How's your 12v battery health?

[TLeaf]

12.27V for my little two-year old (this month!) SL w/ solar panel on this chilly Seattle day.

Even on a relatively cloudy Seattle day, I'd still think the solar panel could make a useful contribution to the SOC on the 12V battery; one of the reasons I'm glad my car came with one no matter how laughable the actual power output.

Point of interest => I work for an organization whose fleet had to move to AGM lead-acid batteries in order to account for parasitic power drains that were enough to drain a large capacity 24V system over the course of a weekend. We used to have to jump start roughly 1 out of every 10 vehicles come Monday morning, but changing to AGM batteries greatly reduced this #.

 

[DaveinOlyWA]

Not good. Low resting voltage but over 14 as soon as you turn the car on is not good. My resting was 12.27. Turned on car and it went to 13.08 after about 15 mins it was like 13.4 or so....

Batteries with wild voltage swings like yours usually means diminished apacity

SL Car/12 volt battery bought 1 1/2 year ago. Driven almost 17,000 miles.

Plugged car in (in garage) on New Year's Eve and Charged car to 80%. Did not drive anywhere on New Year's Day and left car plugged in. (No additional charging occurred that night- was also set for 80%). Normally drive car everyday, but not New Years Day so sat OFF for one day in garage.

Early Wednesday morning (garage about 45 F cool) made the following measurements:

Opened car door to pop hood and measure 12-volt battery voltage (door open lights went on briefly then off). Measured 11.89 V. Left car hood open for future measurements.

Next checked main battery status with CARWINGS, then a minute or two later measured 12 volt battery at 11.93 V.

Next left door open with door lights on and measured 11.73 V. Closed door and measured 11.87 V.

Next turned car auxillary on and radio on (closed door) and measured 11.53 V

Next car on auxiliary and radio off. 11.55 V. (Noticed CARWINGS was downloading something)

Next turned Car auxiliary off, but still humming 11.81 V. After humming stopped, 11.88 V.

Finally turned car ON a minute and measured 14.10 V (with car charging 12 V battery)

Not happy resting voltage was below 12 volts at beginning (11.89 V) - getting ready to go bad? Was CARWINGS draining? Just getting old? Cold weather?

 

[RegGuheert]

I will point out that you need to wait about 10 to 15 minutes after opening the door to pop the hood before you can get a measurement close to the resting voltage of your LEAF.

That said, even if you made some measurements with some of the systems still activated, I will say that measurements below 12V are concerning. That likely means the SOC for your battery is below 50%, perhaps well below. You could end up stranded some day if the car doesn't maintain your battery state higher than that. In addition, the lead sulfate in your battery is likely to harden, permanently reducing the capacity of your battery.

For the record, our LEAF 12V battery was at 12.46V this morning. This was after the car was charged for about 3 hours yesterday and driven for about 1.5 hours. Then it was charged for about four hours this morning. I let it sit for about 10 minutes before taking the reading to let the relays all click off and for the voltage to drift up close to its final value. (Also for the record, the voltage only dropped to 12.35 when the relays were activated.)

This is pretty typical for the 12V battery in our LEAF. I have never seen a reading below about 12.2V, even after the car sat for 7 days (unplugged).

 

[RegGuheert]

Not good. Low resting voltage but over 14 as soon as you turn the car on is not good. My resting was 12.27. Turned on car and it went to 13.08 after about 15 mins it was like 13.4 or so....

Actually, it is normal for the LEAF to charge above 14V if it senses the battery is at a low SOC. But it will later transition to a 13V charging voltage for most charging. I'm guessing Nissan uses the 13V charging to prevent overcharging since the LEAF spends so much more time charging the 12V battery than other cars.

But I don't understand why some LEAFs have battery voltages which appear to indicate a very low SOC. I'm wondering if these LEAFs may be used only for very short trips and therefore do not spend much time either driving or charging.

 

[mwalsh]

I just deleted a post where I told you how I just checked my battery immediately after charging and got 12.25v. But then I read RG's post about giving it 10-15 minutes. So I waited for the dash lights to go off and measured again. This time it measured at 12.38v. So clearly charging and waiting the 15 minutes is the way to go.

 

[DaveinOlyWA]

Not good. Low resting voltage but over 14 as soon as you turn the car on is not good. My resting was 12.27. Turned on car and it went to 13.08 after about 15 mins it was like 13.4 or so....

Actually, it is normal for the LEAF to charge above 14V if it senses the battery is at a low SOC. But it will later transition to a 13V charging voltage for most charging. I'm guessing Nissan uses the 13V charging to prevent overcharging since the LEAF spends so much more time charging the 12V battery than other cars.

