Battery switch questions

[Wxboy]

I would like to be able to switch from charging my agm's to a spare battery and also switch which battery bank the inverter is running on at the same time.  Can I do this with a standard marine battery switch?  If so, I've never wired a battery switch before so I have a few questions below.  If not, why?

Ok, maybe I only have one question to start...

What do you do with the negative battery cables??  Someone told me the negative cables between the 2 battery banks would be connected together.  Is that correct? 

[Westbranch]

Me thinks you will need to give us a lot more info before the question can be addressed... CC, battery capacity, PV array size etc.

[boB]

What do you do with the negative battery cables??  Someone told me the negative cables between the 2 battery banks would be connected together.  Is that correct?

Normally, yes.

[Wxboy]

Me thinks you will need to give us a lot more info before the question can be addressed... CC, battery capacity, PV array size etc.

I'm not sure why this information is needed but it's all at the bottom of my posts.  The only information not there is the fact that the second battery bank will be a 100ah fla battery.  I'm not worried about different charging requirements between the 2 battery banks since the second bank will be an older battery that I'm not looking to optimize the charge on but I would like to know if hooking up a battery switch will allow me to charge the different banks AND use the inverter on the different banks once the switch flipped.  Based on boB's response about the negative wires I think I may buy some more wire connectors and give this a try tonight. 

[dapdan]

wxboy,

Yes can use a marine make before break switch to achieve what you want. I have been doing it for years. First all you will need two switches, one for the inverter and one for the charge controller. I like the blue sea mini switch because of its compact size. What you need to remember is you only install the positive wire on these switches. As confirmed below all the negative are common and can all be connected together (I even do this for different battery voltages). At the back of the switch you will see 1, 2 & Common. Common will be connect to the wire going to inverter positive connection or charge controller positive output. Then the remain 1 & 2 go to the respective battery bank(s) and that is it. You will still need to incorporate a breaker or a fuse to protect the wire(S). Remember if you want to keep the inverter or charge contorller on you must switch through 1&2 to select 1 or 2. Remember the fuse or breaker still needs to be there. It should be between the switch and inverter or charge controller. Hope that helps.

Cheers...
Damani

[Wxboy]

dapdan, thanks for the response.  Do I have to use two switches or can I use one?  I was thinking of connecting the CC and the inverter to the common on the same switch.  Then I figured if I switch between 1 and 2 it would switch both the charging and the inverting to a different bank.  I can see how 2 switches would offer more flexibility but I'm hoping one would work since I only have one switch right now.  It's a Perko 250a continuous switch. 

Now on to the fuse/breaker side of things.  Currently I have a fuse on the postive cable to the inverter and I have a MN Quad box with a battery breaker and a PV breaker.  So I was thinking of having the positive battery cable from each bank go directly to connectors 1 and 2 on the switch and the negatives from both banks would be connected as discussed.  And of 2 negatives wires would go to the inverter and the CC.  Then the common connector on the switch would have a positive cable going to the inverter with a 250a fuse on it and also a positive cable going to a 100a breaker before going to the charge controller.  This would seem to protect everything other than the switch.  Again assuming I can get away with one switch would this wiring setup work?  Is it a problem not to have fuses between the battery and the switch?

[dapdan]

wxboy,

You need two switches if you want to charge and discharge separate banks at any time. Everything you outlined in respect of the wiring is inline with what I had advised. IMHO you don't need a breaker/fuse between battery switch and batteries.

If you want to use one switch you would need to decide if you are going to switch on charging(charge controller) or switch discharging (inverter). As you pointed out if you have both inverter and controller on common they will both be switched together and not separately.

Cheers...
Damani

[Wxboy]

Damani, I agree that I need two switches if I want to charge one bank and discharge another but will one switch allow me to charge and use the inverter off of the same bank?  At some point I think I will want two switches but for now I'm hoping to make it work with one.

[dapdan]

wxboy,

yes. With the inverter and controller both on common you will be charging and discharging the same battery bank(either 1 or2) at the same time.

Cheers...
Damani

[Wxboy]

Great, I'll be getting this wired up soon.  Thanks for the help.

[JuliaAllan056]

Thought I might share this website I came accross which I found very useful: http://www.nauticexpo.com/boat-manufacturer/battery-switch-1483.html