Straight Laced power decisions

[Straight Laced 18]

I know this has been brought up many times, but I'm after plusses and minuses for lithium.

I intend to have 1 x 100w solar panel on the cabintop to run a few lights, music and a small fridge. I know that I will need to install a 2nd supply when cruising, but haven't decided what to run. whether it's a secondary panel on top of a boom tent, charge loop on the outboard or some other source.

How do I plug a 2nd panel into the system (do I need another controller), What are other considerations I should be aware of?

Considering lithium for weight purposes, but happy to be talked out of it. 

[Island Time 1,337]

Lithium is the way to go - IF you are going to keep the boat. Its worth the extra initial cost, as the per cycle cost is way less than lead acid.

Advantages are

1. Weight
2. Speed of charging is WAY better - even with same charging sources.
3. Capacity - you can use 90% of most LiFePo4 cells, but on 50% of Lead acid based.
4. HUGELY better cycle life - like the ones I have are 11,000 cycles - lead acid is about 700

Disadvantages;

1. Cost up front
2. Ancillary changes needed - to protect alternator, and to comply with AS/NZ3004 requirements.

Just remember - There is no such thing as a compliant (to NZ Standards) drop in LiFePo4 battery. To have a safe install you need fusing, Alternator protection, and visual and Audio warnings before BMS disconnect.

Your other question about panels - answer is - It depends. If you add a panel to a solar array, if the controller is capable, you can just plug in another panel. However, if the new panel is in another position, and likely to be in different sun/shade, another controller should  be used. IMO use Victron Controllers, they are just better, and provide more power than others.

 

[Frank 192]

What he said  Only thing i would add is to do the arithmetic on your likely demand, vs batt capacity vs charging current etc so as to get an estimate of how quickly or otherwise you can re-charge. On a short stay trip a slowly sinking SOC is no big deal as you will be home before the food spoils, on a longer trip solar may or may not cope depending on a bunch of variables. I'm guessing your O/B is in the 7 to 15 HP range does it have a lighting coil or alternator ? in any case do your homework but as a taster here is what Mister AI says , some of it is stuff Matt already covered.

 

 

No, you cannot directly charge a lithium battery with a small outboard motor. You need a DC/DC charger to regulate the voltage and current from the outboard's alternator, protecting the lithium battery from overcharging and preventing damage to the outboard's charging system. 

 

Why Direct Charging Doesn't Work

• Voltage Differences:

  Outboard alternators produce a voltage profile not designed for lithium batteries, which require a specific, controlled charging curve. 

   
• High Current Draw:

  Lithium batteries are "power-hungry" and will draw maximum current, which can overheat and damage the outboard's sensitive charging components (like the alternator and regulator/rectifier) if not controlled. 

   

How to Safely Charge

1. 1. Install a DC/DC Charger:

   This is the recommended solution. The charger connects between the outboard's alternator output and the lithium battery. 

    
2. 2. Function of the DC/DC Charger:

   The charger converts the alternator's output into a voltage and current suitable for charging a lithium battery, acting as both a regulator and a converter. 

    

Considerations

• Outboard Generator Output:

  First, ensure your outboard motor has a generator (coils on the flywheel) to produce power. 

   
• Temperature:

  Low and high temperatures can affect lithium battery charging speed and longevity. 

   
• Battery Type:

  Use LiFePO4 batteries designed for marine use. 

   
• Professional Installation:

  Consider having a qualified marine technician install the system to ensure it's safe and functional. 

[Straight Laced 18]

Thanks. It all makes sense.

Victron was at the top of my list to investigate, simply because the boat I am currently sailing on has it. As far as outboard charging is concerned, I know that the same motor in some other countries have it as standard, but not in NZ. This will be my last resort go to as outboards are notoriously hungry little fellas, but I do know that it is an available option.