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lithium aircraft battery BMS microchip

Experimental Aircraft Battery Management System - (BMS)

In addition to the LiFePO4 lithium chemistry Aerolithium uses in its aircraft batteries, the BMS's, we use have a microchip ' brain ' that senses and regulates the parameters of the lithium pack. It checks the charging and discharging to stay within limits as well as equalizing the charge between cells, balancing them for the longest life. These safety protections make Aerolithium batteries the safest lithium battery you can buy anywhere.

Battery Management System Protections

For Peace of Mind - when you need it the most!

  • Balancing - continuous

  • OverVoltage protection from charging, no crowbar needed

  • OverCurrent protection from charging

  • Under Voltage Protection from discharge - UVP - 9.8V

  • Parasitic drain auto shut off - LVD -

  • Low Voltage engine start reserve option

  • Short Circuit protection

  • Thermal: over/under temp protection cell sensors

  • LED Battery status indicator option

  • "Wakeup" button option- saves energy in non-use

  • Heat sink AL plate- keeping Mosfets cool

  • Remote Panel Digital display option

IFR chart

What method of internal balancing does your lithium battery use ??


The basic method of balancing lithium cells hasn't changed in years.

The two types can be divided into Passive cell balancing and and the newer Active balancing type.

Passive balancing drains charge from cells with excess charge and dissipates the drained energy as heat. Active balancing on the other hand transfers charge from  higher charged cells to lesser charged cells.

Cell balancing is not only important for improving the performance and life cycles of a lithium battery, it also improves safety of the lithium battery.

Both Active and Passive cell balancing are ways to improve system health by monitoring and matching each cells SOC. But, unlike passive cell balancing which simply dissipates the charge during the charge cycle, Active balancing redistributes the charge during charge and discharge cycles.

Therefore, Active cell balancing increases system run time and improves charging efficiency without generating the internal heat of a Passive resistor system.

Passive balancing is the method most used today to keep costs down at the expense of battery efficiency. A cheaper type of BMS is used in all lithium batteries seen in the market today using the Passive method where battery performance is not critical or safety dependent.

These cheaper BMS's may try to add other features like alleged redundancy or fault indicators to compensate for the inevitable early demise of the battery due to the imbalanced state of the cell pack.

active balancing


passive balancing

The faster the charging, the greater the imbalance that is occurring.
It is a common weakness with all lithium batteries that cell imbalance is a liability in every battery system. If lithium batteries are overheated or overcharged, those conditions will accelerate battery degradation and quickly shorten the batteries lifespan. Just as there are no two identical snowflakes, so too are there no two identical cells. There are always subtle differences in SOC, self-discharge rate, capacity, impedance and temperature characteristics. This is the case even if the cells are the same model, same manufacturer or same production batch.
Without a robust balancing ability the results are a large difference in voltage over time decreasing capacity.
In Passive balancing, the practical goal is to achieve capacity balance at the end of charge. However, due to the typical low balancing current, if the cells begin to diverge in SOC, it is virtually impossible to correct the charge imbalance at the end of charging. In other words, Passive balancing, while avoiding overcharging of the strongest cells does not allow a full charge of the weaker cells because extra energy is wasted in shunt resisters as heat... a LOT of heat!
With Active type balancing, 2 goals - achieving voltage parity at the end of charge and minimizing V differences among cells can be achieved at the same time. Energy is conserved and transferred to the less charged cells which results in increased safety, discharge capacity and life of the battery.
Unless the cells are well balanced, a ' weaker ' cell in the pack will limit the overall performance of the battery and eventually render the battery unusable. To avoid this, the cells should be balancing at all times  not just while being charged so that the differences between cells are as small as possible.
Operational wise; the Passive method is simple and straightforward - the BMS uses resisters to dissipate energy. It is cost effective and this method is used in all older tech aircraft batteries still available today. However, since 100% of the excess energy is turned into heat inside the battery, and it is incapable of keeping up with the incoming charging current, imbalance is assured and runtimes are diminished.
A typical BMS with Passive balancing comes with 50 - 200milliamps capability. When the charging current is high - such as from an alternator - the resisters are overwhelmed and the heat generated by them degrades the cell pack over time.
Active balancing on the other hand utilizes capacitive or inductive charge shuttling to deliver energy where it is most needed with minimal loss and heat generation.

​These Safety Features engage automatically

  • Overcharge / Over voltage Protection from a regulator Failure which may result in excess voltage and current.

  • Aerolithiums heavy duty circuitry needs no external regulator ( crowbar ) assistance.

  • Max. charge 100 amps protection

  • Over current protection limits maximum charging current to battery from any size alternator / generator.

  • Thermal Protection - sensor in direct contact with the cells vs. board type, automatically adjusts charging and discharging limits per  temperature conditions.

  • AC Ripple Protection - circuit of coils and capacitors to filter this out. Smaller engines really need this feature.

  • Short Circuit Protection - 2 ms

  • Cell Balancing - Smart Float type activated by 0.015ma differential at 40 - 300 ma

  • Sleep Mode - BMS will not drain battery when not in use, < 1 ua

  • Conducted Protection circuitry to abate damage from Back EMF at the alternator. No other competitors BMS, have this important safety feature.

  • Dual Core MCU based system redundancy - monitors cell sensing circuity, sensing wires and thermal sensors against, out of limit variation

  • Heat sink plate for Mosfets - to dissipate excess heat from all that power!

Take the Guess-Work out of Flying!
A visual display is an essential requirement for an aircraft battery. You will absolutely need a visual reference in order to determine battery health. 
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