Some advice on potential used purchase please

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I took another reading today with the battery at 14%. The LS results are below. I also tried to do a range test but neglected to reset the trip odometer so I can bring it back up to 20% and do it again, then do it at 100%. For what it's worth at 15% the guess-o-meter was showing 28 km left, or the more pessimistic figure was 19km looking at the range in the nav menu. At 18% it showed 31/22. There was no sudden plummet in the display at or under 20% but I don't know how reliable that is. As I said I'll do it again using the trip odometer as a guide, if that would still be advisable.

Why does it show the SOC at 19.5% if it was at 14% charge?

Leafspy Jan 10th 2025.jpg

Does this look ok?
 
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But I'm not happy with any kind of poison!

I've changed batteries on multiple cars in the past and have never thought about it much nor had any problems from disconnecting them in order to swap out. It's just this being my first EV it seems there's more to go wrong, or maybe that's true with the electronics in all modern cars. I think I'm probably not going to charge the battery but will renew it over the next while. Any reason not to connect the negative jump lead directly to the negative battery lead instead of to the chassis, just like the positive?



Can't really do a hydrometer test on a sealed/maintenance-free battery can you? I'm not sure why you opt to charge connected even though you say best practice is disconnected, unless using a dumb charger reduces the risk to very minimal. Yes I agree that we shouldn't need to charge the 12-volt much if at all. My relatively low charge is symptomatic of the battery's age so it just needs to be changed.
None of my gp 51R's are sealed, I will not buy a sealed L-A battery with flooded cells. I have 3 gp 51R's and three different charging systems, all work well.
Disconnecting any battery on a vehicle since about the mid to late 80's has an effect on the rest of the car. At minimum, it clears any stored codes, often clears "adaptive learning" on running settings.
The reason it is slightly different with an EV is, there is no engine that has to be in operation for the charging system to be active, the procedure is there to make sure the charging system is inactive, it still clears codes and setting, like engine driven cars also do when the battery is disconnected.
Not really a big issue, and if you disconnect when the charging system IS active, in most cases all that will happen is a bunch of trouble codes being set, but best practice is not to do that.
 
Ok so. As I say I've changed a few batteries and have taken them out for bench-charging in a couple of cars with plenty of electronic gadgets and had no problems after re-connecting. If the only difference with a Leaf is making sure to follow the procedure to disable the charging system, then I don't see there'd be a real issue in disconnecting and bench-charging.
 
That reconnection procedure is pretty involved. What is the difference between ESVE and EVSE, or are they the same thing? I can't find a clear distinction online. I presume it is the same protocol whether one is removing the battery for bench-charging or changing the battery for a new one? And finally, back door = trunk/boot?
It appears the ESVE was a typo from the original person that posted that procedure, I just copied and pasted his post, so should have been EVSE.

The bottom line is that one could possibly have some error codes to clear if not being careful when the 12vdc battery is replaced. Some people even recommend using jumper cables connected to second 12vdc battery when replacing and reconnecting a new 12vdc battery so that there is no disruption of 12vdc to the vehicle. This would prevent having to deal with any possible software issues and subsequent error codes. It would also prevent one from having to follow any reconnection procedure.

Since the Leaf detects the opening of any of the doors, front, rear or trunk, this would apply to all of those.
 
I also charge the 12v occasionally with a desulphate charger, & always while connected to the car.
Since you use a desulfation, aka equalization charge on occasion without disconnecting the battery from the car, it doesn't sound like there is a problem doing such on your Leaf—good to know. What year is your Leaf? What voltage is your charger using for desulfation/equalization and for how long? I've seen some chargers put out 16vdc and above.
 
Yes as I wrote before, that’s what I would be concerned about - the charger putting out too much voltage during desulphation and potentially damaging the electronics. Which is why @cornbinder89 uses an older ‘dumb’ charger which presumably doesn’t have a desulphation stage.

I did the first part of my range test today, starting at 20%. I drove until it went down to 15%, so it used 25% of the available charge. I got 7.9km out of that 5%. Which means I’m getting 1.58km per percentage point at this low SOC. Now this kind of arithmetic has never particularly been my strong suit so feel free to correct me if I’ve got this wrong. However I think that would mean the average range is about 158km on a full charge.

I had LS running all the time and although the difference figure did change as I drove, it mostly stayed under 20mV and closer to 10. I didn’t see any sign of cells dropping out though again, the red bars did move up and down quite a bit. After the trip it looked pretty much the same as my screenshot in post #81.

Forgive my newb explanation!

