Good Practice for Battery Life and Home Charging

greeiig

Active Member
Joined
Nov 24, 2021
Messages
95
Reaction score
75
Points
18
Location
London, UK
Driving
MG5
Hi all,
I just got my home charger installed - a PodPoint.
I'm typically going to do very few miles -just short trips round town - with the off longish trip thrown in.
My limited research would suggest that good practice would be:
1. not to continually recharge the battery - I'm thinking I'll just drive until the battery drops to around 20%, then charge it. This is likely to be less than once a week or until I know a long trip is coming up
2. When charging - best not to fully charge to 100%. I'm thinking I'll try to charge to 80% each time - unless I'm about to go on a long trip where I need the range.

Any views on the above would be appreciated. And also....

Assuming I'm not totally off the mark with the above: one thing I would like to be able to do - but don't think there is a way way with either the MG5 or my PodPoint charger - is to get the charging to automatically stop once I get to the charge level I want to. It would be great if that could be programmed either in the car or the charger. I think this functionality exists with some EV car makes?
Anyway, it looks like if I want an 80% charge, I need to either
1. stop charging manually at the right time - based on the estimated charge time shown. or
2. Set the Podpoint schedule to stop at the right time after I plug it in - but that means updating the time schedule manually once I've worked out how much I need. It seems a bit clumsy. Actually the more I think of it, if I know that it takes - say - 7 hours to charge from 20% to 80%, I just set the podpoint schedule for 7 hours by default. I'd just need to remember to take the schedule off if I want it to go to 100%.

I'm sure some of you clever lot have dealt with all this - I'd appreciate any wise words / suggestions
 

EVsince2016

Well-known Member
Joined
Sep 24, 2021
Messages
533
Reaction score
505
Points
96
Location
Reading
Driving
MG5
What sort of impact would there be, say if only rapid charged regularly to 80% from around 30% so after how many of these chargers would a balance be due? Also shouldn't the battery balance be due to usage than time, i.e the more miles you do to let it balance more often?.
Evidence is that's no difference to slow charging.

30-70% would be better, just depends on your needs. Pre-heating the battery also prolongs battery life when using rapids too.
 
Upvote 0
D

Deleted member 7171

Guest
1. not to continually recharge the battery - I'm thinking I'll just drive until the battery drops to around 20%, then charge it. This is likely to be less than once a week or until I know a long trip is coming up
2. When charging - best not to fully charge to 100%. I'm thinking I'll try to charge to 80% each time - unless I'm about to go on a long trip where I need the range.
Spot on, add to that do a full 100% "balance charge' once a month the night before you are going to use the car. This balances the charge to all the cells throughout the the battery pack.
 
Upvote 0

smokie

Well-known Member
Joined
Sep 9, 2021
Messages
1,068
Reaction score
812
Points
113
Location
Wokingham, UK
Driving
MG5
I met EVsince2016 after Christmas and was persuaded by the 30 - 70% argument, especially as that just about matches the 4 hour cheap slot on Octopus Go.
 
Upvote 0

Gomev

Distinguished Member
Joined
Nov 1, 2020
Messages
2,699
Reaction score
2,839
Points
166
Location
Leeds
Driving
MG5
According to the manual it does self monitor so if it thinks a balance is due and you haven't done one, it will flash up a warning message on the dashboard. I'm not aware of anyone yet seeing such a message.
See my reply in post #11
 
Upvote 0

greeiig

Active Member
Joined
Nov 24, 2021
Messages
95
Reaction score
75
Points
18
Location
London, UK
Driving
MG5
It doesn't make any difference whether you do lots of partial cycles or fewer, deeper cycles. Just be aware that more (very minor) degradation occurs when sitting, charging or discharging at either end of the usable voltage range, especially when it's particularly hot or cold.

