One thing I think the BlueROV2 really needs is a way to turn off the ROV power without having to open the battery housing and disconnecting the battery. It would be much easier, better and safer to be able to hook up the batteries on the bench and simply flip a switch on the ROV prior to launching.
Blue Robotics offers waterproof switches but their current rating is much less than what we need to power off the battery. But it could be used in conjunction with a relay (or MOSFET?) for power control.
Has anyone come up with a working solution? I’m thinking the ideal location for both the switch and control circuit would be the battery housing. Thoughts? Ideas?
I’m working on it. After diving at 5 different sites at the river I was at it was impractical to remove the battery cover and unplug it each time. So the ROV was running the entire day! That makes the electronics housing very warm even though we kept it covered with a towel, never until that day was a way to disconnect the battery more needed. I’m heading toward a simple electric relay that will be controlled from the Blue Robotics switch. The first electronic switch I got is too large. In either case there will have to be some modifications to the battery housing cables as the new large capacity battery takes up a lot of room and only leaves a small amount of space there.
There is space in the rear of the main electronics housing and I may install it there if I cant fit it inside the battery housing.
On a side note. The new Blue Robotics battery totally rocks! I used the hell out of it in my last dive with a lot of current and large volume spring vents all day and it held up fine.
Hey Heinz, have you looked into using a MOSFET transistor instead? The circuit looks simple and small enough for our purposes. Found some 80 amp MOSFETs but am thinking 100 amp is better. Circuit board traces might not be thick enough for the current so maybe just use a round shaped piece of bread board? Any other ideas?
I looked at a few other alternatives including a solid state relay but I’m thinking the simpler the better and an electronic relay is already available, is robust and the correct voltage for our purposes. The problem is getting one small enough with a high enough rating to handle our needs. The 100 amp electronic and solid state relays are too big for our purposes. So I got a smaller 40 amp model with different dimensions to see if that will fit. Its coming from overseas so I’ll have to wait.
Another option I keep coming back to is a bulkhead mounted power disconnect plug. That would allow charging the battery inside the housing as well. The problem being I can’t seem to find a single 2 pin connector that will handle the full theoretical load of the battery. The XT60 connectors are rated for 60 amps, but something like a SubcTech BH-4f connector is only rated to handle 20 amps if I use all 4 pins. And I really don’t want to use multiple pins if I can avoid it. To handle the whole 60 amps, I’d need something like a 16 pin connection, which is both large and expensive, especially since I would need a second external connector for the charging plug. so it would run somewhere around $240 to set up that way. Anyone happen to know of a less expensive 2 pin connector that would handle main battery power without melting? I’m kind of half tempted to make some sort of horrible XT60 external connection abomination, but I’m pretty sure I’d electrocute myself with that one.
@piercet - I’m not sure that charging a LI battery with only the two power leads is a good idea. I would want to use the balance connector when charging the battery. Plus I prefer having the battery outside the housing so I can monitor its temperature while charging.
@force10windsurf - I don’t know that we’ll find a relay small enough to handle 90+ amps, that’s why I’m wondering if MOSFET would be the better way to go. Any electronics engineers want to chime in on this?
@paul-unterweiser,
There should be prepackaged MOSFETs that can handle 100 amps or so, but still might require some heat sinking and will add to the thermal load in the Electronics Tray WTC. There might not be enough room in the Battery WTC for the switch.
Regards,
TCIII AVD
@tciii - Yeah, I’d really like to avoid putting anything else into the electronics housing. I’d really like to find a simple solution that can fit into the battery housing.
Yeah, I think that’s the way to go. It wouldn’t be difficult to make a magnet slider switch that had a waterproof magnet embedded into a 3d printed housing that would bolt to the rear of the battery compartment (or operate as a slip ring around the back of the housing. Stick that chip and a magnetic switch inside the plate, move the magnet to “on” position, and give it a bolt hole and a pair of threaded holes so you could optionally secure the switch in the on or off position with a thumbscrew to prevent accidental operation. Making it mount to the back plate would be simpler logistically to design and print and cause less drag. Making the switch a circular slide switch around the housing might look cooler.
I was going to use a 10A/12VAC / 28V DC relay rated for a max load of 1/4 HP that I had in the drawer when I got around to this. That should be enough, and only pulls 70mA at 12V when closed.
The prototype “use the blue robotics and the other switch thingy to make an external main power switch of doom” thing now exists. Sadly since I don’t have a battery yet, or a charger for the battery, it’s a ways out from testing. But it looks like it will work
I got a couple of those Pololu boards also. I’m waiting for a 100 amp SSR (Solid State Relay) I ordered to try first. I might need a longer batter tube to fit everything.
