Leaf Service EV System Adventures with P0AA6-1A and a Suspect 12V Battery

[knightmb]

This is more of documentation of my experience diagnosing an issue with a relatives 2018 Nissan Leaf. Hopefully this can provide useful information for anyone else in the future that runs into this dreaded error and left stranded.

It started with a call from a panicked relative early in the morning. They tried to start their Leaf in the early hours and got the dreaded "Service EV System No Power" screen. I wouldn't have time to take a look at until around noon, but what choice did they have short of towing it to Nissan and paying a diagnostic fee?

Anyway, fast forward to around noon, I arrive and bring all my equipment and tools with me. The first thing I noticed was the cabin light looked very weak, hmm.
So this is what LeafSpy was able to tell me about their issue (screen shot below). Yeah, that does not look good. But then I noticed the 12V system voltage, it was really low for just getting the dash switched on in standby mode so I could run LeafSpy. 11.44V with only a 24 watt load? I'm starting to suspect the 12V battery. But I don't want to seem like I'm being bias against the poor 12V battery. So I open the hood to take a look at the 12V battery itself. Well, it's an original Nissan factory battery!
Going by the thick later of dust and dirt, no one has probably touched it in years.

Before I start giving the 12V battery the evil eye, I need to check if that P0AA6-1A code is a real concern. Grabbing my socket set and HV gloves I disconnect the 12V battery from the Leaf. I then find a good grounding spot on the frame and then I remove service disconnect from the center of the pack. I use my multi-meter to check both contacts down in the plug to see if any voltages appear between both sides of the pack and vehicle ground. After a long wait for the capacitance to finally zero out the voltage, I am about to confirm that no voltage leaks were found while testing the battery pack. Something interesting I did see after waiting for 0 volts was that the wind blowing across the Leaf was able to generate some Milli-volts of potential from what I can only guess is static build-up. It was weird to see it detected on the meter, but I am pretty certain that some Milli-volts of static potential would not be enough to set off the safety system for that. Nissan must have coding safe guards from something like that.

So I carefully put the service disconnect plug back in, bolt everything back together, snap the plastic cover back on the center, etc. My focus will be on the 12V battery now. I measure the voltage of the 12V battery since it's been disconnected from the Leaf for a while now. Low and behold, I seem to get a solid voltage reading of 12.62V. The weather is warmer now than it was in the morning, so maybe the 12V battery just appears to be ok?

Regardless, I'm going to hook a charger to the 12V battery and top it off before connecting it back to the Leaf. Since it appeared to be mostly dead before, I figured it was going to be a long wait to charge it back up before I re-connect it back to the Leaf. Nope, only took an hour to fully charge it.
Well I knew something was wrong then because I was using 1.5A charger and putting 1.5AH back into a battery rated for 43 AH in no way means that it was fully charged at that capacity. It just means the voltage might appear fine, but once a serious load is applied it will probably quickly fail.

So, I hooked it back into the Leaf anyway to see how it would perform. The voltage appeared to be much more stable now and I was about to clear out all the DTC issues with LeafSpy. I then shut it off, took a 15 minute break, came back to fire it up to see if any more DTC issues arise. Everything appeared to be fine now, not a single DTC, nice!

Final conclusion, I blame the 12V battery. Not that it's impossible that if the internal battery was touching the case somewhere, maybe the warmer temperature fixed that? I highly doubt that, so I think this dying 12V battery is making weird things happen. So, I talk with my relative about options, mainly about replacing this +5 year old Nissan OEM battery with something better. I could be wrong of course, but my next step is to do some load test on the 12V battery from various auto-shops to see what they think and finally I will do a full charge/discharge capacity test to see how much capacity the battery actually has. My guess would be it's so low as to be useless when actually called on to produce a lot of power for any extended amount of time. For now, they want to go the route of "please fix forever", so I'm going to have to do some research to see if I can find any 51R LiFePO4 size batteries (so I can drop-in replace it without having to do custom wiring), but not in the full AH size they don't really need 100AH of capacity for the Leaf but more like maybe 25AH to 30AH to avoid spending a fortune on it. For now, I told them I would not trust it drive around very far away if the 12V fails again and just leave the Leaf "on" and turn off all accessories if parked; if they need to run any errands until they get home and then shut it off at home just in case. I also left them my trickle charger and showed them how to keep the 12V battery topped off until a new replacement can be swapped.

