Basic Battery, Charging and load systems Design
Madeye has evolved a bit as I've built and refined the system. It suffered some setbacks thanks to some hurricanes, but those were taken as lessons and used to improve the system and design.
Madeye is a 1973 Ericson 46 monohull sailboat. The age of the boat means that she's... suffered from various refits and wiring misadventures of the previous owners. With that in mind, I've been replacing virtually all of the wiring and electrical systems on the boat. As part of this refitting, I've developed a power management strategy with the idea of maximum comfort AND safety.
The entire diagram is a bit daunting, So let's start with the batteries. Madeye currently features THREE battery banks. The Engine/Windlass bank, The Solar/Inverter bank and a House/Navigation bank. Both lithium and AGM battery technologies are used for a combination of capacity and reliability.
The large 24v pack is my main large bucket of power. It's charged by solar/shore/generator/etc. It charges and maintains the smaller 12v batteries that operate house systems and the engine battery.
The Engine battery is charged by the alternator but also maintained by the 24v system to ensure that it's always ready to start the engine and power anchor operations. If you've dragged anchor, you know how important this is for the ships safety.
The 24v pack gets the most exercise in this design. It's actively monitored and loads on it are managed on a day to day basis when I'm on the boat. The 24v pack is managed with a few rules:
| Fully Charged | Charging is zeroed out but still scaled to offset loads to maintain full charge if possible. |
| SoC below 20% | 24/12 chargers are disabled |
| SoC below 15% | Inverter is disabled |
| SoC below 10% | BMS disconnects loads and protects the pack |
The Solar/Inverter bank is a 580 amp hour, 24 volt LifePO4 battery pack. It's managed by a REC Q BMS and delivers power for the inverter (120v power for cooking, laptops, appliances, etc). It's directly charged by three MPPT solar controllers, each with a dedicated panel supplying it. In addition, it supplies 12v power to the house and engine packs via a pair of 24/12 DC-DC converters. This pack CAN be fully depleted without impacting the engine or house systems. It is always charged via Solar, but shore power AND a DC generator can be used as charging sources.
The Engine/Windlass bank is a pair of AGM cells. These require little in the way of maintenance and are very reliable. It is charged from the main Solar/Inverter pack as well as the engine alternator.