Do I need 2 x DCDC chargers

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doublebubble asked May 8, '24

Do I need 2 x DCDC chargers

Hi,

I'm about to pull the plug and install 480ah lithium bank for house power on our catamaran, currently, briefly, we have two engines both with their own alternators with external regulators, Multiplus 3kw, three banks of solar with their own Victron mppt's for a total of 900watts, 6kva generator, 400w wind generator. My question is regarding the alternators, can I get away with only one start battery for both engines and one Victron DCDC charger for both alternators? or should I have two start batteries for each engine with it's own dedicated DCDC charger? meaning one DCDC charger for each alternator to charge the AGM start batteries and the lithium bank. Either way the distance from the port engine to the starboard engine which is where the lithium bank will be is a considerable distance of 5mtrs, preferably to have one start battery in the port side of the catamaran for both engines would be preferable with one DCDC charger in the starboard side close to the lithium bank and the Multiplus, any advise would be greatly appreciated.

Cheers

Rod lewis.

orion dc-dc

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Answer 1 · 2024-05-08T14:50:26Z

madmaxx answered · May 08 at 02:50 PM

You should rather consult your question with your catamaran manufacturer as you are basically asking for permission to create a single point of failure - one discharged engine battery will then disable both engines.

Furthermore your concept might lead to overcharging your remaining MadMax style catamaran battery.

Instead you should consider if there are electrical consumers that discharge your starter batteries except for the engine starters - nighttime sailing with all lights on but no engine running, p.e.
Such a case might suggest having a Victron DCDC charger ready that could transfer energy from your lithium bank into starter battery 1 or battery 2 to ensure that you can at least start one engine out of two in case of an emergency.

"meaning one DCDC charger for each alternator to charge the AGM start batteries and the lithium bank."
Your configuration "Victron mppt's" already contains charging components for your lithium bank.
DCDC charger are targeting "batteries" not "alternators".

I strongly recommend you seeking professional assistance.

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doublebubble commented · May 09 at 05:37 AM

That's why I came here for professional advice.

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