Hi what size fuse between 75/15charge controller to liesur battery
asked
What size fuse should be inbetween my victron mppt 75/15 charge Controller and leisure battery. Got 10amp at mo
The MPPT can give you up to 15A, so your 10A fuse will blow if the MPPT gives you full power.
The fuse size also depends on the cable cross-section you are using and the cable length.
I have a similar question - same victron smartsolar charge controller MMPT 75/15 (Ampere Time 12v 200Ah battery)
The manual says this MMPT maximum voltage is 15a & you say use a 15a fuse or circuit breaker; I dont see circuit breakerfor 15a (only much higher).
I do see an Inline fuse holder with copper wire that I can put a 15a fuse - Im not sure how to attach the wire to the wire leading from the charge controller to the battery - just use those plastic twist caps?
What guage wire do I use to go from fuse holder circuit breaker to charge controller?
Also I am unclear what you meant by the cable cross section. Also the length is unclear to me - it was installed by the RV company onto my tow trailer.
I am a newbie and I know some of what I said sounds scattered. Thanks in advance.
I am grateful
Cable cross section is equivalent to AWG. You can easily find conversion tables on the internet.
A fuse at the MPPT between MPPT and battery is not necessary. The MPPT limits current and if the fuse is big enough to carry the max MPPT current, it will never blow.
There should be a fuse or circuit breaker close to the battery, sized for total load on the battery. MPPT should run through this fuse. All loads should connect to this fuse and be individually fused for their loads. Easiest way is a fuse box.
The fuse is to protect the cable. Cable “cross section” is the area of the copper looking end on. As mentioned above you might expect 15A max out of the charge controller. Therefore you should have a cable that can take a bit more than that to allow a margin above max. AWG12, cross sectional area 4mm2, will take 20A in free air, however, there is always an associated voltage drop. So, if you have a long run you may want a heavier gauge. You need to find what cable is fitted in your RV and fuse accordingly. Here is a useful calculator …
https://www.solar-wind.co.uk/info/dc-cable-wire-sizing-tool-low-voltage-drop-calculator
