What inline fuse rating?

Jun 25, 2019
22
20
North Notts
Funster No
61,904
MH
Hymer E700
Exp
Since 2016
Hi all,

I'm planning on adding 3 x 80 watt solar panels (short circuit at 24.3 V and 3.98 A) in parallel to a Votronic MPP 250 Duo. The connection point will be a three MC4 into one adaptor, with 6mm cables running from the junction, through the roof, to the controller. I'd like to put an MC4 inline fuse just before the controller.

Two questions, actually:
  1. What fuse rating would you recommend?
  2. Do I actually need one, as the controller has one built in (I don't know where this fuse sits in the circuit)?
Many thanks.

Peter
 
Dec 8, 2017
159
101
N Wales
Funster No
51,599
MH
Self build PVC
Do I actually need one, as the controller has one built in (I don't know where this fuse sits in the circuit)?
As long as there's a fuse between the battery and the controller, then "no".

Solar panels are incapable of generating enough current to blow any fuse which is rated to pass their working current continuously. That said, fitting one in the feed from the panels provides a means of disconnecting the panels from the controller (for maintenance, etc.) if you so wished. 6mm^2 solar cable is good for >50 amps, so any fuse rating over 12A and under 50A would be OK for that. Otherwise it's just something else to go wrong.
 
Jan 8, 2013
3,294
2,674
Dronfield - Derbyshire
Funster No
24,202
MH
Burstner Nexxo T660
Exp
7 Years
Jan 19, 2014
2,753
6,488
Derbyshire
Funster No
29,757
MH
Elddis Accordo 105
Exp
since 2014
Ordered a 60a breaker for mine just so I'm able to disconnect the solar panel from the controller. If you fit a fuse, make it a big one so it doesn't get warm. If it gets warm there is a voltage drop across it and that wastes power.
The fuse in the Votronic is in the battery circuit.
 
OP
NorthernSands
Jun 25, 2019
22
20
North Notts
Funster No
61,904
MH
Hymer E700
Exp
Since 2016
Thanks for all your help; it's been useful. I like that 15amp breaker. I can see it would be useful to isolate the panels for whatever reason.

All the kit arrived today, but as we're going on holiday tomorrow evening, I have no time to mount the panels. I'll take at least one and stick it outside the van when we're around and staying put for any length of time. I would build a frame for all three, but the garage door has just broken and I can't get in to use my wood and tools. :cry:
 
SMC Motorhomes Newark
RoadPro
Johns Cross
Safeguard Motorhome Insurance
Rhino Installs
Friendly professional service from qualified technicians
Free Club Stickers
Dave Newell Leisure Vehicle Services
Top