I am in a unique situation where I have no access to a 230v wall socket to attach a battery tender. My plan is to use my car which is parked right next to the motorcycle to keep it charged up. In the past, when my motorcycle has refused to star, all I had to do was hook it up to my car battery, not try to jump start it but just leave the two hooked up for a few minutes, disconnect and then the motorcycle would start without any issues. In this case, I am attempting to make a proper charger with trickle charging capability. I want the input to be a car battery (11v to 14.4v 32A) and the output side to be a steady 12v 750mA to 1A to keep the motorcycle juiced up.

Do you think I'm on the right track? If yes, would someone be kind enough to help me out?

  • 1
    one of those DC to DC buck converters which can boost a voltage may help you - some of the selling sites on the www have the. But, the real question is why is the bike battery becoming discharged - how long do you leave it? Or, are you only travelling short distances?
    – Solar Mike
    Jul 14, 2017 at 4:04
  • Sounds like a good idea, and would be healthier for both batteries than using the jump leads regularly. No idea how to build a charger though.
    – Hobbes
    Jul 14, 2017 at 7:42
  • Thanks for the answers. I'm in Mumbai, India. Monsoons generally last 3 months. With my bike being 3 years old already, I am worried about the battery health. This is the simplest way to have it ready for me when I need. Jul 14, 2017 at 9:45

1 Answer 1


What about a solar powered battery tender? something like this http://www.halfords.com/workshop-tools/garage-equipment/battery-chargers-jump-starters/halfords-solar-battery-maintainer-12v-6w

I'm assuming there is some sort of storage location that is relatively secure given you are going to leave a car battery connected to "trickle" charge your bike from it.

The main problem with using another battery to charge yours is that when the other battery drops below the bike battery voltage, the bike battery will try to "charge" the car battery. You could be left with two dead batteries.

Another option - is to physically disconnect the battery using a quick disconnect or battery isolator - I've left mine disconnected over winter and spring in the Scotland (4-5 months) and started first time when reconnecting the battery - just make sure you put fuel stabiliser in the engine before laying it up.

Using a quick disconnect means you can very easily reconnect it should you decide to take your bike to work that day.

  • Main concern is the bike not being used during the 3 months of monsoon here in Mumbai, India. That apart, summers are sometimes force me to take the car to work. Bike & car are in building's parking and very secure. I intend to put on a fairly decent connector that will leave the bike and car properly closed and only one wire running between them. I have seen the solar powered version. Trouble is during monsoons, no sunlight and my location is deep inside. What I need is a DC-DC trickle charger. No worry about car it's used daily. Car battery is 32A. Bike is 8A. Jul 14, 2017 at 10:12
  • A solar panel will work (just not as efficiently) during any daylight conditions, so as long as monsoon season is not a few months of night time (as it could be in the arctic circle) then I think it would still work.
    – Mauro
    Jul 14, 2017 at 10:45

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