Car Battery Replacement Question

LowEndTorque

LowEndTorque

LowEndTorque

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Hi Folks,

Now that the tyres question is out of the way, my next target is getting a replacement battery for my Mk5 Mondeo 2.0 TDCi Estate. As with the tyres I do not want to wait until something goes wrong.

The current battery had shown signs of little struggle over the past month. Whilst doing the tyre replacement last weekend I requested the KwikFit staff to check the battery too. They mentioned it needs charging and suggested a long drive. Now, I cover about 50+ miles each week for my work when I work from office one day a week. Almost 90% of that journey is Motorway and A roads (60 mph). I doubt the battery would need charging.

The current battery is a Lion brand one. As per the battery checker on the Euro Car parts website this battery is not compatible with my car. I presume that's because the battery is not Stop/Start compatible. God knows why the previous owner would do that other than getting a cheap battery. The description states the battery is of the type 'Wet Flooded'. I have tried searching to confirm if that translates to EFB type but I cannot find factual information for that.

My research brings me with two options that I would prefer. I am going with AGM type batteries based on what I read.

1) Bosch AGM Car Battery 12V 80Ah Type 115 S5A11
2) A6 Varta Dynamic AGM 110 Car Battery 12V 80Ah

Coming to my question. Is it worth getting the AGM battery over an EFB? Mind says I can go with either as both are Stop/Start compatible. AGM only for more durability and its maintenance free nature. Since I don't know about the Lion brand and the battery appearing to be incompatible I believe it is best to get it replaced.

TIA.. :)
 
Some vehicles require AGM but a lot of stop-start vehicles are fine with EFB, I'm not familiar enough with your car to know but generally you can use EFB fine (A quick Google suggests using an EFB battery is perfectly fine with that model).

EDIT: Don't know if it is relevant here but it used to be recommended to avoid using AGM if they are in close proximity to hotter parts of the engine and use EFB instead.

Usually there is very little difference between equivalent tier Bosch and Varta batteries - they are basically the same thing under different names. The odd model aside where sometimes they are manufactured by Exide.
 
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@Rroff I will look into the AGM aspect of being closer to the engine. It is closer in the Mondeo, as it sits on the rear LHS of the engine (RHS when you are standing in front of the car). Car is a 17 plate and at about 108,500 miles.

Exide is also one of the brands I incline towards.
 
Regarding brands I only buy Bosch, Yuasa or Varta. I believe halfords batteries are rebranded Yuasa or they used to be. The car will likely need it's battery monitoring software reset, my 62 plate Focus did. This can be done without specialist tools though: To reset the Battery Management System (BMS) on a 2017 Ford Mondeo after a battery change, enter the car, turn the ignition on (engine off), flash high beams 5 times, and press the brake 3 times. A flashing battery light on the dash confirms a successful reset.
 
I called Tayna batteries after doing some light reading on AGM batteries and their degradation when installed in Engine Bay. They mentioned AGM batteries are ok in the Engine Bay and have no issues with regards to their placement.

One interesting thing they said was I cannot downgrade the battery once upgraded. For example, if I upgrade to AGM I cannot go down to EFB as a replacement and similarly from EFB to Standard.

Edit: Fattest finger pressed enter before completing my comment.
 
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I played around with Copilot today and giving the summary below. Please take it with a pinch of salt as I spotted mistakes in it too.

Finding the correct battery for fitment.

✅ Yes — an AGM battery is perfectly fine in a 2017 Mk5 Ford Mondeo 2.0 TDCi after a BMS reset.

In fact, it’s not just “fine” — it’s the correct type for that generation of Mondeo if the car has:​

  • Start‑Stop
  • Smart charging
  • Regenerative braking
  • High electrical load
Most Mk5 Mondeos with the 2.0 TDCi engine were factory‑equipped with AGM.
Click to expand...

Clarifying the differences between Bosch, Varta and Yuasa.

1. Bosch vs Varta — the secret you’re not supposed to notice​

Here’s the twist:

Bosch AGM and Varta AGM are the same battery.
Manufactured by the same company: Clarios (formerly Johnson Controls).

They come off the same production line.Same plates.Same separators.Same chemistry.Same performance.Different sticker.

The only differences are:
  • Bosch tends to be slightly more expensive
  • Varta tends to be easier to find
  • Warranty terms vary by retailer, not manufacturer
So between Bosch and Varta, you’re choosing branding, not engineering.

2. Yuasa — the quiet overachiever​

Yuasa is the one that actually breaks the pattern.

Yuasa AGM batteries are:
  • Built in different factories
  • Using their own plate design
  • With slightly thicker lead grids
  • And a reputation for handling deep cycling better
Yuasa tends to excel in:
  • Cars that do lots of short trips
  • Cars with heavy electrical loads
  • Cars that sit unused for days
  • Cars with start‑stop that triggers frequently
Where Yuasa often wins is longevity — they’re known to last a year or two longer in harsh conditions.
Click to expand...

Summary:

Yuasa YBX9115 AGM​

The longest‑lasting, toughest, most resilient choice.
If he wants the best value:
Strengths:
  • Exceptional deep‑cycle durability
  • Handles short journeys better than Bosch/Varta
  • Often lasts 1–2 years longer in real‑world use
  • Very stable under high accessory load
Weaknesses:
- Usually the most expensive
- Slightly heavier

Best for:
Drivers who do short trips, lots of stop-start, or want maximum lifespan.

