Windlass connected to starter battery - Is this common?

[Tenedos]

I figured that on our boat, the windlass is powered from the Starter Battery. I found it quite odd and wondering if this is common at all.

Oddly enough, we have three electrical winches that are connected to the house battery. Using those winches sometimes reboots the Chart Plotter, even when the batteries are fully charged. I suspect there was a similar thinking behind to connect the windlass to the starter battery instead, maybe to protect the sensitive instruments from surges in power draws (I read similar discussions but is this a thing?)

This setup causes some issues so I am planning to rewire the windlass to the house battery this weekend. My starter battery is 105 Ah and house battery is 6x105 Ahs.

Thoughts or suggestions welcome.

[noelex 77]

Originally Posted by Tenedos

I figured that on our boat, the windlass is powered from the Starter Battery. I found it quite odd and wondering if this is common at all.

Connecting the windlass to the house battery is more common, but connection to the start battery is not unusual.

[Tenedos]

Originally Posted by noelex 77

Connecting the windlass to the house battery is more common, but connection to the start battery is not unusual.

Thanks. What is the thinking behind connecting it to the starter battery?

[noelex 77]

There are pros and cons.

The main advantages of using the start battery is that it avoids voltage spikes in marine electronics and if the alternator charging prioritises the start bank it ensures the alternator is always supplementing the draw.

The main drawback is the start battery is smaller, although it often has a chemistry more suited to high discharge loads.

Often the most important factor is minimising the cable distance between the battery and the windlass. This can favour the start or house bank depending on the layout.

Either using the house or start battery can work well if the system is well designed.

[tkeithlu]

Think about Plan B. The windlass is on the starter battery, so start the engine before using the windlass. That way, you won't get the anchor up and then find you cannot start the engine because the battery is dead.

Plan C. Get a set of jumper cables. Then you can cross connect the house battery and the starter battery, in either direction.

Plan D: have a small battery that is separate from all of this, and can power your VHF when the water coming in floods your batteries. The new hand-sized Lithium battery jump boxes do this very well. It'll also start your engine for you.

[sailingabe41ds]

I see you havea Jeanneau....I have a J 41DS same set up. Add to that that unless the engine is on my windlass wont work.
abe

[moseriw]

Always check the draw while using the windlass My battery was 30 ft away and voltage dropped from 14,4V (Alternator supported) to 8,7V. This ruined the motor of the windlass and the bowthruster. Wires sized to 95mm2.

Solution was another 240Ah bow battery. Now it is OK

[aqfishing]

Originally Posted by tkeithlu

Think about Plan B. The windlass is on the starter battery, so start the engine before using the windlass. That way, you won't get the anchor up and then find you cannot start the engine because the battery is dead.

Plan C. Get a set of jumper cables. Then you can cross connect the house battery and the starter battery, in either direction.

Plan D: have a small battery that is separate from all of this, and can power your VHF when the water coming in floods your batteries. The new hand-sized Lithium battery jump boxes do this very well. It'll also start your engine for you.

Why on earth would you pick up anchor without your engine running? For starters, surely you ease the load by driving up as you retrieve your anchor?

[noelex 77]

Originally Posted by sailingabe41ds

I see you havea Jeanneau....I have a J 41DS same set up. Add to that that unless the engine is on my windlass wont work.
abe

That is worth changing, especially if it uses a relay on the oil pressure switch, or alternator to decide if the engine is running.

If it uses a relay activated by the engine battery switch it is not so bad but still no ideal in my view. At least in this case if the engine is disabled switching the start battery to "on" should still enable the windlass to work, without the engine actually running.

This is usually easy to change and eliminating the relay concerned removes one failure point.

The exception to the above is if the boat is on charter some of the time.

[Tenedos]

Ok, I just rewired the windlass to the house battery. Now it is only the engine itself is on the starter battery.

This brings me to a second question, whether to replace the Magnum battery combiner with a DC-DC charger. For context, my alternator is connected to house battery. Main Magnum Charger/Inverter is charging the main battery. And a separate backup charger (the original Jeanneau charger it looks) is charging the starter battery (has its own switch). These two battery banks are connected via a Magnum battery combiner (with two 30A fuses on each battery connection). From what I understand, the battery combiner is parallelizing the connection when the voltage on either of the batteries is above 13.1V which is configurable. So when either of the chargers, or the alternator is active, I essentially have 7 batteries connected in parallel: 6 house and 1 starter.

