Hi Gabi.
If the battery is faulty the main contactor K1 could not be ON.
This is be cause the capacitor of power unit need to be pre-charged up to around >72VDC then it allow K1 ON. If not K1 is not allowed to be ON.
If you measure the battery 83VDC but when it connect to the load (lifting or driving) it go down to 74VDC means that your battery is faulty.
Try to check the battery:
- Votage of each cell = 1.8-2.1 VDC
- Acid density = 1.25%
- Distill watter level ?
Try to change to battery ?
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