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MG ZS: ZS EV (Gen 1): battery management system faults and range loss after updates

ZS EV (Gen 1): battery management system faults and range loss after updates is a common electrical fault on the MG ZS on the 2020–2021 cars, and we rate it major. Putting it right costs $0 to $800 at New Zealand independent workshop rates. Below is what goes wrong, the symptoms to notice on a test drive, where to look, and what to ask the seller before you hand over any money. It is one of 14 documented faults on the MG ZS.

Vehicle
MG ZS
Years
2020–2021
Fuel
ev
System
Electrical

This page covers the MG ZS as a model. Some faults only affect particular engines or build years — enter a plate below to narrow the list to one car.

All MG ZS faults14 documented faults on this model

What you are looking at

No photograph available

We do not hold a verified photograph for this fault yet. We would rather show none than show a picture of something else.

What goes wrong

Gen 1 ZS EVs (44.5 kWh pack) went through a series of BMS software campaigns in Australia — including the SA015 update in 2020 and further BMS revisions into 2021 — after cars showed cell-balancing problems, falling fully-charged voltage and noticeable range loss over charging cycles. A later update (BMS Update 4, January 2021) largely fixed the balancing issue. Cars that missed the updates can show sudden range drops, stuck charging at high state-of-charge, or in the worst cases an 'EV System Malfunction' warning and shutdown. All fixes are dealer software updates — free — but a used import may not have had them.

What you would notice

  • Indicated range noticeably below ~230 km at 100% when new-ish
  • Charge stops or slows dramatically in the last 10-20%
  • 'EV System Malfunction' warning
  • Range drops in sudden steps rather than gradually

How to check it

Where to look. Battery management system (software) controlling the traction battery under the floor

  1. Ask the dealer or MG service agent to confirm by VIN that all BMS software campaigns are completed.

  2. Charge the car to 100% before the viewing and note the indicated range and charging behaviour near full.

  3. Ask for a battery state-of-health printout from an MG dealer or NZ EV specialist.

What it costs to put right

$0 to $800 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

Ask the seller

  • “Are all BMS software updates done — can the dealer confirm by VIN?”
  • “What range does it show at 100%?”
  • “Has it ever shown an EV System Malfunction warning?”

Now check the MG ZS you are actually looking at

Everything above is true of the model, and it is free. What it does not tell you is whether THIS car has been looked after: its odometer history and whether the reading has ever gone backwards, whether there is still money owing on it, whether it has been reported stolen, how many owners it has had and what it is really worth today. That comes from the official records for that plate. Enter the plate for the free details, or get the full history and a market valuation from $13.49.

Not sure what you would be paying for? See what a full KickTyres check includes.

Where this comes from

The failure described above is documented in the sources below. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them.

  • AEVA Forums: MG ZS EV Battery Management System (Australian owners, SA015 and BMS update history)
  • MGEVs.com thread: Definitive list of updates (BMS Update 4, Jan 2021)
  • Choice Community: MG ZS EV Battery Management System glitch

MG ZS buyer questions

Is zs ev (gen 1): battery management system faults and range loss after updates serious on a MG ZS?

We rate it major and common on the MG ZS. Gen 1 ZS EVs (44.5 kWh pack) went through a series of BMS software campaigns in Australia — including the SA015 update in 2020 and further BMS revisions into 2021 — after cars showed cell-balancing problems, falling fully-charged voltage and noticeable range loss over charging cycles. A later update (BMS Update 4, January 2021) largely fixed the balancing issue. Cars that missed the updates can show sudden range drops, stuck charging at high state-of-charge, or in the worst cases an 'EV System Malfunction' warning and shutdown. All fixes are dealer software updates — free — but a used import may not have had them.

How much does it cost to fix on a MG ZS?

$0 to $800 at New Zealand independent workshop rates. That figure is for this job on its own. A car showing the symptoms on this page is usually worth either walking away from or negotiating down by at least the repair figure.

Which MG ZS years are affected?

Our research records this fault on the 2020–2021 MG ZS. Build dates move around, especially on imported cars, so treat the range as the years to look hardest at rather than a guarantee either way. The official records tell you the exact build and first registration date for the car in front of you.

How do I check for it before I buy?

Ask the dealer or MG service agent to confirm by VIN that all BMS software campaigns are completed. Charge the car to 100% before the viewing and note the indicated range and charging behaviour near full. Ask for a battery state-of-health printout from an MG dealer or NZ EV specialist. Look here: Battery management system (software) controlling the traction battery under the floor