Chargeing on top

[Kristian]

The manual says one should not repeatedly charge on top of the SOC. I wonder why? But I frequently use the preheater when connected. The 10 mA cable will only support up to 2400 kW so the battery will be drained somewhat. I then will let the car "rest" for perhaps 20-30 min and it will the recharge. This is pretty standard procedure for me. Does anybody know if this would cause a problem?

 

[jaapv]

Trying to recharge a (nearly) full battery can result in overcharging which is highly detrimental to battery life. It is wise to let the car run down a few bars before plugging it in again. In general Li-Ion batteries are best recharged when they are partially discharged. For this reason Mitsubishi leaves 27% - 13% reserve in an "empty" battery.

 

[Grigou]

Trying to recharge a (nearly) full battery can result in overcharging which is highly detrimental to battery life. It is wise to let the car run down a few bars before plugging it in again. In general Li-Ion batteries are best recharged when they are partially discharged. For this reason Mitsubishi leaves 27% - 13% reserve in an "empty" battery.

I do not think that there is any risk of overcharging. I hope that the electronical control is efficient enough to avoid that. When the voltage has reached the appropriate level, the charging process stops.

I think that the reason could be that Li-ion batteries don't like to stay a long time at high level of SoC, and if we recharge often at nearly full battery level, it's what happens.

 

[PhevWestNorway]

I think that the reason could be that Li-ion batteries don't like to stay a long time at high level of SoC...

What is "a long time"?

 

[Stvtech]

Speaking of Lithium batteries in general (so probably applicable to the Phev);

I think repeatedly topping up from low levels of charge without reaching full charge will do far more damage that repeated topping to full charge after a short run. This is because cell balancing occurs toward the end of a charge cycle for Lithium based chemistry when the charging process is in CV (Constant Voltage) mode.

Below 80% SOC, charging will occur in CC (Constant Current) mode, where repeated charging without cell balancing can indeed result in overcharging of some individual cells if protections are not in place.

 

[Grigou]

That's why Mitsu recommands one full charge at least every 2 weeks...

What is "a long time"?

I could be wrong, but I think that we have to add all the periods.

For example, if the battery stays at full level 8 hours per day during 30 days it makes 240 hours, and it could be equivalent with 10 days at full level.

I'am certainly wrong :roll:
Who has a better answer ?

 

[jaapv]

Speaking of Lithium batteries in general (so probably applicable to the Phev);

I think repeatedly topping up from low levels of charge without reaching full charge will do far more damage that repeated topping to full charge after a short run. This is because cell balancing occurs toward the end of a charge cycle for Lithium based chemistry when the charging process is in CV (Constant Voltage) mode.

Below 80% SOC, charging will occur in CC (Constant Current) mode, where repeated charging without cell balancing can indeed result in overcharging of some individual cells if protections are not in place.

I do not think this is applicable. The car will, during driving, apply an endless number of part-charges through the charge and save buttons, the maintaining of charge at minimum level and regeneration. If this were harmful for the battery it would not last long.

I do think overcharging was on Mitsubishi's mind when adding the warning to the manual.
Not only will it damage the battery if one manages to bypass the safety algorithms, there is a danger of overheating and even a fire risk.
That this is not imaginary is proven by the fact that the first series of 4000 cars had to be recalled to the factory for exactly this problem, halting production for three months.
Incidentally, Boeing's Dreamliner 787 struggled with the same issue.