I’m going to charge it overnight and repeat the test at 100% tomorrow. Hope I’m doing it right..
 
Yes that makes sense however I don’t have another battery lying around. I suppose I could use my partner’s car though. So would I just connect the jump leads from her battery to my positive and negative leads before disconnecting them from the battery? I don’t see how I could undo them while connected to those cables though. I suppose I’d have to try it and see. Is there any risk associated with having both batteries ‘feeding’ the system, firstly before disconnecting and removing the old one and also while fitting the new one?

Edit: When you charge yours are you not concerned that the charger could output more than 15V during desulphation, as discussed before?

@Bombastinator2 Thanks but I already have the OBD reader and have posted my results earlier in the thread.


I've seen references to using small batteries to temporarily power a car while the 12 volt battery is removed. What I'd suggest though - and this is based on 10+ years of posts here as well as my own experience - is that you leave the battery in and use tender/maintainer of at least 2 amps output to keep it fully charged.

Interesting post above about stress from inrush current. The Vectrix bike forum (I have one that I need to resurrect) strongly advises using an inrush limiter (essentially a 75-100 watt incandescent light bulb, a socket for it, and two wires) to prevent that kind of stress when reconnecting the charger to the bike when the battery is low.
 
Yes as I wrote before, that’s what I would be concerned about - the charger putting out too much voltage during desulphation and potentially damaging the electronics. Which is why @cornbinder89 uses an older ‘dumb’ charger which presumably doesn’t have a desulphation stage.

I did the first part of my range test today, starting at 20%. I drove until it went down to 15%, so it used 25% of the available charge. I got 7.9km out of that 5%. Which means I’m getting 1.58km per percentage point at this low SOC. Now this kind of arithmetic has never particularly been my strong suit so feel free to correct me if I’ve got this wrong. However I think that would mean the average range is about 158km on a full charge.

I had LS running all the time and although the difference figure did change as I drove, it mostly stayed under 20mV and closer to 10. I didn’t see any sign of cells dropping out though again, the red bars did move up and down quite a bit. After the trip it looked pretty much the same as my screenshot in post #81.

Forgive my newb explanation!

I’m going to charge it overnight and repeat the test at 100% tomorrow. Hope I’m doing it right..

You have misunderstood the references to the state of charge, I'm afraid. That's probably my fault. I'll clarify: you want the car fully charged or close to it for the range test, and then you use, for example, 20% of that. Say from 100% charge (indicated on the dash, using the state of charge display option) to 80% state of charge (SOC). Going from 20% to 15% isn't as likely to provide an accurate result, as the distance driven and charge used aren't high enough. The reason to repeat the test at 20% (preferably using LeafSpy Pro) is to look for bad or marginal cells that only reveal themselves at low states of charge.
 
You have misunderstood the references to the state of charge, I'm afraid. That's probably my fault. I'll clarify: you want the car fully charged or close to it for the range test, and then you use, for example, 20% of that. Say from 100% charge (indicated on the dash, using the state of charge display option) to 80% state of charge (SOC). Going from 20% to 15% isn't as likely to provide an accurate result, as the distance driven and charge used aren't high enough. The reason to repeat the test at 20% (preferably using LeafSpy Pro) is to look for bad or marginal cells that only reveal themselves at low states of charge.
I don’t think I misunderstood you, I have just done the test in reverse order because it was low anyway. So rather than charge it all the way to 100%, do the test and then back down to 20% to test again, I started at the lower SOC. Someone else said the order wouldn’t make a difference earlier in the thread. I intend to repeat the test at 100% today.

My rationale for 20 down to 15% was that would represent 25% of the available charge, which is what you advised to do for the full charge test. You did say to repeat it at both levels so I presumed that meant to use the same percentages. Obviously that would mean far lower distance at 20% - it’s not possible to drive any further and I’m not willing to go below 10%. I did try to check this out earlier in the thread but just got a response saying not to worry about, just to see what happens at the lower SOC, so maybe I have got it wrong after all..

I’m not sure if you had a look at my LS Lite reading at 14% in post #81? That looks ok to me but I’d be interested to hear what you or anyone else thinks. I’m not going to keep testing as based on that and the fact that I did get 8km out of 5% charge at the 20% mark, I think the battery seems to be ok. I own the car now so I’m only really interested in establishing if there is anything faulty while the battery still has 6 months of warranty left on it. Other than that I’m happy to just enjoy the car and not obsess too much over measurements and tests.

