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BR switch as a battery disconnect

(Brian) #1

I saw the Switch that BR is selling in its store. I like that it fits in the already made holes for the end caps and is sealed. I know it’s used for disconnecting power to low voltage devices…but I would like to use it as a main battery disconnect.

Has someone rigged this up already? Normally you would use a solid state relay of some sorts and this switch would be the contact side, but I don’t know of a relay would output heat and be a problem within a sealed battery enclosure.

Basically what I want to do is have a way to disconnect my battery from the pixhawk and pi when not in use. I don’t like the idea of having to remove an end cap to accomplish this. Maybe I’m not realizing something and I don’t have to, but I’m not sure.

Any ideas?

(undersearobotics.com) #2

Hi Brian. That switch isn’t rated for the full power that the entire ROV uses, so you -cannot- use it for a main power switch. But, with small amount of re-wiring, you can use it to control power to the most sensitive electronics (Pixhawk, Fathom board, Raspberry Pie, etc.).

(Brian) #3

Yeah I know I can pull the battery directly through, but was hoping i could use the switch on the contact side of a relay or something like that.

(Svein H.) #4

Installed two BR2 switches in paralell and hopefull it Will handle the current peaks. I also changed the switch cable with some thicker ones.Most of the time i use it in 25% gain, sometimes 50%. The enclosure is a bit tight so i might change it to a longer one. I still have to open the enclosure to charge the battery, but this Will reduse the frequency a lot. The screws that hold the enclosure together is modified Gopro mount screws with tread inserts.
If the switches fails i can easy disconnect them inside the enclosure and continue with the battery hardwired as original.

(undersearobotics.com) #5

I’m not sure that I’d recommend doing this but I wish you luck all the same.

(Heinz) #6

That’s not a good idea those switches are only rated for 5 amps. ROV2 draws much more than that, up to 90 amp peaks in full thruster gain

(Svein H.) #7

I am aware of this is a limiter due to max current peaks, but what is the biggest downside if it fails? I have been testing it and it seems to work nice, but i will not use it in 100% gain.

(undersearobotics.com) #8

It could potentially short out, over heat the battery and start a fire. That’s a pretty huge battery and steps need to be taken to prevent shorting it’s leads.

(Svein H.) #9

I have put it back to original again. At least i hade a lot of fun doing it. Will try to combine the swich with a relay instead.

(Jacob) #10

Similar topic here: Remote power shut off?

(Heinz) #11

Svein, that’s a good idea. You dont want to risk damaging that nice expensive battery. To be honest I have been working on this for a while now but have been busy with other ROV related projects. I will get back to this soon as I too would like to have a way to disconnect the battery externally.


(undersearobotics.com) #12

I’ve assembled the parts to do this, just haven’t had the time to put it together. Hope to post something soon-ish.


I adapted a 200A relay to fit behind the electronic tray. Used the existing red power cord after the Pixhawk power supply and disconnected two of the small wires from the power supply. Downside is that I lost the info about power consumption.


I did a similar test the other day. I started with a 100Amp Solid State Relay but unfortunately the relay was “leaking” power through on the secondary side even when it was not energized. The Solid state had a consumption of 0.1 Amp during operation. I then did a test with an 120Amp standard car relay but the power consumption was 0.5Amp when the spool was eneergized and i think that is a bit to much during operation.
If anyone had a successful installation of Solid State Relay it would be nice to know the brand & make of the relay…

(Tim) #15

SSR are leaky by nature, but a good quality one shouldn’t leak much. I haven’t installed it yet but the specs for a Crydom D1D100 are 0.3mA leakage at 100VDC and 15mA draw on the control circuit when operating.

What Brand/Model are you using?


I can’t remember the type of SSR, and I am away travelling now but it was just a cheap Ebay unit so that is most likely the biggest issue… I did not measure how much ampere go through when the SSR was disabled but it was enough to power up the Pixhawk and the ESC’s

Please let me know your experience with the Crydom when you have it installed. I will try to get hold of a Crydom myself and give it a try.

Thank you for your help Tim!

(Tim) #17

You’re welcome! The “cheap” SSR on eBay are notorious for being counterfeit and not meeting stated specs. A D1D100 retails for around $150 and you can get them on eBay sometimes for around $100. D06D100 or DC100D100 would also work. You could probably get away with an equivalent 80A model, but I I went with the 100A because I’m paranoid about releasing the smoke from things, especially where there is no overcurrent protection. Hopefully we will get that in the software soon though.

Good luck!

(Abyss Solutions) #18

HI all,

Thought I’d post the switch I installed yesterday.

I used this 100A Solid State Relay to make a battery switch that sits just before the Pixhawk power module.

Because of a lack of room down around the penetrators, I moved the Fathom X around and put the switch up the front of the vehicle. Have done lots of testing in and out of the water (was a bit worried about heat), but the switch barely moved above the ambient air temp while under load - works great!