Panel Configuration Diagram--Input Needed

Re: Panel Configuration Diagram--Input Needed

Each positive cable that leaves the + battery bus should have its own fuse/breaker per wire (or group of wires).

Use your local electric code for current capabilities of the cables (don't know if you use AWG, mm, or mm².

The idea is if there is a short circuit anywhere in your system, the fuse/breaker will open before any wiring catches fire.

A large fuse on a single string of batteries is usually not done if you have heavy battery interconnect cables.

Also, do you have the DC battery bank is negative grounding to the building AC safety/green wire ground? This is to prevent the negative bus from becoming "hot" (-12 volts). If you have a floating battery bank, you are supposed to have a fuses on both + and - wiring (2x more fuses /breakers). But many people do not do that.

With fusing/breakers--They really are never used if all is working well. They are only there IF something goes wrong. Having a dead short on a large battery bank can be very exciting.

This video (2nd half) shows what 300 amps at 12 volts can do to a nail/screw/bolt in a short circuit:

If the system uses grid power for charging (not on a generator), I would suggest you get the IQ4 module for your Iota. And monitor your water usage in the flooded cell batteries (too much water usage, back the charging/float voltage down; too little water usage, crank of the voltage a bit).

-Bill

Re: Panel Configuration Diagram--Input Needed

semsoblue wrote: »

I've attached another diagram showing the connections between the buss bars and the breakers (the actual breakers I'm using). Do I need additional fusing before these breakers? I'd be using #8, probably about 12-18" between the bars and the breakers. With this setup and these types of breakers, would I still need to ground the negative to the house ground?

I could not tell the Amp Rating of the breakers--But using two pole breakers, you do not "need" to negative ground the battery bus (floating outputs with breakers on both +&- wiring is perfect from a safety point of view).

For 8 AWG wire, in the US we would run a breaker of 40-50 amps (NEC) to 60-80 amps (ABYC).

Also, did I understand you to say that the 125A fuse from the battery bank to the buss bars is not needed?

If the total of your DC Branch circuit breakers is less than 125 amps, then you do not need the battery bus breaker.

if the total of breaker is over 125 amps, then you can use the 125 amp breaker on the battery connection (note, see above charts, 2 AWG cable can carry roughly 95-130 to 280-330 amps--Conservative to not very conservative).

I do have an IQ4 installed. I charge with the IOTA from the grid, but also from the generator when the community power is down. Does that affect the IQ4 or IOTA? Thanks!

The IQ4 is useful when the power supply has a, more or less, continuous AC power supply (grid). If you are running the generator only X hours per day--Then the IQ4 does not help much (or hurt). Once the battery is over 80% state of charge (or over 90-95% SOC, your choice), most people would be turning off the genset to conserve fuel.

The IQ4 will drop the voltage back to "float" voltage if the AC power was on 24x7 and the Iota was set to "Absorb Voltage", the battery would over charge and (for AGM) eventual vent and/or boil dry (flooded cell).

-Bill

Re: Panel Configuration Diagram--Input Needed

I have always been leary of "twist type" battery switches. From an engineering point of view, easy to have arcing if switched under load. Also, there have been reports that the switches do not really do well if subjected to heavy/continuous current (OK for a starting motor, not OK for a 200 Amp draw by an AC inverter for hours on end).

Attachment not found.

If you can swing it--I would suggest a properly rated DC Circuit Breaker for your battery switch.

http://www.solar-electric.com/installation-parts-and-equipment/midnite/cipr1/high-amperage-inverter-breakers.html

-Bill