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RegGuheert
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Leaf Number: 5926
Location: Northern VA

Re: 12v Battery

Thu Oct 13, 2016 4:49 pm

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?
Fluke 77.
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.
RegGuheert
2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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Stanton
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Re: 12v Battery

Thu Oct 13, 2016 4:54 pm

I just left my Leaf for almost 3 weeks and came back to slightly lower SOC (obviously due to charging the 12v battery a few times) and no problems starting. Pretty much validated my decision to go Lithium a couple of years ago (not that it hasn't already saved me from another 12v battery in the Texas heat). :D
2011 Blue Ocean SV w/floor mats & window tint
12v LiFePO4 battery & FIAMM 74100 horns
Wet Okole seat covers (front)
Tor's low-power heater mod
2013 sun visor
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Battery Pack replaced (Rev E) @51 months and 41k miles

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RegGuheert
Posts: 5421
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Location: Northern VA

Re: 12v Battery

Thu Oct 13, 2016 4:59 pm

Stanton wrote:I just left my Leaf for almost 3 weeks and came back to slightly lower SOC (obviously due to charging the 12v battery a few times) and no problems starting. Pretty much validated my decision to go Lithium a couple of years ago (not that it hasn't already saved me from another 12v battery in the Texas heat). :D
I have never argued against the Li-ion replacement recommendation. It's just a very expensive solution. I can achieve the same result (and possibly longer life) by using a flooded lead-acid battery, a high-quality desulfating trickle charger and some of my time. I can certainly see going the route you did.

But AGMs have such a high voltage when fully charged that the sulfation issue which occurs in the LEAF is even worse with that chemistry.
RegGuheert
2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

RockyNv
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Re: 12v Battery

Thu Oct 13, 2016 8:00 pm

I tried going the AGM route here and found it was a mixed bag on my ICE vehicles. Here in Tampa Bay many times your best off with the lowest amperage traditional wet 12 volt battery required for your car with fill caps and a large case that holds plenty of electrolyte so you will see 5 years or so of usage. Many times when they pack in a lot of cranking amps into a small battery case you will only see a year or so of service even with an AGM. Sealed maintenance free just means short lived battery around here.

An old timer who rebuilt wet batteries for years told me that in our heat the best value will be from a taller wet battery with fill caps and plenty of room for electrolyte all around the plates especially above and below. In my RV I put in a float charger that goes into a desulfate mode automatically based on time, temperature and charging history.

arnis
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Re: 12v Battery

Fri Oct 14, 2016 1:48 am

There is no such thing as universal charging voltage. What changes is charging rate. Voltage at the terminals changes according to battery internal resistance while charging,resistance of everything else that charges it and state of charge.
Old-school BMW used constantly 13,7-13,9 as normal "charging voltage" at normal temperatures. If battery is depleted (and not sulfated) it would absorb charge at 100A rate easily for many minutes.
New Leaf + LeafSpy: I observe voltage data in LeafSpy that is comparable with multimeter on the terminals. I've heard that with older model it was not calibrated correctly.

When I said "it charges" I meant that current is flowing in the direction of battery at acceptable rate. Also Leaf does compensate charging voltage (your 13.1V) according to outside temperature (sensor is on 12V current sensor).

There are different types of lead acid batteries and there are different types AGM batteries. Those that have thicker electrode sheets and those that have thinner (for cranking).
Also batteryuniversity and other random sites do mention there are different "100% charged" voltages for AGM batteries (manufacturer based like I understood).

Newer BMW-s do have very smart BMS. In addition to start-stop BMW implemented EfficientDynamics at the beginning of this decade. This clever system keeps AGM battery charged at around 80%. During hard acceleration generator is disengaged. System voltage drops to 12-12,5 according to electrical load. And while decelerating generator is not just engaged, voltage regulator is set to 15,4V for maximum current flow. This results in regen at 3,5kW rate. This is possible as AGM battery is constantly kept at 80% during cruising. And sulfation is not a problem at that SOC (applies to AGM only) as those batteries last for many years (about 300-400Mm, Megametre, 1000km)

Of course sulfation is a huge problem. It is the main problem for any deep discharge scenario battery :)
If it doesn't spend any more time at 14.5V than I have specified, then it has problems.

