Fleming 65 Hull 058 Video + Lithium Battery Overview

May 2022


Cruising the Gold Coast just got a little quieter. Hull #058 of the Fleming 65 was recently delivered to its new owner with a few changes to past models. Every Fleming built is unique, customized to the owner's plans, preferences, and requirements. We very rarely introduce a new model, but rather continually improve and tweak each new Fleming based on owner feedback, our own testing program and of course feedback from Tony Fleming's own personal experiences.

Hull 058 represents a new step forward for Fleming as it boasts an impressive list of standard equipment, including solar panels and lithium batteries. Other options include a Twin Disc EJS Joystick system that pairs the controls of the powerful hydraulic bow & Stern thrusters with the Quick Shift transmissions. This allows the F65 to hold position and heading smoothly and effortlessly with automatic and precise proportional control of shaft speed and thrusters to match the conditions you're in, whether waiting on a bridge to open or preparing the lines and fenders for docking.

Enjoy this video walk-through of Hull 058 and then read about the benefits and installation of the lithium-Ion battery system.


It provides 1,000-amp hours capacity with the ability to be discharged much deeper to 20% state of charge, and then recharged from 20-100% state of charge much quicker than standard AGM batteries. There are three 100-amp chargers that work in combination or individually to manage shorepower draw and 12kw of inverter capacity. In addition, there are two 200-amp brushless alternators for quick charging while underway and 1,430watts of solar for silent charging at anchor.

battery bank



There are many different types of Li-Ion battery but the only type we use are Lithium-ion Phosphate (LiFePO4), which are said to be the safest chemistry. Other types have more energy in a smaller physical size, but are quite volatile - it is these which have caught fire in cell phones etc. The Lithium-ion Phosphate batteries are only slightly smaller than AGM, so there is no space saving, but there is a significant weight saving – on a F65 the Li Ion house bank is 450 lbs. (204 kg) lighter than the standard AGM bank.

Each battery has its own BMS (Battery Management System) its own fuse and an automatic safety switch – if the BMS senses that there is anything wrong, such as imbalance or overheat, it will automatically disconnect that battery from the bank. Each battery is 24 volts so if one battery is disconnected from the bank it does not affect the voltage of the bank, only its capacity, i.e., the system still works with only one of the five batteries connected. We have designed the system so that all charging sources are on the same network and any battery can switch off a charging source if it’s not working correctly. The network includes all battery chargers, inverters, alternator regulators, solar charge controllers, DC-DC converters, and instruments.

mastervolt lithium battery



We prefer to use standalone battery chargers and standalone inverters – these cost more and takes up more physical space than the combi inverter/charger type units but provides additional redundancy, cleaner power with no pass-thru issues/spikes. It also makes it simple to control how much shorepower you are using by simply turning the chargers on and off as required. On the Fleming 58 and F65 we have 3 individual 100-amp chargers, so when using only one shore cord you just use one charger and when on two cords or genset you can run all three together for a faster recharge time. The F55 system has two 100-amp chargers; the Fleming 85 has four.

In our opinion the biggest advantage of the Li-Ion system is the ability to recharge from 20% to 100% state of charge in around 3.5 hours, whereas AGM batteries can only be discharged to 50% and would take three times as long to recharge. The Li-Ion batteries will accept a far higher charge rate and continue to accept it until they are 100% charged. All Fleming’s have two Delstar heavy-duty, brushless, 200-amp alternators. They are controlled by external regulators which are connected to the battery management system and will provide 85+ amps each at idle engine RPM. We are seeing outputs of 200 amps from these alternators at cruising speed. So, you can recharge Li-Ion quickly when underway on short trips, as well as via the genset.



We increase the inverter capacity and run a lot more loads from the inverters, the exceptions are aircon, oven, elec BBQ and the water heater. We have successfully run the laundry appliances, and watermaker via the inverters.

The Fleming 55 has a single 4,000-watt inverter, the F58 has two 4,000-watt inverters and the F65 has three inverters providing 12kw. Multiple inverters are stacked and operate as one unit which allows peak loads to be handled for short periods of time by using battery power – this is especially useful if there is only one shorepower cord, or in areas which can only provide a single 16-amp supply, as it prevents nuisance tripping of the shorepower. There is also an inverter by-pass system for redundancy.

