My Clevo W550EU laptop battery can not be charged with AC-charger, the repairman, from the shop that I bought the laptop from, claims that the motherboard is defect and he hasn't got the parts. Currently I run laptop by taking out battery, charging with same type of laptop nr.2 and then putting back to original laptop (clearly, not the optimal solution to the problem).

1. Is it really possible to run the laptop with battery only and claim that the motherboard is defect?

2. If wanting to fix it, what precautions should I take when finding a new motherboard for that laptop model?

Other suggestions to this case are appreciated.

Does the laptop run if using the AC power adapter but the battery does not charge? Dell is the only laptop manufacture that I know of where the AC power adapter contains a memory chip whereby if it can not be read the battery will not charge.

Yes, the battery charging circuit is inside and I assume it is located on the motherboard for your laptop. The thing you plug into the laptop is just the power supply.

You have to weigh the cost of the replacement board if it can be found and labor costs versus the value of the laptop to decide if it is worth repairing.

The laptop does not run with only AC power adapter. The issue must be then the dc-in jack that is soldered on to the motherboard, by the looks of it in clevo w550eu service manual.

That would be a weak link. Usually there is an LED that indicates the battery is charging or connected to AC power. If that is not illuminated it would be a sign that there is a bad connection.