Twizy, AMI and other EV : save your lithium battery

The question arises of what to do to preserve the battery in order to prolong its life as long as possible. This is what I suggest you discover with these article and video :

Video

General principles :

Lithium batteries do not like extreme states of charge especially prolonged, do not like heat, and age with the number of charge cycles. From these main principles, we will learn lessons at different levels which will first of all be good charging practices, to be implemented naturally when you charge your car on a socket, but also when driving. And good discharge practices that should be followed when you are obviously on the road, but also when the car is stationary.

Charging advices

The ideal is to stay between 20 and 80% of the battery capacity. It is by staying in this zone that it will age best. It is therefore necessary to avoid charging above 80%. But we can qualify because if for example you recharge to 100% at night for use the next morning, the extreme state of charge will not last long and will damage your battery very little.
On the other hand, the battery management system (BMS) which calculates the current charge (SOC) and total available charge (SOH) values needs to be recalibrated from time to time. For that, it is necessary to proceed to a discharge close to 0% followed by a charge to 100% (read also: State of health of lithium batteries (SOH): many problems and some solutions)

Avoid high outside temperatures: As the charge is carried out by an external electricity supply, this necessarily causes the battery to heat up, which is harmful but inevitable. It is therefore not necessary to add even more heat by recharging for example in direct sunlight. A garage or a shady place is preferable.

Note that the cold does not damage lithium batteries but reduces their performance in capacity and available power.

On the road, use the engine brake: electric vehicles have the ability to use the electric motor as a dynamo and thus be able to recharge the battery when you decelerate, this is called regeneration. So every time you take your foot off the accelerator, you recharge the battery a little. There is obviously a direct interest in doing this since it provides more autonomy, but there is also a longer term interest since it increases the battery life by maintaining the level of charge, because batteries prefer stay in a fairly constant state.

Discharge Tips:

Avoid discharging the battery below 20% and above all leaving it discharged in this state. More imperatively, do not drop below 5% repeatedly because this will have a strong impact on its aging. But for example if your daily commute involves a discharge of up to 10% but you recharge immediately, no problem since this state of extreme discharge will not last long.

Avoid using the electric vehicle immediately after a charge: again the problem of heat: the charge already heats up the battery and its immediate use too, so nesting the two is not ideal.

Avoid strong acceleration: the purpose of the battery is to supply the electric motor and therefore to supply it with current, but the more the engine's power is used during strong acceleration, the more current it will need and therefore therefore the more the battery will start to heat up.

If you have to leave your electric vehicle unused for a long time, your best bet is to keep the charge around 50%. During a prolonged shutdown, over several days, the battery will discharge slowly and therefore drop below 20% and this is not good for it. It is therefore necessary to recharge it regularly and ideally maintain it in a stable state of charge, between the famous 20 and 80%, the best being the middle, that is to say 50%.

Under these conditions of non-use, it would also be better to leave the vehicle in a "cool" place, away from the strong heat which degrades the battery.

Despite all that...

Despite all these precautions, a lithium-ion battery inevitably ages simply because it is used! Indeed, it is estimated that batteries of this type have a lifespan of between 1000 and 1500 complete recharge cycles. So, having reached this value, these batteries are not completely dead, but they will have a capacity which will have fallen below 70 or 80% which causes too much reduction in the autonomy of the vehicle and which makes it unsuitable for its initial use.

If we take the example of the Renault Twizy, with pessimistic values ​​(60 km of range on a single charge, and 1000 recharging cycles of life) but with use of the battery taking into account the advice I have just given to give, we roughly end up with a mileage of 60,000 km (60x 1000) before having a battery below 70%. With optimistic values ​​(70 km of autonomy and 1,500 cycles) we obtain 105,000 km. The truth must be somewhere in the middle, which is rather reassuring for standard urban or peri-urban use of this small electric vehicle.

Conclusion:

To put it simply and to summarize, in order to extend the life of a lithium-ion battery, you must avoid extremes, in charge and discharge, in especially high temperatures, and adopt a cool and economical driving style. Finally, it is a very good philosophy of life!