BankManagerPLUS System

Combine Lithium (LiFePO4) and Lead-Acid Batteries in the same system, and charge everything optimally. Introducing the BankManagerPLUS.

BankManagerPLUS technical manual and user information here

In January 2021, Clark posted a video about how we combine our lithium (LiFePO4) batteries and lead-acid (Pb) batteries in the same system aboard our boat. After receiving a lot of questions and doing research, he concluded that while simply hooking batteries together does work, the batteries don't get charged optimally. In fact, it seems that there is no way to charge lithium batteries optimally using any charge controller currently available on the market. So he invented what we now call a Battery Bank Management System (BBMS), aka the BankManagerPLUS.

Many people are familiar with a Battery Management System (BMS), which should be installed with every lithium battery. A BMS monitors the voltages of the individual lithium cells inside a battery and has the ability to shut everything down in an emergency. A BBMS, on the other hand regulates the charging of the lithium batteries. A BBMS does NOT replace a BMS, but when used in tandem with a BMS, it optimizes lithium batteries for smarter charging and longer battery life. Best of all, it allows you to gain many of the benefits of lithium batteries, without upgrading your entire electrical system. Instead, you can simply add one or more lithium batteries to your existing lead system. You don't even have to change your battery charge controllers.

Since launch, Clark's BankManagerPLUS BBMS units have been installed on SV Temptress and SV Tla Hla. We have also sold more than 100 units to boaters, RVers, and other offgridders. In that time, 98% of units have functioned perfectly from the initial installation. The remaining 2% are receiving updated boards designed to accommodate peculiarities in their systems. This page has more information about how the BankManagerPLUS works and how to buy one. If you have specific questions about your system and whether the system is right for you, please feel free to send us an email and we can find a time to chat.


Supply chain issues have delayed the mass production of the BankManagerPLUS. However, as of November 1, we have approximately 60 BankManagerPLUS units in stock. Anyone interested in obtaining one of these units is invited to place and order here:


BankManagerPLUS devices are in stock, but limited

We have already sold 100 BankManagerPLUS units, and have another 50-60 in stock as of November 1, 2022. Sales rates have increased since August. To reserve a BankManagerPLUS please place your order right away! You will usually receive your order within 2 weeks of payment. We are currently only shipping to addresses in the United States. If you are located outside the U.S. and want one, we recommend using a forwarding service such as


To function properly, your BankManagerPLUS will need the following:


  • a working lead-battery-based power system with the ability to set a maximum charging voltage appropriately for lead batteries. BankManagerPLUS units can be used on 12, 24, 36, or 48 volt systems.

  • a lithium (LiFePO4) battery bank (at least one battery) with a BMS.

  • a contactor* (I have some that are compatible, that can be purchased along with your BankManagerPLUS, or you can supply your own).


  • at least 1 small lead battery with a BMS.

  • a contactor* (I have some that are compatible, that can be purchased along with your BankManagerPLUS, or you can supply your own).

*A contactor is basically a relay, rated large enough for your installation. It can be a device that is normally closed, normally open, or bi-stable. The BankManagerPLUS is quite flexible, but it's probably best if you check with me to verify if the contactor you choose is compatible.

I offer a 300A bi-stable contactor (manufactured to the BankManagerPLUS specifications). These will be the same type of contactor that I used on SV Temptress throughout the testing phase of this project, and is the best device I've found at this price point. If you would like to receive one of these contactors with your BankManagerPLUS, please add it to your cart with your BankManagerPLUS order.




Prevents Overcharging

Lithium batteries are extremely sensitive to low-current overcharging. A BMS does not prevent this, but the BBMS can. It is not only possible but likely that you could overcharge your batteries when using any of the lithium-enabled solar charge controllers out there. This low-current overcharge phenomenon causes permanent cumulative damage to your lithium batteries. The BankManagerPLUS can charge your lithium bank of batteries to 100% without fear of overcharging.

Doesn't Cause "Memory"

LiFePO4 batteries can develop memory if charged repeatedly to a point below 100%. This makes it difficult to get the battery to take a full charge in the future. The BankManagerPLUS can accurately charge LiFePO4 batteries to 100% without creating this type of "memory."

Extends Battery Life

The BBMS ensures that every battery in your system is utilized in a way that is appropriate to its longest life. It monitors the voltage and charge of each bank, and disconnects and reconnects individual banks when necessary to optimize your batteries.

Facilitates a Lithium(LiFePO4)/Lead-Acid Hybrid System

A BBMS like the BankManagerPLUS allows you to safely combine LiFePO4 and lead battery banks.

