Is it ok to leave a lithium ion battery on the charger

Aug 20 , 2019

Is it ok to leave a lithium ion battery on the charger

It’s a big G’day from MEGALiFe Battery Australia and we’re back with some more helpful info about lithium ion batteries

Today, we want to answer a common question we get asked, ‘Is it ok to leave a lithium ion battery on the charger’?

Lets start with some basics about lithium charging some of the differences to traditional, lead acid, requirements.  Lead acid based batteries, including all the commonly known acronyms like AGM, SLA, flooded, etc often require quite complicated, multi-stage processes to achieve a full charge.  You might have heard about bulk/float/pulse and all sorts of gimmicks to describe how to get a charge completely and correctly for this last century technology.  The lead-acid based chemistries require quite complicated algorithms to correctly achieve a good state of charge due to the nature of the lead breakdown in the cells. (show lead algo)

Lithium ion batteries require a much simpler, constant current, constant voltage or CC/CV charging profile to be safely and fully charged.  Simply put, the voltage is set and a current is applied until this voltage is reached at which stage the current, by default, stops flowing.  This is the exact method used in your laptop power adaptor or mobile phone charger and also is the same output you get from a car/boat/bike alternator as rectified DC. (show lithium algo)

Armed with this knowledge, it becomes clear that if the correct voltage limit is set for the lithium ion battery you are charging, there should be no issue leaving a lithium ion battery on the charger.  MEGALiFe Battery uses a LiFePO4 cell in a 4S configuration giving a nominal voltage of 12.8v and a fully charged voltage of 14.6v.  A charger with 14.4-14.6v CC/CV output will do the job with consideration not to exceed roughly 1C maximum current output of the charger.  A ‘charger’ can also present in many forms including the more commonly known power adaptor for a laptop, a vehicle alternator, a solar charge regulator, a DC/DC converter……and the list goes on.  As long as the CC/CV profile is used, the maximum voltage is at the correct level and the current is not excessive, you will achieve a safe and full charge on your battery.

As an added level of convenience and safety, our batteries have an integrated battery management system (IBMS) that balances the cells at top of charge and also has a high voltage cutoff (15.6V), high temp cutoff and a high current disconnect just in case there is an issue with the charger being used.

No two electrical systems are designed the same and I would encourage readers to seek out as much information on the subject as possible.  Although the core facts are true, the above example does not talk about some other details that could be included in this topic.  For example, a lithium battery/cell will likely ‘rest’ back to a lower voltage than its fully charged state, at which stage, a charger may kick in with current flowing again until the voltage is back to the preset limit.  There could be a passive balancing function that ‘burns’ the energy at the top part of charging until all cells reach the same voltage levels which would also see a flow of current.  It is also known that LiFePO4 batteries, particularly if used in a deep cycle application, can have an improved cycle life if kept to a maximum 90% SOC and discharged also to not less than 20% capacity.  All of these factors do play a part in the main question but do not change the overall answer for us.

So I’m hoping that sheds a little light on a common topic with lithium ion batteries.  Although it seems like it gets complicated, LiFePO4 cells used in MEGALiFe Battery and other lithium chemistries alike, are actually a much simpler concept in correct charging and keeping your battery topped up and in good condition.

We get a tonne of questions regarding charging of our products and we want to try and cover the many facets of lithium ion battery charging process in details through some of these posts.  You can always search for more info on our site, check us out on social media.