Mo1820
Posts: 18
Joined: Tue Nov 10, 2020 12:22 am

Battery Health Check procedure - correct method?

Tue Jan 19, 2021 1:25 am

Am v. confused - your experience would be much appreciated - I have spoken to several Mitsubishi Dealers (MD’s) in the UK but all have different responses. Please can someone inform me correctly?
I wanted a battery health check done on a 2016 GX4hs before purchase from a car supermarket dealer (SD). Car has full MD service history and 41k miles on clock. I also asked if the MD could take a look at the MMCS computer to resolve why the SD couldn’t turn off a pre-heating timer/remote climate control for all 7 days if needed. I posted this in a different thread so as not to over-complicate this one, under 'MMCS error? Pre-heating timer/Remote Climate Control.'

The SD agreed to take it to the MD to check the MMCS pre-heating timer and get an EV/drive battery health check (as opposed to a 12v battery health check). (In November the battery mileage range said 21 miles after a full charge, then after sitting on forecourt for a further month it said 11 miles, then after the SD drove it around a bit last week it said 17 miles, in low December temperatures in Cheshire.) I realise that the battery range will depend on driving habits of the previous driver/journey(s) as well as what else is switched on at the time and the outside air temperature.

However different main dealers appear to use different methods for the BMU (battery management unit?) health check, so I am confused. Eg.:-
MD ‘G’ said their diagnostic machine would do a full battery health check on the EV battery, under the boot, which only takes 30 mins and costs £54. They also said they do a health check on the 12V battery, under the bonnet, which also costs £54 but takes overnight to do as it’s set on trickle charge and they send the information to Mitsubishi HQ but only if they find a fault with the 12V battery.
However MDs ‘C’, ‘W’, ‘P’ plus Mitsubishi HQ said that in order to do an EV battery health check, its test data should be sent to HQ first, before draining the battery (cells?) then slowly refilling overnight, followed by the new data being sent to HQ the next day for comparison and analysis. Then after analysing the data, HQ contacts the dealer with any diagnoses or advice on what to do, if anything.
Of the above dealers, MD ‘C’ charges £114 to do their overnight battery health test, MD ‘W’ charges £98 and MD ‘P’ charges £0 as they said the test falls under the manufacturer’s warranty, not due to expire until March this year.

So there seems to be a lot of inconsistency between different MD’s battery health check methods and costs? Does the EV only take 30 mins to check if it’s good, like MD ‘G’; or does it take overnight/24+ hours, like MD’s ‘C/W/P’?

MD ‘P’ - the free of £ charge dealer - said from doing overnight TSRs (technical support requests) with HQ using before and after data, they rarely see battery health problems. They said if the result (is it the SOH - state of health?) is above 25.6 amp it means the battery is ok.

Another MD ‘H’ said they don’t do the BMU/EV health check on request at all, as they said any battery faults would be flagged up by warning lights on the dashboard. So they said if there are no warning lights then there’s nothing wrong with the car/battery and that the mileage range is only affected/estimated by the last 5 mins of your previous journey.

Please could anyone advise which is the correct test method to check that the EV battery is good? The 30 min one using the dealer’s own 'diagnostic machine’, or the one that takes overnight/24+ hours using before and after data sent off to HQ? - To help me know which of the Mitsubishi dealers can be relied upon.
Can any harm be done/problems arise if either the MMCS or EV battery are ‘reset’, or drained and refilled?
Also should we be given an SOH print out explaining the battery health results and how do I interpret these please? I just want to know the battery is healthy and if driven properly it will provide the expected mileage range for its age/usage.
Will a battery health check be able to help determine whether any past damage or leaks have been caused by rough driving/accidental damage, or from using rapid chargers/CHAdeMO too much?

Also is MD ‘G’ correct in saying that the 12V/under bonnet battery takes overnight on trickle charge in order to assess it - if ever needed? How often would this 12V need testing, or would it only be necessary if the car kept getting a flat battery?

Many thanks in advance.

greendwarf
Posts: 2299
Joined: Tue Aug 05, 2014 1:32 pm

Re: Battery Health Check procedure - correct method?

Tue Jan 19, 2021 1:48 am

Before our pre-BREXIT friends jump in with their "I wouldn't buy an EV without a battery check" :lol: The problem is UK dealers generally don't want to do this - as you have found out. However, I think the overnight test is likely to be more comprehensive.

But, I have some sympathy with the dealers over this - would you ask for a fuel consumption test for an ICE? :roll:

If you really are worried about range then ask for an extended test drive as see how far you can travel - which, at the end of the day, is all that matters. :idea:

Mo1820
Posts: 18
Joined: Tue Nov 10, 2020 12:22 am

Re: Battery Health Check procedure - correct method?