It's generally better to have the battery sitting as close as possible to 50% state of charge so there's no benefit to letting it run down to 20% before charging. I tend to add some charge whenever I drop below 50%, but won't charge above 80% unless I need the range or need to do the monthly balance charge.
Interesting. I understand the point that having the battery at very high or very low charge causes some degradation.
I thought also that degradation occurred with every charging cycle. Therefore better to (for example) let a battery discharge from 80% to 20-40% (by doing a number of short trips) then charge it, rther than charging repeatedly after each short trip.

You seem to be saying I should not worry so much about the second point?!
Perhaps I need to chill or get out more.. :)
 
Upvote 0

EVsince2016

Well-known Member
Joined
Sep 24, 2021
Messages
533
Reaction score
505
Points
96
Location
Reading
Driving
MG5
Interesting. I understand the point that having the battery at very high or very low charge causes some degradation.
I thought also that degradation occurred with every charging cycle. Therefore better to (for example) let a battery discharge from 80% to 20-40% (by doing a number of short trips) then charge it, rther than charging repeatedly after each short trip.

You seem to be saying I should not worry so much about the second point?!
Perhaps I need to chill or get out more.. :)

This fact!


  • Cycling from 100 to 0 % we get 500 cycles
  • Cycling from 100 to 10 % we get 500 cycles
  • Cycling from 100 to 20 % we get 1.000 cycles


  • Cycling from 90 to 0 % we get 1.500 cycles
  • Cycling from 90 to 10 % we get 1.500 cycles
  • Cycling from 90 to 20 % we get 2.000 cycles


  • Cycling from 80 to 0 % we get 3.000 cycles
  • Cycling from 80 to 10 % we get 3.000 cycles
  • Cycling from 80 to 20 % we get 3.500 cycles


  • Cycling from 70 to 0 % we get 5.000 cycles
  • Cycling from 70 to 10 % we get 5.500 cycles
  • Cycling from 70 to 20 % we get 6.000 cycles
 
Upvote 0

Edoc16

Active Member
Joined
Dec 7, 2020
Messages
350
Reaction score
330
Points
66
Location
Bannockburn Scotland
Driving
MG5
Correct it is a Rover 75, year 1958.

My Father had a 1953 Rover 75, then in 1958 a Rover 90, a 1963 Rover 3 Litre, a 1968 Rover 3500, a 1973 Rover 3500. lastly a 1991 Rover 216.
Wow so your Dad liked rovers ! I drooled over the 3500 but could only afford a Morris Minor in grey :-(
 
Upvote 0

djenson

Active Member
Joined
Nov 29, 2021
Messages
208
Reaction score
162
Points
43
Location
UK
Driving
MG HS PHEV
What sort of impact would there be, say if only rapid charged regularly to 80% from around 30% so after how many of these chargers would a balance be due? Also shouldn't the battery balance be due to usage than time, i.e the more miles you do to let it balance more often?.
Other than the battery going out of balance more quickly compared to an AC, there wouldn't be that much difference. Charging to 100% with an AC will do more damage to the battery than charging to 80% with a DC charger*. Charging speed has less of an effect on battery health and longevity than 1) How close to 100% the battery is charged too and 2) temperature that the battery is being charged at (too hot or cold)

*Provided that the battery is balanced, and that temperature is nominal

With the current MG EV's that have a BMS that only balances at 100%, I'd aim for a balance for ever 180% of charge on a rapid, but you could go further providing that you normally balance the battery anyway.

Also shouldn't the battery balance be due to usage than time,
That's exactly right, and that's why I hate it when people say "balance every month". Sure its a quick and easy to understand suggestion, but it's also like saying "fill up your petrol tank every month".

Hopefully MG sorts out there crappy BMS's and soon. They have had updates that stop balancing entirely, and the BMS is flawed in design if they can't balance constantly. How come MG is the only brand to my knowledge that requires a full battery to start balancing? What do people do who don't have access to a charger at home? Are they meant to leave the car at some AC charger overnight? I get there lower cost EV's, but this is a very stupid design that's caused some people to get in very dangerous situations where the HV battery has just disconnected and left people stranded due to the battery going out of balance.
 