At least I saved them a tow truck fee and Nissan diagnostic fee which could have probably resulted in the dealership charging them a fortune to replace the OEM 12V battery with another Nissan generic.

My next topic update will be when I can get a hold of that 12V battery, inspect it for damage or other issues and run it through more detailed testing of it's capacity.

 

[cornbinder89]

That is the way it should be done, not much time involved,just good diagnoses procedure. You followed it though to a point to where it does point to the battery and you can be reasonably sure of what you are replacing.
I can't help pointing out this would be 1 for 4 over the last few weeks where the 12 volt looks like it was the cause, but the other 3 were not. Still not odds to replace without testing and diagnosing. Of the other 3, two had the battery changed and it did not resolve the problem, the one that as far as we know, did not, had a traction battery showing 0 and was towed to the dealer. Very unlikely that the 12 volt "failed to keep the HV battery charged!"
When I bought my Leaf, I asked what had been done. He told my only Brakes and a 12 volt to replace the original. Yesterday I went poking about and found the date code on the replacement, It was built in Sept of 2022. so the original battery lasted at least 7 from when placed in service, longer depending on when it was made. More than double the lifespan many here say. Your 5 years would be on the low end in my book. I also looked at the Gp51 in my tractor, it has 6 year on it and will start the diesel below zero.
I also ran some baseline tests of the charging system protocol, just for my own education. Instantly starts charging from the HV battery when key on, also when the EVSE cord is inserted. Just as the manual said it would. .
On any "dead battery" call out, I always check the charging system. As most can figure out, if it is not doing its job, it can CAUSE a dead battery.
Thank you for reporting what you found, and I'd be interested on how the old battery fairs in the other tests you mentioned, esp after a long slow charge on a charger to "full".
We all can learn if people post what they did, what they found and what works and what doesn't. That is where the strength of a forum can lie.
HV battery isolation problems can be difficult, as is shown in Dala's video, they can come and go depending on battery expansion and contraction. Even he bought a pack with an Isolation problem, and even when he could resolve the module that was causing the problem from leaking voltage to the case, decided to replace the module anyway, After putting the battery in, having to pull it back out open and disassemble he was not willing to take the chance of having the problem re appear and doing the job all over again.
Thanks again for the write up.

 

[cornbinder89]

Re reading what you wrote, one other check comes to mind. You wrote that the battery voltage came up when it was disconnected from the car while you were checking the HV isolation. That points to a draw on the battery, it could be just interior lights from the doors being open or a really weak 12 volt or it could be more. Worth checking out before you walk away. Any key off, doors closed draw over just a few milliamps will be a problem you'll have to hunt down.
You seamed surprise by the "24 watt load" bringing the battery down, but that depend on if the load goes away when the car is parked. A typical halogen headlight is only 55 watts and the 24 watts is close to leaving the taillights on if continuous. If it is there all the time, how many of you would expect to be able to leave your taillights on over night and not flatten the battery? It is why it is important to check for "key off" loads when diagnosing a "flat battery" problem.

 

[knightmb]

I'm going to "loan" them the 12V SLA battery from my 2020 (I kept it and took care of it, no need to waste a battery) until the replacement is swapped. They can drive without worry and I can fully charge the suspect battery and take it around town and let various auto-shops use their battery testers to give me a pass or fail. Even if it passes all of them, I'm still going to do the very lengthy capacity test to see what it can really do.

Yeah, it surprised me because I had all the accessories off, lights off, etc. It was the middle of the day, much warmer than the previous night where temperatures were just below freezing. That was just the power of the dash being on, probably the cabin lights, whatever computer systems run in standby mode. Relative to the battery size, it should not be struggling with 24 watts of power.

I did have them relay to me exactly what happened that morning. They got into the Leaf, it was freezing cold, it had been charged via a timer, so it wasn't exactly 100% SOC, closer to 95% I think when I looked it later. So the EVSE had been plugged in all night. They unplug the EVSE. They got in, tried to turn it on and the dash just went "dark" they described. Nothing happened, no beeps. So when that failed, it was still in standby mode where the cabin fan was running (auto-heat setting), lights were on (they use the auto-lights setting), radio playing, seat heater was on, steering wheel heater, etc. They are not technical, so I don't blame them, but they were trying to "start" the Leaf with all of these accessories running at the same time , so I imagine the battery voltage was pretty darn low already. Finally after a couple of tries, the message came up. I asked to clarify, this message did not come up first right? It only happened afterwards of trying to start a few times. I asked if they noticed anything, they mentioned dim lights, flickering cabin lights when trying to start, a clicking noise every time the start up failed until the message came up. That was probably some accessory relays dying and coming back to life. I also asked them about their electronic parking break and rear tire pressure because I saw codes for these, they said they never had any issues with those, so I don't know if those codes were also produced because of a failing 12V battery or if they have just been there for years.

