Battery cut off

Re: Battery cut off

You're right, it looks like battery 1 is always connected to the system.

I've attached a picture with two diagrams. Normally the disconnect is connected to the positives. This is because the battery negative side should be connected to ground according to the US electrical code.

Diagram 1 shows suggested wiring given what you have now but with the disconnect on the positive instead. The disconnect switch will disconnect both the solar controller and the inverter.

Diagram 2 goes further. I've added a separate disconnect for the solar controller. This one can be a smaller DC breaker sized to handle the solar controller output. The inverter output is larger and so you have a larger disconnect switch there. One reasons for the separate disconnects is so that you can disconnect the equipment pieces individually depending on which one you want to do work on. This is the way it's normally done.

Also in Diagram 2 I put a ground connection for the battery negative. As well, notice there's only one cable going from the disconnect switch to the positive battery terminal. That's for if you want to make the disconnection at the batteries, there's only one cable to remove.

As for the wiring disconnect order for your current system, I'd suggest disconnecting the two positive connections at the positive battery terminal for the inverter and solar controller first. That's because the negative side is normally grounded. Then I'd suggest disconnecting the inverter and solar controller where they connect to your disconnect switch. Normally it'd be good enough to disconnect just from the positive but your wiring's a little strange so this is just to be extra safe.
-Steve

Re: Battery cut off

greenthumb76 wrote: »

I don't understand the switch you are showing. What I am working with is this.

That's the first time I've seen one of those - but since it's an automotive disconnect that would explain why. It still means you're right, that one battery is always connected.

As for the wiring disconnect order, now that I've seen your disconnect means, I'd still suggest what I said before. Disconnecting all those positive connections at the battery postive terminal so that the solar controller positive, the inverter positive and the battery cable that were all on that terminal are all now separated from each other. That basically opens the circuits. Your automotive disconnect thing with the green knob is of no use on its own as a disconnect means since the components are all hardwired together there. Disconnecting the negatives are optional at this point - unless you have ground connections you haven't told us about.

The large disconnect switch in my diagram was one like this:
http://prismsolar.co.uk/shop/outback/ob-dc175-dc-breaker/prod_94.html?review=write
It's an actual breaker which would trip when there's a short. It's just a very big breaker because if there's a short at your battery bank then there would be a lot of current. I just replaced a customer's inverter last year because of that. They did have a disconnect switch but they'd fixed it so it wouldn't disconnect since "that would be inconvenient". It's the same disconnect switch found in the E-Panel that @hillbilly mentions below.
-Steve

Re: Battery cut off

greenthumb76 wrote: »

Stevend,
so, if I understand correctly, the 100amp fuse I currently have on the cable between the batteries and the inverter would be replaced by the big breaker? Is this necessary for safety, or just for convenience? As I explained, I am severely limited as to what I can afford.

I didn't realize you had a 100 amp fuse there. You still have no switch for disconnect but the fuse will protect your inverter.

Keep in mind, your system won't be in compliance with the electrical code, but I take it you can't afford to anyway.

greenthumb76 wrote: »

Although I'd love to be able to buy a system that could fuel my previous lifestyle--what I'm trying to do now is simply put together a small, safe, functional, completely off-grid system that can fuel my basic needs for a fairly primitive lifestyle.

I currently have a 110 watt array. The most I can conceive of being able to expand to is less than 500 watts, more likely about 300.

I definitely want to be safe, and I'd like things to be convenient, but at this point, that's optional . . .

Out of curiosity, what info did you base your decision on to go solar that made you think it would be affordable?

greenthumb76 wrote: »

so, to be clear: if I disconnect from battery 1, the positive cable that has everything attached to it (controller, inverter, battery #2) . . .

... and separate the cables (controller, inverter, battery #2), then at this point your system is safe. Though before you do anything, make sure your loads are not connected as Neil suggested and that your PV is not generating anything.

greenthumb76 wrote: »

and if I then disconnect the controller cable and inverter cable from the battery #2 cable, and from each other. . .

The above is optional. Also, be careful not to short out your batteries. No positive should touch any negative.

greenthumb76 wrote: »

then it will be safe for me to work on the system, without disconnecting anything else (as long as it is dark, or the pv array is prevented from receiving light)?

Well, working with batteries, even without anything wired to them requires precautions: googles, gloves, don't short out positives and negatives, no sparks. Maybe someone here can point out a good document on safe working with batteries. Given the information you've given us here then it should be safe.
-Steve