Troubleshooting PO extended battery hack

My Nissan Leaf Forum

Help Support My Nissan Leaf Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.


New member
Jun 22, 2023
Hello all, new Leaf owner here. I just bought a 2011, 36k miles, battery SOH about 52% with an extended battery hack. Please see the attached pict, but basically an anderson quick disconnect for an extra trunk battery. In my forum searching it appears there are a couple locations (ie after the shunt, inside the battery being the most desirable??) one could tie this into to, but since I can't really see how or where it was tied in without dropping the battery, is it possible to discern this via testing?

My limited understanding:

1 - Before the battery shunt only works to ~24kwh-ish, then since the car counts kWhs it says enough is enough, so tapping off here isn't much good.
2 - After the battery shunt the car can no longer count kWhs and will just keep going until a cell reaches min cut off voltage. (messes up the mile counter, but....)
3 - Tied in via the battery to inverter cabling, outside the battery, this would be a big no no correct?

Considering there is full pack voltage present when the car is off, that would indicate either 1 or 2 correct? This cabling is disconnected via the battery contractor when the vehicle is powered off?

I might not even utilize this connector, I just bought this thing to commute about 20 miles per day, then was going to repower a Crosley or something with the guts in the future. But in any case I'd like to further understand.


That image is scary. Is there full battery voltage at the Anderson connector? I doubt an Anderson connector is really rated for 400 volts. The standard LEAF LBC (lithium battery controller also called BMS for battery management system) looks at cell pair voltages and cuts off discharge when the lowest cell gets to minimum allowable voltage. It cuts off charging when the highest cell reaches maximum allowable voltage. I think it does try to keep track of charge level by monitoring and integrating the current flow through the shunt, but I think it will allow load current to continue as long as all cell voltages remain above minimum.

If you have appropriate test equipment and a good understanding of electrical maintenance, troubleshooting, and safety procedures, it might be possible to determine how that connector is connected by making measurements with the service disconnect plug removed (which breaks the series string in the middle of battery. The terminals at the service disconnect would give access to each half of the battery.

Do you have any information about whatever was used with the Anderson connector (battery pack, charger, DC power supply, inverter, or something else?
Yes, full pack voltage present, all the time, with the car off, charging etc. Previous Owner did not install, so he was also clueless as to what/why/etc also.

As for safety no worries, I'm an EE from the power plant world, so 400v is nothing.

Maybe if I can get it up on a lift perhaps see more, heck there might be a gaping hole in the lid of the battery pack where the cabling runs though!
I am glad you are an EE familiar with power and working around high-energy, high-voltage equipment. Yes, look carefully to see how those cables are connected. The battery case is sealed so that water does not get in--a gaping hole would be bad news. As a fellow EE in the power industry and long-time LEAF owner, feel free to reach out via PM if you wish to discuss possible troubleshooting/investigation of this hack. Full pack voltage all the time means the cables must be connected to the battery side of the main contactor.

There is some space between the top of the battery case and the body so you might be able to see the cables by removing the cover plate over the service disconnect (on the hump in front of the rear seat). You should be able to use a mirror or inspection camera to look toward the rear of the car and see if the cables penetrate the battery case. You will need to remove the plastic splash/aerodynamic shield (several pieces, but easy to remove/replace) when you have it on a hoist before you will be able to see much.
Thanks Gerry. I will eventually get under it, might be a while, just going to cruise around and enjoy for the time being.

I wish 62kWh packs were more readily available, at decent prices. Around here in Indiana pretty much nothing.