Car sat for 11 days, put charger on and only 50% battery remaining, normal?

[IS300E30]

As the subject states. I had the car sitting for 11 days, I just put a battery charger on and it says 50% battery.

The car sits in the garage and it has been cold other than the last couple of days.

Would this be seen as normal or a concern?

Alternator is only a couple years old

*Update, 10 minutes on charger it is up to 69%

[McGyver]

Some say it's snake oil, but I swear by the "Repair" mode on my NOCO GENIUS10. The e30 battery was barely getting the car started in December 2022 and my FOXWELL BT705 said 323 of 900 CCA dropping to 10.86V when cranking before charging. The initial state of health was 68% and it eventually got up to 80% after several repair cycles. It's still in the e30 and doing fine. The charger also helped on the AGM battery for the f30, which REALLY didn't want to start and was causing some strange things to happen. I've got several more months out of the f30 battery, which isn't happy, but is working. I'll replace it soon.

[Gaarath378]

How old is the battery? Batteries (even new ones) discharge faster when its cold.

[varg]

The stereo, OBC, an amplifier if you have one, and even some gauges, will have some current draw when the car sits, between that and the cold weather you could easily wind up with a battery that won't start the car if it sits for a couple of weeks. If the car sits a lot, keep a battery maintainer on it. The battery in my FD really surprised me when I pulled it out recently to do some maintenance: it is 11 years old and still works fine, though it doesn't get cold here. The previous owner told me he always kept the car on a battery tender when he wasn't driving it, and it always sat during the winter since it gets cold where he lives. Seems it is worth doing, especially since batteries are quite expensive these days.

[Panici]

Some say it's snake oil, but I swear by the "Repair" mode on my NOCO GENIUS10.

Do they go into any detail on the repair mode?
I would be interested to see if it is attempting de-sulfation, and how they go about it.

I have had luck squeezing some new life into an old battery by hooking it up to a running car at 14v+ and leaving it attached for a minute or so with thick jumper cables.
User beware here as you could blow the thing up with the large current inrush. But I believe it can knock the sulfation off the plates. I have only done it with a cold battery that has been sitting, never a recently discharged (and offgassing) one.
I know it works to get a minimum voltage into a dead (but sitting) battery so that a "smart" charger will recognize it and start charging.

The stereo, OBC, an amplifier if you have one, and even some gauges, will have some current draw when the car sits

I have a knife switch battery disconnect on my E30 since it sits for long periods of time.
You lose radio presets (if equipped) and the OBC clock, but the battery can sit for 6+ months and still crank the car without issue.
I suppose a factory ECU would lose long-term adaptations (Does the Motronic in the E30 even have these?), but I have a standalone so I don't have to worry about that.

----------------------

Since I have a bunch of vehicles, here is my general strategy. The ones sitting outside unused for the winter get the batteries taken out and put in the basement. Any vehicles in the attached garage keep the batteries installed, but negative terminals disconnected.

Then I rotate a trickle charger between all the sitting batteries. I used to do this every weekend but I have been lazy the past few months, and just left the trickle charger on the motorcycle. That said it's above freezing today, so I'm going to open up the garage and put the charger on the E30 battery since you brought it up!

[reelizmpro]

11 days is a long time for a battery to sit. 50% after 11 days isn't too bad though. My H6 AGM's would be at 50% after a week so now I charge them every 3-4 days between drives to keep them happy since I don't drive my E30's that much and I suspect the short canyon drives aren't enough to fully charge the battery. Ideally, you don't want the SOC (state of charge) to ever drop below 50% or doing so will shorten battery life. When 2 of my cars were hit while parked, they spent 6 months in the body shop and they never charged the batteries. They both were dead a while before I picked them up. I was able to revive them both but one is at 85% health, the other (3.5 years old) wouldn't hold a charge and had to be replaced shortly after.

Repair mode or pulse repair does work to bring back severely discharged batteries back to life. It also slowly charges the battery which is why it often takes 24-48 hours to complete the cycle. I used it on a used discharged AGM I picked up recently and it's perfectly fine now at 90% health. I have read, that it's mainly designed for deeply discharged batteries that won't take a normal charge and that using it on a good battery would unnecessarily stress it out.

[roguetoaster]

Folks seem to be glossing over the 50% reading on the charger a bit, so I'll call BS on that being accurate, at least in terms of starting a car, especially after a fairly large jump in minutes.

Clearly, some cars without any faulty drains can flatten batteries quickly, but a healthy E30 should probably be able to sit for months connected, as my 318i was able to do. Even my most modern vehicle, a 16 Colorado had no issues after sitting almost two months in winter while I was running the winter beater. Typically, if a vehicle struggles to start after a couple of weeks, either the car has a large drain, or the battery is old/insufficient for the cranking needs.

If you ever hook a scanner up to a modern car it is amazing the amount of variability that goes in to charging/maintaining a battery while the engine is running. Decent chargers are undoubtedly doing the same thing, minus the load end, and I can echo the utility of the Noco Genius line.

Also of note, the battery analyzer that went along with the really nice scanner at a shop I worked at probably reported 95% of all batteries tested as bad, including brand new or freshly charged new units. The majority of these batteries had no issue starting their vehicles.

[McGyver]

Do they go into any detail on the repair mode?
I would be interested to see if it is attempting de-sulfation, and how they go about it.

From their website:

Not all batteries can be recovered. Batteries tend to become damaged if kept at a low charge and/or never given the opportunity to receive a full charge. The most common battery problems are battery sulfation and stratification. Both battery sulfation and stratification will artificially raise the open circuit voltage of the battery, causing the battery to appear fully charged, while providing low capacity. Use 12V Repair in attempt to reverse these problems. For optimal results, take the 12-volt battery through a full charge cycle, bringing the battery to full charge, before using this mode. 12V Repair can take up to four (4) hours to complete the recovery process and will return to Standby when completed.

https://no.co/support/sulfation-and-battery-repair-mode

[e30davie]

should be able to sit for months and still fire up. charge up the battery and get it load tested, that's the only way to tell if the battery is at fault. Batteries these days seem to just fall over one day, rather than degrade over time. dunno why, had the wifes one working perfectly one day, dead the next. They drop cells i think.

[Northern]

Some say it's snake oil, but I swear by the "Repair" mode on my NOCO GENIUS10.

This is cool... I have 3 or 4 NOCO tenders for bikes/shitboxes that used to sit around all winter, as well as a GENIUS2, and I didn't even realize it had this mode. I'll look into whether it needs the size or if the 2 is enough for a car battery, because I have a handful of shitty old batteries that would be nice to use.

[packratbimmer]

What brand is your battery?

[McGyver]

This is cool... I have 3 or 4 NOCO tenders for bikes/shitboxes that used to sit around all winter, as well as a GENIUS2, and I didn't even realize it had this mode. I'll look into whether it needs the size or if the 2 is enough for a car battery, because I have a handful of shitty old batteries that would be nice to use.

Yeah, it's not a cure for an old battery, but it can get some extra life out of it! My e30 battery is about to be 7 years old and still working fine. Was hoping to get a few months, but I guess I've gotten 2 years. The battery in the f30 is probably original, so 10 years old. It doesn't seem as happy, and the car is more susceptible to issues from low/fluctuating voltage, but it's gotten several more months for me so far. Not to mention that it works great as a trickle charger when a car is sitting or I'm doing work with the doors open and the interior lights on.