Wire Size Between Batteries

BB.

Re: Wire Size Between Batteries

democopy wrote: »

If I use the MPPT Morningstar Controller and add a remote display box, then do I need the shunt?

The typical solar charge controllers only measure the current that they produce. Loads and battery charging are "unknown" with Charge Controller monitoring.

A typical Battery Monitor uses the shunt to measure current into/out of the battery bank. Those numbers are used to estimate the current state of charge of the battery bank.

Also, shunts+battery monitors tend to be much more accurate at measuring current flow than typical solar charge controllers.

Is the shunt wired right after the batteries on the negative side?

The Shunt is wired between the negative post and the chassis/common ground bus. Exact position does not matter. Normally all negative/return wires are connected to the negative/common bus and not the battery negative lead (so that all current into/out of the battery is measured).

The Blue Sea Fuse you linked below, would go on EACH battery? So FOUR of them if I have FOUR batteries?

You have 4x 12 volt batteries in parallel--so four fuses would be required--one from each battery to the common positive bus/connection point. Each lead that leaves the + common point should also have its own fuse (solar charge converter, inverter, other DC loads, etc.).

The fuse I linked to would handle all the batteries after the lead comes off the battery, correct?

What size fuses on the batteries?

Pick the fuses either based on NEC wire current rating, or on some generic chart like these (note: the chassis wiring rating is 2x that allowed by NEC... Example 14 awg is 15 amps NEC and 32 amps in this chart).

What size fuses going to the inverter?

Basically, the wire and fuse should be at least 1.25x the expected maximum continuous current rating of the inverter.

Note, you may have a 1,000 watt inverter and only plan on 500 watt loads--so you could fuse/wire based on 500 watt load limit.

• 500 watts * 1/0.85 eff * 1/10.5 volts min batt * 1.25 NEC derate = 70 amp minimum wire+fuse rating

What size fuse going from the panels to the controller?

If you have two parallel panels (or strings of panels), you don't need any fuses/breakers.

If you have 3 or more parallel strings of panels--then each panel string should have its own series protection fuse/breaker (fuse rating should be in data sheet). There are Combiner Boxes with lots of breakers for solar systems.

If your panel specs do not list a series protection fuse--then use a fuse at least 2x the Isc (short circuit current rating) of the panel (round up to next standard fuse size).

-Bill

icarus

Re: Wire Size Between Batteries

Couldn't have said it better myself,,, no really couldn't have!

T

PS The bluesea fuses are really clever, such that it makes a very clean installation with plenty of fuse protection. I wish I had know about them when I built my system.