Re: Upgrade to Lithium batteries, detailed circuit #solution

Jose Venegas

This is the updated schematic of the Ipanema’s electrical system following the installation of Battle-borne lithium batteries.

The main aim of the design was to minimize the need to modify any ac electrical connections inside the boat. 


The system is similar to that described by Brian Trautman for SV Delos with a few differences.  On the schematic, all new devices are in orange and new connections in red.  All connections represent positive and negative cables for DC (Solid lines), and hot and common for ac cables except for those connecting the controls of two new NC relays. 


The design uses an existing white box in the engine compartment. My boat was built for an American customer and included a white box with two electrical outlets: one for direct 220 V shore power and one for 120 V shore power transformed to 220 V.  Boats built without this box could use a switch that could be conveniently installed inside the boat.


A 5KW inverter was mounted on the bulkhead next to the battery compartment.  This has enough power to run any of the 220 V ac current devices of Ipanema (not at the same time of course).  The 5KW inverter output was connected to a third outlet that I added to the engine compartment white box via a 30 amp 3 wire AC cable.  Not easy but a lot easier than passing several large DC cables from an inverter/charger installed in the engine compartment and minimizing their length.  The inverter is kept out of the engine compartment to avoid the heat while keeping two battery chargers in the engine compartment using the two existing medium-sized DC cables of the old chargers sending current to the new battery bank.  Note that the max DC current that could ever be sent to the lithium batteries is 320 amp (160 chargers +100 solar panels + 60 engine alternator) gives a C<1. 


Another feature of this design is that the Genset can be turned on at any time, and the existing AMEL relay automatically disconnects any connected AC power source.

To avoid the possibility that the battery chargers could remain active while the Genset was OFF and the inverter was connected as the power source on the white box,  I added two small NC 220V-220V ac relays to the ac panel that automatically open turning OFF the AC current to the battery chargers if the inverter was left ON.  So, the only modification of the ac AMEL circuit inside the boat was adding these two NC relays with their control lines fed by: 1) to the hot wires feeding the Battery chargers (red dotted), and 2)  to the common wire output from to the inverter at the corresponding outlet of the white box (brown dotted).


 Because the shore power in most of the marinas of the Caribbean is 60Hz, to use the cloth washer, the dishwasher, or the microwave oven, that need 50 Hz  I disconnect the shore power and connect the 5 KW 240 volt 50 Hz inverter to the white box.


With this large inverter the water maker can be used with the batteries for the first hour, and during a second hour with the Genset that keeps making water and charging 160 amps back into the batteries. So with only one hour of Genset, I get two hours of water making.  Also, the boat can be cooled for one hour in the evening by running the AC with the lithium batteries and still leave plenty of energy in the batteries to keep the regular DC loads running overnight.


In summary, this design is simple to implement, leaves the AMEL AC circuits virtually intact, allows the use of all the AC 50 Hz devices, and more importantly, is simple to use.  No need to think about changing different switches for different conditions to create specific results.


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