Project:
Replace lead acid batteries (3*180 ah) in the 12V house bank in my boat with lithium battery (1*300ah). Note: intention is to remove the lead acid batteries completely from the house bank.
Challenge:
How to charge a lithium-only house bank with an alternator?
House battery bank @ 12V:
Currently 12V house bank with lead acid batteries (3*180 ah) charged with Victron EasySolar 12/1600 charger (300W solar panels and shore power) and dedicated alternator. Alternator is from 1990's (nothing smart in this either).
Lead acid batteries to be replaced with single 300ah lithium battery. Battery charged with the Victron EasySolar 12/1600 charger (300W solar panels and shore power) and possibly with the alternator (based on advice).
House bank is used to power inverter (EasySolar 12/1600), bow thruster (thruster specifications 12V, max 350A, measured ~230A) and other house loads such as lighting, fridge etc.
Starter battery bank @ 24V (separate from the house bank):
24V Starter battery bank (2 * 180 ah, 12V lead acid batteries), charged with it's own 24V alternator and a shore power charger (24V/5A). Alternator is from 1990's (nothing smart in this).
Starter bank is used for engine start and 24V stern thruster.
Option 1:
Can the lithium battery be charged by placing a Victron Orion-Tr Smart 12/12V 30A DC-DC charger between the existing 12V alternator and the lithium battery (without lead acid battery in the circuitry)?
Note: intention is to remove the lead acid batteries completely from the house bank circuitry.
Option 2:
Disable the 12V alternator by removing the belt and disconnect it from the 12V system. Use the 24V starter bank as mediator between the engine charging by using Victron Orion-Tr Smart 24/12V 30A DC-DC charger (using the 24V alternator as charging source and starter bank lead acid batteries as buffer).
Option 3:
Keep single lead acid battery between alternator and DC-DC charger (typical setup seen in the Victron diagrams). This of not preferred due to space constraints and the wish to keep the house bank clean and simple.
Option 4:
Disable the 12V alternator by removing the belt and disconnect it from the 12V system and relying only to shore power and solar charging. This would simplify the system, but far from optimal especially considering unpredictability of solar power.
Are there other options?
What is the recommended approach/solution? Any diagrams available for reference? Anything else to consider especially if several approaches are equally good from technical perspective?
UPDATE
Project has progressed with installation of the lithium bank and Orion DC-DC charger. However I'm having a problem.
To summarise, the setup consists of an engine alternator (old style without any intelligence) which is connected directly to Orion DC-DC charger (isolated, 12 | 12, 30A) which in turn charges lithium battery bank (2 * 200 ah batteries). This setup was in advance verified from Victron by the local reseller/distributor.
Alternator is Bosch K1 14V, 55A 20 (original for the Volvo engine).
There is a problem where the input voltage from the alternator to the Orion fluctuates from ~9V to ~36V causing the Orion to intermittently go offline ("charge is disabled due to: Input voltage lock-out"). This happens regardless of the state of charge of the lithium batteries.
Is it possible that the fluctuating voltage is caused by insufficient resistance from the Orion DC-DC charger or is there something else that may explain such a phenomena?
Is it possible that the alternator is faulty, or is such a fluctuating voltage a common issue under some specific circumstances?
Any idea how to rectify this? Do I need to replace alternator and/or place a led acid or agm battery in between the alternator and the Orion (exactly the scenario I was hoping to avoid)? If an intermediary battery is required, what would be the recommended chemistry and size? Needless to say that I'd prefer small, lightweight and affordable solution...
