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Background: I’m considering removing the 12.5kW Westerbeke diesel genset from a boat that has a pair of Cummins 330B engines (2001 vintage).
I want to replace the genset with a pair of Magnum Inverter/Chargers (stacked) and a roughly 48kW-Hour battery bank (LiFePO4).Ā This will cover our requirements for 24-72 hours.
When away from shore power for extended periods I want to re-charge the LiFePO4’s by replacing one or both of the existing Cummins alternators with high-output models ~250A each (Balmar or equivalent).
Use Case: Under normal conditions we’d recharge the batteries from shore power or, while underway recharge them from the alternators while cruising at 1,400-1,600 rpm, but there will be times when we’ve spent a few days on the hook and then I will need to run an engine or two to recharge the battery bank.Ā I believe 2-4 hours of runtime with the alternators putting out ~400-500 amps will be typical.
Question:Ā Will there be any considerations or negative impacts from running these engines lightly loaded at a ‘fast idle’ (800-1,000 rpm, transmissions in neutral) for about 2-4 hours every two or three days, perhaps for several weeks between cruising them at normal speeds/engine loads?
I think the ideal RPMs I’d want to run will be dictated by the alternator output I need in order to re-charge the batteries as quickly as possible, but would I do better to run higher RPMs than needed to prevent problems with the engines? Is extended running at relatively light loads ok?
Lastly, would it be better to run one engine for six hours (alternating Port and Starboard) or both engines for three hours?<br /><br />Thanks in advance!
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