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Twin Volvo Inboard Diesel - New Wiring for Start and Charging

simzpilot

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I have a Broom 35' with Twin Volvo TMD40A (130Hp each) diesel engines and the boat is in need of a rewire. I have started to map out both the existing, and some of the new features (smart chargers, solar, etc.) that I would like to add to improve the boat. It has both 24V and 12V on board and is wired mostly typical of the period in early 80's. My question is mainly around advice on possible wiring arrangements for starting and charging of the battery banks underway. The power audit I just completed suggests I would need about 330Ah of 12V, and 125Ah of 24V if we are moored for 2 days without power. My start batteries need to be replaced, and the 450Ah 12V bank shown is a plan for early next year when I complete the refit. I omitted on the diagram that I have a dedicated 12V charger that is spare and I will probably fit that to the start batteries so they are fully ready for cranking when I am on shore power.

I would be very happy to hear suggestions for VSR/ACR's to help manage the starting of both engines, and the charging of the batteries. In particular advice on more current practices to reduce complexity and better utilize the two 12V (60A each I believe) alternators while underway. Also glad to hear any advice on protection for devices such as the Pro-Chargers or solar system when cranking, charging from alternators.

Let me know if I need to add more info that I may have missed.
 

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OK, So based on previous posts by RicardoMarine and others, I have revised to Draft 2. I would very much appreciate comments and suggestions pleaseTwin Inboard Diesel Wiring Draft 2.jpg
 
Quite a few things I would be looking at. I can't see the drawing well enough so apologies if you have covered these already and also if I talk about stuff you already know. These are just first thoughts and there could be more.

1) Battery technology. Your house battery A/H rating should be at least twice your draw to stop the batteries degrading fast. So 330A/H draw into 450A/H batts will kill the batteries early if you do that a lot. You can go for bigger capacity flooded cell or AGM etc, or go for lithium or the new Lead Crystal batteries. They can both be drawn almost flat with no long term degradation. That means if space or weight is an issue you can get enough batteries into the boat to properly cover your usage.

2) Charging. Yes do put VSR's or ACR's on both alternators and use that to feed the 12v House batt from both engines. This works fine so don't worry about having the two alternators on the one battery. 60 amp alternators are very 'last year' now so I would hunt down some 100A alternators that fit and change them out. Another alternative is to put a 2nd alternator (like your 24v one but a 12v one) on your port engine if possible. Say a 150A alternator dedicated to the house batteries and use the VSR's as well. You need to see what amps the batteries you choose can handle under charge and work the alternators back from that. Lithium and lead crystal batts will absorb stupid amounts of current and hence charge really quickly. Flooded cell and AGM etc have a massive tail off issue that makes charging much slower. This can alter the equation in many ways depending on how you use the boat. You can also look at smarter external regulation on the alternators which can speed up charging as well as supply temperature regulation etc to look after the batteries better. If you did say put a 2nd alternator on the port engine and had lithium or lead crystal batts you might be surprised how much of a charge top up you can get by running the engine at a fast idle for an hour or so per day while anchored up. Think of it as your 'genset'. The other thing on charging is that Solar is cheap. Use a MPPT controller (not PWM) and max the panels you can install. You can buy flexible panels that you stick to the boat and can even walk over.
3) 24v. What is this doing? Is it for a 24v inverter to drive the fridge? I can't see from the drawing sorry. DC/DC 24v/12v converters are cheap. Can the 24v loads be driven with converters and then turn the 24v alternator into your big 12v dedicated house alternator? If you need an inverter for the fridge and some other loads buy a 12v one and sell the 24v one.

I can't see enough detail in the drawing to say much more than that to start with, but hope those thoughts are of interest.
 
I have setup a few boats now for extended use on battery power & inverters vs running a genset. The thing people often forget is how important the recharge side of the power budget is.
 
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