Reversed 12v

[imolazhp]

Hello there, owners of a 2015 SL, still at 85% health at 46k miles…

Found a 2011 for sale on Marketplace, owner claims he put the 12v in backwards. Says he wants to sell the car for what the battery is worth, but notes that it only had 35 miles of range when this happened.

Event happened in December and the car has been sitting since at an unknown state of charge.

I can borrow a truck from work and rent a trailer, it’s a few hours out of town.

What am I looking at here? I told him the unknown state of charge is concerning because if it was high or low, the pack could be actively degrading and might not be worth anything.

I have searched but only found one guy that said a new 12v fixed the problem. Not much more info, I think that lead included him taking it to the dealer so who knows if there was additional damage or not.

Asking $3k, 35 mile range car with 55k miles. Should I offer $500?

More importantly, what could have been damaged? It’s 12v, not high voltage, a could of fuses right?

 

[alozzy]

You can use Dala's solution for obtaining the state of health (SOH) of the high voltage pack, via LeafSpy. If the SOH is less than 70% then the high voltage pack isn't worth much unless you can find a buyer that wants the cell modules for a solar project or similar...

https://github.com/dalathegreat/Nissan-Leaf-Battery-to-OBD2

This New Zealand company has a turnkey device that does the same thing:

https://evsenhanced.com/product/obd2-to-leaf-battery-adapter/

Shipping to the US would likely be expensive though.

 

[coulomb]

You can use Dala's solution for obtaining the state of health (SOH) of the high voltage pack, via LeafSpy.

Yes, assuming that none of the needed ECUs have fried.

Reversing power to electronics could lead to serious problems. Think of all the free-wheeling diodes across switching semiconductors. And even the DC-DC output diode; it and the transformer's output winding would be a low-impedance short circuit across the battery.

Since it's a few hours out of town, it's hard to say if it's worth the trip. Ideally, you would get the present owner to replace the auxiliary battery and do the Leafspy thing; I think even the free Leafspy Lite would tell you the SoH. But he's unlikely to want to spend money on that, and likely won't know enough to diagnose issues that might come up.

If you're keen, I'd bring a new or known-decent auxiliary battery and a few packets of spare fuses. Wild guess: 25% chance you can get an SoH reading. 99% chance that some electronics has fried. 25% chance that most of that will be easy to fix if you know your electronics. Fuses prevent wires from burning, but they're generally not fast enough to save electronics.

Are you more interested in the HV battery or the mechanics of the car?

 

[imolazhp]

You can use Dala's solution for obtaining the state of health (SOH) of the high voltage pack, via LeafSpy. If the SOH is less than 70% then the high voltage pack isn't worth much unless you can find a buyer that wants the cell modules for a solar project or similar...

https://github.com/dalathegreat/Nissan-Leaf-Battery-to-OBD2

This New Zealand company has a turnkey device that does the same thing:

https://evsenhanced.com/product/obd2-to-leaf-battery-adapter/

Shipping to the US would likely be expensive though.

With 35 miles at a full charge, the pack certainly has less than 70% SOH. I appreciate the response.

You can use Dala's solution for obtaining the state of health (SOH) of the high voltage pack, via LeafSpy.

Yes, assuming that none of the needed ECUs have fried.

Reversing power to electronics could lead to serious problems. Think of all the free-wheeling diodes across switching semiconductors. And even the DC-DC output diode; it and the transformer's output winding would be a low-impedance short circuit across the battery.

Since it's a few hours out of town, it's hard to say if it's worth the trip. Ideally, you would get the present owner to replace the auxiliary battery and do the Leafspy thing; I think even the free Leafspy Lite would tell you the SoH. But he's unlikely to want to spend money on that, and likely won't know enough to diagnose issues that might come up.

If you're keen, I'd bring a new or known-decent auxiliary battery and a few packets of spare fuses. Wild guess: 25% chance you can get an SoH reading. 99% chance that some electronics has fried. 25% chance that most of that will be easy to fix if you know your electronics. Fuses prevent wires from burning, but they're generally not fast enough to save electronics.

Are you more interested in the HV battery or the mechanics of the car?

Are there not fuses to prevent damage from such an occurrence? I have a good battery in our 2015 that I could take with me and I have a leaf spy dongle for the 2015. I'm not sure if I were the seller that I would let me work on it before buying it. I found in some posts from this guy on a FB group that the cooling fans would come on after he hooked up the battery correctly when he would plug in the EVSE, but eventually that stopped working too.

I'd like to fix it and drive it, my non-bike-friendly commute is 2.2 miles each way, so a 35 mile car would work all week. When it doesn't work for me anymore, pass it along to the next owner. Caravan came back with a reasonable offer when I put in the VIN so I believe it has a clean history. Typically if you put a VIN with bad history into Carvana's web site it will spit back a crazy offer like $100. I have a friend that owns a dealership that can probably run the CarFax for me though just to be sure.

 

[alozzy]

With 35 miles at a full charge, the pack certainly has less than 70% SOH

It's possible that there are one or more bad cells, which trigger a low voltage cutoff by the BMS. If those bad cells get replaced, then the usable range can increase considerably. However, given it's a 2011 with the original pack, the pack is probably just more evenly degraded.

 

[imolazhp]

Here is a potato phone photo of the fusible link on the positive 12v connection.

It looks different than our 2015, but can’t quite tell if it’s popped or not.

He said the fans were running and they’ve got to be 12v, so it’s not that cut and dry.

https://share.icloud.com/photos/0e59b1xopc3R6EggovjoBauQQ

 

[LeftieBiker]

That photo, sir, is an insult to potato phones. Seriously, I can't make head nor tails of that.

 

[RNeil]

Check for blown fuses. You don't need to install a new battery, just use jumper cables to connect 12 volts, with the correct polarity. Then you can check for functionality and use LeafSpy.

 

[nlspace]

i'm not sure that is good advice for laef owners--here's a guy that tried to drive off while on jumper cables and now has a butcketload of DTCs

https://www.diyelectriccar.com/threads/interpreting-leafspy.207236/post-1095912

 

[GerryAZ]

i'm not sure that is good advice for laef owners--here's a guy that tried to drive off while on jumper cables and now has a butcketload of DTCs

https://www.diyelectriccar.com/threads/interpreting-leafspy.207236/post-1095912

All of those DTC's are typical for 12V battery failure. Many can be cleared with LEAF Spy, some will require disconnecting/reconnecting a good condition, fully charged 12V battery a couple of times along with clearing codes with LEAF Spy.