This most recent of the Hedge Trimmer types has also seen probably the most development work on the part of manufacturers, and the greatest improvement in machine capabilities.
At the heart of this innovation lie the new types of battery that are available. The types used now are either Nickel Cadmium (NiCd) or Lithium Ion (Li-ion). Former problems of 'memory effect' that used to shorten effective battery charge life have been banished. They are lighter, more powerful, charge quicker and last longer.
Generally speaking NiCd is used in cheaper models and the more expensive and powerful Li-ion batteries are deployed in higher-specification machines: but this is not an infallible guide to performance.
The small Bosch 16" has a 14.4V (NiCd) power rating rather than the 18V normally found on others but it boasts the longest running time of its class at 55 minutes (others manage less than 30 minutes).
A feature worth looking for when choosing a cordless hedge trimmer is a pivoting head or rotating handle, which allows you to cut precise angles or vertical faces easily. This sort of function is built in to the Black & Decker 20" model and the Gardena 19" Ergo Cut.
Because batteries are expensive and more and more cordless tools are appearing, it is high time that there was some standardisation in the power packs and their charging apparatus. Two manufacturers that have grasped this nettle are Ryobi and Bosch, who offer units that will power not one but many compatible machines of different functions, such as drills and chain saws. Ryobi call their initiative the ONE + concept. Their latest charger will work on either type of battery.
Check, by the way, that your chosen machine does include a battery: if you do not read the advertisement closely you may find that the surprisingly good headline price for a smart machine may in fact be because it is battery-free.
Weight may be an issue for some users who do not pump iron and would rather avoid repetitive strain injury. The latest designs from Bosch have aimed for weight reduction and have gone down by 30%: they are achieving as low as 2.2kg, whereas others weigh in at more than 4kg in the same sub-18" category.
Other nice-to-have features in your trimmer are good ergonomic design that incorporates soft-grip handles: low vibration (such as Black & Decker offer with their asymmetric blade design) and it is worth checking that the blades are laser-cut and diamond ground for maximum effectiveness.
Be aware that after your cutting session of (usually) 30 to 50 minutes, you are in for a lengthy charging period. You can of course avoid this problem by acquiring another battery and charging it offline. However you should also see how long your planned machine requires for a recharge. Most manufacturers quote 3 hours for their 18V units. One notable exception is Bosch, which offers two different novel solutions.
Their 20.5" machine carries a twin pack of 14.4V (1.5 amp-hour) batteries. By this means it achieves a running time of 70 minutes (2 x 35 minutes per battery) and a recharging is made easier using standard Bosch units charged offline while you work.
Cleverer still is the 21" premium model that has a 36V Li-ion battery, a 50 minute run time and charges itself in just 45 minutes: if you are really in a hurry it will be 80% recharged in 25 minutes. Barely enough for a coffee break.
This same Bosch model adds features like 20mm blade spacing and a sawing function at its tip which means that branches of up to 25mm diameter can be despatched, something that previously was unthinkable from a cordless hedge trimmer. An electronic anti-blocking feature protects the machine from damage. There is also an extra protector for safe cutting along edges of walls or near the ground.
Right at the top end of the cordless market, in terms of size, specification and price, is the professional 21.5" Makita. This achieves the same 36V as the Bosch by packing two 18V Li-ion batteries. It claims a lower than usual noise level of 86.5dB (these are not quiet machines even in electric form due to their high-speed reciprocating blade mechanisms). It also carries features that include a battery protection circuit, and protection from over-discharge, high temperature and overloading. These are very wise precautions because Li-ion batteries are more prone to damage as a result of such abuses.
Most machines sold in this market are the smaller ones with blade lengths of under 20 inches. In this mainstream sector it is worth mentioning the models from German garden equipment specialist Gardena. In addition to their typically well-designed and constructed Easy Cut 19.5", which has a large starting button for easy operation, they have an Ergo Cut version with relatively wide blade spacing of 16mm to deal with thicker growth than you can normally tackle. (Most competing models are for light duties and have tooth spacings of 10mm to 12mm). The same model has a blade protector.
For most users in the hedge trimmer market, there is a cordless model that will suit: and when you add into the equation the extra safety of not trailing a live cable near a cutting device, and it makes the cordless route a very attractive one.
