Munnsy

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Joined
Feb 28, 2026
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Location (town/city + country)
Marlborough, UK
Driving
MG4 (2022-2025)
Hearing that some people have had issues about the factory standard 12v lead acid battery going flat and not lasting very long,

I have bought and fitted a 40ah LiFePO4 battery.

Many of these batteries are not suitable for year round automotive use as they cannot accept a charge at temperatures under 0c degrees,

But this is a "Sub zero" type from the UK company Beyond Batteries, good for as low as minus -20c.


Fiting was easy, only slight hassle is the terminals on this battery are on the wrong side, so I used some very hefty 2awg gauge cable (way overkill) to bridge across to the terminals. Seemed a much better solution than trying to pull the factory cables into a postion they didn't want to sit and risk cable damage..

I can/will swap the original battery back in for when the car goes to the main dealer for a service..just incase they don't like it.

Also I fitted a new battery fabric strap, original too slack.

Another bonus, I have saved a whopping 6.5kg compared to factory!

...Yes I know i need to find a little rubber boot to fully cover the positive terminal!
 

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The battery has Bluetooth built in and you can use the Beyond Battery app to view the charge and discharge status...

Car is currently plugged in at home charging the main EV battery, and voltage on the LiFePO4 is spot on.
 

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Looking good , keep us informed about its longer term usage please. Have you buggered up your 50/50 weight distribution ? :D
Thanks. haha.... If I go on a diet to lose the same weight myself, it will even out lovely as drivers side is opposite the battery!
 
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