The lithium-ion batteries used on electric bikes have a finite life. Traditionally they've lasted for a few hundred charges, but some manufacturers are now making claims of many hundreds of charges, giving the capability to take you thousands of miles before the battery needs replacing.
Yamaha claim 700-900 charges for their new battery system, while the new Derby battery (as reviewed on the Kalkhoff Pro Connect Disc) has had claims of 1,100 charge cycles made for it.
However, it appears the new batteries are still subject to a two-year guarantee. As most riders aren't going to exceed the new higher recharge figures within two years there hangs the question of why the manufacturers haven't extended their guarantees along with their claims for battery life.
David Henshaw of A to B magazine, which specialises in folding and electric bikes, has conducted long-term tests on li-ion batteries. His latest findings suggest that long-life batteries could already be here – but that more real world testing is needed.
He told BikeRadar: "Current figures for our Panasonic batteries suggest about a seven percent drop in capacity per year, which is the best of the five lithium-ion batteries we've tested long-term so far. The generally agreed failure point is 80 percent capacity, so that only implies a life of just under three years. But batteries don't necessarily die at 80 percent and it might go on for years.
"I'd say 50 percent capacity was still viable for light use, which implies a life of five years – but we have no idea whether it'll make that. It's impossible to be precise while the battery technology is still young. However, these German- and Japanese-made batteries are already looking much stronger than the Chinese lithium-ion batteries that have caused a lot of nervousness in the industry, so we must be optimistic."
Extended battery guarantees
Replacement batteries for electric bikes aren’t cheap – costing anything from £300 to £1,000 – so, while Yamaha and Derby seem to be sticking with their two-year warranties, an increasing number of manufacturers and dealers are now offering extended battery guarantees. Koga-Miyata offer up to five years, and Kalkhoff three to five years, via UK importers 50 cycles .
The longest warranty, though – 10 years – comes from the Electric Transport Shop. If this sounds too good to be true, the catch is that you have to have the bike serviced by them twice annually (current cost £40 per service plus parts). While this adds up to some £800 over 10 years it could prove cost effective for heavy users of electric bikes who don't do their own maintenance. The warranty, available on selected makes, is transferable to subsequent owners if the bike is sold on. ETS have shops in London, Oxford, Cambridge and Bristol.