What's Wrong with this Picture?

[Kimberly Dawn]

We have a 2019 R27-OB with (4) 12v, 110 ahr batteries: (1) starter, (2) house and (1) thruster. I believe they are all identical, the starter in the starboard locker and the house bank and thruster batteries in the port, all side by side.

Last year at Princess Louisa Inlet our power management skills got put to the test. This year should be better after attending Fluid Motions power management webinar. But it got me to thinking... ouch!

Without a lot of effort, I could add (in parallel) the thruster battery to the house for a 12v, 330 amp hour house bank. Currently, the house bank has a 300 amp buss and the thruster has a 200 amp buss.

So, what's wrong with this picture?

Bob
The Doghouse 2

 

[Hydraulicjump]

Nothing is wrong with this. Pain that it is to search, you will find lots of discussion on this. Many of us have paralleled our thruster and house batteries to give more amp hours on the hook. It is easy to do. And since you only run the thrusters and windlass when the engine is running there is no impact. Just to be certain I have put in a Blue Seas battery switch on the positive cable so I can disconnect them if needed. Haven’t found the need.

 

[BB marine]

There is nothing wrong with parallel circuit house and thruster. The fuse protection is protecting anything downstream of the fuse. The battery output capacity of one battery is more than 300 amps the CCA. The rated 330 AH is a time rated capacity. An easy way to parallel the thruster and house and still have the option of having them in separate circuits is use a battery switch. In my installation I have an inverter. The inverter battery switch is required between the house bank and the inverter. I installed a 4 position battery switch in place of the 2 position battery switch. The functions are: Off (no power to inverter) battery 1 (inverter powered by house circuit) battery 2 (inverter powered by the thruster circuit) both ( inverter powered by house battery and thruster battery in a parallel circuit.) I normally keep the switch off position unless I am using the inverter. If I'm using the inverter and engine is running I use position battery 1. The ACR are functioning as design. If we are on the hook for over night or multiple nights I will set position on both. I keep the inverter power push button off unless I'm using the inverter this helps conserve the draw from the inverter when not in use but powered on..

 

[NorthernFocus]

The theory behind having the thruster on its own battery is to avoid momentarily pulling house voltage low enough to cause electronics to trip. Is it a realistic concern? That's an individual decision based on how we each use our boats. BB Marine's idea is a good one. Install a switch to parallel the house/thruster batts when on the hook and separate them when likely to use the thruster. Or just tie them together and test the design concept ...

 

[Bobby P.]

Great post and responses. My wheels are turning!

One thing I see not mentioned is that one of the thruster batteries is also the starter batter for the genset (for those boats so equipped). For me, I like to safe guard that, just as we do with our engine starter battery, just in case. In my old boat we had a big bank of batteries and everything was connected to it, except a separate battery for the genset. If we ran too far down, we might not be able start the big engine. We just fire up the genset and wait for the the charge to build.

This is why I like some separation. Although all that energy just sitting there, and not being used... is very tempting. I'm always eying that one battery that is dedicated to only one thruster... Seems like a waste....

I think there also must be some other things hooked up to the thruster batteries that I am anaware of. The other day, when simultaneously use both thrusters, I heard a beep from down below (I was on the bridge). I'm pretty sure it came from the smoke detectors. Could that be?

 

[Kimberly Dawn]

Thanks for the feedback!

Decisions, decisions... Adding or replacing a battery switch to accommodate either permanently incoporating thruster battery into the house bank, or having flexibility for maintaining separation of the thruster bank together with its addition on demand... I'll figure out which is my best long-term solution versus the complexity of the installation.

Another concern I have to figure out is how I can "tweak" Victron battery monitor configuration to suit the flexible condition rather than the permanent addition of thruster bank into the house bank.

Bob
The Doghouse 2