First off im from germany, so i apologise for my bad english in advance.
I recently had the issue that the battery was running shorter and shorter and in addition to that, the unit went off with a loud knocking sound.
So i opened the xtreme.
I removed the totally debalanced battery.
Its a 2 cell battery, one cell was at 3.29V and the other one at 4.26V!!! overcharged.
My guessing is that the circuit board from the battery was faulty and it was not balancing the battery cells, but i dont know if the board is designed to balance.
But i found a bad solder spot also, so who knows.
The good news is, 18650 cells fit barely.
I spotwelded 4 sony 18650V3 (drift free) cells together as a 2s2p pack and threw the original battery circuit board together with the old battery in the trash.
The sony cells wont need a bms board, i use them for years in ebikes, they dont drift.
I was a bit concerned that the xtreme would not boot up without the battery board but it did.
You can also swap the original battery but these 18650 cells are way better in therms of quality and long time stability.
Another problem is that i didnt found the original battery in europe, so i need to order it from china.......too much time.
You get these 18650 cells everywhere.
The xtreme is playing while im writing this......... ;-)
The unit wont charge without the circuit board from the original battery.
The internal charger checks the temp probe which is on the board from the battery.
But its quite easy, just give the charger a ~10k Ohm resistor between the minus from the battery and the temp cable coming from the connector.
My xtreme is charging now.
Next step is tune it up with 3500 mAh 18650 cells.
With my old 2250 ones the xtreme was playing the whole night, so i guess with new 3500mAh cells this thing will run way longer.
Also i will try to extend the base/foot/pedestal for 20mm so a whole pack of 18650 cells will fit underneath the unit.
I just need to get a cable to the outside and isolate it to get it airtight.
With this the xtreme will run half a week i guess.