But I don't understand why some LEAFs have battery voltages which appear to indicate a very low SOC. I'm wondering if these LEAFs may be used only for very short trips and therefore do not spend much time either driving or charging.

unlike most 12 volt charging systems, it would appear the LEAFs system does not put out large amperage so the voltage rise is not immediately up to the 14 level that is being inputted. for a battery that needs a charge, this is very normal.

keep in mind, the 12 volt battery has a load on it ALL the time.

if charging and it immediately goes to near the input voltage from 11 something, that means its on its last legs. most 12 volt chargers work on the voltage curve. it charges at full speed until voltage hits a parameter that varies by battery and type (flooded, AGM, etc) but is usually in the high 13's. then it reduces current to slowly approach its target voltage which is in the low 14's. his battery is at target voltage immediately after he plugs in which means its like filling a shot glass. u sip a little, u put a little back in.

example. this morning, i checked car, charging completed last night 3:30 am.

checked it at 6 am. 12.08 volts. its 22º outside, garage temp is in upper 30's
power on, check voltage at 6:02 its 13.04 volts

checked it at 6:10 its 13.07
checked it at 6:25 its 13.25

get the picture?

**edit** just drove to drop off kid at school, etc. come back check voltage before turning off car and its 14.6 volts. turn it off. wait 15 minutes, its 12.68 volts and i suspect still dropping.

but a "good" 12 volt battery under load should be in the mid to upper 12's. will be checking to see how fast it drops.

 

[RegGuheert]

unlike most 12 volt charging systems, it would appear the LEAFs system does not put out large amperage so the voltage rise is not immediately up to the 14 level that is being inputted.

Actually, my experience is that if the battery is low, it will immediately charge at slightly over 14V and then it will drop down to 13-ish V shortly after that.

for a battery that needs a charge, this is very normal.

So the question is why so many LEAF batteries are sitting at a low SOC. That is not healthy.

keep in mind, the 12 volt battery has a load on it ALL the time.

Sure, but it is a very small load after most of the system have clicked off. I have measured a resting voltage over 12.7V in our LEAF with the battery terminals connected.

if charging and it immediately goes to near the input voltage from 11 something, that means its on its last legs. most 12 volt chargers work on the voltage curve. it charges at full speed until voltage hits a parameter that varies by battery and type (flooded, AGM, etc) but is usually in the high 13's. then it reduces current to slowly approach its target voltage which is in the low 14's. his battery is at target voltage immediately after he plugs in which means its like filling a shot glass. u sip a little, u put a little back in.

example. this morning, i checked car, charging completed last night 3:30 am.

checked it at 6 am. 12.08 volts. its 22º outside, garage temp is in upper 30's
power on, check voltage at 6:02 its 13.04 volts

checked it at 6:10 its 13.07
checked it at 6:25 its 13.25

get the picture?

Most automotive chargers simply charge at a temperature-compensated voltage around 14.5V since they have no idea how much current is going into the battery or is being used elsewhere. But clearly the LEAF is different in what it is doing. It may use more standard deep-cycle battery-charging algorithms, as you are indicating, since it possibly has access to the battery charging current, but if this is what Nissan has done, then that was an unwise decision. Why? Because it is critical to get lead-acid batteries back to a 100% SOC quickly without overcharging. Those normal algorithms work because there is charge continuously available (or often, as in PV applications). But in the LEAF, charging is available only occasionally, at best.

I'm not sure what Nissan has chosen to do, but it seems there are WAY too many issues with 12V battery discharge in the LEAF.

In your case, Dave, I would say that a reading of only 12.08V a couple of hours after a charging session is really too low.

 

[DarkStar]

Checked mine last night: At rest it was at 12.55 volts. Fully charged, a 12 volt battery should read 12.7 volts at rest.

Here are no-load typical voltages vs state of charge (figured at 10.5 volts = fully discharged, and 77 degrees F):

State of Charge   12 Volt battery   Volts per Cell
     100%              12.70             2.12
      90%              12.50             2.08
      80%              12.42             2.07
      70%              12.32             2.05
      60%              12.20             2.03
      50%              12.06             2.01
      40%              11.90             1.98
      30%              11.75             1.96
      20%              11.58             1.93
      10%              11.31             1.89
       0%              10.50             1.75

 

[DaveinOlyWA]

Actually, my experience is that if the battery is low, it will immediately charge at slightly over 14V and then it will drop down to 13-ish V shortly after that.

ok then it would seem mine would have gone to 14 volts right away then and it did not even after it was on for 15+ minutes. has anyone ever seen a voltage below 13 when car was in ready mode?

wondering if the car is providing the 12 volt feed and taking the battery out of the equation. then that would mean the 13 volts seen immediately after power on is not a result of a 14.5 volt feed and the drop across a low SOC battery?

check my edit. after a short 15 minute drive, i come back and LEAF is at 14.6 volts. i shut it down and checked it after it sat it a bit and its at 12.68 volts.

if your supposition is correct and the only time the battery is being charged is when its reading the 14+ volts then maybe short trips are too short to effectively charge the battery and over time, the SOC is slowly wearing down?

 

[RegGuheert]

check my edit. after a short 15 minute drive, i come back and LEAF is at 14.6 volts. i shut it down and checked it after it sat it a bit and its at 12.68 volts.

It appears to me that both your and mwalsh's batteries have very little of their capacity left. To charge a lead-acid battery from below 50% SOC to full should require many hours, particularly if the charger is limiting the charging voltage to around 13V.

I'w wondering if there might have been some firmware issues in the 12V charging system of the early LEAFs.

