Not proud of it, but hit 0% battery range a mile from home and made it back!!!!

[siteguru]

Note: the advice is to take the car below 10% state of charge not 10 miles range.

 

[gwig66]

Note: the advice is to take the car below 10% state of charge not 10 miles range.

I don't have a percentage battery display in my '70 plate MG ZSEV, only range in miles.

 

[Rolfe]

Couldn't you work it out?

 

[gwig66]

It was a spontaneous decision to run flat before a long trip

Need to dust off my abacus

 

[Andrew Sinclair]

I took the car down below 10 miles range to condition the battery yesterday. It was interesting that as I drove around the block in Sports mode, dropped to 9 miles, then the screen was flashing that I needed to charge, so I dropped into Normal mode and circled until that dropped out into warnings to charge, popped it into Eco mode where I again saw 10 miles range, but a couple more circuits and heaters blasting and I was below 10 and ready to go home for a charge.

Is conditioning the battery in this way something you do frequently?

 

[gwig66]

Is conditioning the battery in this way something you do frequently?

After sharing a low battery near miss, the forum reminded me that it is good to condition the battery by taking it right down every 6 months.
I may have misinterpreted that as below 10 miles range, rather than below 20% battery SoC.

 

[Rolfe]

It's below 10% battery state of charge.

 

[gwig66]

So in a car that allegedly does 165 miles on a full charge, that is16.5 miles or less, in the absence of a battery percentage display in the car.

 

[siteguru]

Pretty much.

 

[Gomev]

On the Mk1 ZS EV that I used to own the HV battery status consists of 8 blobs on the dash at the bottom of the power dial.
From all showing at 100% SOC the first 7 then disappear at 11% intervals with the last blob representing the final 23%. This final blob then flashes when about half used. Unfortunately there is no more accurate display within the car until you start charging, which then flashes up briefly the actual SOC.
So maybe drive until the flashing starts.

 

[DixieTGS]

Does the manual for the car mention doing full calibration charges (10 - 100%) every 3 to 6 months as well as the more frequent conditioning / balancing charge to 100% ? If not, doing the calibration charge may have no effect on your car.

On the MG4 the calibration only improves the accuracy of the GOM and the balancing charge improves the long term health of the battery.

 

[Rolfe]

I don't see how any GOM can be accurate if it doesn't get a long charge now and again. Imagine you're trying to keep track of the depth of water in a well by counting how much water flows in and how many buckets are drawn out. If you never see the bottom then after a while you're guessing. One day when a lot of buckets are drawn out you may suddenly see the bottom and get quite a shock.

Getting a good look at the bottom then measuring how much water flows in in a single uninterrupted fill is necessary to recalibrate your understanding. So it is with cars.

 

[DixieTGS]

You would hope that is the case for the most recent designs, especially for LFP batteries.

For older designs they could be more basic, e.g. they could spot the high and low thresholds and use a standard curve in between. Maybe with the smaller batteries they assume you'll reach the low threshold on a regular basis anyway? For NMC it wouldn't surprise me if originally they simply converted from voltage to percent or kWhr with a fixed curve.

Hopefully one of the ZS drivers will have read something about it.

 

[Gadget Geek]

Hopefully one of the ZS drivers will have read something about it.

Yep. It's a bit complicated.

Prediction of Electric Vehicle Range: A Comprehensive Review of Current Issues and Challenges

Electric vehicles (EV) are the immediate solution to drastically reducing pollutant emissions from the transport sector. There is a continuing increase in the number of EVs in use, but their widespread and massive acceptance by automotive consumers is related to the performance they can deliver...

www.mdpi.com

 

[DixieTGS]

Quite an interesting backgrounder, thanks.

A lot of the article deals with conversion of SoC to range which most EV drivers who read around the subject get to grips with quite quickly. But there are some useful nuggets of information throughout and also some numbers to put the different factors in to perspective.

Regarding the calculation of SoC, one interesting bit was "The errors that occur in the estimation of SOC by current methods are relatively small (1–8%)", although it doesn't mention the battery type in question or if that included the need for regular recalibration.

 

[Gomev]

Personally I don't think I have ever seen anything in any user manuals for the EVs I have owned re calibration. Certainly mentioned to charge to 100% for balancing in every one.
I understand what everyone here is saying and the assumptions/beliefs they are making to arrive at them, however wouldn't the manufacturers point this out to us ??

There is an old old thread on SpeakEv about this and someone on there seems quite knowledgeable, however I offer no opinion as I simply don't know.

Link to SpeakEv thread, see post #7

Battery calibration; A genuine thing or another EV myth...

Is calibration really a ‘thing’ or another one of those EV battery myths that seem to become law? After watching Andy Till/Mr EV’s video earlier, do we really need to do this like in the days of NiCd batteries? Some people say as long as the cells are balanced when charged to 100% and you know...

www.speakev.com

 

[gwig66]

I don't see how any GOM can be accurate if it doesn't get a long charge now and again. Imagine you're trying to keep track of the depth of water in a well by counting how much water flows in and how many buckets are drawn out. If you never see the bottom then after a while you're guessing. One day when a lot of buckets are drawn out you may suddenly see the bottom and get quite a shock.

Getting a good look at the bottom then measuring how much water flows in in a single uninterrupted fill is necessary to recalibrate your understanding. So it is with cars.

I like your explanation

 

[Wil Tryharder]

Just putting our MG4 down for the long sleep. 9% to 100% every 6 months. Sounds like good advice ? Every 2 two hours we’re betting on how far it’s got. The winner gets to visit the fridge ? the loser gets earl grey tea ?‍?

Ok, the result are in. Our Evnex session history reads as below. I make that 9 quid for 200 miles finished on time as predicted in the Ismart app. And still managed to use 11% solar to get the job done. But didn’t do the balancing thing this time. Mmmm wonder why?
Can’t say I’m impressed with how much renewable energy is being generated in Queensland on a Sunday.

 

[Luckyrobp]

Drove for about 15 miles with no range showing on the car, was about 3% when i got home. approx. 20 mile trip with 25 miles showing, dropped like a stone as i was going along.

 

[gwig66]

Well it seems that the battery percentage is more reliable than the range guessometer!