MG HS not starting flat battery

We have had our MG HS Vibe for less than 2 years now and it has been a very reliable car. Just recently it has been hard to start and required a few jump starts to get it going.

Being less than 2 years old I was worried that the problem was not the battery but maybe some sort of battery drain or a faulty alternator. There are a lot of electronics in this car so it could have been anything. So it was off to the MG service department for its 30,000km service and to check out the battery.

The stock MG HS 55ah battery was charged and tested ok at the workshop and no other faults of the car could be found. So we took the car home only to have the car not start again 2 days later, another flat battery. Now I’m getting frustrated so another booking was made to the MG service department. This time they replaced the battery under warranty.

Symptoms of a faulty MG car battery.

Symptoms of a faulty MG car battery.
Jump starting our MG HS Vibe with a lithium-ion jump starter

We had to jump-start the MG HS Vibe 5 times before the battery was replaced. As an electrician, I was able to check the voltage each time the battery was depleted and I found a voltage of around 12.1 volts.

The dashboard of the MG HS would display around 20 faults or alarms one at a time such as Emergency brake unavailable, lane change assist not available, low battery voltage, and many more. The car would click a few times before turning itself off. The slow clicking sound was the starter motor relay coming in and out as the voltage failed under 12v due to the load placed on the battery.

Usually, this clicking is rapid and fast on other vehicles like my Toyota Corolla which had a flat battery. Which made me think there was another problem.

The tachometers would also spin around but not return to their normal positions. Holding the start button on was the only way to completely turn off the vehicle dash lights.

Why did the MG battery fail?

There are many reasons why a car battery may fail such as:

  • Low battery acid level.
  • Internal lead plates shorted or broken.
  • Sulfation of the lead plates.
  • Contamination of battery water/acid.
  • Underrated low-capacity battery.

I am wondering if the original 55ah battery is undersized and was destroyed by overloading it. Or the battery is older than 1.5 years old and has been sitting on a shelf somewhere.

Vehicle batteries only tend to last 3-5 years depending on driving conditions and if they are topped up with a smart charger such as the Ctek.

How long is the warranty for MG car batteries?

MG in Australia has a great 7 warranty on the vehicles. But we have to look at the MG limited warranty coverage for items such as a 12v battery which is 2 years unlimited KMs


For some special parts, warranty conditions are as below for a complete list please see below:

ItemPart NameWarranty Period
1Lamp and Light Bulbs (Excludes Zenon Globes)3 Months/5,000KM
2Remote Hand Set Battery6 Months/10,000KM
3Battery2 Years/Unlimited KMs
4Accessory Decal Kits – Personalisation2 Years/Unlimited KMs

What battery for the MG HS?

mh hs battery DIN53lh agm
The new replacement Century AGM DIN53LH 60ah battery.

The original battery on the MG HS was a Yuasa DIN53LH MF 55ah 500cca. The replacement battery is a Century DIN53LH 60ah 640 cca battery. So a higher capacity and higher cold cranking amps battery. It is also an AGM battery which should last longer than a wet cell.

It’s interesting that there is room in the battery tray for a larger or longer battery.

I did notice that the original MG HS battery had KIA branding on it.

MG Smart Alternator

mg hs smart alternator detection
The MG HS smart alternator needs to know the discharge current which is this electronic circuit on the negative terminal

The MG incorporated a smart alternator to help with charging the battery and prolong the life of the alternator. A smart alternator will regulate the charge voltage to only charge the battery when it needs extra power.

The video below explains how the MG smart alternator will increase the voltage to the battery when the lights and radio are turned on.

I have noticed that during the day the voltage of the alternator will be around 12.6v and will increase to 13.6v or higher during nighttime driving. This is the smart alternator clicking in to provide extra voltage to the battery and driving lights.

We got over 300,00km with our Toyota Kluger (Highlander) alternator and 230,000km with a ford focus alternator before they failed.

It will be interesting to see how long the MH HS alternator will last.?

How to replace the MG Smart key fob battery.

The 3v lithium batteries in the MG ZS and HS should last around 2 years depending on use. I replaced my remote battery with a CR2032 lithium button battery. Check out my video below on how to open up your MG car remote.


After the MG HS car battery was replaced we have had no more problems starting it. I just wished the service department had replaced it the first time I reported the problem. It was a good thing I always keep a jump starter in each vehicle. The NexPow 2500A jump starter is my favorite jump starter now.

If you have any problems starting your MH HS Core or Vibe get the battery replaced. If your vehicle is under 2 years old it will be covered under warranty. MG has been excellent in this regard. Thanks, MG.

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