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Is it a good idea to have a disconnect/kill switch for a 12v system?

forscience

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I'm using a BMS with a battery in a 12v 4s configuration and the BMS has a bluetooth function that lets me toggle battery discharge on or off from my phone. I was wondering if it is still a good idea to have a physical disconnect/kill switch or would it be pointless?
 
When I built my electrical system for my trailer I knew that many of the components had fancy features with Bluetooth and app control. My main design criteria was that the use of those fancy features should only be a convenience when used, not a necessity. I develop software for a living. Things go wrong. Vendors drop support. Software stops working. Your phone battery is dead. Whatever. I did not want to risk my system going down or running into a safety issue just because some phone app is out-of-date.

So, in short, yes, you should still add physical controls.

And in this case you may need a physical switch because the BMS went bad or it's having some other issue. I wouldn't want to be playing with wires with the knowledge that the only thing keeping me from getting badly shocked is that some software told the BMS to stop discharging. I would not want to trust that.
 
When I built my electrical system for my trailer I knew that many of the components had fancy features with Bluetooth and app control. My main design criteria was that the use of those fancy features should only be a convenience when used, not a necessity. I develop software for a living. Things go wrong. Vendors drop support. Software stops working. Your phone battery is dead. Whatever. I did not want to risk my system going down or running into a safety issue just because some phone app is out-of-date.

So, in short, yes, you should still add physical controls.

And in this case you may need a physical switch because the BMS went bad or it's having some other issue. I wouldn't want to be playing with wires with the knowledge that the only thing keeping me from getting badly shocked is that some software told the BMS to stop discharging. I would not want to trust that.
That's a very good point. Though it is a 12v battery/system so wouldn't that be pretty safe to handle even without any sort of disconnect since the voltage is low to begin with?
 
12 volt --- safe to handle...
Do not wait until you short out a LiPo battery circuit.
You should have a battery disconnect switch. It needs to disconnect the battery from the system. It can be on the negative or positive. I have two switches, 1. disconnect the charge controller from the panels and the battery. 2. Disconnect the battery from the system.
 
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Like @rmaddy, I'm a software developer and I too have a physical disconnect switch. Mine is a 12 volt system. I've used the switch recently when I powered down the system to do work on it. Once powered down, everything downstream of the switch was safe to work on
 
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