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Old 07-02-2021, 13:29   #31
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Join Date: Aug 2009
Location: Norfolk, Virginia
Boat: 1984 Passport 42 pilothouse cutter
Posts: 383
Re: Electrical Design Lagoon Catamarn with Victron

Thinking on this more, I think my biggest issues is the connection of the alternators. Connecting dual alternators is a common issue with big powerboats with two engines and you should be able to find examples there.

You have the alternator output connecting to the argo, which splits the charge current to all three banks. The voltage sense is either at the alternator, the argo, or the start battery. The problem lies in the different battery banks. There isn't a smart regulator so the alternators are pushing full voltage. More like a car. Even if there was a smart alternator the voltage sense cable is not on the correct battery or location. You either don't see the correct voltage at that location or your only seeing the voltage off the starter battery.

As other posters are stating the starter banks only need a trickle charge. So they are full quickly. Your house bank is not so lucky. 6volt cells will boil if charged to much, losing all their electrolyte, and as it's an acid can cause damage if it leaks somewhere. If the car style system is just pushing a set voltage it will damage your house bank over time. Worse if you don't continually check your electrolyte and say the level drops an inch, you lose capacity, even if you catch it and top of later. You destroy your batteries over time.

If there isn't a smart regulator the voltage sense is the alternator terminal usually. Resistance in the cables means it sees a lower voltage than what's actually at the batteries, specifically the house bank since it's farther. That means the excitation voltage is throttled up to push more juice to the battery. this can boil or explode a battery.

If the voltage sense for an alternator is on the argo. Your closer but it's a similar issue. The starter bank voltage will overcome the house bank. If I am understanding things correctly this will overcharge your starter batteries and undercharge your house bank

If the voltage is on the start bank than it's only seeing the starter voltage. Seeing that quickly tops off your house bank really gets under charged

I deployed for 6 months at a time. I have a smart regulator. The charger would be left on when I left. 24v system with 6volt batteries. The electrolyte evaporates and drops anyway. Come back I topped off. Couple years of this and my battery capacity definitely dropped over the years. You don't get the ah capacity from all that exposed lead plate surface back. Life of the bank dropped got 7 years roughly and have to replace now. Should have lasted 10-12years. Your 6v cells are more expensive than mine. Trust me it hurts the pocket book replacing those things early. If you ever switched battery chemistry your system definitely would not work. Just fix it correctly now, simplify and protect your batteries.
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Old 07-02-2021, 13:40   #32
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Re: Electrical Design Lagoon Catamarn with Victron

If this was my boat. Or say I get a generator so I have 2 alternators. than the only way if do it is charge the house bank with both using smart regulators, then use a DC t DC charger to charge the start battery banks. I have a 24v system with 12v starter banks so the cyrix doesn't work well here. I do have a 24v bank for the windlass battery bank in the veeberth. That uses a cyrix. If/when I switch to lithium in the future I have to use DC to DC chargers due to the different chemistry voltages, and will have to upgrade to a better smart regulator that works with lithium and the Victron colorgx/Venus system.
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Old 07-02-2021, 13:54   #33
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Re: Electrical Design Lagoon Catamarn with Victron

When I bought the boat it had a non smart SP charger. Previous owner had switch to AGM batteries. Totally fried those batteries after 6 years. Similar to the same reasons I'm saying your system will possibly fry yours.

At work we have twin Cummins or twin yanmar engines. They had big truck alternators with an internal regulator that could adjust the voltage. If an alternator was replaced we had to adjust the voltage or it would fry the AGM banks. Similar wiring as what you have. It's government and we don't even track how long the batteries last. Just throw new ones in. I can assure you you don't want to do the same.

From experience electrical work is really expensive, most boat owners don't understand it. You have 2 options. pay out the nose for someone else to figure this out for you at $100/per hour. Or learn marine electrical, simplify your systems and do the work youself. Everyone on here is roughly telling you the same things. Trust us, but verify. Look in the manuals, try to figure out or dive into books or you tube so you understand how things interrelate and influence each other. Be prepared to make expensive mistakes. Learn how to do things right, and make yourself do it.

Not saying your doing things bad, I like your labeling and wire routing in your pictures. But you do seem to have gaps that need to be filled. We can't help you with $ if you have to replace expensive things. We have our own mistakes and learning to pay for lol.
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Old 09-02-2021, 01:06   #34
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Boat: Lagoon 380S2
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Re: Electrical Design Lagoon Catamarn with Victron

Yesterday I worked with the local Victron dealer on the electrical system. Before arriving, he told me that the trickle connection on the Multiplus is not a solution. On the boat he proved to me that this connector runs in parallel to the main 12V leads, thus defeats the purpose of my goal. I don't want the house/domestic batteries charging (or connected to) the engine batteries while sailing (engines are not running). The Cyrix provides this solution partially. We tested this. When the House/Domestic batteries drop in voltage below 12.8VDC the Cyrix disconnects. A more robust solution was to connect the start assist to the Venus GX and program the dry contact to engage the start assist only when connected to shore power. I opted to keep the system simple.
Regarding other comments made.
The basic electrical system is planned by the mfg - Lagoon. The alternators are connected to the engine start batteries and house/domestic batteries.
This is the diagram as supplied by Lagoon: Totally wired - Lagoon inside
As far as I know the Volvo Alternator has a regulator which should prevent batteries from frying. The Multiplus also is regulated when charging. We have this boat for about 15 years - over charging was never our problem (this of course does not mean that in the future such a problem might occur). I will continue to monitor the system - I am connecting the Victron system to the internet and can monitor using Victron VRM website as well as configuring alarms. 2021 Feb 9 Anika Elec plan-1.pdf
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Old 12-02-2021, 08:19   #35
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Boat: Leopard 40
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Re: Electrical Design Lagoon Catamarn with Victron

Manny,
We have a Leopard 40 cat and victron gear like you and a much simpler system for charging the start batteries.
Each alternator is connected to the house bank. Blue Sea ACR 7610 on each start battery connects the starter battery to the house bank when the house bank reaches the charge voltage threshold. This way the engine batteries don't connect to the house bank when the house is at low voltage. We have the BMV-602 to monitor the house with shunt and starter battery voltages through a rotary switch that allows selecting which starter battery voltage to display as the 'start' battery. So it doesn't matter which charging source brings the house bank up, all batteries eventually receive charge. More info here:
S/V LUX: Getting Juiced Under Way - Battery Charging
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