 

[cornbinder89]

Does the '18 have an "electronic parking brake"? I know the early ones did, the mid ones like my 2015 have the foot pedal I have no idea about the later ones.
Don't over look battery post connections , dirty connections that can't handle current can still effect Leafs just like a conventional car.
I think the important take a way is do the work, don't guess.
On a side note, I was trying to read up on the P0AA6 code because it is a bad one if the condition exists for repair, not cheap and easy. Dala's video shows his, and while he didn't list costs they weren't small, and that doesn't include his labor.
Anyway in my reading, and I'm not 100% sure on this yet. A true P0AA6 code isn't only for the HV battery, but could be anywhere in the HV system. Unfortunately, just about any componant in the HV system is going to be costly. So PDM/inverter, Charger, AC compressor and drive motor all could have a HV leak and set the code. I also looked to see if it said how much of a "leak" had to be present to toss the code, and so far haven't found that info.
Please follow up with all you find out.

 

[cornbinder89]

To be clear, I have never said a 12 volt can't fail and/or leave erroneous codes, at best it looks like this one is weak. If they had turned off the pre-heater, heated seats/steering wheel and auto headlights, before dis connecting the EVSE, my guess is it would have started fine. That doesn't change the condition of the battery one bit, but could point to why the erroneous codes get set. I would try and coach them on better starting protocol, for less chance of problems in the future.
I never want to start anything under load if that is possible. The car will run in "pre-heat" mode for a set time after the EVSE is disconnected, I don't remember the time limit but have read it somewhere.
When I deal with something like this, at the end I check the charging system with a carbon pile (yeah, I'm old school) clamped on the battery cable ends of the battery terminals, this will show not only if the charging system (via a clamp on ammeter) is up to snuff but will "load test" the cable connections.
Out in the field, I have diagnosed many poor start, by cranking the engine and feeling each cable and cable connection for heat. Any warm/hot ones are bad. Not the best way, but if you are working away from shop equipment and on the side of the road somewhere, it is a fair "quick and dirty" test.
If your "few year old" L/A battery was well cared for in its storage, they should have plenty for time without problems for you to source a new replacement for them. No Battery will never fail, and if I can see 7+ years from a flooded cell lead acid, the cost factor make them my "go to" battery. It is just hard to justify the cost difference for an admittedly better chemistry battery.

 

[knightmb]

Does the '18 have an "electronic parking brake"? I know the early ones did, the mid ones like my 2015 have the foot pedal I have no idea about the later ones.
Don't over look battery post connections , dirty connections that can't handle current can still effect Leafs just like a conventional car.
I think the important take a way is do the work, don't guess.
On a side note, I was trying to read up on the P0AA6 code because it is a bad one if the condition exists for repair, not cheap and easy. Dala's video shows his, and while he didn't list costs they weren't small, and that doesn't include his labor.
Anyway in my reading, and I'm not 100% sure on this yet. A true P0AA6 code isn't only for the HV battery, but could be anywhere in the HV system. Unfortunately, just about any componant in the HV system is going to be costly. So PDM/inverter, Charger, AC compressor and drive motor all could have a HV leak and set the code. I also looked to see if it said how much of a "leak" had to be present to toss the code, and so far haven't found that info.
Please follow up with all you find out.

Yeah, has the exact same one that my 2020 has, the switch is between the front seats in the center console. If that had failed, they certainly would have noticed or remembered that I hope. It's hard to forget that you can't set the parking brake.

Good idea, I do have one of those metal brush terminal cleaners so I made sure everything was shiny and clean. Cleaned out the clamps for the battery post as well just in case.

My hopes are the codes do not return since the only variable right now is that they have my loaner 12V battery. If it happens again, I'm not the one that is going to be taking the pack apart to check each component, will leave that up to Nissan techs.

