Originally Posted by OKflyboy
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.
BTW- that amperage for the fuse is correct. I used an automotive blade fuse. The fuse holders are available in auto parts stores.