Saves Money

With the BankMangerPLUS, you can upgrade your lead-acid system with as few as 1-2 lithium batteries, rather than replacing all your batteries. In addition, the BankManager allows you to keep your existing charge controllers.


The BankManagerPLUS user interface allows you to fine-tune your charging levels and methods to your needs.





Price: $380.00 USD


  • automatically configures itself to a 12-, 24-, 36-, or 48-volt system.

  • has an OLED display and control knob that lets you control the unit via a menu system, and track the status of your power system in real time.

  • includes a modern Hall effect current sensor that accurately tracks the current going in and out of your lithium bank, without causing the voltage drop that old fashioned resistor-type shunt current sensors cause.

  • (most importantly) allows you to choose to charge your LiFePO4 bank to a percent-of-charge level. This is much more accurate and safe. With accurate current and voltage sensing, the device can see what's happening with the chemistry within the lithium bank and stop charging when the desired charge level is reached.

  • though not recommended, the BankManagerPLUS can charge your lithium bank to a set voltage (like most chargers on the market, but with a few added safety features).

Why does the BankManagerPLUS matter?

The problem is, charging to voltage alone (as a traditional battery charger does) will not safely or fully charge a LiFePO4 battery bank.

For example, if you only consider voltage, charging a 12V, 100A battery bank to 14.6V could mean several things:

  • If charging at exactly 50A, your batteries will charge to 100%.

  • If charging below 50A, your batteries will be overcharged and sustain damage.

  • If charging above 50A, your batteries will be undercharged. (For example, if the charge current is 500A, the batteries would reach 14.6V at only 5% of full charge!)

On a boat—where cloudy or windless days can effect the power available, and varying loads are being applied to the system—the charge current is always changing; you cannot rely on charging at exactly 50A (or any particular amperage). Therefore, charging to a cutoff voltage (as a traditional charger would) is neither safe nor effective! In fact, charging at low current to a set voltage will likely cause permanent damage to your batteries.

In contrast, the BankManagerPLUS senses the state of your LiFePO4 battery bank many times per second and reacts quickly to its needs. This allows you to charge your batteries safely and optimally.

  • You can tell the BankManagerPLUS to fully charge your battery (to 100%), and it will do just that, based on clues it gets about the internal chemistry of the battery (from watching the charging amp flow and voltage levels).

  • You can tell the BankManagerPLUS to charge your bank to 50%, 80%, or 90%, and the BankManagerPLUS will stop the charging process when that level is (more-or-less) reached.

In either case, if your charge controller tries to restart a charge cycle when your bank is already charged to the level you want, the BankManagerPLUS will "mark" your LiFePO4 battery bank as charged, and prevent it from being charged again until its voltage falls beneath a threshold you set.

In fact, if your LiFePO4 bank is quite large and your nightly needs are modest (as is the case for our friends on SV Tla Hla), you may be able to go multiple days between charging your LiFePO4 bank, while your Lead bank continues to charge daily.

In short, the BankManagerPLUS allows you to monitor and charge EACH of your battery banks in the safest, most optimal way based on its chemistry.


Due to the state of international shipping, we currently only ship BankManager units to addresses in the United States. (This allows us to accurately track packages to your door, and avoid lost shipments.)

  • If you have a U.S. address already, your shipping cost will be approximately $25.00.

  • If you do not have a U.S. address, you can use a service like to obtain a virtual address.


Jack and Lisa live aboard their Hunter 410, "Shore 'Nuff" and have been happy with their system since installing it in January 2022:

Simon in the UK had a rather complex installation, but worked with Clark to incorporate the BankManagerPLUS:

Mark Z aboard "Zee Cat" recently installed the BankManagerPLUS BBMS on his boat with a single 100Ah LiFePO4 battery in SW Florida. He is routinely seeing 13.1 or 13.2V first thing in the morning!

If you have installed your BankManagerPLUS unit and would like to share your story, please email


If you're interested in adding a BankManagerPLUS to your boat, RV, or other offgrid system, we recommend you place an order ASAP to reserve your unit. We have a higher influx of orders in the months before peak sailing season. Global supply chain issues can often interrupt production, so we generally have fewer than 100 units on hand at all times, and often less than 50.


My good friend Conrad Grillo (who lives aboard his sailboat, SV Tla Hla) has taken the lead in testing the BankManagerPLUS unit on his own battery system since 2021. He has been instrumental in the development of the BBMS. Conrad has written up some thoughts and research to share with you. You may access his notes as a PDF file here.