 

[cornbinder89]

Yeah, me too (on the codes) I don't want a HV isolation to be a common fault on these cars, it would make them economically un repairable, if they have an insulation problem as they age. But as you found in this instance, it doesn't seam to be that way every time the P0AA6 code pops.
Unfortunately for the one member here, he cleared it and it came back, but that doesn't mean every time it rears its head it is true.
I'd love to ask Nissan, what the heck is wrong with a foot operated E brake? Simple, effective, only drawback is the cables can rust, but tend not to if used on a regular basis.

 

[knightmb]

More data from today's 12V battery saga. I found out today the battery is not the original, but a replacement from 2020. It seems back in 2020 they had an "EV Service" issue after trying to fast charge at a QC station. They could no longer QC the Leaf, but it was still drive-able. When they took it into Nissan, they were told the 12V battery was bad and it was replaced under the original bump-to-bumper warranty. The sounds a little suspect to me since that DTC error could easily be reset in LeafSpy. But it was free warranty work and a free battery, so who am I to judge the dealership.
So the 12V battery is roughly +4 years old now.

I have the suspect 12V battery at my home and I clean it up and check the water levels in the battery. Everything appears to fine, didn't see any cracks or damage on the battery visually anyway.

I top off the battery again to 14.4V so I can take it around town and have it tested at a couple of shops and battery stores.

My first stop was O'Reilly Auto Parts. They have a large machine that can print out test receipts, so they put that tiny battery (relative to how large the machine was, it looks like it could test batteries the size of a person ) They input in the CCA rating for the battery (410 CCA) and do (2) back to back test because I asked them too.
The battery passes as good. I did notice during the test that the battery voltage dropped to 9V during the test, but I seem to remember that putting a SLA through a high load test like this will result in large voltage sag so usually normal.

Next I move on to Batteries Plus to see what their 12V mobile testing device shows. The print outs for it were not working, so the guy was nice enough to let me take a picture of the results. It passes as good again, but I did notice that it was not able to reach the max 410 cranking amps during the test. I noticed this as O'Reilly Auto Parts as well. 377 cranking amps isn't bad, it's still around +91% of the original rating. For all intents and purposes, this 12V SLA appears to be fine for its age. I'm sure it would be able to crank up an ICE vehicle just as easily. The final test will be the long and boring capacity test. So I have the battery on the charger again and waiting for it to reach full charge before I start this long test.

More to follow in 20 hours or less, depending on how long the battery lives.

 

[knightmb]

I'd love to ask Nissan, what the heck is wrong with a foot operated E brake? Simple, effective, only drawback is the cables can rust, but tend not to if used on a regular basis.

I said the same thing because my 2013 had the foot brake that never had any issues. When I moved to the 2020 I thought of the e-brake as kind of "gimmicky" and my initial thoughts were "well this e-brake thing will probably fail in a few years" but surprisingly after so much constant use, it still works without any issues. It is convenient in that if I'm parked on a steep hill and I need to reverse up it, I just apply some power and it automatically disengages and then the motor can take over to move the Leaf. I am kind of spoiled by that feature now (works in forward too).

 

[cornbinder89]

My mind is not what it used to be, but from what I remember, to pass a carbon pile test it shouldn't dip below nine volts.
Given what you are finding, I would take a hard look at the DC to DC charging system on the car and make sure it is functioning as it is supposed too. To be that "dead" and still be able to kick out some amps in a load test, makes me worry something is wrong with the charging system. It could be as simple as a corroded terminal at the battery, High resistance, the current drops off quick, the Dc-DC sees that as a full battery and drops to float, and the poor battery never gets charged fully.
Unless they were using one of those meter that just checks the internal resistance and uses an algorithm to "guess" at output amps.
Given what you see so far, I'd put that battery back in a car.
I still have a carbon pile load tester, and like it a lot better than the "input your battery and WE"LL decide how to test it" type testers.
One shop I worked at had a Vat that you had to enter the VIN to test the alternator, owner couldn't understand why I wanted the old VAT back and on occasion threatened to toss is new high dollar machine in the nearest creek!

