BankManager™ System

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

BankManager™ technical manual and user information here

Click here for Frequently Asked Questions (FAQs)

Click here to buy a BankManager™

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 BankManager.

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 BankManager™ BBMS units have been installed on SV Temptress and SV Tla Hla. We have also sold more than 500 units to boaters, RVers, and other off-gridders. In that time, 99% of units have functioned perfectly from the initial installation. The remaining 1% have received updated boards designed to accommodate peculiarities in their systems. This required a small change to the software, and we've updated the software on all future versions of the BankManager™. This page has more information about how the BankManager™ works and how to buy one. 


Anyone interested in obtaining one of these units is invited to place and order here:


Introducing the new BankManager™ Generation 3 

Our newest offering, the BankManager Gen3 is now available for order. It has every feature that the Gen2 has, plus a whole lot more.

This unit works for 12V, 24V, 36V, or 48V systems, and can be used for marine, RV, off-grid homes, and other hybrid battery applications. This unit includes a sensor and is compatible with Gen3 and universal spare/replacement parts listed below.

The Gen3 is a fairly major respin of the BankManager™ line. It is based on a more capable microprocessor that allows for new functionalities and operates 25% faster. There is a very long list of new features included in the Gen3. It…

But likely the most interesting new feature is that the BankManager comes with a BlueTooth LE radio. It transmits both instantaneous and historical data about the operation of your BankManager in your system. At the time of this writing there is no app available yet but it’s being worked on and will be able to be downloaded and connected after installation of your Gen3 BankManager. We will be making the technical specifications to this interface available (see this link) to allow anyone to use this data stream to build their own app or integrate this into your own boat or house management system. A lot of the early adopters of the BankManager are very capable engineers and this has been one of the most asked for features. I’m very sure in the near future BankManager will be integrated into many open projects. If you integrate BankManager into your system please contact me and we will add your system link here.

We still intend to offer and provide support for the BankManager™ Gen2 model, as it is a very good device that provides effective protection for your LiFePO4 batteries in a hybrid environment, and is more economical to produce. Over 500 Gen2 units have been shipped, and we receive emails weekly saying that these units are performing well in the field. 

Gen2 and Gen3 BankManager™ units are available for order to anyone with a US address. We still hope to offer them from international shipping locations, but until we get our CE certification, they will only be available to ship within the US, shipped out from Wisconsin USA. For the rest of the world outside the US, we still suggest you use a forwarding service such as to get your orders. Many BankManagers™ have arrived safely using this method, and it comes out safer and much cheaper than direct mail.

Order processing and delivery times: We are a small family business that processes orders weekly. Typically, we download order data on Sunday mornings and ship out UPS on Monday. (Tracking numbers are generally not active until mid-week.) So in general, if you order your BankManager™ unit before 10am EST on Sunday, your order should arrive at your US address by the end of the week. To prevent delays with your order, please confirm your address and phone number are correct, and order all your items at the same time. 

The Gen3 is available in 3 case styles:

The “All-In-One” unit takes all the hookup wires right to the one unit. If you are upgrading from a Gen1 or Gen2 BankManager this would be the easiest upgrade as the case has the same footprint as the Gen2 and uses the same hookup wire order as the earlier offerings. This case is the least complex, with everything in the one box. This is especially useful for installations that mount the BankManager™ near the batteries, or if the user doesn't mind running several wires to the display unit. 

Split Units

We also offer two models of the Gen3 BankManager where the functionality of the unit is split between 2 boxes. In both models, the first box is the auxiliary unit. It has the screw terminals for all the hookup wires and can be installed near the contactor and current sensor (usually near the batteries). The second box, the display unit, provides the user interface and is designed to be installed where you can easily see it. The two boxes are connected by two regular ethernet cables, provided by the user.

The surface-mount unit offers the smallest head unit, and does not require holes to be drilled into your installation site.  Its ethernet wires come out of the bottom of the display unit.

The back-mount (optional flush mount) unit allows you to hide the wires going to the BankManager™, as all wires enter the unit through the back. Optionally, it may be flush mounted, similar to other modern boat instruments, and includes a trim ring that helps achieve a professional-looking installation.


To function properly, your BankManager™ will need the following:



*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 BankManager™ 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 BankManager™ 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 BankManager™, please add it to your cart with your BankManager™ 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 BankManager™ 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 BankManager 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 BankManager™ allows you to safely combine LiFePO4 and lead battery banks.

Saves Money

With the BankManger™, 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 BankManager™ user interface allows you to fine-tune your charging levels and methods to your needs.

Why does the BankManager™ 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:

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 BankManager™ 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. 

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


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

An actual customer install, explained:

Andrzej developed his own approach to mixing lead and lithium batteries, but decided in the end that the BankManager helped him create a more hands-off system. 

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

Mark Z aboard "Zee Cat" recently installed the BankManager™ 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!

Dustin and his family live on an offgrid homestead and have combined the BankManager with their Growatt Inveter charges. This system shows the BankManager's ability to handle very large power levels: 

This YouTube user shared their Lithium+Lead Hybrid Battery system with Litime 12V 100AH batteries and the BankManager. Since it's a large residential installation and not as tight as most marine installations, you can clearly see how everything is connected:

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


If you're interested in adding a BankManager™ 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 BankManager™ 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