Coconut Battery

I am having problems with my MacBook battery so I downloaded coconut battery but now I am not sure how to understand the stats it gives me.
Here is how it reads:
Battery Charge
current charge: -1 mAh
maximum charge: -1 mAh
100%

battery Capacity
Current Capacity: -1 mAh
design capacity: 5020 mAh
0%

Details
Mac model: macBook 4,1
Age of your Mac: 41 months
Battery loadcycles: 671
Battery temperature 30.5 C
Battery Power usage 0.0 Watt

I think I just need a new battery but is there a way to tell that is the problem for certain? I just bought a new charger and batteries are expensive so I don't want to keep putting money into this computer if there is a bigger problem with it.

Thank You

Well, for comparison

my MBPro is 13 months old and coconutBattery says

current charge 6666 mAh
Max charge 6726 mAh
Current capacity 6726 mAh
design capacity 6900mAh
battery power usage 7.4 Watt

A lot different than yours!

I think I just need a new battery but is there a way to tell that is the problem for certain? I just bought a new charger and batteries are expensive so I don't want to keep putting money into this computer if there is a bigger problem with it.

Click to expand...

According to coconut battery, your battery is "toast". Since you have more than 600 cycles on a battery that was only designed to give 300, consider yourself lucky. Yes, you need a new battery. And, don't buy a cheap knock off battery or you'll be replacing it again.