There are so many cordless trimmer and weed eater products on the market, I decided I would offer up my opinion on the best cordless trimmer products based on the anticipated use:

WORX GT WG151.5 18-Volt Cordless Electric Lithium-Ion String Trimmer/Edger

Pros:

reported long run times with new Lithium-Ion battery technology

wheel guide mode for easy edge trimming

30 minute run time with with 30 minute recharge

good ergonomics with rotating handle and 90-degree tilting shaft orients the cutting head for sloped and hard-to-reach areas

effective or light duty weed trimming

Cons:

Expensive at $149.95

only one battery included

Amazon Stats:

ave rating 4.2/5.0 based on 51 reviews

#1 seller string trimmer category

Link to WORX GT WG151.5

Heavy Weed and Brush Clearing:

Black & Decker NST2036 Heavy-Duty 36-Volt Cordless Electric String Trimmer

Pros:

proven in test to rival and in some cases exceed gas and corded trimmers

good reported battery run times

14 inch cutting pattern

0.080 string diameter-largest among cordless trimmers

effective for heavy brush and weeds

Cons:

Expensive at $199.99

some reliability issues reported by users

relative heavy at over 20 lbs

Amazon Stats:

ave rating 3.57/5.0 based on 53 reviews

#19 seller string trimmer category

Link to Black & Decker NST2036

Best All All purpose Trimmer:

Black & Decker NST2018 18-Volt Cordless Electric 12-Inch Grass Hog String Trimmer With Two Batteries

Pros:

affordable at $103.93

comes with 2 batteries

12 inch cutting pattern

light weight (6.5 lbs) and good ergonomics

Cons:

not as good for edging as the Worx

the bump and feed feature is difficult to master for some

lengthy recharge time-up to 9 hours

Amazon Stats:

ave rating 4.09/5.0 based on 482 reviews

#2 seller string trimmer category

Link to Black & Decker NST2018

Video Review of Black & Decker NST2018