?

Appears to handle up to 50v

I'd like to keep alternator/solar charging in one unit if I can....
BUT open to persuasion.

 

[wildebus]

Interesting. looks like it should be good.
There is "Input Voltage - PV" and "Input Voltage - DC" ... I wonder what the "Voltage" input is for?

 

[ScoTTyBEEE]

Get the ring, they're the best item out there. I think the 'voltage' input just means you can charge a 12v battery from a 24v alternator like in trucks.

 

[wildebus]

Get the ring, they're the best item out there. I think the 'voltage' input just means you can charge a 12v battery from a 24v alternator like in trucks.

Except "Voltage" has 12V in, 14,8V out.

The "input voltage - DC" range does look like it will work as a 12V-12V OR a 24V-12V system. The purpose of "Voltage" is very unclear though.

 

[ScoTTyBEEE]

It is badly worded, but fortunately I have one in a box right next to me now and it doesn't have that ambiguous bit on it.
I had one before in an old van and the manual said max 450w of solar and a sticker on the side said max 500w, also the manual says it won't overvoltage until 55v so it seems ambiguity comes naturally to them lol.

 

[st3v3]

Except "Voltage" has 12V in, 14,8V out.

The "input voltage - DC" range does look like it will work as a 12V-12V OR a 24V-12V system. The purpose of "Voltage" is very unclear though.

I have one of these charging the 12V LB from the trucks 24V system. I did have it as the solar controller, but have since moved to a Victron, mostly because of the monitoring. Now the Ring is just doing the 24V - 12V charging.