This answer comes from an expert in both the automotive battery field and also the automotive charger field as well.

I realize many people answering will have their own opinions and guesses, as I've seen some wild guesses already.

One thing you should know here is that you don't have to spent over $50 for a GREAT BATTERY CHARGER!

Reason I say this is because my original SCHUMACHER FULLY AUTOMATIC ANALOG model battery charger model # SE-520MA is going on over 9 years old now after charging hundreds of my personal AGM batteries, and still works as good as DAY ONE! Great analog charger which I bought at WALMART for roughly $43 + tax.

Not bad at all considering DACOR DIVE CO wanted to charge me $180 for a 3-amp (hopefully fully automatic) charger in which to keep my DPV underwater dive vehicle AGM batteries fully charged. OUCH!

After testing that SE-520MA charger to factory AGM battery specs, it worked so perfectly as to the CYCLIC charging rate. PERFECT right on the money voltage wise! Still is today! Great charger! Both 2 amp & 10 amp rates plus a 3-way selector switch for all 3 types of batteries.

One position for FLOODED LEAD ACID batts on MANUAL mode, one position for FULLY AUTO mode AGM & GEL CELL batts, and one more position for FULLY AUTO mode DEEP CYCLE batts.

My original AGM type YUASA DPV scooter batteries are still factory fresh strong after some 9 years of use, so it pays to use a GREAT charger!! Fully automatic battery chargers are the only way to go if you want your batteries to last over many charge cycles!

Henry, who is now retired from SCHUMACHER, was terrific in going over the SE-520MA charger specs with me to assure me it would match my battery needs perfectly! Great engineer and can't say enough about him. He will be missed!

Steve, who now has taken over his place, is very knowledgeable also and knows the product line very well. We talk quite regularly on battery charger applications. I helped field test the newest SC-1200A mentioned below as to the computer ALGORITHM TWEAKS

So when SCHUMACHER was coming out with the newest (revamped second generation models) FULLY AUTOMATIC SPEED CHARGE series I had to have one of the SC-1200A models to test.

I was so pleased with the computer ALGORITHM that I only had a few minor inputs as to the ALGORITHM TWEAKS. Other then that it was almost a mirror image of my SE-520MA analog charger. Only better and computerized!

It has 3 selectable rates at 2-8-12 amps respectively. It has 3 types of batt selection as to FLOODED LEAD ACID, DEEP CYCLE, or AGM & GEL CELL.

One other great feature of the SC-1200A is that it checks the batt for any signs of early SULFACATION and runs it through a DESULFATION mode if the batt is questionable.

If the batt truly is bad it will fail it and end the charge test. I purposely tried a known bad AGM battery on it and it sure does work great! No other charger out there that I'm aware of has this feature!

I would also recommend first fully charging any/the intended battery, to be stored or FLOAT MAINT CHARGED, with a home/auto FULLY AUTOMATIC TYPE CHARGER similar to say a SCHUMACHER model# SE-520MA, or their newer SC-1200A FULLY AUTOMATIC SPEED CHARGE computerized switching type model.

The WALMART model # is WM-1200A and cost is roughly $42 + tax.

These are my 2 personal choices, which I use everyday to charge all my AGM type 12-volt batts that I use in my under-h2o diving equipment and AGM type batts I use for all my computer UPS units as well.

They both work flawless and to perfect battery specs I might add. I also use both chargers as well on all my other car/motorcycle type flooded lead acid batts because they are FULLY AUTOMATIC selectable type chargers for under $50.

WALMART, SEARS, and others sell the same or similar model # as well, as they are all made under the SCHUMACHER name. Price will be the cheapest no doubt at WALMART, as I seen it around $42 + tax.

I hope this helps everyone out to make a good choice when buying a great long term charger!

Thx for your time!