On the F55 and F58 its only possible to have one genset with the Li-Ion house bank, and whilst it’s possible to have Li-Ion and two gensets on the F65 we recommend a single genset and carry adequate genset spare parts. The stacked inverters provide as much power as a second genset and squeezing in two gensets as well as all the electrical components takes up a lot of space, reduces accessibility, adds weight, and increases heat.




Mastervolt claims that under ideal conditions the batteries can be cycled 3,500 times – a cycle being a discharge to 20% state of charge and recharge to 100%, at 25 degrees C (77 F). Lifeline AGM claim their batteries will provide 1,500 cycles if only discharged to 50% state of charge. However, there are many variables and all batteries regardless of type are greatly affected by temperature.

All Fleming’s with Li-Ion batteries also have engine room aircon which is run whenever shorepower or genset power is available. The Li-Ion batteries are installed on a platform in the port aft corner of the engine room, with good spacing between each battery and a stainless-steel frame around them with a shelf over. This provides additional storage space, but the primary purpose is to create an air tunnel around the batteries so the engine room aircon flows through this channel to keep the batteries cool. It’s hard to see in the photo but each battery has a pair of custom-made stainless-steel brackets securing it to the platform, and they sit within a grid so they can’t move in any direction. Controlling the engine room temperature also increase longevity of chargers, inverters and other components in the engine room.

The initial cost of the Li-Ion system is significantly higher but even if the actual number of cycles is only 50% of what the manufacturer claims they should still last 8+ years, if looked after. So, in the long run it is a cost-effective solution; and we expect battery technology will continue to improve and become more economical by the time the systems we are installing now require replacement. All battery data is logged, so depth of discharge, battery temperature, and charge rates can all be reviewed.



We include a Mastervolt touchscreen which shows all data on the Masterbus network, and we also feed that data into the Fleming First Mate Monitoring System so that the entire DC system can be viewed on a single page. Below are screen shots of this system from a Fleming 65 (the F58 is very similar) AC Page, DC page, and House Battery Bank page. The AC page shows shorepower and genset power, voltage, frequency and current draw, and allows you to switch on and off the shorepower circuit breakers, as well as the 100-amp battery chargers. The DC page shows house bank state of charge and all your charging sources including solar, engine battery chargers and the DC-DC converters.

We also include a 4.3” touchscreen screen in the master cabin on all models; in addition to being an alarm repeater, this screen can also be used to control cameras, view battery bank state of charge and start and stop the gensets. On boats with the iPad integration all the Li-Ion system data is also included on the iPad.

DC Power


House Battery Bank


AC Power



To understand the advantage of solar it’s helpful to consider what we call “Standby DC load” this is the amount of current being drawn from the house battery bank under normal conditions, i.e., no shorepower connected, no genset running, some lighting is switched on, refrigeration is running, some electronics are on etc. For most F65’s this is approx. 50 to 60 amps (24v DC). During the day it can be higher, and overnight it typically reduces to around 35 amps. Ideally you want the house battery bank capacity to be large enough to run these loads overnight without requiring a genset. With our 1,000 A/H Li-Ion system on the F65 we can handle the standby load and run the master cabin aircon overnight via the inverters, without requiring genset power.

Our solar panels are semi-flexible and bonded directly to the hardtop. These panels can be walked-on and have a non-slip surface, but care must be taken not to drop things on them, such as tools. The solar power option is slightly different on each model and of course requires a hardtop as well. The F55 solar option is 690 watts which in perfect conditions would produce 23 amps charge current, the F58 has 830 watts (28amps), F65 has 1,430 (49 amps), Fleming 85 has 1,800 watts (62 amps) – in reality you won’t see these max figures it will be slightly less and very dependent on the brightness and angle of the sun, and will also be reduced if there is any shading, We try to reduce the effect of shading by using multiple charge controllers and have had very good results on the last two F65’s with this system. So, if you are anchored on a nice sunny day, not running the genset, your standby DC load is 50 amps, but the solar is providing 20 amps of current, reducing your standby load to 30 and increasing the time you have before needing to run the genset.




For more information about purchasing a new Fleming, please contact us. Enjoy this customer video below from the owners of Freja who have owned both a F55 and a F65 now from Fleming Yachts Australia.