Don't count on a "battery tender" to charge a low or discharged battery. They are only designed to keep a charged battery up and not re-charge one. I've got 2 "Battery Minders" w/desulphiting and I guess they work. I don't use any meters on the batteries but I haven't had any low battery problems with them. I only use mine during the really slow use periods in winter low temps and never in the summer...
Battery Tenders are somewhat pricey for the defect rate we see from selling them over the years. If you get a good one great but read directions.
I use a 10 amp auto type from shumacher that I use to bring low charge batteries up to full.
Then I use a cheap 1.5 amp schumacher auto charger for occassional maintenance in my boat. At our business we've adapted this same model to provide bank charger power for up to 8 motorcycle and lawn batteries after they've been activated from dry state.
The best thing about Battery Tender is the optional detachable leads with hoops and clamps ends that can be interchanged on their chargers.
Yep them battery tenders works realllllllly goods. Many years ago I was way up north, and a car would would not start. So we had a starting unit on a tow truck and i hooked up the jumper cables and told the guy to give it the juice Bruce. And I did not know the battery was frozen, And there I was looking at a bomb to go off. And bang it was like a hand grenade. Frozen battery went everywhere in 1000 pieces hitting me in the face. Well let me tell you that did not help my good looks at all. So after that I do not really like battery's to much cuzz I know what they can do to you. Man that heart like ****.:crybaby:
I've used a battery tender for years on my motorcycle without problems. Turns out my battery is fine but the tractor isn't used much during the winter. So I thought the tender might be the best thing to preserve my battery and ensure it will start when I need it to. I have heard of people having motorcycle batteries last over 10 years using a battery tender. I did see the Schumachers but wasn't sure about their performance.
I have an on-board battery charger permanently installed on the BX, and all my other vehicles. I think they are a schumaker brand. they have been super reliable. I use them with block heater and oil pan pad because of the extreme cold we get. My extra work lights drain down the battery this time of year, 3.5 hours of sunlight today, the shortest day of the year.