12 Volt Technical Articles, Battery Management Systems

What is Active Balancing in Lithium?

Posted on by JTS 12volt

Active Battery Cell Balancing Lithium

With the majority of Camper trailer and caravan lithium battery manufacturers, there are 2 main ways to keep your lithium cells balanced. Passive and Active cell balancing.A critical role of the BMS is to monitor each cell in the battery stack. This helps to maintain a healthy battery state of charge (SoC), extending battery cycle life and providing an added layer of protection as it prevents damage to lithium cell caused by discharging over overcharging.

Passive balancing results in all battery cells having a similar SoC by simply allowing excess charge to bleed through from one cell to the next. A good analogy for this may be the way a Battery Isolator allows an auxiliary battery to float the same charge level as the main start battery.Active Lithium Cell Balancing is a far more complex and accurate technique, Essentially it redirects charge between the battery cells while being charged and discharged. Doing this can increase system run time by increasing the total useable charge in the battery stack.
300Ah Slim Lithium Battery 12V EPL-300AH-12V-SLIM
300Ah Slim Lithium Battery 12V
EPL-300AH-12V-SLIM

Mismatched Discharge and recharge

A lithium battery as we know it is made up from either cylindrical or prismatic cells joined together inside a case. Balancing refers to keeping these cells at an even capacity. During standard use there may be quite a bit of capacity left in several cells, but if there are a few weaker cells in the battery it may limit the runtime of the system.

A battery mismatch of 5% results in 5% of the capacity unused. With large batteries, this can be an excessive amount of energy left unused.

With active balancing, the charge is redistributed in a controlled (active) way from the stronger cells to the weaker cells, resulting in a fully depleted battery stack profile.

Passive balancing, Using a relatively low current balancer, it drains a small amount of energy from high SOC cells during the charging cycle so that all cells charge to their maximum SOC. This is accomplished by using a switch and bleed resistor in parallel attached each battery cell, like the image below

 

Active Balancing In Summary:

Passive balancing rely’s on the resistance of each cell “sorting it’s self out” while Active Balancing creates a controlled enviroment to give the best result possible.

As a very loose analogy, you may say passive balancing is like running an Isolator Battery System and Active Balancing resembles using a BCDC Charger.

In the JTS Lithium range, we can offer you both Active and Passive balancing systems depending on your requirement.

The team at JTS can offer a large range of solutions for your 12 volt Setup, we offer Lithium, AGM and calcium setups depending on the enviroment, budget and customers needs.

If you want advice on the right setup give the team a call

1300 377 128

 

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