Tips to Avoid Lithium Ion and Lithium-Polymer Battery Problems.

 

There are four elements that can cause problems with Lithium batteries, these are.

1. Heat

2. Damage

3. Discharging

4. Charging

A Lithium battery will undergo thermal runaway if the temperature of the battery exceeds 80oC.  When thermal runaway occurs, as the name suggest, you cannot stop it, as it is an exothermal chemical reaction.  All that is required to do to stop thermal runaway, is not to let the temperature of the battery get above 80oC.

Damage.

If a battery suffers damage, it will increase the internal resistance of the battery.  An increase in resistance will increase the temperature of the battery while undergoing charging and discharging.  It is the increase in the battery’s internal resistance, which has the most effect on the battery’s performance and the likely hood of the battery temperature to increase above 80oC.

Damage may also create a fault in the battery where an internal chemical reaction will produce CO2 gas, this is commonly seen as swelling of the battery.  A swollen battery will still work; however, the performance of the battery will be degraded as the internal resistance will have increased and therefore elevated operating temperatures.

All battery manufacturers recommend that swollen batteries are disposed of.

Temperature.

Lithium-Polymer batteries do not work very well at temperature below 5oC and if the internal temperature of the battery is below -7oC will not work at all. 

Most battery chargers/dischargers will have an auto cut off if the internal temperature increases above 60oC, however, some batteries do not have thermal cutouts, if used when the battery has been kept at an elevated temperature (say stored on the back shelf of the car, on a very hot day), then there is the very strong possibility of the battery temperature increasing “during normal operation” to over 80oC.  Therefore, always store batteries at room or slightly below room temperature and never in a fridge or cool box.

Charging and Discharging.

Manufactures recommend what has now become known as the 80% rule.  All manufactures have data sheets for their batteries.  These data sheets will have the charging and discharging rates, and all other relevant information.  Use the information given for your battery type.  Note, there are many different types of what is the essentially the same battery, i.e., cell number, mAh, C rating etc. all with different abilities regarding charging and discharging.

A battery should not be discharged below 20% of its maximum charge.  If a battery is discharged to say below 5%, then the battery will recharge inefficiently.  This means that there will be an increase in internal temperature while charging.  This will also cause an increase in battery resistance. 

If a battery is discharged to a low level, then the battery can be recovered by charging at a low amperage, say around 0.4A.

A battery should be kept or stored at a constant temperature.  All manufacturers recommend that the battery should be stored at around 60% charge, and that a battery at 100% charge can be kept for up to 5 days.  Lithium-ion batteries will slowly discharge over time to a base voltage, Lithium Polymer batteries tend to hold their voltage (if not damaged). 

 

I have personally kept Lithium-Polymer batteries at 95% charge for over three years without a problem and any noticeable loss of charge.  However, this is not recommended.  Here are some tips for good housekeeping of Lithium-Polymer batteries.

1. Proper charging – Make sure you charge your battery properly using a quality battery charger.

2. Don't over-discharge.  Make sure you stop using your battery before the voltage gets to the minimum cut-off voltage.

3. Lithium-polymer batteries are safe.  Lithium-polymer is even safer than lithium-ion, as there's less risk of leaking the electrolytic component.

4. Note, LiPo batteries and cold temps don't mix well. The discharge rating of a LiPo battery is directly affected by the temperature of the battery. When the temperature of the battery is below 10°C, you will start to notice performance drops; significant issues start to occur when the battery gets below -7°C.

5. Aim to draw less than 60% of the maximum continuous rated current of your LiPo's. If you draw less than 60%, your cells will last even longer. Avoid discharging more than 80% of the cell’s capacity. If you consistently put less than 80% back, you will increase the life of your cells.

 

Storage and Transportation.

Store in a container that you can pick-up, can also be put/throw into a bucket of water or moved outside quickly.  The only way to deal with thermal runaway is to immerse the battery in water and keep it immersed for at least 24 hours or move to a safe location outside and let it burn itself out.

Never have a lockable lid, which is airtight, if a battery did undergo thermal runaway, then you have created a potential explosion.

Always transport in a container where the batteries are kept secure, i.e., cannot move around.