I'm sure normal voltage I observe on BMW-s is enough, 13,7-13,9V (fluctuates due to temperature) to not let battery sulfate. Except that if it is drained during resting periods of 5 days. That is bad.

Random unverified data. I have OEM BMW battery available and it rests at 12.7V after a long week of float charge and a week of rest.
Image

I will report back with 2014 Leaf voltages once I have some free time.

RegGuheert wrote:a lot
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arnis
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Re: 12v Battery

Fri Oct 14, 2016 4:20 am

RockyNv wrote:I tried going the AGM route here and found it was a mixed bag on my ICE vehicles. Here in Tampa Bay many times your best off with the lowest amperage traditional wet 12 volt battery required for your car with fill caps and a large case that holds plenty of electrolyte so you will see 5 years or so of usage. Many times when they pack in a lot of cranking amps into a small battery case you will only see a year or so of service even with an AGM. Sealed maintenance free just means short lived battery around here.

An old timer who rebuilt wet batteries for years told me that in our heat the best value will be from a taller wet battery with fill caps and plenty of room for electrolyte all around the plates especially above and below. In my RV I put in a float charger that goes into a desulfate mode automatically based on time, temperature and charging history.


AGM battery is not always plug-and-play with ICE vehicle. AGM is very very afraid of boiling electrolyte. Float voltage is lower than on normal flooded battery. But electrolyte does not tend to evaporate during normal operation as fast as flooded battery, especially in hot climate.

AGM accepts charge faster but if it is full it is bad to charge it further (or keep at 13,8V) . Something similar with Li-ion battery.
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powersurge
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Re: 12v Battery

Fri Oct 14, 2016 5:19 am

I have been with cars for many years, and have never heard so much arguing over a darn 12 volt battery!! Let's get realistic...

First, with the standard Leaf 12v battery... Buy a $40 plug-in "Battery Tender" for your garage, and every few weeks, or every month connect it to the battery until the "green light" lights. That means that your battery is fully charged. The Battery Tender is computer controlled, and can be left connected to the car indefinitely. I have a Miata that I do not use regularly, and it is connected to the Battery tender year-round.

When your small stock battery bites the dust, measure the size of your battery tray (and its height), go to Costco, and buy the biggest 12v battery that fits... EASY PEEZY.. PS - using this method, I still have a 10 year old battery in great shape in my car.

PS- for those without a garage or an outlet, get a Harbor Freight solar battery charger, and connect it to the battery when you are not using the car for a while.. I have this on all my cars that live outside, and the batteries are always fully charged...

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Marktm
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Re: 12v Battery

Fri Oct 14, 2016 6:10 am

powersurge wrote:I have been with cars for many years, and have never heard so much arguing over a darn 12 volt battery!! Let's get realistic...


powersurge - you think "on and on" discussions on this forum are excessive? - go to the off-grid solar forums for real excessive!! HOWEVER, battery/capacitance technology (IMO) is one of the important factors in our future success with our conversion to "renewable" based grid (and off-grid) energy supply.

I do agree, the 12 volt battery has literally been "beat to death" with good/bad information, but the more good information, the less dead lead goes to recycle.
2012 Leaf SL; 34,000 miles. 12 bars - Battery replaced November 1st, 2016.
4000 watts Grid-tied solar. 3000 watts (level II) off-grid solar Leaf charging capable.