 

[knightmb]

I'm posting this test result sooner than I expected, but here is the technical data. I first started with a fully charged battery.
To do a capacity test for a SLA, you need to convert the Amp-hours to something that can be measured. Watt hours is an easier metric to work with, so simply take nominal voltage for the battery, 12V and multiple it by the rated amp hours and you come up with (12V x 43AH) = 516 watt hours. But... this is a SLA, so you can't run a 516 watt load for an hour. SLA batteries have to be measured over a 20 hour period. Why? Well blame that on manufactures I guess. It looks more impressive to say a battery has 43 AH than to say it only has half-that if you try to use it all in an actual hour.
So, that means we have to take the watt hours and divide that by 20 and that is the hourly load to test with; to match up with the battery specs. So, (516 / 20) = 25.8 watts per hour for 20 hours until the voltage reached the depleted state of 10V. That means I only need to create a 25.8 / 12 = 2.15 amps test load.
The closest I can get to this was to use an inverter to run a fan at a constant speed for a constant load. But, it's running a little more than needed at 2.359 amps. That shortens the 20 hour test window since I'm using more power, but I can work out the math later to determine what the "tested" capacity ended up at. So I really expected to start this and probably by tomorrow morning I would know a result. That was the plan anyway.

Well, didn't have to wait that long. After only 3 Hours and 49 minutes, the battery was depleted to 10V. A lot faster than I expected, very surprising actually.

So what does that mean then? Here's the math for it.
2.359 amps with a 12V nominal works out to 2.359 amps x 12V = 28.308 watts per hour
Converting the time to a decimal number, that's 3.82 hours x 28.308 watts per hour = 108.14 watt hours total.
Total amp-hours (AH) would then be 2.359 amps x 3.82 hours = 9.01 AH
So this battery capacity is operating at roughly 9.01Ah / 43AH = 21% of it's rated capacity, ouch.

Ok, certainly has some capacity issues, but why did it pass literally 3 back to back load test from two different stores? Well, I needed some more math to figure that out, but I first had to do some research. I ended up going online to look up the manufacture of the test devices used at those stores to download the user manuals.
I needed to find out how long they test for and how much power they use during a test. As luck would have it, they both seem to standardize around a 120 amp test load and 10 second test duration. With those numbers I can work out that if the battery was fully charged, why can it past the load test but fail the capacity test?

More math fun. I did observe during the test that the battery voltage dropped to +9V during all the test. According to the manuals, +7.2V or higher is the passing voltage for the SLA battery family. Knowing that, it's easy to figure out the power per second. So 9V x 120 amps = 1080 watts. So each second of testing was pulling +1080 watts of power. To convert watt seconds to watt hours, you take 1080 watts and divide it by how many seconds are in an hour, which is 3,600. That gets you 1080 / 3600 = 0.3 watt-hours per second. The test was 10 seconds long, so simply multiply that out and you get a final number of watt hours each test is draining in capacity from the 12V SLA or 0.3 x 10 seconds = 3 watt hours for every load test. I did (3) load test, so I drained the equivalent of 3 x 3 = 9 watt hours of capacity for 30 seconds of testing. That means I could have run the test 108.14 / 3 = 36 times in a row. Realistically, the battery capacity would plummet even faster trying to do that many high power test back to back. Should I have tested the battery over and over until it failed? Who really does that when checking for a "good" battery? 2 times, maybe, 3 times, kind of pushing it, but 4 or more for an automotive battery? You can only imagine the comments you would get from staff if you wanted to run a battery test that many times in a row. Seems like you are just trying to kill the battery on purpose at that point.

If this battery was being used in an ICE vehicle the "engine cranking" would probably be more than enough to never know that the battery has a major capacity shortage.

But, it's being used in a Leaf and if the charging system does not keep this battery at maximum (that it can handle) capacity all the time, throw in cold weather and a poor charging routine to create a disaster recipe for a Leaf that can't simply turn on anymore unexpectedly. Throw in some random dash errors, then you feel sorry for the non-technical EV owner because they never saw stuff like this driving ICE vehicles.

Conclusion: Battery needs to be replaced. Sure, it can pass a load test just fine, but if the capacity is this low now, it's only going to get worse with time.

Also:
Do any methods exist to restore the capacity of a SLA battery?

 

[nlspace]

That's a great set of test data. Thanks for running it.

How long did it take to fully charge it when out of the car?

You can see the tricky part when you disconnected it and the voltage recovered up to 12.62 --that would be considered a "good" battery by nearly everyone.

But only after doing the capacity test (or measuring specific gravity of the electrolyte), could you see how degraded it really was.

Add a less-than-fully charged condition on a bite-ass- cold morning with a 4-year old battery => asking for trouble starting/ lots of DTCs/ possible lack of HV charging, etc.

