One Lithium banc for all users including engines

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jachtservice asked Jan 2, '24

One Lithium banc for all users including engines

Lithium batteries are very well suitable to start the engine but I see a lot of systems with lithium is used for everthing except the engines where lead batteries are used. This results in a complex system with different types of chargers, separators ect. What is against a system with only ONE battery ?
Of course the alternators need protection against a to high load and the batteries need protection against a too deep discharge in case the engines do not start after a reasonable time but if these issues are tackled the system becomes quite simple. What am I overlooking ?

Lithium Battery

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Answer 1 · 2024-01-02T13:16:57Z

kevgermany answered · Jan 02 at 01:16 PM

Your alternators cannot charge lithium direct. You must fit DC:DC chargers. A possible exception is if you use drop in lithiums which are designed to replace lead acid.

The other consideration is the current drawn by starter motors (CCA rating). Lithium often will not provide this, the BMS will simply cut the power.

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jachtservice commented · Jan 03 at 08:24 AM

You are not answering the question and you are wrong with your statements.

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Answer 2 · 2024-01-03T09:27:31Z

prein answered · Jan 03 at 09:27 AM

You aren't really overlooking anything. You can fit a suitable BMS which can handle the power.

The only thing you will lose is redundancy. Which on yachts is something very appreciated..

One thing to keep in mind: if your motor doesn't start so well, the start-motor will (more) easily overheat, since the lithium battery is capable of delivering so much power.

The answer of Kev is not wrong per se, but you will definately have to design your system correctly (place a BMS with external contactor instead of mosfets, have a lithium bank capable of providing enough current etc). My (600Ah) lithium bank on my (sail)boat is perfectly capable to start my engine (as well as cook on induction etc). But I still decided to keep the standard battery for redundancy.

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