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Re: Replace small 12v battery to regular one.

Posted: Sat Apr 13, 2019 12:05 pm
by LeftieBiker
Leaf and many modern vehicles charge 12V battery to very optimal state of charge, around 80%.


Lead-acid batteries like to be at 100% state of charge, or as close to it as possible. 80% may be good for a lithium battery, but 80% on a LA battery will cause gradual but significant sulfation.

Re: Replace small 12v battery to regular one.

Posted: Sat Apr 13, 2019 1:35 pm
by arnis
Correct. Though charging to this high state of charge results in excessive gassing (electrolyte loss - aka water boils out).
Salt deposition starts at around 60%.
Keeping charging voltage up to around 80% state of charge does not result in excessive gassing.
Ideal window is narrow though definitely doable.

Re: Replace small 12v battery to regular one.

Posted: Wed Apr 17, 2019 6:28 am
by powersurge
I don't seem to see the need to worry about the 12V battery. After 4+ years and 55K miles, my battery is perfectly happy with good voltage numbers. I don't see the 12v battery to be a "maintenance" concern for most drivers. Also, if you put the battery on a "battery tender", then you really will not have issues......

BUT....... You should open the battery and check the water level on the cells regularly... That will kill the Bat.

Re: Replace small 12v battery to regular one.

Posted: Thu Apr 18, 2019 7:22 am
by arnis
Only if cells can be opened. Valve regulated battery with 13.0V charging voltage will not let electrolyte to evaporate nor boil even in hot weather.

Re: Replace small 12v battery to regular one.

Posted: Thu Apr 18, 2019 1:02 pm
by LeftieBiker
arnis wrote:Only if cells can be opened. Valve regulated battery with 13.0V charging voltage will not let electrolyte to evaporate nor boil even in hot weather.


The North American Leaf 12 volt batteries use flooded cells that can (and should, annually) be opened.

Re: Replace small 12v battery to regular one.

Posted: Mon Apr 29, 2019 10:25 am
by powersurge
arnis wrote:Only if cells can be opened. Valve regulated battery with 13.0V charging voltage will not let electrolyte to evaporate nor boil even in hot weather.


The only "sealed" 12v car batteries I have seen were the tiny GM with the little green sight glass (green when it was fully charged) in the 1970s.. All "NORMAL" 12 volts have either individual screw top plugs, or the have 2 sets of square covers that you pry open with a screwdriver...

Either way, you got to open up the plugs to clean the top of the battery and check the water levels every once in a while..

Re: Replace small 12v battery to regular one.

Posted: Mon Apr 29, 2019 10:26 am
by powersurge
powersurge wrote:
arnis wrote:Only if cells can be opened. Valve regulated battery with 13.0V charging voltage will not let electrolyte to evaporate nor boil even in hot weather.
..


The only "sealed" 12v car batteries I have seen were the tiny GM batteries with the little green sight glass (green when it was fully charged) in the 1970-80s.. All "NORMAL" 12 volts have either individual screw top plugs, or the have 2 sets of square covers that you pry open with a screwdriver...

Either way, you got to open up the plugs to clean the top of the battery and check the water levels every once in a while...

Re: Replace small 12v battery to regular one.

Posted: Mon Apr 29, 2019 9:32 pm
by GerryAZ
AGM and VRLA (absorbed glass mat and valve-regulated lead acid) batteries are sealed, but have a pressure relief valve to release excess pressure if they are overcharged. If they are overcharged frequently, they eventually lose electrolyte and fail because there is no realistic way to refill them. They generally last much longer than conventional batteries if they are never overcharged.