Deep Dive: Demystifying the Fogstar Drift Battery Management System

Did you know, we use a JBD Battery Management System (BMS) inside our Fogstar Drift batteries? If you're a battery enthusiast or someone who values precision, stick around as we discuss how your Fogstar Drift BMS operates in a bit more depth…

While a BMS offers valuable insights, it's not solely focused on precise measurements

New to the term 'shunt'? Think of it as a traffic monitor for your battery's power flow, tracking both incoming and outgoing energy. The shunt is the component responsible for measuring your remaining power.

To start, it's worth pointing out that your JBD BMS was never designed to be a dedicated battery shunt. Its sole purpose is to protect the user, and the battery, via an extensive list of protective features.

The shunt built into the BMS is a good basic monitor that is great for most people. However, if you have an inverter with high current demands, a multi-battery set-up, or experience a small parasitic drain from your system, it can cause the state of charge (SOC) monitor to get out of sync pretty quickly. 

How does the JBD BMS measure the state of charge?

The JBD BMS has been designed to encompass a unique hybrid approach when it comes to measuring your battery's SOC.

Cleverly marrying coulomb counting, and voltage-to-percentage calculations, the BMS shunt will analyse your battery's SOC. These calculations work in tandem to give the user a good estimation of the battery's remaining capacity - this is often represented as a voltage indicator, and SOC % bar, in the Fogstar Drift App. 

But let’s talk about an important caveat. There is no BMS shunt in the World that can measure accurately below 1 Amp — the only way to get extremely accurate measurements is by using an external Shunt. 

Due to technological constraints, the JBD BMS used in our Fogstar Drift batteries cannot accurately measure currents below 0.7A. This unfortunate kink in the system could potentially skew your readings if you're consistently dealing with low currents, or even pulling extremely high currents through your system. However, this inaccuracy is a small price to pay for the vast number of safety-critical features that come packed into your JBD BMS. 

Another interesting feature to take into consideration is how this particular BMS resets its SOC calculation. This happens at 14.2V or 3.5V per cell. Charging your battery to these precise voltages helps your battery to reset the capacity - ready to go again on a more accurate footing.  

So, why 14.2V you may be wondering? Well, charging to this precise voltage helps the BMS shunt function accurately, resetting the capacity to 100% SOC. If you're finding your state of charge doesn't quite marry with your battery voltage, it's worth putting a full 14.2V charge into the battery to hit reset on your capacity.

Let's talk about calibration...

Then we come to calibration. The Fogstar Drift’s BMS takes around 4-5 full charge and discharge cycles to actually calibrate and show a correct reading. Over this time, it helps if you can charge your battery to a full 14.2V and discharge it down to cut-off during the first few cycles.

During this initial period of calibration, your SOC % reading may be a bit askew. The advice here is to check your battery's SOC via the voltage rather than relying on the percentage. The calibration process helps the BMS accurately learn your battery's capacity, ensuring you get the most bang for your buck in the long run. 

It's also worth noting that there is a self-discharge rate programmed into the BMS which will automatically reduce the SOC over time - you can mitigate this issue by putting a full 14.2V charge into the battery and re-setting the capacity regularly.

Remember, understanding your battery's BMS isn't just for tech heads or battery buffs, it's for everyone who wants to maximise their investment. Just follow the user instructions to the tee and you'll have yourself a system that ensures optimum performance every time.

A little bit of due diligence can make a world of difference in managing your batteries.