score:4
As you are travelling on Lufthansa, Google's answer for "lufthansa battery policy" points to:
http://www.lufthansa.com/mediapool/pdf/74/media_1070298774.pdf
Which states:
Portable electronic devices with lithium
Description: portable electronic devices containing lithium-metal or lithium-ion cells or batteries, e.g. watches, calculators, cameras, mobile phones, laptop computers, camcorders, etc., when these are intended for personal use.
- Checked baggage: Yes
- Carry-on baggage: Yes
- Carrierβs approval required: No
Rules for spare batteries:
- Spare lithium-metal or lithium-ion cells or batteries with a nominal energy of up to 100 Wh for these everyday objects:
- may only be carried in carry-on baggage and for personal use
- these batteries must be individually secured against short circuit.
Each installed battery or spare battery may not exceed the following values:
- lithium-metal or batteries with lithium alloy with a lithium content of 2 g, or
- for lithium-ion batteries a nominal energy of 100 Wh.
Spare lithium-ion batteries for the above-named everyday objects with a nominal energy between 100 and 160 Wh:
- maximum of two spare batteries per person
- only permitted in carry-on baggage
- each battery must be secured individually against short circuit
- the carrierβs approval is required
No mention of a requirement to turn on the laptop. But don't forget to either wrap each space battery individually, or add a bit of tape on the contact to avoid any unwanted short-circuit.
Nowadays, the problem with batteries is more that they tend to burn/explode than the risk of someone placing explosives instead (I believe this would be detected by current generation luggage scanners).
Note also that: