my Karcher profi line HD650 doesnt start up withy battery what can i do?

Both batteries are probably dead. You need to replace them. It may be cheaper to replace the whole thing as those batteries are often more expensive than a new tool that comes with new batteries.

If you let Li-ion batteries totaly discharged for a week or more, they die.

You need to recharge those batteries as soon as possible when they are discharged, and preferably before they are totaly drained.

Also, they sloowly loose charge over time. Every 6 months or so of storage, you need to check if they are still charged and recharge them if they are under 50% charge.

This apply to ALL Li-ion batteries, not just those for power tools.

Electro
May 2014