arnis wrote:13.1V is definitely charging voltage.
No, 14.5V is a charging voltage. 13.1V is known as a float voltage. It should be used after a full charged is achieved. And 13.1V is a very low float voltage, too low for an AGM battery. High-quality battery chargers tend to use 13.5V for a float voltage.
arnis wrote:Though it is way too low for occasional use.
It's way too low for a car which needs to return the lost charge to the battery quickly.
arnis wrote:Is it verified with multimeter?
arnis wrote:13.1V might be reported by LeafSpy but what about real voltage @terminals.
LeafSpy readings are worthless, IMO.
arnis wrote:I checked my 2014 Leaf with voltmeter and clamp-on DC ampmeter, it charges as it is written in the literature.
Do you have some literature which tells you what voltage the LEAF uses to charge the 12V battery? If so, can you please point us at it.
arnis wrote:Maybe you have deep cycle AGM battery?
Yes, I'm talking about an AGM battery.
arnis wrote:On vehicles I've never seen that kind of resting voltage.
Once you look at this plot
, then you can say you have seen such high resting voltages in an automotive AGM, in this case that voltage is seen even when loaded by the LEAF.
arnis wrote:BMW uses AGM batteries for a decade already. Almost all start-stop vehicles use AGM type.
That's fine, but BMW does not use a charging or float voltage of 13.1V with those batteries.
arnis wrote:I bought a second hand AGM battery that was tortured by 5-series for 6 years. It has more than 55% life left.
That's great! That doesn't mean an AGM is a good choice for a Nissan LEAF which "charges" at 13.1V.
arnis wrote:Depending on how discharged battery is it can swallow up to 4Ah during that period.
Agreed. Charging will occur quickly if the battery is at a low SOC. But that doesn't address the issue of letting the battery sit not fully charged, which leads to sulfation.
arnis wrote:I will verify my observations in near future but I'm pretty sure 2014 Leaf does NOT have 12V battery problems.
If it doesn't spend any more time at 14.5V than I have specified, then it has problems.
arnis wrote:PS! AGM batteries do not sulfate faster than flooded.
Sulfation of AGM batteries is a huge problem in PV applications.
arnis wrote:Also their sulfation is not thick due to absorption mats inside.
I'm sure that's true. That is why I am able to recover the capacity for badly-sulfated AGMs. But it may take many MONTHS to break down all the sulfate. That's O.K. since I am using them for emergency backup. Any desulfation I can achieve is like getting a free battery.
arnis wrote:And lead acid batteries should not sulfate AT ALL if used properly.
We can agree on that. But they need to be returned to a full state-of-charge frequently to prevent the lead sulfate from hardening.