Bowthruster windlass 3rd battery wiring

[E-mac]

First post on this great site.

I am planning to install an additional battery fwd to drive both the bowthrust and windlass. The current system has both wired independently to the start battery via long runs of 35mm2 and a 50mm2 cables. Domestic and Start batteries are controlled via SmartGauge / SmartBank relay. One reason I wish to change is that I have fitted a new house bank of 4 x Trojan T105 deep cycle batteries, with the thruster running and the engine on there is a 100 amp discharge on the T105s (not good?). The Smartbank relay is closed with the alternator charging.
Alternator is an 80 amp Hitachi with original standard regulator.
Windlass is a 1000 watt SL
Thruster is a SP55i, 12v 3.1kw
Start and Fwd battery are / would be Bosch 740 cca 80 amp/hr

What would be the best way to connect the battery banks? (obviously with fuse, isolator switch, TCB). I plan on leaving either of the existing 35mm2 or 50mm2 cables.

1. Treat the fwd battery as part of the start battery bank and accept any discharge on the domestic bank. I’m not keen on reconfiguring the SmartGauge relay opening closing settings.
2. Fit a VSR between the start and fwd battery. Not sure if this will open immediately I start running Windlass / Thruster and will it close to charge with the low battery voltage after running?
3. Fit a Battery to Battery Charger (30amp?). Most expensive.
4. Anyone any better ideas?

The boat is ashore for winter, so I’m not able to do any running tests.
Many thank

 

[Poey50]

Battery to Battery Charger (used) 6 months warranty- several remaining

Might make your option 3 more attractive. I bought the 60 amp version (which can also be used at 30amp). Just a few cosmetic marks - otherwise fine. I have no personal connection to Sterling.

 

[Keith-i]

I went through a similar conundrum a little while ago and also looked at battery to battery chargers. Eventually I chose a 3 output MOSFET split charge unit to replace the VSR which sat between the start and domestics. This means all three battery banks are independent from each other, but as soon as the start bank is up to charge from the alternator the other two banks come on stream for charging. So far it seems to be working. I kept 50mm cables linking the bow battery to the split charge unit so minimise voltage drop. As soon as you opperate the thruster the engine revs drop so the alternator is clearly feeding some juice as well. My alternator is theoretically 180A output hence the large charging wires.

 

[pvb]

I'd go for option 1. The current draw from the house bank shouldn't be huge, as the dedicated battery will supply most of the current. You need to fuse the interlink cable at both ends.

 

[Boathook]

Option 3. I fitted many years ago an Adverc battery to battery charger that keeps the BT and windlass battery (110 amp) topped up. It is only a 4 amp job but does the job well. I did consider heavy cables to the battery but the cost of suitable size made the charger a lot cheaper I seem to remember.

 

[pvb]

Option 3. I fitted many years ago an Adverc battery to battery charger that keeps the BT and windlass battery (110 amp) topped up. It is only a 4 amp job but does the job well. I did consider heavy cables to the battery but the cost of suitable size made the charger a lot cheaper I seem to remember.

But the OP already has the cables in place...

 

[Mistroma]

First post on this great site.

I am planning to install an additional battery fwd to drive both the bowthrust and windlass. The current system has both wired independently to the start battery via long runs of 35mm2 and a 50mm2 cables. Domestic and Start batteries are controlled via SmartGauge / SmartBank relay. One reason I wish to change is that I have fitted a new house bank of 4 x Trojan T105 deep cycle batteries, with the thruster running and the engine on there is a 100 amp discharge on the T105s (not good?). The Smartbank relay is closed with the alternator charging.
Alternator is an 80 amp Hitachi with original standard regulator.
Windlass is a 1000 watt SL
Thruster is a SP55i, 12v 3.1kw
Start and Fwd battery are / would be Bosch 740 cca 80 amp/hr

What would be the best way to connect the battery banks? (obviously with fuse, isolator switch, TCB). I plan on leaving either of the existing 35mm2 or 50mm2 cables.

1. Treat the fwd battery as part of the start battery bank and accept any discharge on the domestic bank. I’m not keen on reconfiguring the SmartGauge relay opening closing settings.
2. Fit a VSR between the start and fwd battery. Not sure if this will open immediately I start running Windlass / Thruster and will it close to charge with the low battery voltage after running?
3. Fit a Battery to Battery Charger (30amp?). Most expensive.
4. Anyone any better ideas?

The boat is ashore for winter, so I’m not able to do any running tests.
Many thank

Your setup sounds almost identical to mine apart from a spiral battery for the bowthruster. I replaced the battery/engine wiring with 50mm2 tinned cable, fitted 4xT-105s and also have Smartgauge/Smartbank advanced. I didn't touch the forward wiring apart from cleaning up the connections. The bowthruster is powered by the forward battery but the windlass still gets power from the start/domestic batteries. It has all worked well since 2009 and the load from the windlass has never seemed to be excessive.

I didn't change the link to allow the windlass to run without the engine and the 80A alternator supplies about 40+A when raising the anchor.

Only problems so far:

1) Bowthruster battery not charging because the connector was dirty inside and had been sparking and pitting where it couldn't be seen. No problems at all after a thorough clean up and some Contralube 770 on the connections.

2) Windlass trip died and was replaced. A fair bit of internal damage inside and obvious it wasn't a good choice. I managed to source one which could cope with the initial surge for longer but had the same trip level for normal use.

3) Spiral battery replaced after almost 10 years use. Not bad as it had been abused for about 18 months because of the bad connection and wasn't being properly charged. I used it as a replacement for the start battery and managed another 8+ years use.

The standard wiring to the forward battery hasn't had a problem keeping it fully charged. I rarely use it and there are long periods between any heavy use. I didn't see any reason to change the forward battery charging system after the initial cleanup.

I haven't really seen any problem with the standard setup for the windlass and use it almost daily during the summer months in Greece. The windlass is connected to the start battery, only works when engine is running and Smartbank usually has T105s in circuit at that time. Option 1 seems reasonable. I haven't altered Smartbank setting specifically for the windlass. I have made changes to manage forced ventilation when charging and also prevent MPPT solar providing too high a voltage to Start & bosthruster batteries (T105's go to 14.8V daily but I disconnect other batteries above 14.4V).

A bit rambling but I hope some of the information is useful.

 

[E-mac]

Many thanks for all the advice. I'll think try option 1 and see how it goes. I can move on as required.
Mistroma, my sailing buddy has a 42DS. I have been re-engined to a 4JH4A-E, the same as you? Do you have a 3rd part alternator regulator, if so what do you have? I never see 40 amps when hauling in the anchor.