Battery Cross Over Switch

[Bobby P.]

2017 R31 CB
One switch for House
One switch for Engine
One switch for Bow Thruster
One switch for Bow Thruster and Generator
One Parallel switch

If my House switch and Bow Thruster/Generator switches are "on" and I turn the Parallel switch to "on", will it parallel all of the batteries that are "on" and leave the Engine battery on its own (because it is turned off)? Or does turning the Parallel switch on connect all batteries, regardless of which ones are in the "on" position?

Thanks,
Bobby

 

[Osprey]

The parallel switch connects the house bank to the engine battery. It is intended as a means of starting the engine in the event that the starter battery is too depleted to do the job. Note that the switch connects batteries, not various loads. If your intent was to start the engine the “starter battery” switch would have to be turned on. The various house circuits would only be "in play" if the house switch were also turned on.

 

[BB marine]

Parallel / Cross over switch only parallels house bank and engine bank. If the parallel switch is on the engine battery bank is parallel to the house bank even with the engine battery switch off. With the engine battery switch off the engine and engine's 12 Volt system have no power. Leaving the parallel switch on with house battery switch on and using 12 volt house components, Refrigerator, lights, navigation equipment ........ over time will discharge both house and engine battery banks. The parallel switch should only be used for emergency when a battery bank is fully discharged. The thruster/generator battery banks are not Paralleled with a switch (factory)

Installing a parallel switch between the thruster banks and the house banks to increase battery AH capacity while anchoring is something that can be done.

 

[Bobby P.]

Thanks once again, Brian! I’m going to add a battery to my thrusters (I already have the battery) and I’d also like to introduce a crossover switch between that bank and the house bank. Can you recommend a specific crossover switch and cable size? Thanks much.
Bobby

 

[BB marine]

I have selected a couple of 4 position switches with specifications. The switch you use should be based on estimated current you expect to go though the switch.

Example: If you are using a 2000W inverter maxed out the amount of 12V dc amps is around 166 amps + any other house draw amps. You do not want to pull more amps than the switch is rated for.

Example : The thruster on my boat draws approximately 200 amps X 2 if I am using them at the same time, that would be considered intermittent . If my house and thruster batteries are connected and I use the thruster. The max possibility 200 or 400 amps could pass through the switch intermittently or momentary. Always consider worst case.

The medium duty would probably be sufficient it would be a rare situation that you would over load the switch. There ia a service factor built in but that should never be relied on.

The heavy duty would be over rated but using it would save a lot of time doing calculations. 3X more in cost.

The best way to rate the switch used is to look at the main circuit breaker or fuse used in the combinations of circuits.

Perko 8501DP Medium Duty Battery Selector Switch continue Capacity - 250 AMPS Continuous, 360 AMPS 5 Mins. Intermittent
Terminal Stud Size: 5/16"

Perko Heavy Duty Battery Selector Switch-Continuous Amps: 380A Max
Momentary Rating: 850A (5 min on / 5 min off)

Cable size is based on the length and maximum amperage draw
http://assets.bluesea.com/files/resourc ... hartlg.jpg

 

[Bobby P.]

Is there any concern (other than expense) with just going with the heavy duty switch and using 2awg or 4awg terminals?

When connecting the cross over, I assume I am just dealing with the positive (red) terminals. Are all of the grounds connected, ie, can I assume that the neutral yellow terminal grounds are all connected?

Thanks again!
Bobby

 

[BB marine]

There would be no issue using the heavy duty switch. If you are adding an additional battery it would require a negative yellow cable sized by length. The larger cables will not hurt. To small cable is what you want to stay away from. Over kill is good. It just cost more.

 

[Bobby P.]

Thanks again, Brian. I am just going to go with 1 AWG terminals and hook my extra Battery in parallel with the thruster Battery. I’m also going to get the heavy duty switch, just because...

When I wire in the switch, it has 1,2,all, off. Can you advise on connection between the main bank and this switch? Is there a preferred sequence for 1,2 and all? Also, I don’t believe I need to mess with any grounds at the switch site because I assume that all of the grounds do connect somewhere. Is that right?

I also have the emergency switch that connects starter battery to house bank and obviously I want to keep the starter battery isolated.

Thanks once again for the great support!

Bobby

 

[BB marine]

Give me a call Bobby. It is easier to explain. I’m not busy just hanging out in the keys.