Tue Jan 19, 2021 2:12 am

Many thanks GD. :) We are in London and the car is in Cheshire, so I'm trying to head off any potential problems before payment and collection as it's so far to return the car if anything goes wrong. (FYI the only other car I've found in the same year, mileage, spec and colour I want is 1k dearer in Surrey).

The SD will let us test drive within 100 miles, or for 2 weeks - whichever comes first. We obviously can't stay overnight these Covid days, let alone two weeks and ideally the only driving we want to be doing, after coming to collect the car by train, would be the drive back to London upon collection (obvs more than the 100 miles permitted).

However I suppose we could do 'an extended test drive' whilst we are in Cheshire? By that do you mean for say 10 miles, or how far do you mean? Sorry I am such a novice!

Mo1820
Posts: 18
Joined: Tue Nov 10, 2020 12:22 am

Re: Battery Health Check procedure - correct method?

Tue Jan 19, 2021 2:20 am

I forgot to add - in November another MD service dept. told me that the way to get the average mileage range would be to fully charge the car by plugging in using normal charge at 13 amp mains. Then drive the car around to decrease the battery/range. Then repeat this - full charge and driving around - for 5 more times/days.

They said that this would then give me the average mileage range expected for the car as the 5 journeys would have reset the computer/battery to my driving habits, to change from the previous owner's habits?

outlander660
Posts: 19
Joined: Tue Dec 05, 2017 1:13 am

Re: Battery Health Check procedure - correct method?

Tue Jan 19, 2021 3:35 am

It isn't called a guessometer for nothing, I've had mine for over 3 years and have seen anything between 14 and 42 miles on it. If it's low it will drop more slowly and if high very quickly. When it showed 42 miles it dropped 2 miles just getting off the drive, no I don't live in a mansion the drive is 5 yards long. It usually shows 23 miles in summer and 21 miles in winter and that's roughly what I get without using heating or AC. Hope this is of use to you.

Mo1820
Posts: 18
Joined: Tue Nov 10, 2020 12:22 am

Re: Battery Health Check procedure - correct method?

Tue Jan 19, 2021 8:46 am

Thanks a lot Outlander660. It does help to know what readings other people are getting in summer and winter, even if your car sounds a bit younger than this one.

ThudnBlundr
Posts: 751
Joined: Mon Mar 12, 2018 2:18 am
Location: Yorkshire end of M1, UK

Re: Battery Health Check procedure - correct method?

Tue Jan 19, 2021 11:20 am

There's a lot of rubbish quoted to you by the main dealers. Checking the 12V battery, which is in the boot, is a 2-minute job once they've removed the trim to access it. There is no 12V battery under the bonnet, merely a fuse box with a connection to be used when jump starting the car. The EV battery is mounted underneath the car between the wheels. Checking it properly is an overnight job; you can read the SOH stored in the BMU quite easily, but there's no guarantee that the figure is close to reality on newer cars. That's why the full diagnostic is required

The battery warranty is 8 years on any UK car registered after mid-2015; the warranty for the remainder of the car is 5 years.
2015 GX4hs since 03/18
2015 Renault Zoe R240 owner since 11/17

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littlescrote
Posts: 272
Joined: Fri Jul 26, 2019 3:52 am

Re: Battery Health Check procedure - correct method?

Wed Jan 20, 2021 2:27 am

Welcome to the world of Mitsubishi dealers where very few of them know what the hell they are talking about.

Honestly, I would say that a battery problem is so unlikely as to not be worth thinking about. If it really does turn out to be a dud, which you will find out after some months of use, then there is an 8 year warranty on it as said. Probably at 8 years old, most of them are going to be very close to the threshold of replacement anyway. I would buy on the condition of the rest of the car, paintwork, tyres, equipment spec etc and not worry about the battery or you will go round and round in circles confuse yourself and any dealers and sellers and get caught in paralysis by analysis.

greendwarf
Posts: 2299
Joined: Tue Aug 05, 2014 1:32 pm

Re: Battery Health Check procedure - correct method?

Wed Jan 20, 2021 2:47 am

To answer question about how far is an "extended test drive"? No need to do anything more than the distance of a full charge if all you are doing is checking the battery. People seem to get unnecessarily hung up about battery condition and predicted range. The only relevant issue is how far will it actually go at 30 mph on a full charge? So in winter on a second hand car it would be unlikely to be more than 25 miles - about an hour of normal urban driving - at the best of times, before the ICE cuts in. No need for overnight stay!

But frankly, unless you live in NW London (in which case you have a service only dealer in Hendon) for 1k difference, I'd be going for the one in Surrey, in case you have an post-sale issues, anyway.


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