Battery Box Disconnect

vtmapsvtmaps Solar Expert Posts: 3,739 ✭✭✭✭
Hi everyone, great forum! I have learned a lot by lurking here.

I have an outback vfx3524 on a midnight solar E-panel, and am planning a few upgrades of my off-grid system.

I need to work in my crowded E-panel in order to perform the upgrades, and I don't want to work around the extensive positive battery bus when it is hot. The only way to deactivate the bus is to disconnect the battery cables.

As a first step, I would like to put a battery disconnect between the battery box and the E-panel. I have seen a dozen or so off grid systems, but have not seen a battery disconnect.

Are there any downsides or NEC considerations I should know about? Is it OK to attach the disconnect box to the surface of the (plywood) battery box, or must the disconnect box be on the wall between the battery box and the E-panel?

Thanks, in advance, for your thoughts and advice.
4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i


  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Battery Box Disconnect

    Glad you've been helped so far. Let's try a little more help! :D

    The most basic battery disconnect switch:
    There are also breaker/switches like this:

    Be sure you power everything down (inverter and charge controller) before taking the battery cable off to install such a switch.

    Not sure how picky NEC gets about these things, but I'd just mount it where it's convenient for you. Switching within/too close to the batteries may present an ignition hazard for gasses.
  • 2manytoyz2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: Battery Box Disconnect

    I'm using those same Blue Sea switches. These are excellent! Intended for marine use. They are sealed to prevent sparks and water intrusion.

    Since I'm a DIY type of person, and don't necessarily conform to regulations, I use these switches. Not necessarily being unsafe, but might use other products, or more fuses than required. These may not be approved by the NEC as they were intended for use on boats. However, if they are robust enough to survive a marine environment, they're certainly good enough for my garage. This was my previous "experimental" setup. Working on a more finished looking layout, hiding most of the wires. But you can see the switch & quick disconnects on the battery cables.


    I also went a little further and used large Anderson type quick disconnects on each pair of 6V batteries. Each pair of batteries is tied in series to make 12V. They are then connected to a busbar via a QD connector. I have 4 pairs of batteries in parallel. If any set of batteries has an issue, they can quickly be removed from the circuit.


    Rated at 175 Amps, made by Anderson. Often find these on forklifts, golfcarts, etc. If I max out my my inverter, it'll pull about 200 Amps. With 4 pairs of batteries sharing the load, that's about 50 Amps per pair of batteries. So each connector would see a maximum of 50 Amps, well below the rating. But if I have a battery failure, pulling a connector won't overload the rest of the connectors. FWIW, I never run my inveter near max anyway.

    The 12V inverters I use were intended for marine/RV use, so I'm following the guidelines provided by the manufacturer.
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