Upvote 0

Kithmo

Distinguished Member
Joined
Feb 4, 2020
Messages
4,125
Solutions
1
Reaction score
4,324
Points
166
Location
Rotherham
Wow so your Dad liked rovers ! I drooled over the 3500 but could only afford a Morris Minor in grey :-(
I loved my 1988 Rover 216 EFI Vitesse.
Rover-216-Vitesse.jpg
:giggle:
 
Upvote 0

Gomev

Distinguished Member
Joined
Nov 1, 2020
Messages
2,699
Reaction score
2,839
Points
166
Location
Leeds
Driving
MG5
...

Hopefully MG sorts out there crappy BMS's and soon. ... the BMS is flawed in design if they can't balance constantly. How come MG is the only brand to my knowledge that requires a full battery to start balancing? ...
MG is not the only brand with crappy BMS's that balance at 100%. It wouldn't surprise me if they all did, to my knowledge.

From the Tesla website Tesla battery management system (BMS) calibration

Cell balancing​

While the battery cells will sort themselves out up to a point if the car is simply left, there can still be some residual imbalance in the cells. It used to be sugegsted that the cars was charged slowly from a slow state of charge to 100% to do so. We certainly think it is a waste of time using a rapid charger to charge to 100% because the car will slow the charging right down to a crawl.

  • Plug the car in to charge, preferably on a AC charging point
  • Set the charge limit to 100% and leave to charge.
  • When the car reashes what appears to be 100% it may well say its continuing to charge. This can take some time (an hour or so). The charge limit may drop to under 10A which is fine. Let the car do what it needs to do.
  • Eventually the car will stop charging.
  • If the car won't allow 100% to be set, let the car charge to what it will allow. Try increasing the charge limit as the car fills up.
Hyundai 100% / Balance Charge

etc. I'm sure you can google other makes if necessary.
 
Upvote 0

Jomarkh

Well-known Member
Joined
Apr 5, 2021
Messages
2,124
Reaction score
1,328
Points
116
Location
Southampton
Driving
MG5
How can you balance the battery cells if they don't go to 100%. I thought the idea was that all the cells have the same voltage at 100%. I you only charge to 80% if afte8r 6 months youbdid a balance that would take hours and couldn't be done in a 4 hour off peak tariff
 
Upvote 0

djenson

Active Member
Joined
Nov 29, 2021
Messages
208
Reaction score
162
Points
43
Location
UK
Driving
MG HS PHEV
What's wrong with filling up your petrol tank every month ? 🤔
What if you do more miles in a month than your go can go on a tank of petrol? Bit of a crap analogy, I get it, but the point is cell balancing is more to do with how much the battery is used, not how long the battery is left for.
From the Tesla website
Note how the website says "While the battery cells will sort themselves out up to a point if the car is simply left" I don't even know what the source if that info is. Just had a look though in entire model s manual and the only mention of balancing was that the AC system "[Balances] the temperature of the high voltage Battery. Would tesla not put it in the damn manual of the car if balancing was needed? There probably is other vehicles that behave like this, but I still find it plain stupid.
How can you balance the battery cells if they don't go to 100%
Balancing is simply making sure that all the cells in the battery are at the same voltage. I.e cell 1 and 2 are both at 3.2 Volt's. Different BMS's have many different ways of balancing the battery. Some put a small load like a resistor across the high cell's, this isn't a great approach as its a waste of energy and could mean all the other cells in the battery need to drain a little bit just because 1 cell is a bit low. Other BMS's can drain cells like this, but also charge them with the rest of the battery, meaning that each cell can be individual charged and discharged.

See this from the Wikipedia page on cell balancing

Balancing can be active or passive.[3] The term battery regulator typically refers only to devices that perform passive balancing.

A full BMS might include active balancing as well as temperature monitoring, charging, and other features to maximize the life of a battery pack.[4]

Battery balancing can be performed by DC-DC converters, in one of 3 topologies:

  • Cell-to-battery
  • Battery-to-cell
  • Bidirectional
Typically, the power handled by each DC-DC converter is a few orders of magnitude lower than the power handled by the battery pack as a whole.

