12v Battery pack help?

I have a satellite meter for aligning satellite dishes, the battery pack is faulty, a new replacement one costs almost €100 for 10 x 1.2v rechargeable batteries. This is 13 years old and I want to fix my dish alignment rather than pay someone to come in to do it, I was a keen satellite hobbyist back in my younger days which is why I have the meter to begin with.

I took apart the old pack and I spotted there is some type of fuse or capacitor, pictured.

I was planning to just solder the negative and positive to a longer lead and rigup some crocodile clips to power it from 12v a car battery with a longer lead, this might be the last time I will ever use the meter again. The old power pack has a capacity of 1,800mah, obviously a car battery would be far more powerful, I am conscious of blowing the meter with a surge. Alternatively I could buy a shot of 1.2v rechargeables and make a similar battery bank again but it was always underpowered and the charge would often die in the middle of a job and you could not use it whilst on charge.

Any recommendations, I am particularly concerned about the fuse item.