- My model of MX-5 is: __ND 2023 2ltr
- I’m based near: __Manchester
- I’m looking for technical help or recommendations on: __Battery issue
Hi I purchased my brand new car 12 months ago.
A couple of months ago the Istop stopped working. I reported this as a fault at the first service.
The car has done 1800 miles in its first year and is garaged when not in use.
The service department said that the battery SOC is only just getting to 70% when they tested it yesterday and I need a new battery.
My question is- what would cause this to happen?
I’ve had several MX5’s over many years and I know that they are not good with batteries and have had to replace them in the past but I normally get at least 3 years from a battery if not longer.
I would be interested to know your thoughts please
If the battery has ‘failed’ then you should get a new one under warranty.
Have you let the battery get very low on numerous occasions? Have you used a smart battery charger to maintain the battery when not used for a week or so?
The ND2 batteries need very high constant amps to charge and your dealer should have the correct charger to try and get it going again.
If your stop start ceases to working then removing the earth from the battery for 15 minutes usually sorts it out.
This is the curse of Mazda iStop. Just disconnect the battery and reconnect it. The computer thinks the battery is finished when it isn’t.
iStop saves such a tiny amount of fuel compared to the cost and environmental impact of a new battery that it’s ridiculous.
When the car is in the garage it is connected to a CTEK charger. However, I only purchased the charger in October last year so from April to October it was not connected to a charger but the car was driven on average 30 miles a week during that time. Prior to leaving home to drive to the dealer the car had been connected to the charger for a week with the charger showing green lights etc. The drive to the dealer takes over an hour and is about a 30 mile drive. I would therefore assume that the battery should have been fully charged on arrival at the dealership.
The dealer went through the reset process for I-stop twice yesterday but without success. Due to the reset process failure they then checked the state of charge (SOC) on the battery which was below 70%. They were unable to improve the SOC.
I’m not really interested in fuel saving although every little helps of course. My liking for i stop is more about not putting unnecessary fumes into the atmosphere when in stationary traffic etc
This is the CTEK charger which I reconnected when I got home last night from the dealership.
I have it set on the “normal” car battery setting and not the AGM setting. Please advise if you think the setting is incorrect or if it should be on the AGM setting.
You are doing all the right things. If the battery is not ok I would ask for it to be replaced under warranty.
Do try the negative battery terminal disconnect, it fixes most stop/start issues. I have to do it may be twice a year and it works every time.
It will do no harm to try another setting but if it ain’t full after a 1 hour run it looks like the battery is not at it’s best.
I did all the same stuff when I had a Mazda 6 - got a CTEK charger, fitted a new EFB battery. The new battery solved it for a few months until iStop stopped working again. Then I realised it was the disconnection that was fixing it, not the new battery. The defective battery system was a major factor in me changing that car.
The iStop in the CX-5 that replaced it, and my current Mazda 3, have been trouble-free. It’s a software issue that Mazda seem to have quietly fixed on later models. The MX-5 may still have the old system.
