Charging bow thruster battery

[Huzie]

Hi there,

I have a Jeanneau 42.2 1995. She has 3 battery banks. Engine, Domestic and Bow thruster

We have Solar and Wind Gen but neither are connected to the bow thruster battery

I have an issue where we are rarely connected to shorepower and the amount we use the engine results in the battery going flat quite regularly

I am thinking of adding an isolated DC>DC unit between our domestic bank and the Bow Thruster battery.

Will this need its own cabling? If so do i just run cable with Amperage to match the DC DC

Sorry for my poor diagram!

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[tkeithlu]

The central problem appears to be that you are using more power than you are generating. A suitcase inverter generator plugged into the shore power line when needed could solve that problem.

I don't know where your wiring runs, but...
In my arrangement any energy source (shore, genset, little genset, engine alt, genset alt, engine starting alt) can be connected to any energy storage (house, engine start, genset start, backup battery) sometimes by a crude a means as jumper cables. That supplies maximum redundancy. In addition, any battery can supply any user (house batteries start engine, etc.) As the worst case scenario - everything flat - pulling the recoil starter on the portable genset charges the starter battery on the engine and so forth, rebuilding the supply.

Aside from getting an additional energy source, I recommend your thinking in these terms as you redesign your energy system. Good luck with it.

[SailingHarmonie]

No, no, no...

If the situation is as the OP describes adding a generator is NOT needed. He apparetly can charge his house batteries with his wind and solar just fine, but there is simply no way to transfer that energy to the bow thruster battery with the system as configured.

Adding a battery to battery charger is the right answer. It does not need its own cabling, as long as the existing cables from the battery isolator can handle the load, which need not be large. If it is more convenient to run its own cabling, then those cables just need to carry the new charger load. Be sure to put fuses where the charger connects to the house and the bow thruster batteries.

You also do not need an isloated unit if the house and bow thruster share a common negative, which is the common, but not universal, situation.

[Huzie]

Originally Posted by SailingHarmonie

No, no, no...

If the situation is as the OP describes adding a generator is NOT needed. He apparetly can charge his house batteries with his wind and solar just fine, but there is simply no way to transfer that energy to the bow thruster battery with the system as configured.

Adding a battery to battery charger is the right answer. It does not need its own cabling, as long as the existing cables from the battery isolator can handle the load, which need not be large. If it is more convenient to run its own cabling, then those cables just need to carry the new charger load. Be sure to put fuses where the charger connects to the house and the bow thruster batteries.

You also do not need an isloated unit if the house and bow thruster share a common negative, which is the common, but not universal, situation.

I was thinking the DC DC was the right way.. but how would you use the cabling from the charging isolator? I cant quite work that one out

There is a common negative between the house and the bow thruster

[Huzie]

Actually i assume the DC DC would do the same job (in the fact it would charge the Bow Thruster battery when the house is being charged) so i could essentially disconnect it from the Battery Isolator and use that cabling for the DC DC?

That way it would charge the Bow Thruster whenever there was spare power in the house bank?

[smac999]

Originally Posted by Huzie

I was thinking the DC DC was the right way.. but how would you use the cabling from the charging isolator? I cant quite work that one out

There is a common negative between the house and the bow thruster

Get an non isolated dc- dc. Take the input from house battery. (Fused). Run the output to the bow thruster battery cable at the alternator isolator.

No need to run a 2nd cable to bow.

[smac999]

Originally Posted by Huzie

Actually i assume the DC DC would do the same job (in the fact it would charge the Bow Thruster battery when the house is being charged) so i could essentially disconnect it from the Battery Isolator and use that cabling for the DC DC?

That way it would charge the Bow Thruster whenever there was spare power in the house bank?

This would also work to just disable the battery isolator to bow battery.

[KeepInTune]

Can't you simply tie your solar and wind into the isolator -it will then feed into charge all three banks (engine, house and bow-thruster)?

[Huzie]

Originally Posted by KeepInTune

Can't you simply tie your solar and wind into the isolator -it will then feed into charge all three banks (engine, house and bow-thruster)?

Yes!.. nice idea. This sounds like it could work but i think the isolator only has one input.

I would need an isolator with 2 inputs and 3 outputs.

I assume there would be some efficiency lost though?

[smac999]

Originally Posted by KeepInTune

Can't you simply tie your solar and wind into the isolator -it will then feed into charge all three banks (engine, house and bow-thruster)?

no you would never do this... solar controlers, mppts anyways, need to see the battery for one thing.

[KeepInTune]

Originally Posted by smac999

no you would never do this... solar controlers, mppts anyways, need to see the battery for one thing.

My Cristec isolator specs says that you can add in an MPPT to the isolator input lug to provide this added power (which is shared with alternator positive). I'm curious and not at all arguing this, but very interested to your insights on why this is not advisable.
Thanks.

[Huzie]

Ok so it sounds like using DC DC is the way to go. Perhaps it would be better to replace the Isolator and replace with two DC DC units. If so could I do so similar to the method outlined below?

Thanks for your patience with me on this while I learn!

[Huzie]

primarily the thought here is that the Bow thruster battery would be charged by both the Alternator, Shore power & also now the Wind gen

[Tin Tin]

In our system all electric generation goes to the House bank bus bar, alternator, generator, shore power charger, solar etc. From there you can connect cables to a DC DC charger direct to the thruster battery. Set the DC DC charger parameters for cut in and cut out voltage so it can not flatten the house bank. This way when ever there is charge going into the house bank above the cut in voltage it will charge the thruster battery. If you have Lithium house bank. then the alternators (if standard) should also go through a separate DC DC charger.

[Huzie]

ok thanks, so something more like below?

The Shorepower charger and the Wind gen have multiple outputs. I suppose i could use these or simplify as below?