Dead battery after long time not driving

[John Finney]

I have been in hospital for a couple of months and my 12v battery is now flat. New battery fitted very recently. I have used a jump start to move it back onto the drive. My question is will it charge if I just leave the car in ready mode after I jump start? If so how long will it take to charge to an acceptable level so it will restart as it should. Many thanks, hoping for your advice Best John
My dead battery under the bonnet is a mystery to me.

 

[Jomarkh]

Hi John,
The 12V battery will charge off the traction battery (in ready mode) or EVSE (wall point). What SOC are you at?

 

[Alb]

There's no way anyone here can give you an accurate figure plus if the battery has been left in a discharged state for an extended period it may not even be recoverable.
An overnight charge using an external charger would be my preferred option.

 

[Spinynorman]

I think a good investment would be a mainrenance charger that you can leave in maintenance mode I.e. connected after the charger says it’s fully charged, if you’re likely not to be driving for extended periods.
The fact that you could jump start could mean there’s still some life left in the battery, so I would leave the car in ready mode - either drive it for half-hour or sit in it for the same time then turn it off.
If you can turn the car back on normally, your battery might be save-able with a charger.
The biggest problem I used to have was plugging the booster in inside the house and running the cables out via a window securely. I have windows that lock with a small gap so that was OK but the better solution is either a hole in the wall or an outside, weatherproof 3 pin lockable plug box.
If you have one installed make sure you have an isolation switch fitted inside so that no one else can use it without your say-so.
HTH

 

[John Finney]

Hi John,
The 12v battery will charge off the traction battery (in ready mode) or EVSE (wall point). What SOC are you at?

Sorry what's SOC

I think a good investment would be a mainrenance charger that you can leave in maintenance mode I.e. connected after the charger says it’s fully charged, if you’re likely not to be driving for extended periods.
The fact that you could jump start could mean there’s still some life left in the battery, so I would leave the car in ready mode - either drive it for half-hour or sit in it for the same time then turn it off.
If you can turn the car back on normally, your battery might be save-able with a charger.
The biggest problem I used to have was plugging the booster in inside the house and running the cables out via a window securely. I have windows that lock with a small gap so that was OK but the better solution is either a hole in the wall or an outside, weatherproof 3 pin lockable plug box.
If you have one installed make sure you have an isolation switch fitted inside so that no one else can use it without your say-so.
HTH

Thanks for the reply

 

[aleks57]

The state of charge (SOC) is a measurement of the amount of energy available in a battery at a specific point in time expressed as a percentage. For example, the SOC reading for a computer might read 95% full or 10% full.

What is SoH in a battery?

SoH= State-of-Health

The state-of-health (SoH of a battery describes the difference between a battery being studied and a fresh battery and considers cell aging. It is defined as the ratio of the maximum battery charge to its rated capacity. It is expressed as a percentage.

 

[Spinynorman]

Sorry what's SOC


Thanks for the reply

Mainrenance =- Maintenance

 

[Lovemyev]

An overnight charge using an external charger would be my preferred option.

I agree !.
John - Charging slowly and more gradually from external 12volt battery charger overnight, is likely the best option to help recover your now depleted ( newish ) battery.
This is assuming you already have one of the newer smart chargers at your disposal of course.
When the smart charger is first connected and turned on, it will initially interrogate the current condition of the battery.
Then it will automatically set up program schedule length / rate and time best suited to the present status / condition ( SOH - State Of Health ) of your 12 volt battery.
It will then commence the charge cycle very slowly at first and then it will ramp up the charge rate progressively, then returning to a lower rate before finally finishing the charging cycle.
I have the CTEK smart charger that you able to purchase the optional quick connect loom.
This short loom is very easy connected to the main battery terminals all of the time.
It has a fool proof quick release connector that you then use to quickly attach your smart charger.
A better option than using the crocodile clamps they give you.
This maybe ideal option for you, if you want to put your battery on charge on a fairly regular basis, given your low usage case.
The SMART unit is small and can be left protected from the elements under the bonnet.
Here is a link to the CTEK GO unit and the quick connect lead that I have, plus the quick connect extension lead, but shop around for best prices !.

CTEK CT5 Time To Go 12V 5A Battery Charger - 40-162

CTEK CT5 Time To Go 12V 5A Battery Charger - 40-162 • STAY IN CONTROL - Life is great – and even greater when you have control over your own time. When you're dreaming of the freedom and adventures offered by driving your vehicle, charging the battery might not be on top of your mind. But...

www.tayna.co.uk

CTEK 56-260 Comfort Connect M6 Eyelet Adapter

This CTEK connector is designed to stay permanently attached to the battery in the engine bay via the eyelets. This is ideal for batteries that are awkward to access as the charger simply plugs into this adapter without needing to remove the battery and attach crocodile clips.

www.tayna.co.uk

CTEK 56-304 2.5 Metre Comfort Extension Lead

The CTEK Connect Extension Cable is convenient the solution if your CTEK charger needs the longer length. Simply connect the 2.5m cable to your charger and attach the other end to the sockets on your other CONNECT accessories.

www.tayna.co.uk

Good luck with your continued recovery John ! .