To save scrolling back, here is the reading from yesterday at 15% after the range test:

Screenshot_20250111_184417_com.Turbo3.Leaf_Spy_Lite.jpeg
 
. I own the car now so I’m only really interested in establishing if there is anything faulty while the battery still has 6 months of warranty left on it.

View attachment 6455
I think your battery is fine.
Keep in mind LS isn't a predictor of things to come, it is an indicator of what is today. It is more a diagnostic tool.
Since you now own it, the real metric that matter is: does it do the job you bought it to do?
 
I don’t think I misunderstood you, I have just done the test in reverse order because it was low anyway. So rather than charge it all the way to 100%, do the test and then back down to 20% to test again, I started at the lower SOC. Someone else said the order wouldn’t make a difference earlier in the thread. I intend to repeat the test at 100% today.

My rationale for 20 down to 15% was that would represent 25% of the available charge, which is what you advised to do for the full charge test. You did say to repeat it at both levels so I presumed that meant to use the same percentages. Obviously that would mean far lower distance at 20% - it’s not possible to drive any further and I’m not willing to go below 10%. I did try to check this out earlier in the thread but just got a response saying not to worry about, just to see what happens at the lower SOC, so maybe I have got it wrong after all..

I’m not sure if you had a look at my LS Lite reading at 14% in post #81? That looks ok to me but I’d be interested to hear what you or anyone else thinks. I’m not going to keep testing as based on that and the fact that I did get 8km out of 5% charge at the 20% mark, I think the battery seems to be ok. I own the car now so I’m only really interested in establishing if there is anything faulty while the battery still has 6 months of warranty left on it. Other than that I’m happy to just enjoy the car and not obsess too much over measurements and tests.

To save scrolling back, here is the reading from yesterday at 15% after the range test:

View attachment 6455

No, I didn't use the phrase "available charge" for just that reason. You need at least 10% of a Full Charge in order to get good numbers, IMO. Since I was rereading it I copied it:
"I'll check the link later. The only real way to compare the Leaf's displayed capacity bars with its actual capacity is to do a range test. Reset the trip odometer. Then drive the car on a full charge if possible, and with the dash display configured to read the charge as a percentage. If possible, drive until the car goes from 100% to either 90% or 75%, so you are using either 10% or 25% of the charge. Then simple multiplication will give you the approximate range of the car. Then - and this is important - repeat the test with the state of charge at, say, 20%. This will reveal any bad or marginal cells in the battery, because the range will plummet at lower states of charge even driving the same route at the same speed, as any weak cell(s) 'drop out' and cause the Battery Management System (BMS). to shut it down early to avoid pack damage. There are some really good 30kwh batteries out there. It's just that there are so many defective ones as well."
 
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I think your battery is fine.
Keep in mind LS isn't a predictor of things to come, it is an indicator of what is today. It is more a diagnostic tool.
Since you now own it, the real metric that matter is: does it do the job you bought it to do?
Thanks for that reassurance and yes the car does seem to be doing what I need it to. The acid test will be how I get on when I drive the 100km to visit my daughter. No doubt I will have to charge once there but as long as I only have to do that once per trip, I’ll be happy.

No, I didn't use the phrase "available charge" for just that reason. You need at least 10% of a Full Change in order to get good numbers, IMO. Since I was rereading it I copied it:
"I'll check the link later. The only real way to compare the Leaf's displayed capacity bars with its actual capacity is to do a range test. Reset the trip odometer. Then drive the car on a full charge if possible, and with the dash display configured to read the charge as a percentage. If possible, drive until the car goes from 100% to either 90% or 75%, so you are using either 10% or 25% of the charge. Then simple multiplication will give you the approximate range of the car. Then - and this is important - repeat the test with the state of charge at, say, 20%. This will reveal any bad or marginal cells in the battery, because the range will plummet at lower states of charge even driving the same route at the same speed, as any weak cell(s) 'drop out' and cause the Battery Management System (BMS). to shut it down early to avoid pack damage. There are some really good 30kwh batteries out there. It's just that there are so many defective ones as well."
Thanks and I do appreciate your help and input. Where I seem to be getting confused is when you say to repeat the test at 20%. Repeating it would surely mean using “10% or 25% of the charge” once again, no? Since we’re quoting past posts here’s what I asked about that way back:

“If I do the range test as described by LeftieBiker, when I repeat it at 20% do I regard that figure as the new 100% and drive to 90% or 75% of that, i.e. 18% or 15%? Or do I drive it to say 90% of the original 100, i.e. to 10%? I hope that makes sense!”

