Hi. I am beginning my journey to mod/build a motorized Micargi MTB Mustang. I recently found a great deal on retro headlamp and tail lamp, both wired to run off of a 12v circuit. Since I don't have a motor setup yet, can I simply wire the lamps and a switch directly to the 12V source, or will I need fuse/relay to avoid problems? Thanks. Great forum.
Running Lights
- Thread starter drakep
- Start date
If they are 12v, you will need a 12v battery. I would most definitely fuse the positive side. No need for a relay. The engine puts out closer to 6v and 3 watts, so it will not run the 12v lights. See what the wattage draw is, they you will know what size battery you need. I have full turn signals, turn, brake and headlight. I use a 7ah 12 volt rechargeable and it will run the lights for hours, but I only have a 7 watt headlight that I use for a daytime running light, I do not ride at night. If I did, I would want at least a 20watt headlight (35 is better), and the battery would still run the lights for over a 2 hours.
Good luck!
Good luck!
Thanks Hough. What's easiest way to install a fuse inline, and how do you size capacity? Lights will be used sparingly. Mostly for show at the present time.
If you know the wattage of your lights, you can divide that wattage by 12V to get the current draw. In your case 20W/12V=1.67A, so a 3A or 5A fuse should do just fine. As for mounting it, they sell screw-cap fuse holders at Radio Shack, just wire that in series using either solder or wire-nuts if you don't have an iron (just watch out for vibration).
Last edited:
Just wondering out loud here, but I wonder how long a 12v lawnmower battery would run a 20w headlight. At $20 (Walmart) they're cheap enough to replace if needed, large for a bike but small enough to make it work. Add a float charger and just remember to plug it in when you get home... Hmmmmm
That's close to what I have. I have a 7ah battery and I had figured that with a 20w headlight (my brake, tail and turn signals are LED- therefore very little draw), I would get a very conservative 2 hours+, probably over 2.5 hours. With a larger battery- longer run time.
One thing about a float charger- that is fine if the battery is not too discharged, but once the battery falls much below 12 volts (fully charged, should be close to 13 or a bit over), the float charger will not like charging it. Most float chargers are made to maintain a charge. When my battery is discharged to any great extent, I have a "fast charger" which is just a 14 volt DC converter i found at a thrift store. It supplies only 1500 ma, which is below the max rec. charge rate of the battery of 2100 ma, and I use that until the battery is at 12 volts. Then I disconnect that, and leave it plugged into the float charger until the next ride. A Multimeter is essential....and I may be a bit obsessive.
[edit]
BTW- that amperage for the fuse is correct. I used an automotive blade fuse. The fuse holders are available in auto parts stores.
Last edited:
Well, there's only about 4 miles of suburban streets between my home and work, so I'm not too concerned with a long run time, but I do work nights and early mornings quite often, so I am concerned with maintaining good visibility during that short commute (IOW, I want a bright light for my 8 mile total commute). Since I'm a DIY kind of guy, I plan to make my own 20w headlamp inspired by what they did over at KLORG (klorgdotcomslashbike) . (I would post a real link, but since I'm new, I guess I can't). He used different batteries, but I can get lawnmower batteries cheap, so I figure they're worth a shot...
Edit: Your "fast charger" is a really neat idea. I think I may steal it (the idea, that is, not your charger.
)
Edit: Your "fast charger" is a really neat idea. I think I may steal it (the idea, that is, not your charger.
)
Last edited:
I made a battery case out of an old Polaroid camera case. I put a plug on the back of the case so all I have to do is plug in the charger. The case has a battery curoff switch on the front. I ran the charger wires directly to the battery, not through the switch so I can have the battery off and still charge. However, I originally did not fuse the charger circuit...then I went to check the voltage throigh the charger jack...and promptly caused a short (jack is kind of small) and had to replace all of the charger circuit wires as I burned all the insulation off. Now I have it fused with a 3A fuse- I have a 5A on the light supply circuit. Lessons learned.
BTW- I have seen the light you referred to- it's a good project.
BTW- I have seen the light you referred to- it's a good project.
