Hi Russell,

Yes, unfortunately it can be a bit of a minefield trying to bring together the right system to meet your needs and there is a fair bit of misinformation out there. Hopefully we can identify some key points here to make it easier.

Lithium batteries require a proper charging profile to maximise their lifetime and your investment. Here’s why you should only charge a 12V lithium battery with a charger specifically designed for lithium batteries and not a standard lead-acid charger such as the BMPRO J35C.

Lithium and lead-acid batteries require very different charging algorithms:

• Lead-acid batteries use a multi-stage charging process (bulk, absorption, float) and can tolerate trickle charging or being left on the charger.
• Lithium batteries typically need a constant current / constant voltage (CC/CV) approach and do not benefit from trickle or float charging — in fact, it can damage the battery or reduce its lifespan.
• Lithium batteries have an inbuilt Battery Management System (BMS). This is a set of electronics that monitors charge to the internal cells, cell voltages and provide a range of fault protections. A lithium-specific charger is often designed to work with the BMS, ensuring safe and efficient charging. A lead-acid charger may confuse or conflict with the BMS.

It is possible to upgrade your J35C to the capabilities of a D version through the BMPRO upgrade program.  Checkout the website for more details.  Your current unit needs to be removed and then sent away for an upgrade.  As part of this it receives additional warranty. The returned unit will then be set as Lithium ready, and you will need to utilise the settings through the screen or app to ensure you set the right battery capacity so that it can effectively monitor battery state of charge.

Great that you have upgraded your DC-DC capabilities as the J35 series can only provide a trickle charge through it’s DC-DC input and can’t compete with the newer vehicle smart chargers to boost voltage and charge a battery properly on the go.  Suggest that you install the BC300 shunt to ensure that all current that goes into the battery directly from the DC charger is captured in the charging algorithm. In addition, the DC charger should be providing MPPT solar charging to keep the batteries topped up.  If not, you can always wire the solar panels into the integrated BMPRO system which has its own proprietary charging algorithms.

In regard to the communications and brains trust of the system – the ControlNode it will need to be upgraded to the latest version of 103.  This will also enable a range of new features such as the integration of gas bottle, temperature and TPMS sensors, increased Bluetooth range and more. This device is more of a communication device and will leave the battery monitoring to either the J35 or the BC300.

Trust this has helped in bringing together the story for a more intricate system that allows you more power options and extended off grid camping options.  One closing piece of advice is that your system continues to evolve, to try and bring together as many parts from one ecosystem as possible as this enables a higher chance of compatibility for the entire system.  Therefore, maximising your investment and opportunities.

Safe travels,

12V Guru