You might be able to recover some capacity using a so-called smart charger that charges up to 14.4, holds it there a bit, and then does an series of pulses or sinusoids. i have dismantled and tested dozens of those small tender-types, and the best i found was the Yuasa 1A smart charger, about $40 at motorsickle shops. Check out Yuasa's website for tech battery info.

This type of charging cycle can partially desulfate a worn out battery but it takes a long time and may not be worth the effort. Lots of variables affect restoring degraded capacity.

The lead acid batteries need to be kept fully charged all the time or they will become degraded due to sulfation damage and will shorten their life.

Hot weather shortens the service life, but Cold weather reduces the available capacity.

 

[cornbinder89]

So , what you came up with is: after the equlvliant of leaving you parking lights on for 3 1/2hrs it wouldn't have the power to start the car, nothing too surprising there.
I can give you history lesson on why the 20hr rate was used for batteries, but the long and short of it is, that is the std all storage batteries are rated at, Some will also list capacities at other rates, but 20 hr is the std used. Not mfg choice.
I'd say you still need to confirm the charging system is in good working order and the connections are clean.
While your test shows it isn't great, I wonder how you came up with the amp draw? I have the exact same fan and running it on an inverter on low, it was drawing closer to 5 amps on my meter. Inverter efficiency and other small loads I had on in my truck may account for the difference. I used to sleep with that fan on all night.
Remember, when you saw it back in the car with the key on you had a 2.4 amp draw, so your tests show it could do that for over 3 hrs, so it should still start the car.
The way the charge protocol works on the Leaf: when 1st started, the charge voltage goes to 14.5 volts, the Dc-Dc converter monitors the voltage, amps and battery temp via the connection/shunt at the battery, For that to be accurate, the post connections have to have low resistance, Once the current the battery will accept at 14.5 falls below a set value the DC-DC converter starts to taper the charge voltage down to float.
1st order of business would be check how clean the connections are, then check the voltage reaching the battery on start of charge, if you are seeing anything less than 14.5 volts, start looking for bad connections in the charging circuity. If you have a good inductive ammeter clamp it on one batter lead and see at what current the DC-DC starts tapering to float voltage. Check against spec.
For any charging system to work, the voltage drop across connections has to be kept low, this is even more important on a system and usage like the Leafs. If not kept in good working order it will undercharge. Because the Leafs usage is low, the recharge regimen is different. My cars and other have reported battery life that rivals any other automotive use battery. Mine at 7 years+ is about mid range of what I would expect. So saying the Leafs system is faulty doesn't fly. It can and does work.
You can keep the charge voltage up by turning on the wipers if you need more time to check connections on the "high rate" cycle of the DC-DC charger.
To answer the question on reversing sulfation in lead-acid batteries, I haven't found a way once it has set in. some claim success with pulses of high voltage, but from what I've read, it doesn't do much for a battery where the sulfation has hardened. Equalization charges do more to prevent it in 1st place than anything can once it has happened.
That battery has shown it still has enough power to start the Leaf, even if not up to original std. My guess is the discharge from running the 12 volt accessories without being connected to the EVSE along with some poor connections in the circuit caused the no start. Any replacement will suffer the same fate eventually if the poor connection is not found and fixed. If it was the battery post itself, than replacing with another battery would do that, or cleaning the old one would do the same. Most people with a conventional car, don't get in and turn every accessory on high before trying to start, and most cars cut these things off when the key is in the start position anyway.
If the charging has and remains poor, any battery put in will suffer a short life. SO CHECK the charging!

 

[knightmb]

While your test shows it isn't great, I wonder how you came up with the amp draw? I have the exact same fan and running it on an inverter on low, it was drawing closer to 5 amps on my meter. Inverter efficiency and other small loads I had on in my truck may account for the difference. I used to sleep with that fan on all night.

I put my meter in-line with the 12V connection to the inverter. (it looks real messy in the picture) The fan actually uses less power, but the inverter needs power itself to function. For that exact reason, I needed to see the power draw of the entire system. It was actually a little too high, but I couldn't find anything else to get close enough (like some old school light bulbs, etc.) The inverter has the added bonus of keeping the power draw constant (for the fan) as the voltage of the battery changes over time and it has a very loud and annoying beep when the voltage gets into the low 11.x voltage range to let me know when I need to start paying attention to it.

