Disconnecting battery for long storage

[anchorman]

On 11/20/2022 at 12:58 PM, TonyHSD said:

Let share something about batteries and chargers. 
My neighbour works abroad and often are away for months 6-10 at a time. They used have petrol manual corsa and they were changing battery every two years because the obvious, lack of use. Last year before they got rid of the car they bought a large solar panel smart charger (20w or more). They attached to the windscreen and plugged in directly into the obd 2 port. The summer was hot and sunny, the smart charger worked well and even after many months of not using the car they were able to unlock and start first time. 
They decided to go full ev and bought a leaf first gen facelift.  The leaf has same function as my gf Hyundai, the traction battery to maintain and charge the auxiliary 12v battery while car have not been used. These cars has 3 large blue led’s built in top and middle of the dashboard to indicate traction battery charging or auxiliary battery charging while car been parked and locked, off charger too.
The Nissan been left over the summer and never seen the blue lights flashing = charging the 12v battery, which proof the solar charger did its job well., however recently I saw the blue lights flashing, it seems that lack of sun energy trigger the car valet function and the car started charging the 12v battery itself. My girlfriend’s car was doing exactly the same when I looked at hers, it seems these cars are smart indeed. Unfortunately Toyota hybrids has very small traction batteries and similar functions are impossible. 
For the op question, best to connect the battery to smart charger which will maintain it healthy and ready to go when they return, or at least a solar charger. 👍

What is the relevance of comparing an EV Battery to a Hybrid?  

[anchorman]

On 11/20/2022 at 7:54 PM, Cyker said:

Or even that Esso E5 that doesn't apparently have any ethanol in it!  

From Esso’s website;

How much ethanol is in Esso's E5 fuel?

Esso Synergy Supreme+ 99 contains zero ethanol, except (for logistics reasons) sites supplied from Scotland, North Wales, North England and Cornwall.

[anchorman]

On 11/19/2022 at 6:14 PM, TonyHSD said:

No, you should not disconnect the 12v battery but instead you can attach smart charger either on plug or solar panels. Otherwise after 6 weeks you very likely will find your 12v battery been completely dead., and new battery will be needed. 

Why would a new Battery be needed after 6 weeks?

[RobertR]

Because the Battery will be drained below its healthy level and this may damage the Battery, maybe not be that bad that you need a new Battery asap, but it has an impact on battery lifespan. If you have a garage or any other opportunity to safely put a charger on the battery(maintaining full state of charge) while undrived for a long time, do it.

[anchorman]

1 minute ago, RobertR said:

Because the battery will be drained below its healthy level and this may damage the battery, maybe not be that bad that you need a new battery asap, but it has an impact on battery lifespan. If you have a garage or any other opportunity to safely put a charger on the battery(maintaining full state of charge) while undrived for a long time, do it.

It won’t go flat from day one, IF it goes flat it will only be flat towards the end of the period and batteries are quite capable of being charged after being discharged.  Such drama.  

[Roy124]

43 minutes ago, anchorman said:

Why would a new battery be needed after 6 weeks?

Probably not, my new 12v Battery, as did many, went flat at the start of Covid and before, AFAIK, we were advised to use Ready mode frequently. 

Within its first year it went flat twice more and was changed under warranty.  Not dead like a Norwegian Blue but certainly on its way out. 

[RobertR]

2 hours ago, anchorman said:

It won’t go flat from day one, IF it goes flat it will only be flat towards the end of the period and batteries are quite capable of being charged after being discharged.  Such drama.  

of course after a while...not overnight. But if you own a charger and garage, it's good to plug the charger into the Battery to prevent it to go flat in the first place. They are hundreds of measurements on the internet that say a deep discharger is bad for the Battery, no reason to deny this. But of course, your Battery will be able to charge and work properly but if you do this often then the battery lifespan will be not 8 years but 3 years for example.

[Cyker]

It depends on the Battery, but it's known that esp. starter-type lead acid batteries will suffer a continual loss of capacity when discharged below a certain level (I think it's about 50%?) and left there for too long, with the effect accelerating the lower the level of discharge.

This is why, unlike e.g. NiMH batteries which almost always need to be charged by you when you buy them, lead acid batteries are usually sold at 80-100% charge, because they *have* to be stored at full charge to stop them degrading.

The problem is the lead plates dissolve slowly in the acid when it's not charged up and they can't be reformed, and the doilie-like lead plates of the starter batteries (For maximum surface area to allow maximum current delivery) are particularly vulnerable. The thick solid plates of deep-cycle Pb+ packs are more resilient to this, which is why Toyota really should be using them in their hybrids but I'm not sure if they actually are... (NB: Just because a Battery says AGM *doesn't* automatically mean it's a deep-cycle Battery!)

So generally, if the 12v is allowed to go flat a lot it will likely be beyond recovery very quickly, although some fancy chargers can somehow 'recondition' them if they're not too far gone.

 

[TonyHSD]

My hybrid Ni-mh Battery is always full since I moved to my current house., bottom of a long downhill 🔋👌 Let see how long will last. 🤞🫢