As I say the only response I got to that was to drive it as far as I was comfortable at 20% but I was still left with the same question. So I suppose what you meant was to drive the same route and distance at both 100% and 20%, which would only be possible if I drove to 90% for the full test and to 10% (from 20%) for the low test, given I don’t want to take it below 10%?

Anyway, I did another test at 100% earlier. Drove it down to 80% and got 38.6km on a similar though obviously longer route. That makes it 1.93km per percentage which is more than I got previously, though as you say that might not have been a very accurate result. My LeafSpy reading after the test:

Screenshot_20250112_145347_com.Turbo3.Leaf_Spy_Lite.jpeg

It behaved in a similar way to yesterday while driving with the mV figure and red lines moving around quite a bit, though averaging between 10 and 20mV.

Lastly, I can’t find a way to get the car to display the SOC as such, just the charge available as a percentage, which is what I’m basing these tests on. Is that the same thing or am I missing something?
 
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It's quite safe to drive from 20% charge down to 10% - unless you have bad cells, in which case you should be able to creep home. Still, I should have added that you should stay near home the first time you try that. Once you've established that there are no bad cells - and it appears that you have done that, and that the battery is good - you can use 10% SOC as the 'bottom end' of your range. Just remember that whenever you get down below 20-25%, you should plug in to recharge when you get home. The only exception would be if you arrive home with 20-25% and the battery is Hot. In that case, you'd want to wait a couple of hours to plug in, or plug in for just long enough to bring it up over 25%.

I'm not sure what you mean by "as charge available" unless you mean the charge estimate that appears at the end of a drive when you shut the car off. Even an S should have the % SOC option in the display. I'm blanking on how to switch to it in a Gen 1.5 Leaf, but hopefully someone will chime in with that info. Most of us have it as the default display option, as it's much useful and accurate than the range estimator, aka "Guess O Meter." That uses driving info from the most recent few minutes of driving, and possibly also a Magic 8 Ball. :)
 
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Thanks, good to hear it seems I have established that the battery is ok, within reason anyway. In terms of the display I simply meant the default which shows both the range and the charge left. Here is what I'm seeing, taken yesterday when parked after the low test.

Dash display.jpg

Yes, regarding 10% as my lower limit makes sense. Actually the car started warning me about low charge yesterday at 14%. I plan to keep it between 20 and 80% except when making the longer trips I mentioned. Another thing I should mention is I did leave it sitting for a couple of hours yesterday at 14% then charged it to 29%, also later on left it for about 6 hours at 15% after testing as I wanted to start charging it late at night in order to estimate the cost of home-charging. I won't be doing that again given what you say, however I did a search beforehand and found some info that said it wouldn't do any harm to leave it sitting for a while at a low SOC. I hope that’s true!

One strange thing is I have the NissanConnect EV app and as soon as the car finished charging to 100% I got a notification informing me of this and saying that I had 12 out of 12 bars. However I only have 11. Does it know something I don't?! :unsure:
 
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Since you use a desulfation, aka equalization charge on occasion without disconnecting the battery from the car, it doesn't sound like there is a problem doing such on your Leaf—good to know. What year is your Leaf? What voltage is your charger using for desulfation/equalization and for how long? I've seen some chargers put out 16vdc and above.
To answer your question, I have a 22 plus Leaf that has done just over 50k miles.
The 12v isn't in the best condition being original & only charges to 14.2 volts which then drops back to 12.2v after a few days use, so will need changing soon.
The charger runs the desulphation regime automatically so I usually leave it connected for several days.
I've never seen more than 14.2v charging this battery, but have seen it at 14.4v charging my ICE car.
But as I understand it, desulphation involves discharging the battery in pulses as well as charging.
I don't have an instrument that can measure these pulses, an ordinary DVM just gives you an average voltage.
 
I've seen references to using small batteries to temporarily power a car while the 12 volt battery is removed. What I'd suggest though - and this is based on 10+ years of posts here as well as my own experience - is that you leave the battery in and use tender/maintainer of at least 2 amps output to keep it fully charged.

I was thinking of connecting up my partner’s car and using its battery while taking mine out but that’s a good suggestion about maybe getting a small battery, maybe like a motorbike one or similar. Once I was sure the maintainer would not exceed a safe voltage then I might well do that, though I would have thought a battery in a healthy state wouldn’t need extra charging unless the car was sitting for long periods.
 
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A healthy battery disconnected from the car wouldn't need one, but if connected the car pulls power from it even when turned off and sitting un-driven. If you are worried about too much voltage from the maintainer, just get one with no de-sulfation cycle.
 
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