Charging regime advice

Forums › Transport (cars, bikes and boats) › Charging regime advice

PSLog

291 posts

Ultimate Geek

#314980 5-Jun-2024 01:09

Have just upgraded from a BMW i3 33kW (5 years) to a new MG4 Excite 64kW.
Had been using just the 3 free hours electricity a night from Z energy for charging at home, every couple of nights, which was enough for my very modest needs. That added about 18% to the i3 battery.

Now, with 64kW that will add only 8% to the MG.

I know that will be enough for the amount of driving I typically do, but I'm concerned about the long-term effects that a frequent shallow charge will have on the bigger battery.

BTW I intend to do a full 100% equalisation charge once every 1 or 2 months.

So, do we have any lithium battery gurus here who can advise on this?

I could upgrade my 8A granny charger to a 16A one. That should then add 16% in the same time.
Would that make any difference?

1 | 2 | 3

13411 posts

Uber Geek

ID Verified

Lifetime subscriber

#3244564 5-Jun-2024 05:24

i charge 3 hours every night, which adds 30% to my leaf (3.5kW/h), which is less than I drive daily so it's slowly dropping over the week, by Friday I'm down to about 30-40% by the time i get home, i fully charge it for on Friday and Sunday nights

GoodSync

GoodSync. Easily back up and sync your files with GoodSync. Simple and secure file backup and synchronisation software will ensure that your files are never lost (affiliate link).

michaelmurfy

meow
13191 posts

Uber Geek

Moderator

ID Verified

Trusted

Lifetime subscriber

#3244843 5-Jun-2024 15:22

8a is bugger all (literally 5.52kwh or around $1 worth of power on an average off-peak power plan) and the problem is with this plan it is highly likely you're paying far more than just being on a flat rate plan due to the higher daily charge + higher per kWh charges you get outside of the 3 hours.

Upgrade to a 16/32a Type 2 charger if you want more - 32a will give you around 22kwh of charge. But really, a provider like Octopus Energy who have offpeak power and reasonable daily rates will be your best bet once you've got a quicker charger to overnight charge.

Michael Murphy | https://murfy.nz
Referral Links: Quic Broadband (use R122101E7CV7Q for free setup)

Are you happy with what you get from Geekzone? Please consider supporting us by subscribing.
Opinions are my own and not the views of my employer.

PSLog

291 posts

Ultimate Geek

#3244844 5-Jun-2024 15:28

Maybe I shouldn't have written so much - it distracted you from the point of my post, which was:
will frequent shallow charges have a detrimental effect on the life of my battery?

I actually did research on the plans available (armed with my actual usage etc) and determined that the plan I'm on is great for me - possibly even "the best" eg I'm also getting ALL my hot water for free.

trig42

5796 posts

Uber Geek

ID Verified

#3244845 5-Jun-2024 15:34

I have a 32a charger (and a 64kWh MG4).

it pretty much gives me exactly 10% charge per hour.

As for shallow charging, I don't think you're going to hurt it. I think they really don't like being fast charged up to 100% a lot, and would rather not be drained down below 10.

AC Charging is not fast charging, so I think the BMS can deal with whatever you need doing.

My car has just ticked over 30,000km, I haven't noticed any difference in battery range (except on really cold (0 or below) mornings, when it doesn't get the range). I charge to 90% most of the time (I think the car has only ben to 100% about 3 times).

jonathan18

7413 posts

Uber Geek

ID Verified

Trusted

#3244846 5-Jun-2024 15:37

We used to charge primarily within an even narrower window when we had the one hour of free power with EK! (Ie, we charged basically every day for that one hour, sometimes a bit more.) While I can’t prove causation, I would note that both our EVs seemed to have suffered faster battery degradation over that period than is typical for these models.

Agree that having a much longer window to charge is less hassle; while three hours may be adequate for general charging, charging back from a low SOC will usually need longer. We find the 2100-0700 ‘night rates of our plan means we only need to charge when either car is down to 50-60%, and equally it’s feasible to charge the cars back up after a long trip (over 50% charge overnight on both cars).

(While many will argue that 32A is worth it, personally I’m completely happy with 16A via a caravan plug, and most of the time 8A would be adequate, if a bit less efficient. I understand some Tesla owners have gone with 15A sockets as the Tesla UMC comes with a 15A tail.)

PSLog

291 posts

Ultimate Geek

#3244847 5-Jun-2024 15:39

Thanks Trig42.

Useful feedback. I guess the most important thing to do is give it a good equalisation or balancing charge (charge to 100% and hold it there on charge for a further hour) every one or two months.

For interest, what real-life range do you get out of your MG?

Thanks again.

michaelmurfy

meow
13191 posts

Uber Geek

Moderator

ID Verified

Trusted

Lifetime subscriber

#3244850 5-Jun-2024 15:40

PSLog: Maybe I shouldn't have written so much - it distracted you from the point of my post, which was:
will frequent shallow charges have a detrimental effect on the life of my battery?

No. Just charge and enjoy your EV and don't worry about your battery (seriously) as they don't degrade as people think.

But also really look into the charging setup also and get a proper Type 2 charger installed. Also change your power plan as the 3hrs free will be costing you far more than just a standard flat rate plan as you'll never make up for the extra kw cost outside of those 3 hours.

CYaBro

4532 posts

Uber Geek

ID Verified

Trusted

#3244854 5-Jun-2024 15:46

michaelmurfy:

No. Just charge and enjoy your EV and don't worry about your battery (seriously) as they don't degrade as people think.

