connecting the house and engine battery with a switch to assist bow thruster

[pskudlarski]

Hello,

My house battery bank is weak, but probably does not need to be exchanged yet. The only serious problem I am having now is that it is too weak to run the bow thruster. I have a well running generator so I feel can afford to have a weak house battery as I can recharge it when needed. The engine battery is good.

I am thinking of adding a switch that would allow to temporarily connect engine battery and house battery outputs (the way it is already done for the engine starter). This would be turned on only when bow thruster is needed and engine running thus limiting the risk of depleting the engine battery.

If this is not a completely bad ideas should I use a switch that makes a connection for both positive and negative wires such as this :
https://www.amazon.com/gp/product/B0...KIKX0DER&psc=1
Or can I connect the black negative terminals permanently and put a switch connecting only red positives?

[meridian28]

I would run the generator when using the bow thruster if the engine alternator is not charging the house bank. You do run the risk of dragging down your good battery and then having nothing.

[pskudlarski]

Originally Posted by meridian28

I would run the generator when using the bow thruster if the engine alternator is not charging the house bank. You do run the risk of dragging down your good battery and then having nothing.

Tried it, was not enough. Generator helps via battery charger thus gives at most 40-60 amps. Does not help much with the sporadic demand of bow thruster.

[smac999]

fix the real problem. don't come up with band aids

is the voltage drop happening at the batteries themselves? (bad batteries) or at the thruster? (bad cables / connections)


the neg should already be perminatly connected. if you already have a parallel swtich for starting (which you stated) then you already have the swtich you want...

the bow thruster will certainly deplete the engine battery if you combine. as it will be more amps then your alternator.

[pskudlarski]

Originally Posted by smac999

fix the real problem. don't come up with band aids

is the voltage drop happening at the batteries themselves? (bad batteries) or at the thruster? (bad cables / connections)


the neg should already be perminatly connected. if you already have a parallel swtich for starting (which you stated) then you already have the swtich you want...

the bow thruster will certainly deplete the engine battery if you combine. as it will be more amps then your alternator.

So is it OK to permanently connect negative poles of house and engine batteries? I was afraid that there may be a reason why they were not connected to begin with!

As for band aid, I pretty much know the problem is with the batteries, voltage drops on them, but am hesitant to dispose of them, not only for monetary but for environmental reasons as well

[ranger58sb]

Originally Posted by pskudlarski

My house battery bank is weak, but probably does not need to be exchanged yet. The only serious problem I am having now is that it is too weak to run the bow thruster. I have a well running generator so I feel can afford to have a weak house battery as I can recharge it when needed. The engine battery is good.

If your house battery bank ran your bow thruster properly before...

And if the genset/charger combination don't give you enough extra juice now...

My guess would be your assessment is incorrect and I suspect your house batteries have reached end-of-life. Maybe a long time ago.

Bringing your start battery into the equation just puts that at risk, too.

The new battery seller generally wants your old batteries in exchange...

-Chris