Re: [Amel Yacht Owners] Re: Generator charging question

Ryan Meador

At first glance, I thought it could be dangerous to use multiple smart chargers because they could get into different states, but after thinking through all the possible combinations, I've convinced myself it is actually safe -- provided the total current is less than what the batteries can accept.  It might not produce the optimal results for your battery lifespan, though: they could transition from bulk to acceptance or acceptance to float before the battery is actually ready, because each charger can only sense its own contribution to the charge current.  Chargers in different stages shouldn't fight each other directly because they sense the current/voltage of the system.  Floating at different voltages should be safe; the charger with the lower float voltage would just not be doing anything.  If one or more chargers has a float voltage above that which the batteries are designed to handle, that would be bad... but that's also bad with just one charger.

I do not think it is safe to mix smart chargers and dumb chargers without knowing exactly how the dumb charger works.  It is conceivable that the dumb charger just puts out a constant voltage, and would act as a sink for a higher voltage -- then you'd get the two chargers directly fighting each other, possibly tripping breakers, and definitely wasting power.  The same could happen with two dumb chargers that have different voltage setpoints; presumably the ones Amel installed as stock were configured with the same voltage and/or were smart enough to shut off if they started acting as a sink.

As an aside, is a 16A shore power connection typical in some parts of the world?  At 230V, that's about the same wattage as the "small boat" 30A@120V connections in the USA.  A larger yacht like a Super Maramu is expected to connect to 50A@240V in the US, but usually also has the option of connecting to two 30A@120V connections.  I assume you can't connect to two 16A@230V connections because the 230V parts of the world don't use a split-phase power system like we do in the US, but perhaps I'm wrong about that.

SM 233 Iteration
Boston, MA, USA

On Wed, Jan 10, 2018 at 2:11 AM, svperegrinus@... [amelyachtowners] <amelyachtowners@...> wrote:

Our solar chargers by Genasun are not properly adjustable to the voltages required by Trojan for our AGM batteries.  So we disconnect solar when on shorepower to prevent over-voltage charging of full batteries.

We routinely turn on both battery chargers as follows:

(1) When charging from the generator.
(2) When we will have shore power for only one day or two.

Evidently after one hour or less the batteries charge at less than 100 A, and at this point it makes no difference whether you have one or both chargers on.  So we routinely turn one off.


SM2K N. 350 (2002)

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