 

[Herm]

Traditionally anything below 12V no-load resting voltage for a fully charged lead acid battery is considered dead.. you should let the battery rest disconnected from any draw for a couple of hours before measuring. Some people say overnight.

 

[DaveinOlyWA]

check my edit. after a short 15 minute drive, i come back and LEAF is at 14.6 volts. i shut it down and checked it after it sat it a bit and its at 12.68 volts.

It appears to me that both your and mwalsh's batteries have very little of their capacity left. To charge a lead-acid battery from below 50% SOC to full should require many hours, particularly if the charger is limiting the charging voltage to around 13V.

I'w wondering if there might have been some firmware issues in the 12V charging system of the early LEAFs.

i agree that it would take much longer to charge a near dead battery or even one that 50% SOC but...

just checked checking every 30 minutes it actually went UP from the 10 minute check to 12.74 from 12.68 volts. its been 90 minutes now and still holding at 12.72. remember it was charging and at 14.6 volts before powering off after only a 15-20 minute drive which leads me to think that the 13 volt measurement is not "charging" but the inverter simply supplying the 12 volt system when the car is on. then the charging cycle kicks in and it goes to the 14+ volts. now mine being so high at 14.6 volts in such a short period of time i think is probably not good.

i need to start checking to see how fast the voltage drops off when parked. either way, getting ready to head out for a few so will be checking it some more

 

[RegGuheert]

just checked checking every 30 minutes it actually went UP from the 10 minute check to 12.74 from 12.68 volts. its been 90 minutes now and still holding at 12.72.

That's a good voltage which indicates you are right around 100% SOC.

i need to start checking to see how fast the voltage drops off when parked.

I agree you should check that. I have posted data somewhere here showing our unplugged 12V battery voltage, including one 7-day period during which the car was not touched, including not even opening doors. That should be a reference point. If your voltage drops off much faster than that, then you either have a much larger current draw or the battery has lost significant capacity or both.

FWIW, when I went out this afternoon I tested the battery voltage with the remote climate control running while charging. The voltage was 14.70V, which should be about right for 35F.

 

[Boomer23]

21 month old SL with almost 20,000 miles. Car sat in garage for 8 days unplugged with 59% Gid (63% SOC by Gidmeter's new firmware). Measured 11.9 V before starting car this morning at about 50 degrees F ambient.

Car has not been charged for 8 days.

After driving 20 miles and sitting in sun for about 2 hrs, measured 12.2 V with car off, 13.03 V with car on, radio on.

By the way, HV battery charge did not degrade significantly in 8 days unplugged in closed garage. Gids before trip 173, after 8 days Gids 169.

 

[LEAFfan]

2011 SL, 19 Mos., driven 22 hours ago, 61F ambient now, 12.59V (a little higher than when new)

 

[DaveinOlyWA]

ok, some more info. pretty convince when the car is on, it regulates output of 12 volt system to 13.1 ish.

i took off, came home and checked voltage before turning it off and it was 13.06 then turn it off, plugged it in and went inside. came back out about an hour later and checked it and it was at 14.6 again.

about 20 minutes after that, came out and checked it was back to 13. unplugged and took off. came home. powered off, unplugged and it went the 12.72 volts after 10 minutes and stayed about the same for the entire 2 hours that I was home

so apparently the 13 volt reading is what the car maintains the 12 volt system at while its on. now my battery "seems" fine but still a bit disconcerting that it was barely over 12 volts this morning. wonder what would have happened if I had let it sit all day before going anywhere?

 

[RegGuheert]

21 month old SL with almost 20,000 miles. Car sat in garage for 8 days unplugged with 59% Gid (63% SOC by Gidmeter's new firmware). Measured 11.9 V before starting car this morning at about 50 degrees F ambient.

By way of comparison, our LEAF went from 12.60V to 12.38V while sitting unplugged for seven days. You can see the measurements in the graph in this post for days 14 through 21.

 

[DaveinOlyWA]

21 month old SL with almost 20,000 miles. Car sat in garage for 8 days unplugged with 59% Gid (63% SOC by Gidmeter's new firmware). Measured 11.9 V before starting car this morning at about 50 degrees F ambient.

By way of comparison, our LEAF went from 12.60V to 12.38V while sitting unplugged for seven days. You can see the measurements in the graph in this post for days 14 through 21.

that graph is a perfect illustration of what the LEAF 12 volt system was designed to do but problem is, most are seeing the same curve action but half a volt lower and that is cutting it too close.

 

[JeremyW]

12.42 V after being previously driven an hour and a half ago for a short trip (5 mi with a lot of CC use). Car is 11 months old.

I foresee many more 12V battery failures in the upcoming months. Lead acid loves to be full as much as possible. These voltages you all are reporting are downright abysmal. :? Except for LEAFfan who seems to being doing fine.

Charging the car now for an hour on L2 to see what my aux battery voltage recovers to. Edit: ~12.8 after unplugging, 12.78 after sitting for 15 min.

Here's a good deep cycle lead acid FAQ, which covers a lot in the world of lead.

 

[surfingslovak]

Here's a good deep cycle lead acid FAQ, which covers a lot in the world of lead.

Very handy! Below is the SOC vs voltage table from that FAQ.