What should you look out for in your decommissioned electric car?

Time changes lithium-ion batteries

In an electric vehicle, a lithium-ion battery can have a lifespan of about 8 to 10 years, sometimes even longer.

With an energy capacity of less than 75%, it is still possible to use the batteries for a stationary storage unit, for example in conjunction with intermittent renewable energy sources (wind, solar), fast charging stations (to avoid a connection that requires costly subscriptions and construction work), with a domestic or professional grid connection (as a backup or to save money on the electricity bill).

Various reasons can cause additional damage to traction batteries, some of which are caused by the shutdown of the motors.

Storage when empty

Between 1995 and 2005, it was recommended to store the batteries of electric cars when empty. But that was at the time of nickel-cadmium technology, when such a scenario was beneficial in terms of longevity, provided that the consumer was not active.

For lithium cells, it is absolutely necessary to avoid deep discharge, which results in a voltage of about 2.5 and 3.3 V respectively for lithium-ion and lithium-ion polymer cells. Otherwise, irreversible damage can occur due to undesirable chemical reactions.

In extreme cases, this damage can be the cause of the ignition of the batteries, either during charging or after a long period of immobilization. A phenomenon that is becoming increasingly rare and that tends to disappear with technical progress. On the other hand, the final loss of the cells is still present in an empty or almost empty state after prolonged storage.

In this regard, two points should not be forgotten: lithium-ion cells are subject to a monthly self-discharge of about 3% (a value that depends on the chemistry of the elements); Devices in standby mode draw power weakly but safely, directly or indirectly, from the traction battery.

Storage at 100%

Storing a lithium-ion pack at 100% capacity is also not recommended. Even in the case of self-discharge, such a practice would lead to premature aging of the cells.

For example, this 2011 Nissan Leaf, which has been at a dealer for 5 years with a full battery and a range of only 45 kilometers was issued in 2019. The 70% loss of capacity is also due to other factors, including a consistently high ambient temperature between 28 and over 35°C.

In any case, owners of electric cars that have been stored with a full battery for a long time report an early loss of range. A mobile device such as a mobile phone or laptop would have been unusable much earlier.

However, it should be borne in mind that an electric car, even with a battery stored in optimal conditions, would have lost part of its range in 5 years without driving due to its age. However, in a much less pronounced way.

50, 60, 75%?

What is the best energy capacity for an electric car to be immobilized for several weeks, months or years? Preferably between 50 and 75%. This range is wide enough that monitoring doesn't become too tedious – apart from the fact that lithium-ion batteries work best with regular use. For a few weeks, it should not be a particular problem to store them in this size. However, if the immobilization exceeds one month, one should plan for some activity by charging the battery from time to time for a few tens of minutes and leaving the vehicle running from time to time.

This is all the more so because the 12 V accessory battery can be empty after a few weeks. This is especially true for certain models of electric vehicles, but also and especially when these devices reach the end of their service life. With regular use of the vehicle, this phenomenon is almost impossible to observe. But after a few weeks of standstill at negative temperatures, the aging of the lead-acid battery will quickly be observed.

Ways to unload an electric car

In the current situation, where you should only drive when absolutely necessary, it may not be easy to drive several dozen kilometers to reduce the load capacity a little.

Ideally, it would still be best to lend the vehicle to a person who urgently needs a vehicle for one or more important trips. Provided, of course, that no person involved in this case transmits or receives the Covid-19 virus.

Another option is to operate the biggest power guzzlers – such as the heating – while making sure to leave the windows open. The greater the capacity of the battery, coupled with an efficient device (heat pump), the more time is spent on this process.

Professional vehicle fleets

What applies to the individual is even more true for a company with an electric vehicle fleet.

With the exception of the models equipped with Bolloré's LMP battery, installed in Bluecar and its variants (Bluesummer and Citroën e-Méhari), it is not recommended to leave electric vehicles connected for several weeks or months without driving.

This does not apply to vehicles equipped with devices that stop charging when the vehicle is more than 80% full. This precaution also applies to non-professional electric vehicles. Such an automatic system is likely to facilitate the current crisis management... if it has been scheduled in advance.

Tomorrow: V2X

With a bidirectional charger, it will soon be possible (for some privileged people it already is), starting with companies, to draw energy from the batteries of electric cars to feed the power grid (V2G = Vehicle to Grid), the home network (V2H = Vehicle to Home) or a building network (V2B = Vehicle to Building) when needed.

From then on, for all vehicles connected through such a system, all our advice will be null and void, and that is a big step forward! The batteries are thus regularly subjected to a life-saving measure, in which they go through phases of discharge, charging and rest up to several times a day.

Summary

Conclusion: It is advisable to keep the battery of your electric vehicle at a state of charge between 50 and 75% only for a few weeks of standstill.

If this situation lasts longer than a month, consideration should be given to providing the battery with actions that alternately charge and discharge. This should always be done within the mentioned energy range.

source : Coronavirus: What should you look out for in your decommissioned electric car? (chargemap.com)