partial loading of the drive battery

[Harald]

Hi All,

I usually do not need my car every day.
Having learned that a Lithium battery should not be stored fully charged, I started to to charge the car as follows:

When arriving at home with a battery that is (close to) empty, I charge it immediately for approx 2 hours at 10 A which is approx. 50% SOC.
Having the battery at 50%, degradation should be minimized and I still have some electric range for an unexpected short drive.

Knowing when the next longer drive is expected (which I usually can predict), I set a second timer for loading the car up to max. in the night before a longer drive.

My questions to readers with more knowledge/experience with Li-batteries:
- Is it worth doing so? My "standstill period" is usually less than 1 week.
- When loading to 100 % SOC, how much time does the balancing process prolong the loading process?
How much spare time should I consider?

Any other hint to details I might not see is of course also welcome.

Harald

 

[elm70]

I don't think you need to charge the car after the trip .. actually it is not even a good practice .. since is better to charge a Lithium battery when it is not "hot" .. and after usage it may have increase the temperature above 30/35 deg (based on usage, temperature, etc etc)

When the PHEV dash shows 0 battery left, in reality the battery has over 35% capacity left, that is already the ideal status for leave the battery for long storage.

 

[ThudnBlundr]

Mitsubishi recommend having at least a bar on the display if you're leaving the car for a long time, but they're talking months. Managing the degradation of lithium batteries seems to be something of a dark art, but for best long-term performance, it could be worth giving the batteries a short charge some time after you get in, and then do the second charge as you do now. But to be honest, I'm not too sure you'd notice any difference either way...

 

[Tipper]

Surely the battery management unit in the car manages the battery and the charging of it?

Seeing as Mitsubishi have done such an excellent job designing everything else I have every confidence that the battery management will have been foremost in there minds. :shock:

On this basis my car is plugged in on every return home and left plugged in until next needed...sometimes left 2-3 days at a time. It doesn't seem to be suffering at all and no particular change in range has happened excluding ambient temperature and 'who drove it last' influences.

(It also means my wife doesn't forget to plug it in as it is now an 'arrivals procedure'!)

 

[anko]

Surely the battery management unit in the car manages the battery and the charging of it?

Seeing as Mitsubishi have done such an excellent job designing everything else I have every confidence that the battery management will have been foremost in there minds. :shock:

But they do not know whether you need a full charge every day or not. There are many things they cannot know about your usage pattern. So, their results will, almost by default, be sub optimal.

 

[elm70]

Surely the battery management unit in the car manages the battery and the charging of it?

Seeing as Mitsubishi have done such an excellent job designing everything else I have every confidence that the battery management will have been foremost in there minds. :shock:

On this basis my car is plugged in on every return home and left plugged in until next needed...sometimes left 2-3 days at a time. It doesn't seem to be suffering at all and no particular change in range has happened excluding ambient temperature and 'who drove it last' influences.

(It also means my wife doesn't forget to plug it in as it is now an 'arrivals procedure'!)

Tell us how old is the car, how many km/miles have been done ... and what is the real battery SOH from the PHEVWatchDog .. and then we can know if your battery is better or worst then other PHEV battery

Leave the Lithium battery fully charged is not a good practice

It has to be said that these battery got charged "only" up to 4.1v .. vs other that goes up to 4.2v ... but 4.1v is the max voltage suggested by the producer too ... anyhow ... it is well known now that storing the lithium battery around 3.8v is the best practice for preserve them ...

 

[Harald]

I don't think you need to charge the car after the trip .. actually it is not even a good practice .. since is better to charge a Lithium battery when it is not "hot" .. and after usage it may have increase the temperature above 30/35 deg (based on usage, temperature, etc etc)

Thanks for the hint.
And no problem in that regard: I wrote "immediately", but should have better written "some time the same day or night".
This would better describe the way I charged the car the last times.

(And unfortunately, the underground garage is still f...... cold! It has not realized yet that we have summer temperatures outside...)

 

[Tipper]

Surely the battery management unit in the car manages the battery and the charging of it?

Seeing as Mitsubishi have done such an excellent job designing everything else I have every confidence that the battery management will have been foremost in there minds. :shock:

But they do not know whether you need a full charge every day or not. There are many things they cannot know about your usage pattern. So, their results will, almost by default, be sub optimal.

Old habits die hard...during my ownership of fossil fueled cars I always fill them up completely whenever they are empty and still do with my current other cars, I have two MGs, except when they are going into storage. Unlike some friends who only put in a few litres at a time to last them the next day or so!

For the PHEV my rationale is that I probably don't know how many miles I will do on the next day so I fully charge it to be sure of maximum electric range being available. I don't know what mileage I will do because I no longer commute being retired and every day is different.

 

[Tipper]

Surely the battery management unit in the car manages the battery and the charging of it?

Seeing as Mitsubishi have done such an excellent job designing everything else I have every confidence that the battery management will have been foremost in there minds. :shock:

On this basis my car is plugged in on every return home and left plugged in until next needed...sometimes left 2-3 days at a time. It doesn't seem to be suffering at all and no particular change in range has happened excluding ambient temperature and 'who drove it last' influences.

