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.