Passive balancing​

In passive balancing, energy is drawn from the most charged cell and dissipated as heat, usually through resistors.

Passive balancing equalizes the state of charge at some fixed point – usually either "top balanced", with all cells reaching 100% SOC at the same time; or "bottom balanced", with all cells reaching minimum SOC at the same time. This can be accomplished by bleeding energy from the cells with higher state of charge (e.g., a controlled short through a resistor or transistor), or shunting energy through a path in parallel with a cell during the charge cycle so that less of the (typically regulated constant) current is consumed by the cell. Passive balancing is inherently wasteful, with some of the pack's energy spent as heat for the sake of equalizing the state of charge between cells. The build-up of waste heat may also limit the rate at which balancing can occur.

Active balancing​

In active balancing, energy is drawn from the most charged cell and transferred to the least charged cells, usually through capacitor-based, inductor-based or DC-DC converters.[5]

Active balancing attempts to redistribute energy from cells at full charge to those with a lower state of charge. Energy can be bled from a cell at higher SOC by switching a reservoir capacitor in-circuit with the cell, then disconnecting the capacitor and reconnecting it to a cell with lower SOC, or through a DC-to-DC converter connected across the entire pack. Due to inefficiencies, some energy is still wasted as heat, but not to the same degree. Despite the obvious advantages, the additional cost and complexity of an active balancing topology can be substantial, and doesn't always make sense depending on the application.
The way MG (and other manufactures, thanks for the heads up GomEV) Is just the cheeps way (passive balancing). Active balancing should be a must on something that's costing 30K and is just a joke and a waste of energy.
 
Upvote 0
D

Deleted member 7171

Guest
One thing to be aware of....when you charge to (what you understand is)100%, you aren't actually charging to 100%. There is a buffer above what appears as 100% to specifically protect from over charging. Likewise there is a buffer of reserved battery charge below what appears to be 0% to protect from totally discharging the battery.

We know the new ZS EV LR has a total battery size of 72.6 KWh but only has a useable battery of 68.3 KWh (according to the reliable EV Database). That means that only 94.1% of the battery is useable. Therefore we might be correct to assume there is a 3% (2.15 KWh) buffer at the top and 3% (2.15 KWh) at the bottom end of the battery pack to protect it.

With this in mind I am comfortable to follow keeping the battery between 20%/80% with the additional "full" monthly balance charge.

Of course it is up to the individual to do what they are comfortable with.
 
Upvote 0

bwanamdevu

Active Member
Joined
Nov 21, 2021
Messages
259
Reaction score
248
Points
46
Location
Newark
Driving
MG5
One thing to be aware of....when you charge to (what you understand is)100%, you aren't actually charging to 100%. There is a buffer above what appears as 100% to specifically protect from over charging. Likewise there is a buffer of reserved battery charge below what appears to be 0% to protect from totally discharging the battery.

We know the new ZS EV LR has a total battery size of 72.6 KWh but only has a useable battery of 68.3 KWh (according to the reliable EV Database). That means that only 94.1% of the battery is useable. Therefore we might be correct to assume there is a 3% (2.15 KWh) buffer at the top and 3% (2.15 KWh) at the bottom end of the battery pack to protect it.

With this in mind I am comfortable to follow keeping the battery between 20%/80% with the additional "full" monthly balance charge.

Of course it is up to the individual to do what they are comfortable with.
This is good to bear in mind! My commiserations for the result this afternoon!
 
Upvote 0

C6MFC

Active Member
Joined
Apr 12, 2021
Messages
378
Reaction score
248
Points
46
Location
Telford
Driving
MG HS PHEV
See my reply in post #11
Still good question. I only ever see "connected-uncharged" after charge and 100% SOC. I have never seen "Finished" even if left on for balance should I ?
 
Upvote 0
Support us by becoming a Premium Member

Get your MG5 charging tee

Latest MG EVs video

MG electric car news and chat in our final podcast of 2022.
Subscribe to our YouTube channel
Top Bottom