 

[Spinynorman]

I agree !.
John - Charging slowly and more gradually from external 12volt battery charger overnight, is likely the best option to help recover your now depleted ( newish ) battery.
This is assuming you already have one of the newer smart chargers at your disposal of course.
When the smart charger is first connected and turned on, it will initially interrogate the current condition of the battery.
Then it will automatically set up program schedule length / rate and time best suited to the present status / condition ( SOH - State Of Health ) of your 12 volt battery.
It will then commence the charge cycle very slowly at first and then it will ramp up the charge rate progressively, then returning to a lower rate before finally finishing the charging cycle.
I have the CTEK smart charger that you able to purchase the optional quick connect loom.
This short loom is very easy connected to the main battery terminals all of the time.
It has a fool proof quick release connector that you then use to quickly attach your smart charger.
A better option than using the crocodile clamps they give you.
This maybe ideal option for you, if you want to put your battery on charge on a fairly regular basis, given your low usage case.
The SMART unit is small and can be left protected from the elements under the bonnet.
Here is a link to the CTEK GO unit and the quick connect lead that I have, plus the quick connect extension lead, but shop around for best prices !.

CTEK CT5 Time To Go 12V 5A Battery Charger - 40-162

CTEK CT5 Time To Go 12V 5A Battery Charger - 40-162 • STAY IN CONTROL - Life is great – and even greater when you have control over your own time. When you're dreaming of the freedom and adventures offered by driving your vehicle, charging the battery might not be on top of your mind. But...

www.tayna.co.uk

CTEK 56-260 Comfort Connect M6 Eyelet Adapter

This CTEK connector is designed to stay permanently attached to the battery in the engine bay via the eyelets. This is ideal for batteries that are awkward to access as the charger simply plugs into this adapter without needing to remove the battery and attach crocodile clips.

www.tayna.co.uk

CTEK 56-304 2.5 Metre Comfort Extension Lead

The CTEK Connect Extension Cable is convenient the solution if your CTEK charger needs the longer length. Simply connect the 2.5m cable to your charger and attach the other end to the sockets on your other CONNECT accessories.

www.tayna.co.uk

Good luck with your continued recovery John ! .

I must say that as a low user with a maintenance charger (NoCo), I leave mine plugged in until I need it, which keeps the charge at its optimum - rather than allowing it to drain with periodic use. Of course the charger is designed for this -YMMV

 

[Eryk in a MG4]

This is my experience and how I overcame it. When I bought my MG4 X power it had a flat 12V battery (from being in the showroom for 6 months and travelling only 240 miles from new), because I still had some time to go on my current lease Nissan leaf, I hardly used the X power resulting in the 12V battery depleting alarmingly within a week or so. I had it changed under warranty and was told the car needed to be started regularly to keep the 12V battery charged. (Although it is not a starter battery, as in an ICE car, it was still needed to power the auxiliary systems, alarm, door opening, telematics etc). When you connect the car to a charger the 12V battery automatically gets charged also. I have a Zappie 7kW charger connected to Octopus on the intelligent go tariff, this meant that I can connect the MG and tell it (via the octopus app) when to charge and to what level. Therefore for me the solution to a discharging 12V battery over extended periods of none use is this:- prior to leaving the car for an extended period of time, say going on holiday I ensure the traction battery is discharged to below 25 - 20%, I connect the MG to the zappie and every two or three days wherever I am in the world I initiate a short charge of say 5% (i.e. from 20 to 25%, first time the 25-30% and so on till I return, or if I'm longer away, extend the charging delay from 2 or 3 days to 4 or 5 (keep checking MG I-Smart app for state of 12V battery SOC and if it drops below 12.2V initiate a charge cycle to bring it back up). Bingo job done. I recently went away for three months and used this system to trickle charge the traction battery to full ensuring the 12V battery never lost charge over that period of 3 months. As I now use the MG every day so this is no longer a problem until I go away on holiday when I use this system and all is tickety boo.
Of course this system cannot work if you leave your car at the airport for two weeks while away, in which case I have a 12V battery booster to jump start a flat battery, once the contactors have initiated the traction battery the 12V battery will get charged from it directly. If, like me when I got my MG, your 12V battery is constantly flat you need to change it for a new one, its been said elsewhere here, a 12V wet battery if discharged constantly or left in a discharged state for too long will damage cells within and there is little can be done to recover it. BTW the MG dealership told me leaving it for two weeks shouldn't be a problem unless there is some other parasitic drain on the 12V battery causing a faster discharge. If this is the case with you get it checked out and changed (particularly if your car is still under warranty).
Hope this helps others.