I find this setup a bit confusing. One idea is to replace the combiner with a DC-DC charger, to charge the starter battery from the house battery.

I should also add that, I am thinking of replacing the house batteries with drop-in LiFePO4s at some point in the future that have integrated BMSes. There is an entire thread about protecting the alternator in this setup and one good solution seems to be having a FLA battery connected in parallel to the lithiums. My existing setup essentially provides that since when the alternator is charging, battery combiner is open, so essentially I have 7 batteries in parallel: 6 LiFePO4 house batteries and 1 FLA start battery. So I guess this is a better configuration for future lithium expansion?

I am debating, if I should keep the setup as is for future LiFePO4 expansion or consider a DC-DC charger. Thoughts welcome.

[waterman46]

Originally Posted by moseriw

Always check the draw while using the windlass My battery was 30 ft away and voltage dropped from 14,4V (Alternator supported) to 8,7V. This ruined the motor of the windlass and the bowthruster. Wires sized to 95mm2.

Solution was another 240Ah bow battery. Now it is OK

Bow battery for the windlass is always best and really required if you have a bow thruster. And if the OP's electronics need a reboot each time he uses a power winch, that is intolerable. I'd add a dedicated battery for the winches - should not be deep cycle, rather a standard car battery.


All those batteries must be isolated on the charge side, so it's not a cheap project.

[kish]

Originally Posted by Tenedos

I figured that on our boat, the windlass is powered from the Starter Battery. I found it quite odd and wondering if this is common at all.

;;


This setup causes some issues so I am planning to rewire the windlass to the house battery this weekend. My starter battery is 105 Ah and house battery is 6x105 Ahs.

Thoughts or suggestions welcome.

This arrangement is often seen as a cost saving measure in boats built down to a price, rather than up to a specification.

It is functional, but sub optimal.


The house bank, assuming it is of lead acid chemistry, has a construction optimized for deep cycle usage,

The starter battery has a plate construction to allow several hundred amps to be delivered in a few seconds to start the engine and a windlass will typically draw 50 to 100 Amps probably for several minutes.

Accordingly a starter battery is more appropriate as a windlass battery.
Also the starter battery is under rapid charge while the engine is running


To use a deep cycle house bank as a starter or windlass battery is detrimental to the long term health of the house bank and the voltage drop it encounters may cause electronic instruments to drop out as the house bank takes a voltage hit.
That is why a windlass should not be connected to the house bank.



Voltage drop is an issue.
A windlass is typically 10 metres [33 feet] from the starter and the cable length will be double that for a voltage drop calculation.
The cable to the windlass from the starter to the windlass terminals over that distance should be a minimum cross section area of 70 sq mm section [2/0 AWG]

If the battery voltage drops from 12.8 v to 10.8 volt in windlass operation, the windlass will only deliver 70% of its potential due to the lower voltage.

A separate battery up forward nearer to the windlass and connected in parallel with the starter battery, through a voltage sensitive battery combiner relay, will improve the windlass performance and allow a smaller cross sectional area cable to be used to link the windlass and starter batteries.
This arrangement works well with a bow thruster also.

Purists will argue about the extra weight of a battery forward, but when compared to the weight of anchor chain forward, a 15kg [33lb] battery is insignificant. but locker space needs to be organised to house the battery!

[noelex 77]

Originally Posted by waterman46

Bow battery for the windlass is always best and really required if you have a bow thruster.

Hmm...

This can work, but has some drawbacks. It is generally not the best solution, but is useful to consider if the battery cable run would otherwise be long and impractical.

A bow battery is a common solution, but often the main advantage is that the installation costs are less because there is no need to fit larger cables.

[wesevans]

Correct procedure is for windless to have it's own battery located close to the windless.

[dfelsent]

Yeah I’m not at all sure that a bow battery is the “best” solution.
Charging and maintaining a third battery adds complexity and reduced reliability compared to big cables.
Start and house banks are messy enough.