Basic Connection Help!

That is a very nice fuse--You will probably find it pretty expensive. But, anyway, lets back up a moment.

Fuses/circuit breakers are there to protect wiring from excessive current/overheating/fire. It is not really there to protect devices, batteries, etc.. For example, you can easily damage/over heat a 100 AH lead acid battery with just 10 amps of current--If the current is supplied for a long period of time/gasses the battery dry/etc.

So--You have "layered protection". You have a fuse/breaker per wire to protect against over current, and you use charge controllers/dump controller+loads/etc. to prevent the battery bank from being over charged/over voltaged. Some battery types (various Lithium rechargeable types, others) which are sensitive to over/under voltage may even have a per cell battery management system/disconnect.

In general, think of the battery bank as the heart of your off ground power system. It is generally the souce of very high current levels--Most other devices (charge controllers, inverters, AC battery chargers, solar arrays) have only a limited capabilities to supply excessive current.

So--Typically you will have a + and - battery bus connection (common connection point). Every + lead that leaves the battery bus terminal should have a fuse/circuit breaker that protects the wire against excessive current if there is a short.

So, using the National Electric Code (NEC), you will find tables that tell you what is "acceptable" current flow through a wire+insulation type+conduit fill+ambient temperature+copper/aluminum, etc.

For typical house wiring, as an example, you want to supply 12 amps (whether at 12 VDC or 120 VAC, it really does not matter), you should use a fuse/breaker/wiring rated for:

12 amps * 1.25 NEC derating = 15 amp branch circuit rating.

In the NEC, you will see that 15 amps means a minimum of 14 AWG copper wiring.

So, in general, we do not fuse the battery based on its capability, we base the protective device on the size of the copper wire connecting to the battery. And there are different standards.

NEC tends to be conservative:

http://lugsdirect.com/WireCurrentAmp...ble-301-16.htm

While marine wiring is a bit less (note SAE gauge is slightly smaller than American Wire Gauge AWG):

http://www.boatus.com/boattech/artic...-terminals.asp (see table 3)

There are also other design consideration... Many times in solar we use larger diameter wire because we do not want much voltage drop--Especially at lower DC voltages (i.e., a 1 volt drop at 12 VDC is a serious issue; a 4 volt drop on a 120 VAC circuit can be normal).

There specific cases were we do fuse solar panels (typically when we have 3 or more panels/strings of panels in parallel) and battery banks (when we have 3 or more parallel battery strings).

The simplest way to see how all this works together is to paper design a system for your needs. It is usually much less confusing that speaking in "General Design Rules and Requirements". Small systems a usually easier than large/complex systems to understand--And mixing the requirements for your first system design can be frustrating.

-Bill

PS: I should add that fuses have their place, but many times a circuit breaker is a better choice. No spare fuses needed, easy to turn off power for servicing, etc. Larger fuses can be very expensive, and the price of a large fuse+holder+spare+on/off switch may be the same price or more vs a circuit breaker.

And 5% rate of charge would be:

220 AH * 15.0 volts equalizing * 1/0.77 panel+controller deratings * 0.05 rate of charge = 207 Watt array

Should be enough to equalize quite nicely.

-Bill