Hyundai i40 1.7 diesel (2015) - Battery keeps dying

Honest John Back Room » Technical matters
What is life like with your car? Let us know and win £500 in John Lewis vouchers | No thanks
View Threaded
Mon 27 Apr 2020 19:25
Hyundai i40 1.7 diesel (2015) - Battery keeps dying - TopScot

Hi all my Dads i40s battery keeps draining, over the past month I have replaced the battery, and alternator but still every morning the battery is stone dead and nothing whatsoever in form of electrics is to be seen or heard. I've checked over and nothing is been kept on, lights etc. Any ideas/solutions would be highly appreciated. Thank you

Reply | Report as offensive | Link
Mon 27 Apr 2020 20:15
Hyundai i40 1.7 diesel (2015) - Battery keeps dying - Railroad.

Batteries discharge for one of three reasons.

1. The battery has come to the end of its service life.

2. A fault with the charging system.

3. Something which is not switching off when it's meant to be, or left on accidentally which is draining the battery.

You say you've checked it over and nothing is left on. Well assuming 1 & 2 are good then something has to be. Connect an ammeter inline with battery negative and read what current is being drawn. Close the bonnet, lock the car up and wait a couple of minutes for everything to shut down. Then see what current is being drawn. If the battery is discharging overnight it'll have to be a fair amount. A drain of more than 0.1A (100mA) is considered unacceptable.

Reply | Report as offensive | Link
Mon 27 Apr 2020 20:18
Hyundai i40 1.7 diesel (2015) - Battery keeps dying - TopScot

It's a brand new battery. Thanks for that. I haven't got those tools. When I charged car I took it a good 20 min drive averaging 60 mph

Reply | Report as offensive | Link
Mon 27 Apr 2020 20:29
Hyundai i40 1.7 diesel (2015) - Battery keeps dying - elekie&a/c doctor
For the battery to be stone dead overnight, you have a serious drain . As it’s a diesel , the first thing I would be looking at is a fault with the glow plug circuit . There will be a high rated fuse located near the battery for this circuit. Possibly labelled around 60 amps . Remove this and retest the system . A 20 min drive will not charge a flat battery .
Reply | Report as offensive | Link
Tue 28 Apr 2020 13:59
Hyundai i40 1.7 diesel (2015) - Battery keeps dying - Railroad.
A 20 min drive will not charge a flat battery .

A drive of however long will not charge a flat battery. An alternator is very good at keeping a fully charged battery fully charged. It is nowhere near as good at getting it there. A battery needs to be charged on a charger for 8 - 10 hours, ideally overnight.

If the OP's battery is a calcium type it will need to be boost charged initially at around 16v before it will accept charge at a normal rate. The OP should check to see if a calcium battery is fitted to this vehicle.

Reply | Report as offensive | Link
Mon 11 Jan 2021 20:40
Hyundai i40 1.7 diesel (2015) - Battery keeps dying - Safety Steve

TopScot, did you ever find out what was draining your Dads battery?

Reply | Report as offensive | Link