Educate Me Regarding the 12V Battery

I've seen a lot of posts concerning special chargers for the 12V battery, and the need for periodic charging or conditioning.

Are those things really necessary? I'd think the LEAF would do a good job (or as good a job as an ICE car) at keeping it healthy.

Please 'splain it to me.

Queue "opening can of worms" :shock:

A nickel's worth of free advice: replace it BEFORE it dies.
That and checkout my thread about replacing the (stock) 12v lead acid battery with a 12v Lithium battery (LiFePO4).

PianoAl said:

I've seen a lot of posts concerning special chargers for the 12V battery, and the need for periodic charging or conditioning.

Are those things really necessary? I'd think the LEAF would do a good job (or as good a job as an ICE car) at keeping it healthy.

Please 'splain it to me.

Click to expand...

There are several threads on this topic, but I will give you my perspective after 74,000 LEAF miles: I have never charged the 12-volt battery in either LEAF with an external charger because the DC-DC converter does a good job of charging for my climate and usage patterns.

The DC-DC converter charges at about 14 volts until the charging current drops below a threshold and then floats at about 13 volts. This is ideal for a sealed AGM or any other battery that has low internal resistance so that the battery is nearly charged before the DC-DC converter drops to float mode. Unfortunately, the original Nissan batteries have relatively high internal resistance so they don't get well charged before the DC-DC converter drops to float mode. If driving/charging patterns do not have long time periods for float charging, the 12-volt battery may not get fully charged every day so it will eventually sulfate (which increases the internal resistance more). A trickle charger will charge the battery more fully under these conditions and may prolong its life. A conditioning charger may even eliminate the sulfation and restore some capacity.

Since I prefer to just charge and drive, I replaced the original battery in the 2011 with a sealed AGM deep-cycle battery rather than getting a warranty replacement from the dealer (failed after 2-1/2 years which is normal for OEM batteries in Phoenix). I wish I could have removed it to keep for a spare when I removed personal items after the car was declared a total loss, but the insurance company storage yard would not allow that. The original battery in the 2015 is still OK, but it will get replaced with a deep-cycle AGM as soon as it starts showing weakness.

Gerry

As Gerry can attest, some Leaf drivers have no trouble with the 12 volt battery. Some only have it rarely, others more often. I'd drive the car for two weeks, let it sit an hour after shutting if off (and opening the hood to avoid using any power later), and then measure the "rest" voltage of the battery. If it's above 12.6 volts, you're fine; 12.6 to 12. 4 and an occasional charge is called for. Below 12.4 and you need to either top it off regularly with an external charger/maintainer, or install hardwired leads and do it regularly when you plug the car in to charge. That gives you the added advantage of being able to leave the car plugged in but not charging, safely.