The battery might be straight swap just like any other traditional 12v battery but this does not mean that the CAR generates enough power (Amperage) to charge it and supply power to other stuff. You must verify that first.
I have replaced the battery in my S90 T8 (2018 model year) with a P34B (34Ah, with new cathode). Upgrading to the latest long-range battery wasn’t possible due to compatibility issues with the battery voltage, rear motor, voltage converters, and other components.
I purchased a low-mileage battery from a scrapyard in Sweden, and everything was plug-and-play. I also used VIDA to load the official software, and the system has been working perfectly for over two months now.
The only issue I’ve encountered is with the small water drop indicator in the speedometer what indicates how much load you can give to car. In newer models (possibly from MY2021 onward), this indicator moves to the end when PURE mode is activated. However, in my case, it remains at the same level as before—about halfway on the scale.
Previously, my actual range in PURE mode was around 18-20 km, but with the new battery, it has increased to about 32 km. While this isn’t a huge gain, achieving a longer range wasn’t my primary goal—I mainly wanted to educate myself through this upgrade.
(03-25-2025, 07:39 PM)naxitrall Wrote: Upgrading to the latest long-range battery wasn’t possible due to compatibility issues with the battery voltage, rear motor, voltage converters, and other components.
I’m considering a cell level swap since I read that the latest one is of compatible chemistry and same number of cells in series. So it “should work” with the old bms, SoC calculation might be off but same voltage limits etc.
What did you find when you researched this for your car? Please share any details
Yesterday, 07:29 PM (This post was last modified: Yesterday, 08:03 PM by Nazsky786.)
Well what I've found out is the connections to the battery are all the same, so a plug and play, and bolts up, however the car will no longer starting, since it uses the HV battery to power the ISG to turn engine.
This is a software issue preventing this, but there is also the more powerful rear motor, which also mounts up as the orginal but the coolant piping and some wiring is routed differently.
I'm thinking with the battery is it possible to replace the management system which is under the boot floor and see if that would allow to start or is it the ISG at front that maybe the issue?
Also I think the rear Motor etc modules wont effect the starting, The issue is going to be from the ISG to the BMS and HV side.
So we know if you change the HV battery the car wont start, but would the orginal BMS inside the old battery work on the 18kwh battery or is it something else. Thats the question?
Would you need to replace the HV battery with the ISG? Program should be correct but not in the car.
VOLVO made a upgrade software depending on battery size but was limited to the 11kwh battery. Not further upgrade software avaliable.
Attached the rear motor of my XC90 T8.
Thanks that's good info. I haven't seen a teardown of the new pack but I assume the cooling channels etc. are different between generations so it won't be possible to swap over battery modules from the new battery to the old one. I'm leaning towards switching over all the electronics, the BMS, temp sensors, etc. from the old pack to the new one. Only question is if they can physically fit inside the new pack with the bigger modules taking additional space the new pack may have smaller electronics.
Anyway if all the electronics are the same the car would not need software update. The BMS will see SoH >100% but hopefully not throw a DTC
Not possible the newer battery pack is a stacked designed, and the older version is a cubed design.
The battery cooling itself is the same.
Its just finding out what actual module will see the larger battery and stop the car starting. Is it the Battery monitoring system or something else.