(It also means my wife doesn't forget to plug it in as it is now an 'arrivals procedure'!)

Tell us how old is the car, how many km/miles have been done ... and what is the real battery SOH from the PHEVWatchDog .. and then we can know if your battery is better or worst then other PHEV battery

Leave the Lithium battery fully charged is not a good practice

It has to be said that these battery got charged "only" up to 4.1v .. vs other that goes up to 4.2v ... but 4.1v is the max voltage suggested by the producer too ... anyhow ... it is well known now that storing the lithium battery around 3.8v is the best practice for preserve them ...

Sorry I don't have the Watchdog. I go on how many miles it shows on the electric range each morning. After a winter of lower range, 18-21 miles, I am glad to report the range is rising as the ambient temperature rises here in UK. 25 miles this morning. The car is 3 years old and has shown this same range profile for those 3 years so I would suspect the battery is doing very nicely.

With respect to level of charge, it has been much discussed that the battery never goes above about 80% or below 20% by design, so surely Mitsubishi's designers have taken optimum Lithium battery performance into account.

On another point, I've noticed that if I've returned home with a completely 'flat' battery following a high speed motorway run the next morning after being put on charge straight away the range is really good, say 28 to 32 miles. So I would have thought charging a flat 'hot' battery actually works well.

 

[greendwarf]

On another point, I've noticed that if I've returned home with a completely 'flat' battery following a high speed motorway run the next morning after being put on charge straight away the range is really good, say 28 to 32 miles. So I would have thought charging a flat 'hot' battery actually works well.

This mirrors my experience but I put this down to journeys home having a larger downhill component i.e. more coasting, so guesstimate thinks I will continue in same vein. When I do a more normal journey (with less coasting) the miles drop off rapidly. However, I too think I am still getting an actual 25 miles per charge after 3.5 years - not that I bother to check very often. :lol:

 

[elm70]

...

On another point, I've noticed that if I've returned home with a completely 'flat' battery following a high speed motorway run the next morning after being put on charge straight away the range is really good, say 28 to 32 miles. So I would have thought charging a flat 'hot' battery actually works well.

I also notice that after ICE usage on motorway I can get higher EV range, independently by when I charge my car .. like I notice I get 5 leaves of "eco" if I drive in the motorway in "CHARGE" mode

Anyhow... This is one way to read data ... clearly I read data in the different way

I also notice that every time I disconnect the 12v battery ... and then reconnect the 12v battery, and later charging the car .. I get as EV guessed range back to the "magic" 52km value

Should I read this that disconnecting the 12v battery help the main battery to be charged better ?

For me ... These are all limitations of the Mitsubishi firmware in the car ... I don't want to call them bugs ... since guessing state of charge and the state of health in a battery that can't be fully discharged , it is practically impossible

BTW ... The BMU in our PHEV does not use the battery in the 80% to 20% range ... it does use the battery from 100% down to 30% (with special exception down to 25% for driving very very slow in the last km ... or down to 16% driving very very fast with with ICE running , before kick in the reduced power mode for bring back battery over 30% or whatever threshold is used in this special mode)

PS: Without the watchdog I would say it is impossible, or very difficult to state the battery condition ... I also get more range now from my car compared to 1y ago ... not because the battery got better, just because I did adapt to the "ECO" driving style that our PHEV "appreciate"

 

[elm70]

On another point, I've noticed that if I've returned home with a completely 'flat' battery following a high speed motorway run the next morning after being put on charge straight away the range is really good, say 28 to 32 miles. So I would have thought charging a flat 'hot' battery actually works well.

This mirrors my experience but I put this down to journeys home having a larger downhill component i.e. more coasting, so guesstimate thinks I will continue in same vein. When I do a more normal journey (with less coasting) the miles drop off rapidly. However, I too think I am still getting an actual 25 miles per charge after 3.5 years - not that I bother to check very often. :lol:

I just got my "record" yesterday ...

I made 24.5km +24.5km trip with full battery and 0.1L of fuel (the car at 1km EV range left decided to start the ICE while going very slowly an uphill ... on the downhill and next traffic light (red) ... regen breaking allowed to stop the engine and I made the last km left in EV mode ... trip was mainly done at constant 80km/h speed on motorway

My PHEV is a Dec 2013 ... and I know that my battery is down almost 10% (90.3% SOH for be precise) from the ideal/new battery state

 

[Harald]

... So I would have thought charging a flat 'hot' battery actually works well.

As the loading procedure takes some hours, I expect that the starting temperature does not have any big influence on the end of the loading cycle.

 

[anko]

... So I would have thought charging a flat 'hot' battery actually works well.

As the loading procedure takes some hours, I expect that the starting temperature does not have any big influence on the end of the loading cycle.

I don't know if it does. But I would think the temperature at the end of a 3.5 hour cycle will not be that much lower. The battery is a very dense mass and I think it does not loose heat that easily.