Modern Vespa

On the battery tender, I am curious, is it safe to charge the battery while its connected? I know the battery tenders have those quick disconnects you can install, but when I last charged my battery, I was unsure if it was safe, so I disconnected. Lost my clock/metric system settings of course as well, and been too lazy to reset it as of yet but thats another matter.

So all in all, is it safe?

Provided you do not try and run the bike engine or have the ignition turned on while charging with a battery charger you are safe to do so with the battery connected as the ignition switch cuts off any connection to the bikes sensitive electronics.

Another point to mention on an related topic is never try and run any device intended for vehicular use while the battery is being charged by a battery charger. Reasoning is simply that battery chargers are designed to put out a certain percentage of AC modulated onto the basic 14 or so volts DC, this is required as the chemistry of a lead acid battery requires the AC component while charging.

Obviously devices designed for cars or bikes are designed to run on DC only and can react badly or be completely destroyed by the AC part of a battery charger output.
And before someone emails, yes the bikes alternator also puts out AC but it is rectified by the system and is basically smoothed out by the bikes battery being in parallel with the charging circuit which effectively soaks up or swamps any AC component before it reaches the devices on a bike (or car).
Simplistic answer but should qwell any fears :-)
Dave Vancouver BC Canada

leave the quick connect plug on the scoot. unplug the tender prior to starting there is no need to completly remove the quick connect leads from the scoot.

I travel back and forth from FL to NY all year round. I have a battery tender hooked up (with quick loop/rings connected to terminals) to both my MP3 and Honda Shadow while I'm away. When I get home, both start up...no problem...first shot. Wouldn't be without them!! Much cheaper than buying a new batteries. Leave the quick loop/rings, connected to your battery terminals at all times, then connect the other end to your battery tender plugin wire when your scoot is not being riden (the lights on the plugged in unit (red/green/yellow) will keep you informed of its status. Pray you don't loose power....I know I do while I'm away afterall, FL has mucho storms...been lucky so far.
Hope this helps....hope I explained it right 8)

I don't know the internal wiring design of tha Battery Tender specifically but if it is designed correctly there will be a cut off or bypass diode to isolate the battery if the power goes off.

If not it's an easy mod to do yourself. Providing you are comfortable opening and soldering inside the unit of course.

Simply put, all needed is a diode soldered into the circuit reverse biased across the voltage regulator, this way if the power cuts off unexpectedly the diode shunts the current around the regulator and doesn't damage it.

To be really secure it's better to insert a relay into the circuit, the power for the coil of it should be 120vAC and connected to the AC input (or 240v if your are in Europe), the unit should be capable of handling (switching)12vDC at say 20 Amps on the contacts......then wire the contact set in series with the battery supply lead (either lead will do). This way if the house current goes off the battery will automatically be disconnected and will not discharge back into the charger.

Dave Vancouver BC Canada.

Wow Dave, a lot of important info....thanks.