Compared to your truck battery, this battery is probably "tiny". It's the smallest SLA automotive battery I've seen in my experience with ICE vehicles over the years. I am curious about doing a capacity test on my loaner 12V SLA to them now when I get it back.

Great advice for the rest, I just didn't put all of your original quote in to save space.

 

[cornbinder89]

Yes, it is tiny in comparison. Depending on which truck (which foot print battery group and how many) I had up to 620 amp/hr in the truck. The inverter was bigger also and might be less efficient at lower loads. Most nights I didn't use much, but very cold and fairly hot I used more. At -25F, running a diesel fired heater all night and a fan with the reduced capacity lead acid sees in the cold, came close on some of the smaller pack, which was just over 400 am/hr.
With the Leaf's use and re-charge system, the old adage of 0.3 volts drop per connection would not be valid. You can use the voltmeter to check the connection under load, the connection being the resistance and the meter being the shunt. Any small resistance in the circuit could result in the float voltage actually reaching the battery to be too low to prevent sulfation.
I think this time around it is neither totally a battery problem nor totally not a battery problem. Test show it has degraded a fair bit but also that it can provide what is needed to start the car. A new one would, at least for a long while, relieve anxiety over if it will go in the morning, but I would still be using the old battery myself after checking and cleaning cable connections.

 

[knightmb]

Remember, when you saw it back in the car with the key on you had a 2.4 amp draw, so your tests show it could do that for over 3 hrs, so it should still start the car.

That is a good point and I've seen it posted here over the years about using a jump from another car's 12V battery or using a plug in charger to top off the battery and then try to start the Leaf. My only counter to this logic would be that with a 2.4 amp draw, you would have to add in the additional +185 watts of power to engage the traction battery and since the 12V battery voltage is usually low in those circumstances, taking the battery I am working with above at the time taking voltage readings that show 11.44V means it would take an additional (185 amps / 11.44V) = 16.17 amps plus the 2.4 for a total of 18.57 amps for a few seconds to properly start that trouble Leaf. Basically 185 + 24 = 209 watts of power.

As a human, that seems to me that the battery should be about to scoop out +209 watts of power for a few seconds, but I don't know at what voltage that would be produced. Just because I calculated that 11.44 volts should be about to do this at 18.57 amps doesn't mean the battery itself is going to hold that voltage at that power load. It might drop to 9V or 10V to do that. In an ICE vehicle, the voltage dropping low isn't a big deal as long as that starter can turn, but in the Leaf for some reason, Nissan is way to picky on the voltage tolerances it seems.

 

[knightmb]

I think this time around it is neither totally a battery problem nor totally not a battery problem. Test show it has degraded a fair bit but also that it can provide what is needed to start the car. A new one would, at least for a long while, relieve anxiety over if it will go in the morning, but I would still be using the old battery myself after checking and cleaning cable connections.

I agree, once I had the battery charged up, it appears to work fine in the Leaf and technically the degraded capacity isn't a big deal as long as it can churn out a few hundred watts of power for a few seconds, much much less stress than trying to spit out +1000 watts to start an engine.

I will take your advice from all the other postings you have here and check everything for some weak points to address. In theory, they could put a 12V battery maintainer on it every full moon just to make sure the battery stays properly topped off if they decided to stay with it. I have a feeling though, technical discussions aside here, that "one time the Leaf didn't turn on because of the old 12V battery" has spooked them from trusting it. I could try to explain all the technical jargon about their problem but I'm pretty sure once I got to "it's only at 21% of it's original capacity but it can pass a load test" their minds will shift to "it's a dead battery "

 

[cornbinder89]

I pinch pennies on stuff, so for me, I'd throw it back in, but I will concede there will be another time it will let me down, only question would be how far in the future that would be? Others have different risk tolerance then I!

Try as I may, I can't come up with a way to push start, or hand crank a Leaf! I do have a hand crank for my 83 year old 5 ton truck, and have hand cranked my 525 CID Buda generator (Don't recommend it as a daily chore)!

 

[LeftieBiker]

"Do any methods exist to restore the capacity of a SLA battery?"

There are at least two kinds of capacity loss. Heavy sulphation of the plates, and lighter, "surface charge" sulphation that blocks most of the plate area from charging by instead covering it with a thin layer of sulfate. You can only do a partial, gradual recovery of the first type (PLEASE don't watch or, especially, act on, those YouTube videos of fools using welders to "recover" batteries) as noted, but the second type can be helped by applying the highest charge rate the battery can handle.