DC Fused Disconnect

[sundog01]

I am installing a new Xantrex TrueCharge 2 battery charger this weekend and am trying to figure out the “DC fused disconnect”. The directions state “Install a DC circuit breaker or fused disconnect in each positive cable within 7 inches of each battery.” What will work for the disconnect?

I have two battery banks and want to go straight to the batteries from the charger on the positive side then back to the charger via the neg. bus bar on the negative side. The charger is capable of up to three banks.

Thanks in advance for your help.

[negrini]

A circuit braker on such instalation seems too much inconvenient location to operate, thus a waste of money. In these cases, most common a fuse on each positive cable going to your batt. Westmarine does sell "in line" fuses for high amperage (your manual should state the desireable amps for each).

[Waltthesalt]

I don't know it this will help but relatively recently I've been seeing fuses that fit over the battery terminal to meet these ABYC requirements. A bit pricey but a slick solution.

[mitiempo]

These are the kind I use - they accept 30 - 80 amp maxi fuses.
Brian

[BELLATRIX1965]

The ABYC regs require what amounts to a fuse for the battery itself, thus everything connected to the battery is fused. Check out Blue Sea Systems web site; search for PN 5191 - Terminal Fuse Block, 3/8" Mounting Hole, 1 Terminal Stud. You need the fuse block AND an appropriate fuse module to go with it - make sure it is heavy enough to handle the whole battery load!
Good luck!

[mitiempo]

bellatrix
It has to be 2 separate fuses. Xantrex calls for a fused disconnect between the charger and the battery. This is a dedicated wire from the charger. I agree the battery should be fused in any case (unless it is a start battery in which case ABYC says it is optional). That fuse should be less than the ampacity of the main feed cable and close to the battery(s) capacity in amp hours. It is designed to protect the main feed wires in the case of a short - ie loose battery due to rough conditions, etc that would cause the battery to short out. The fused disconnect on the other hand should be sized for the wire gauge used for the charger's output. This will vary by both distance and charger model being installed.
Brian

[osirissail]

The one battery that really needs a main fuse is the engine starting battery. I have witnessed two boat burn up when the starter solenoid stuck and the battery cable caught on fire. A average starter can suck over a thousand amps out of the battery for the initial rotation of the engine. Since this only lasts for a few seconds it is not a problem with wiring or the battery. But if the solenoid sticks then the very high amperage continues and the cable catches on fire. I use a 350 amp buss bar fuse on the battery feed to the engine starter for a 6-cylinder Perkins. It has not blown so far as the engine starts in a few seconds. Too short a time for any heat to build up in the cable and fuse.

[mitiempo]

I agree a fused start battery is a good idea - just stated that ABYC considers it optional.
Brian

[Maine Sail]

Originally Posted by BELLATRIX1965

The ABYC regs require what amounts to a fuse for the battery itself, thus everything connected to the battery is fused. Check out Blue Sea Systems web site; search for PN 5191 - Terminal Fuse Block, 3/8" Mounting Hole, 1 Terminal Stud. You need the fuse block AND an appropriate fuse module to go with it - make sure it is heavy enough to handle the whole battery load!
Good luck!

ABYC requires a fuse within 7" a power source. A battery fuse of 250 or 300 amps will not protect a 12GA wire for a charger..

[osirissail]

Whoo there, a 12 ga wire for a charger? it must be a rather small charger - 20 amp output or less. The big battery fuses are to protect the large battery cables which in my case are 4/0 cables.
Fusing the DC output of the shorepower charger is rather unusual so I assume the manual in post #1 is talking about the main batteries having fused protection, not the battery charger.
- - My battery chargers feed my DC system at each battery cable connection to the main DC switch. Then I use battery combiners to bridge over to the other battery bank should I be operating the main battery selector switch in any position other than "both". Only if the battery charger voltage exceeds the threshold will it charge the opposite bank protecting the other bank from discharging in to a lower voltage bank.
- - Hot wiring anything directly to the batteries rather than the main DC distribution panel is a recipe for an electrical fire - - unless the item has a fuse or c/b rated for lesser of the items wire size or operating amperage. And the fuse or c/b must be at the "supply" end of the wire feeding the item. This means a clutter of C/B's or fuses at or near the batteries which are subject to corrosion from battery gases.
- - If the proper size battery cable is used to feed the main DC distribution panel there is not logical reason to "hot wire directly to the battery(s). For protection of "loads" hot-wiring disables the purpose of the main battery switch which is to quickly and with one action totally disconnect all loads from the batteries to stop an electrical fire.