I have a Battery Tender Jr. and although I haven't had for a long time, it seems to work very well. I just keep it plugged in constantly and my quad starts fine even though it has not run in quite a while. I might add that we've had night time lows consistantly in the low teens but the battery cranks right over.

 

The Battery Tender Jr. "charges" at 3/4 amp, the standard Battery Tender "charges at 1 1/4 amps. Neither are above the "gassing" level of the electrolite which means there will not be boil off of the electrolite. There is a franchise battery place called Battery Plus here in San Diego. They have any battery you would ever need. The owner showed me his back room. He had 12 (I counted) 12V auto batteries he maintained with one Battery Tender Jr. They were all wired in parallel (of course) and he said he had no problems. Of course they were new batteries. You'll play hell trying to "charge" your battery with a Tender or Jr. if it's older. Both come with pig tails so you can "plug and play" at the end of a ride. True story, I kept a battery in operating condition (notice I didn't say good condition) for 16 years with a Battery Tender. The car was driven part time and at the 16th year was stolen. I got it back sometime later but the battery was allowed to significantly discharge and was toast. Still, 16 years is good in my book. Those battery maintainers are worth every penny.

 

I have 3 Battery Minders. I love them.. 1 is on my classic car, 1 is on my quad, and the other is pig tailed on my street bike and dirt bike. They work great.


I got mine from vcd electronics. Their customer service is excellent. I got one of the minders off of ebay. It turned out to be a 6 volt one vs a 12 volt one.. THe tech that helped me out told me to return it to him. He sent me back a 12 volt one... I also had one go bad on me.. Replaced no problem. If that dosent scream excellence I dont know what does.

As far as the Harbor frt ones. I dont know anything about them.. I know the Battery minders and Battery Tenders are great. If it was me spring the 40 bux and get a good one.