Size for fuse at the Batteries (2x 6v)

[er78mph]

Hello and thanks to all in advance!
I have a pair of 6v batteries and wanted to place a fuse at the batteries. My trailer is 30 amps and I currently have 6 gage cables. Also, would the fuse be attached to the +? Would I simply have a short cable from battery terminal > fuse and from fuse to house? Thanks again!

[wa8yxm]

The fuse size depends on the wire size more than anything I have 3 "Fuses" (one is a circuit breaker)

1: 40 amp, 10ga stranded wire feeds a distrubition panel next to the driver's seat which in turn feeds a bunch of stuff (Radios, Fans and such) it is an anderson power pole panel (West Mountain Radio)

2: 80 amp self resetting breaker (Factory installed) the main "House" fuse.. My converter is also 80 amps.. Same make as yours, just bigger, also has wizard.

3: 300 amp. Feeds the inverter, nice BIG welding cables 0000 gauge as I recall.

So the answer depends on wire size.... The bigger the wire the bigger the fuse.

[RoyB]

X2 on purpose of the fuse being to protect the burning of the battery cable in the event of a dead short on the equipment side of the battery cable.. My Converter/charger is a PD9260C 60AMPS setup and I used a 80AMPs FUSE for my setup for awhile and then I added a Power Inverter with larger size battery cables that wanted to see around 120AMPS DC current. I now use a 130A DC fuse for my trailer system main feed setup and a 175A DC Fuse for my Power Inverter main feed cable...

My setup uses the four position BLUE SEA switches as close to the battery terminals as I can get. My large fuse is on the selected DC OUTPUT leg right off the switch lug terminal... This 4AWG cable is about 5-feet long before hitting the Power Inverter and PD0260C Converter/charger unit. The DC Power Distribution panels is another 5-feet away from this point where my WF-8900 series Power Distibution Panel is located that houses the 120VAC Circuit breakers and the 12VDC Fuse panel for my system use.


Roy's image

My new battery bank will be using two groups of 6VDC bartteries is series and I will most likely have to re-visit the fusing. I kinda like the idea of the Auto Circuit Breaker like mentioned above...

My main layout will look something like this...

Roy's image

Having never run the 6VDC batteries before I do not know how much DC current the 6VDC batteries will demand when first hit with the 14.4VDC my initial charge voltage. My 12VDC batteries always demanded around 17-20ADC current for the first 15 minutes or so of charging... When I make adjustments for this with my new battery bank I will most likely add the AUTO CIRCUIT BREAKER protection.

Roy Ken

[opnspaces]

Does your 6 gauge cable run all the way back to the converter or only to a junction box on the tongue? Personally I would fuse based on gauge of the smallest wire between the battery and converter. Anything more is just risking a fire.

[time2roll]

55 amp converter & #6 wire? I would fuse at 60 amps. Get a Bussmann Hi-Amp breaker or a Maxi-Fuse holder.
Chuck the auto-rest nonsense.

[DrewE]

Fuse size is determined by the wire size (and type and installation) that the fuse is protecting. Recall that the purpose of a fuse is to prevent a fire due to the wire overheating from excessive current.

50A is a conservative size for 6 gauge wire; the NEC permits between 55A and 75A depending on the temperature rating of the wire. These guidelines are not immediately applicable to low voltage wiring (as the wire types are usually different), but do give a reasonable starting point. Often the 12V fusing is more permissive. At any rate, I'd feel entirely comfortable using a 50A, 60A, or even 75A fuse or circuit breaker in your situation.

The 30A AC inlet has absolutely nothing to do with this; the 120V electric system is quite separate from the 12V system. Likewise, the details of the battery are irrelevant; any 12V house battery could supply many times the current that the wire could carry safely. The fuse would be put in the positive line, as close to the battery as reasonably practical. The negative battery lead connects to ground directly. (If you have a battery monitor or battery ammeter, the shunt is usually placed in the negative lead.)

[Boon_Docker]

12v inline circuit breaker, real easy install.

http://www.ebay.com/itm/CAR-STEREO-AUDIO-12V-CIRCUIT-BREAKER-FUSE-INLINE-FITS-4-8-GAUGE-WIRE-50-AMP-/222336672482?hash=item33c44c62e2:g:paIAAOSwo4pYReLN

[Sam_Spade]

enblethen wrote:
Fuse for 50 amperes.

If that battery will be used to start an onboard generator, 50 amps might not be nearly enough. But then the main cable should be larger than 6 probably.

BUT.....why ? In most cases, the + cable to the fuse panel is fairly short and well insulated and isolated and should not really need a fuse.

[enblethen]

Fuse for 50 amperes.

[er78mph]

Here's my converter

Progressive Dynamics (PD4655V) 55 Amp Converter/Charger with Built-In Charge Wizard

[Boon_Docker]

..

[enblethen]

#6 wire could have a fuse/circuit breaker to 50 amp.
What size is your converter? I would protect the same size as the converter output amperage rating.