Not any real difference in capacity in most tenders. Sears often sells one on sale for about $20
And WalMart has a Schumacher battery maintainer for about that price also.
Harbor Freight has the cheapest units at about $10.
They all work.
I have several Schumacher units and am happy with them.
schumacher battery maintainer - Walmart.com

ride safely,

 

Answer: Battery Tender Jr. or a maintainer that puts out less than 800 milliamps. Rule-of-thumb, take the Amp Hour (AH) rating of the battery (8._ in our case) and only charge it with amperage of no more than 10% of that number, or the 800 milliamps.


I'm curious, why you think you need one? For regular lead acid, sealed or agm batteries, I rarely think they're necessary for regular use. Bike been sitting for a couple of months? Then yeah, plug a battery tender Jr. in to charge it up. Live in Nova Scotia and you don't want to pull your battery and put it inside over the winter, ok I can see putting on the tender out in the unheated garage.


Overall, my totality of observation over the years has seen regular usage do more harm than good in the way of premature failures. (Yes, I realize that there are the % of people that use them religiously and swear by them. To those I say, " Fine, do what you want, I'm not telling you to stop." Imho, it's mostly placebo.


OP, if you don't have any type of low amperage charger, a battery tender Jr and the pigtails are a good, reasonably priced, way to go for charging motorcycle batteries.

 

I ask because I have two bikes now. One is going to be a DD and the other my weekend bike. This is just for preventive measure.

 

I think a battery maintainer is good "insurance". I don't plug one in unless the battery has sat for about 3 weeks.

It is so nice when the amber (charging) light turns green (full charge) is less than 30 minutes!

ride safely,

 

If it's not cold I wouldn't bother with it. I bought one and only used it only once. I keep my bike in a heated warehouse in the winter. I try to get it out for a ride at least once a month if there are warm days. After three winters with the same battery, it still fires right up.

 

I bring the battery in for the winter and charge once over the winter, and once while putting it back in. I use the junior model.

 

CTEK, Noco, and Optimate make darn good smart chargers as well. For those like myself who actually have to winterize the bike and leave the battery in an unheated garage, having a charger with a cold mode is a nice feature.

 

I run the bike all year. The only time I've put it on a battery tender was when I had Megumi off the road for 3 weeks in February due to snow and sub-zero (F) temperatures. It was decent insurance. I got a cheap-o model from Cycle Gear that puts out 12V at .75A (750mA). It worked just fine.

[edit 2]
While all batteries do self-discharge, Lead Acid are relatively good about holding a charge as long as the temperature is reasonably warm. They lose around 5% charge per month on the shelf. You'd have to wait almost a year to lose 50% of the charge in a favorable climate. That said, you don't want a battery to go completely flat. The chemistry in the battery may not fully recover.