Actually there's no reasonable substitute for a properly operating charging system and that's because the FI bikes need a properly operating charging system to even run at all. If the charge is low many systems on the bike will shunt down and the draw on the system between the pump and other devices will pull a battery down real fast.
The battery tender has been discussed in great detail on the forum many times over.
Thanks for your input.
The battery tender has been discussed in great detail on the forum many times over.
Thanks for your input.