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RegGuheert
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Re: 12v Battery

Fri Oct 14, 2016 6:46 am

arnis wrote:Also batteryuniversity and other random sites do mention there are different "100% charged" voltages for AGM batteries (manufacturer based like I understood).
And there are significant variations between different batteries of the same make and model. I have a "twin" to the battery which rests at 13.25V that rests at 13.0V.
arnis wrote:
RegGuheert wrote:]If it doesn't spend any more time at 14.5V than I have specified, then it has problems.
I'm sure normal voltage I observe on BMW-s is enough, 13,7-13,9V (fluctuates due to temperature) to not let battery sulfate.
Yes, you can charge at 13.7V to 13.9V. It just takes longer. But the Nissan LEAF NEVER charges at that voltage. It is either 14.5V (temperature compensated) or 13.1V (not temperature compensated). The result with our LEAF is that the 12V battery sits at about 60% SOC much of the time unless I intervene.
arnis wrote:I have OEM BMW battery available and it rests at 12.7V after a long week of float charge and a week of rest.
That's the symptom of a sulfated lead-acid battery: the resting voltage is lower than when it was new because some lead-sulfate has hardened. The result is that the battery is never fully recharged. If you use a high-quality desulfator, you will be able to recover some or all of the lost capacity.

The large (400Ah) AGMs that I am recovering currently have a resting voltage of 12.65V. Their current capacity is less than 50% of their original capacity when the resting voltage was 13.05V. When I got them, they only had about 100Ah of capacity and resting voltage was below 12.6V. These batteries are L16 style, which is tall and thin. As a result, they sulfate from the bottom up. It may take another six months or a year to recover all of their capacity, but I'm in no hurry since they are not in daily use.
powersurge wrote:PS - using this method, I still have a 10 year old battery in great shape in my car.
The OEM battery in our MY2011 LEAF is over five years old now and works like new by using a similar technique to what you do. I expect to get 10 years or more out of it.

FWIW, I will hate to see that OEM battery go, since it appears to be very well made and it came in a translucent case. That makes checking electrolyte levels a snap. Also FWIW, the battery has only lost about 10% of the water level between the full and empty marks in the five years I have had it.

By comparison, our MY2003 Honda Civic Hybrid used about ALL of the water above the lead in a couple of its cells in about 2.5 years of light use. The charging system in that car is opposite of the LEAF: it always charges at around 14.5V which keeps the battery from getting sulfated. OTOH, it uses significant amounts of water, requiring that water be added occasionally. I just have to be sure not to purchase a battery which cannot be filled.
RegGuheert
2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

arnis
Posts: 713
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Location: Estonia, Europe

Re: 12v Battery

Fri Oct 14, 2016 12:20 pm

Checked again. My findings.
It is true, that Leaf tends to keep system voltage at 13V. It does raise it as soon as windshield wipers are used.
If they park for more than 20 seconds voltage drops back to 13 something.

Also it appears that with any cycle (plugging in or putting car in Ready) it first goes to 14.x mode and (I expect) when
amps fall too much (or voltage gets too high) it switches to 13.x mode. And that is perfectly normal.
This can also be tested by draining 12V battery and then cycling the controller.

I also checked for amps going in/out. At 13.x there was 1-2A moving in.
After a wipe voltage raised but amps not much. That means my battery is completely full.
If voltage spikes to 14.6V and amps still don't rush in that clearly says battery is either sulfated or charged.



And most important for convenience: LeafSpy 12V reading is DEAD-ON. It does lag for a second or two but it
keeps numbers very close (max 0.05V difference). Anything less than 0.1V is marginal.
Now the last thing is to measure draw during sleep.

PS. Low end APC UPS devices tend to keep their AGM battery at 13.5V. This always kills them within only few years of use.
This means this voltage is too high. Nissan, most likely, tries to keep 12V not boiling. They, most likely, failed with standby
consumption. My vehicle is fine after a week of doing nothing. Had no opportunity to test for longer.

13.1V definitely charges the battery (very slowly) as OCV is lower for most 12V batteries, even AGM.
Though it is STILL unreasonable to keep system voltage (during READY or CHARGING) below 13.5V.
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