Varta A6 AGM​

Same performance as Bosch, lower price, excellent reliability.
If he wants the Bosch badge:

Strengths:
  • OEM‑grade quality (Clarios manufacture)
  • Excellent cold‑start performance
  • Very stable under smart‑charging
  • Usually the best price-to-performance ratio
  • Widely available
Weaknesses:
  • Not the absolute longest lifespan under harsh short‑trip usage
Best for: Drivers who want top performance without paying a premium.

Bosch S5A11 AGM​

A Varta in fancier armour.

Strengths:
  • Identical construction to Varta (same Clarios factory)
  • Strong brand reputation
  • Excellent cranking and stability
Weaknesses:
  • Often priced higher than Varta for no technical advantage
Best for: Drivers who like the Bosch name or find a good deal.
Click to expand...
 
Got the new Varta battery fitted today. Car started with ease. When the old Lion battery was out I lifted it and it was considerably lighter than the Varta. I couldn't find the weight of the Lion battery wherever it was listed for sale. My guess is, it is at least 5-6 kgs lighter.

Happy days! :)
 
bainbridge said:
Lion batteries are pants. At ECP I've seen the staff just swap them for customers with no questions asked.

The one and only Lion battery I bought lasted one winter.
Click to expand...
The car had a set of RoadX tyres at point of advertisement. Take your guess on other aspects of maintenance to cheap out. :)

I am actually staggered that they got a non compatible battery fitted in.
 
AGM or EFB are both fine. It's easiest to fit the same type and spec as what is already in there. If you change battery type or size it should be programmed into the car so it knows it's capacity and type.
Either way you'll need to do a BMS reset to reset the age of the battery.

Did mine last year in my Mk5, my original EFB lasted 10 years ago was more than happy just putting the same again in.

If you use Forscan it's under the Wrench menu and Bdycm, then search for Battery Type.
It alters the charging curve, if you don't change the type you can over or under charge the battery, by default the BMS tries to maintain 80% charged to give maximum service life.
 
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@robj20 Yes, the Lion battery was a Standard type, the auto stop start never worked. Since fitting the Varta it is working again. For the BMS reset I had to be a bit quicker with the steps to get it to trigger.

I don't have Forscan. Is that necessary to check via the software even after a reset?
 
Last battery I bought was an exide which I believed was as good as the bosch/varta's I'd had previously, and similar 3 year warranty,
I'd probably stick with exide for AGM I'd now need for Audi.

so, for mondeo, perhaps a ek820 @ £115 /tanya https://www.ebay.co.uk/itm/277188720505
e: I'd thought audi one would be £150+ but for petrol audi vs mondeo diesel less than £100, maybe with newer car volume sales they are now cheaper
 
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jpaul said:
Last battery I bought was an exide which I believed was as good as the bosch/varta's I'd had previously, and similar 3 year warranty,
I'd probably stick with exide for AGM I'd now need for Audi.

so, for mondeo, perhaps a ek820 @ £115 /tanya https://www.ebay.co.uk/itm/277188720505
e: I'd thought audi one would be £150+ but for petrol audi vs mondeo diesel less than £100, maybe with newer car volume sales they are now cheaper
Click to expand...
I did see the Exide AGM battery, but the Varta one was only £16 more with 5 years warranty. Hence picked the Varta. Bosch was further £5 extra but it is essentially the same battery as Varta with a different sticker job.
 
I've mostly used Varta, though not really relevant to this thread but as an aside I'd recommend using Exide on Nissans from approx. 2010 to 2018-19 or so with stop-start as they seem to trash a lot of battery makes/models but Exide seem to have better "charge acceptance" or something with them.
 
Just to conclude this thread.
I had contacted a official Ford service center to ask about any need for FORScan post the battery swap and informed that I have done the manual BMS reset. The Service Center confirmed there is nothing more to do. :)

P.S. - Please feel free to use this thread as a car battery related discussion for any queries or inputs for any car or battery.
 
LowEndTorque said:
Just to conclude this thread.
I had contacted a official Ford service center to ask about any need for FORScan post the battery swap and informed that I have done the manual BMS reset. The Service Center confirmed there is nothing more to do. :)

P.S. - Please feel free to use this thread as a car battery related discussion for any queries or inputs for any car or battery.
Click to expand...
They won't tell you anything related to Forscan it being unofficial software. You can do stuff with it that even they don't know about. You only need it if you are changing battery size, or to more easily reset the BMS (its a single button press)
But yes if you fitted the same size battery and you have reset it, that's all there is.

I changed some nifty stuff such as disabling the auto fold mirrors on keyfob press they only open now when you open the drivers door.
Enabled the digital speedo.
Changed the 12v socket to switch off 2 minutes after you lock the car so i can leave my charger plugged in.
Enabled auto locking at 5mph.
Enabled tyre pressure display.


jonathangazeley.com

Unlocking features in your mk5 Mondeo with FORScan

The Ford Mondeo mk5 (from 2015 onwards) has a number of useful features that are disabled in the factory but can be unlocked using free software and a USB cable, without any special knowledge. Here…
jonathangazeley.com jonathangazeley.com
 
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