Installing Switch to control dual 24V power sources

[nautibake]

Hello all, would sure appreciate any thoughts. I can usually tackle basics but this one has me perplexed.

We installed a Xantrex 3000W inverter with a 24V battery bank on Sea Joy over 2 years ago. It has worked extremely well, and as we are anchoring out more often it was a very important upgrade.

We have 2 Seakeeper gyro stabilizers that require 24V DC. Although the big gyros themselves are 220V, they each have a controller / display that require the 24V DC. Previously, that DC power was provided through a Newmar 32 to 24V step-down converter connected to the 32V starboard main engine bank.

Recently, the controller / displays had to be replaced with a newer style color display that seems more sensitive to power fluctuations than the older monochrome units. The last few times I started the starboard engine, both controllers rebooted the instant I engaged the starter. These are expensive new displays and the Seakeepers require them to operate so I want to see if I can power them from our 24V newer inverter bank and prevent the power fluctuations.

I bought a Blue Sea 6008 3-position switch thinking I could keep the old Newmar 32 to 24V converter as a back up power source (#2 position) and add the 24V inverter bank as the primary (#1 position) power source for the Seakeeper controller / displays (I would of course be able to switch the power off with the same switch since I leave them off unless we are using the gyros).

However, there are only 3 terminal bolts on the back of the display (1, 2, and “output). I expected to see a power and a ground for each, which I believe is what is coming off the Newmar and going to the Seakeepers. I am pretty sure that both the 24V inverter bank and the Newmar converter are also connected to the main negative of the boat, so perhaps it is as simple as connecting both negatives to that (here is where I am perplexed).

I could sure use any advice on how to install the switch so I can power the Seakeeper controller / displays from the 24V inverter bank and still be able to switch back to the Newmar as a backup power source?

Would appreciate your thoughts, thanks in advance!

 

[Pascal]

I m not familiar with seqkeepers but usually systems with displays/controls whether active fins, watermkaers etc are powered at whatever control box the system uses, not the display. I wouldn’t be surprised if the wires behind the displays don’t just go to the gyro control unit which is where the power will be hooked up Can you the trace the wires from the converter ?

 

[Boatsb]

I'd be careful with that plan.

I replace dc to dc converters all the time. If you don't use a good quality isolated converter the power varies.

First make sure there is a constant voltage from the device. Then add charging and see if there is a rise. If not it's probably isolated.

If the power drops when starting you have a battery issue.

Dont use the inverter bank without adding another isolated converter or the voltage drop could be a problem.

 

[nautibake]

I m not familiar with seqkeepers but usually systems with displays/controls whether active fins, watermkaers etc are powered at whatever control box the system uses, not the display. I wouldn’t be surprised if the wires behind the displays don’t just go to the gyro control unit which is where the power will be hooked up Can you the trace the wires from the converter ?

Thanks Pascal, you are correct, the 24V power currently runs from the Newmar DC-DC converter to the gyro control box mounted on the gyros. From the control box, a separate cable runs to a serial connector which then runs to the display. I am now wondering if what I am trying to do is even feasible. Maybe I should forget the switch and just wire directly to the 24V bank (with proper fuse/breaker)? If I needed to revert back to the Newmar I would just need to disconnect batteries and reconnect Newmar?

 

[tonytrakovich]

You could probably do what you want. I don’t know if you have to switch the grounds, or if all the grounds are connected together on a multiple DC voltage boat. And easy way to isolate the grounds would be with a 2 pole 3 position switch. Like this. https://www.ebay.com/itm/Rotary-Cha...biL7i:sc:ShippingMethodExpress!53125!US!-1But I think I would just wire it to the 24v bank. You would be running genny anyway when using the gyros. The inverter will keep the batteries charged.Then save your dc to dc converter for another project.