They do degrade but most of it happens in the first couple of years and then levels off.
Our gen1 MG ZS EV, which is just over two years old and done almost 60k, shows the battery SOH as being 92.8% when I checked a few weeks ago.
It dropped to about 94% in the first year.
It means we've lost about 20km of range.

We only use the 8A charger at home.

Opinions are my own and not the views of my employer.

PSLog

291 posts

Ultimate Geek

#3244857 5-Jun-2024 15:50

Jonathan

I had a similar experience with my i3. I had been graphing the SOH religiously every month while we had it. SOH had been declining slightly but steadily for those 4 years then suddenly, after a month of the shallow charging regime, SOH fell off the cliff.
28.7kWh to 27.3kWh in 3.25 years and then (after the shallow charging regime for 9 months) down to 24.4kWh.
Admittedly I didn't rigorously do a couple of balancing charges to see if it recovered (did do one, with no noticeable effect)

Hence my original question.

PSLog

291 posts

Ultimate Geek

#3244863 5-Jun-2024 16:01

But also really look into the charging setup also and get a proper Type 2 charger installed. Also change your power plan as the 3hrs free will be costing you far more than just a standard flat rate plan as you'll never make up for the extra kw cost outside of those 3 hours.

Sorry, Michael, but you are wrong.
a. As far as getting enough power into my battery, my current 8A charger is perfectly adequate. And I only need to use it once every 2-3 days (how sad is that!). If I did move to a 16A charger, it would only be to reduce the frequency of charging.
b. My current plan, with all hot water heating, EV charging and dishwasher use moved to the 3 free hours each night, gives me a little more than 50% of my power usage with no charge. I use Shelly smart power switches to control the timing of these devices (although with the MG, that Shelly is redundant)

alasta

6671 posts

Uber Geek

Trusted

Subscriber

#3244876 5-Jun-2024 16:28

I'm the same as you - I use minimal electricity in the household and only use the car two or three times a week. Incidentally I own a petrol car but if I had an electric car then I reckon I could get away with just plugging it into a three pin plug for a few hours a day.

trig42

5796 posts

Uber Geek

ID Verified

#3244883 5-Jun-2024 17:02

PSLog: Thanks Trig42.

Useful feedback. I guess the most important thing to do is give it a good equalisation or balancing charge (charge to 100% and hold it there on charge for a further hour) every one or two months.

For interest, what real-life range do you get out of your MG?

Thanks again.

Most of my driving is open-road (Paeroa to Auckland and back a couple of times a week). From my 90%, I'd get ~390km, maybe a bit less.

If I did more around town, stop start I'm confident it would get the advertised range (which at 90% would be 405km based on 100% being 450km).

The long straight 100km roads really chew it up - especially the rough chip seal roads. I get more efficiency on the smooth Motorway surface. I try and sit at around 85-90 on SH2 from home to Auckland (I leave home at about 445am). If someone comes up behind me, I'll speed up for them. Usually quite happy to sit behind a truck, as you get an efficiency boost from drafting - just gotta watch the stones (paint work on the MG4 is pretty thin).

PSLog

291 posts

Ultimate Geek

#3244894 5-Jun-2024 18:02

Interesting. Thanks for the info.
Haven't had mine long enough to get a feel for range - but my impression is that it may be less around town (because of frequent moving away from dead stop) compared to open road running.
We'll see.

Good to have your open road figure, though.

Scott3

3921 posts

Uber Geek

Lifetime subscriber

#3245120 6-Jun-2024 11:33

NMC batteries like being near the middle of their range. (mostly for calendar time, but also for cycles). For best battery health, avoid storing the pack in above 80% or below 30%.

(It's OK to charge to 100% for a long trip, and then run down to your safety margin, but avoid having the car stored for days in extreme high or low states of charge).

For most people this means setting a charge limit to 80% (or 70% if you really want to look after the battery health), and plugging in fairly frequently.

Speed of charging isn't going to any detrimental impact on battery health (other than DC fast charging, which is slightly detrimental as it is fast enough to heat up bits of the pack).

Only issues with slow 8A charging on a big battery car are:

Reduced efficiency. Generally the chargers are more efficient near their rated output, and whenever the car is in charging mode, there are a few hundred watts of overhead (cooling pumps, computers etc) which eat into your efficiency percentage at very low speeds.
Hours on the coolant pump. Charging at a very slow speed is going to see the coolant pump seeing a lot of running hours.
Harder to fit your charging time into an off peak window if you have time of use power rates

So yeah, a faster AC charger is better, but this needs to be weighed against the cost of the install.

PSLog

291 posts

Ultimate Geek

#3245241 6-Jun-2024 13:02

Thanks for that detailed and useful answer, Scott3.

Sounds like my best plan is to:
upgrade to a 16A charging cable,
Manage my battery by charging for 3 (free) hours whenever the charge falls to around 50%
3hrs x 240V x 16A = 11.5kW or 18% of my battery capacity, taking it back up to around 70%

Every month I'll do a balancing charge at 100% for an hour.

Looks like I can swap my 3 pin socket out for a 20A model, replace the the charging cable plug with a 20A model.
I MAY put an in-line RCD or switchboard mounted RCBO into the charging circuit too. Not very expensive at all.

Thanks all for your help. :-)

1 | 2 | 3