The operative term is "hand held", anything that fits in the hand isn't gonna have a carbon pile sufficient to put a real load on the battery.

Not sure why you think you need a battery tender. I just pull one of the cables in the fall, and reattach it in the spring then fire it up. Any battery that can't hold a charge with no load on it for six months, is ready for replacement anyway.

That's the long and short of it. Just pulled my 92 diesel out for the summer. Sat for 6 months, didn't disconnect the battery. Turned the key and fired right up just like every year for the last 7.

Ditto my roadrunner.

This has worked well for me also. Less expense, less fire risk vs trickle chargers and batteries seem to do fine for many years.

Used one of these for years when I was wrenching in the past...


So did a lot of other guys I knew, too...

I have used Battery Tenders for about 15 yrs. Before that, I used one of those switches on the similar to this:
https://lmr.com/item/BDS-14301/79-04-Mustang-Top-Post-Battery-Disconnect-Switch

My experience with these switches is only good for the season you are using the car. I used these switches but in the end, my batteries were lasting 2-3 yrs. I'm guessing its because the batt is switched off during a long Fall/Winter period. That gets expensive buying batts that often.
That is when I went to a Battery Tender. On my Turbostart agm red cap battery, it is working great since 2010. I never had a battery last this long. Now I leave the Batt Tender on the battery all Fall/Winter storage and when Im not driving the car in my garage and it keeps my clock ticking. I have gone thru 1 batt tender that lasted about 8 yrs. All that happened was the Grn and Red LED stayed on ALL the time. Never turned Green only. Stuck a new one on, my batt is still going strong.
I would not use the Batt tender that is 1.25amp on a small motorcycle type battery. I used this Batt tender on my Honda Generator with the small m/c battery. It did dry it out. Get a Batt tender that is .75 amp for m/c batteries. For me, love them.

We switched from Battery Tender to Tecmate - Optimate "smart" chargers after several failures of the Tender's.

Yes they were very popular back in the day.

There is a reason that they cost 30 bucks and the good ones cost 600 bucks.

I just installed a Noco genius charger for my trailer onboard charger. Nice unit. The are marine units. Not cheap though.

You can get them for multiple banks, so one charger can charge different banks at different rates.

Ctek is another good one. I have one where you can switch from car batt to m/c batt. Looks like they make charging kits for Ferrari too.

https://smartercharger.com/

https://www.ferraripartscatalog.com/ferrari_70003483_battery_charger_kit_p/70003483.htm

The battery in one of the road runners is at least 12 years old (red top optima that was in the car when I got it) and is still good...it's on the battery tender whenever the car is in the garage. The battery in the Indy Ram is about 10 years old, also on a battery tender.

We had a carbon pile big tester at work.Then we got the new hand held ones.I always used the big carbon one.It actually put a load on.it was adjustable so if you had a say 400 amp or 800 amp you adjusted the pile for the amps.Rocky

I am two years in on the third battery in 25 years of road time...


The first two went 10+ years...


Neither were ever on a 'tender'...

I am the GM for a battery distributorship so I will see what I can add.

We sell the Deltran "Battery Tender Plus" they have a ten year warranty and we have had to warranty one or two in the last 6 or 8 years. At $60 they seem to be a good value, they are reliable, and they seem to do a good job. That being said if you unhook the battery you should be good for months. I would put them on some kind of charge every 3 or 4 months just to help fight sulfation. We use 4 months as a benchmark to charge the warehouse inventory and the batteries we have in the field.

Load testers, the hand held ones are junk, they put a fixed load on the battery, so if that load is suited for the CCA of the battery you are testing you are in good shape. However those testers are more likely to tell you that a bad high CCA battery is good and a good low CCA battery is bad. The only way to test batteries is with a hydrometer and an adjustable carbon pile tester. More and more batteries are being made "Maintenance impossible" these days so using the hydrometer is getting more difficult. There is also lots of digital testers out there, they are not bad but nothing beats a carbon pile load tester.

Chargers, in my experience anything with a digital read out or that tells you percent of charge isn't all that good. When you have a battery that is drained below 12V the automatic chargers will shut off too early %99 of the time. They simply sense voltage and that doesn't always correlate to the battery actually being charged all the way, using a hydrometer to get the specific gravity right is the end all reading for state of charge. Often with the auto chargers you can unhook them for a few hours and hook them back up and they will continue the charge. I will say this, we actually use one of the chargers that Challenger 1 posted and it is pretty good for an automatic charger. It was given to us by a salesman and we have used it for AGM batteries for about 5 or 6 years now and it does pretty good but like all auto chargers it falls short on batteries that are below 12V at the start of the charge.

What do I use with my stuff? I have the small optima battery charger, it has worked great for the optima battery in my Barracuda(8 years old) and the one in my Jeep. It has also done a good job of charging the small SLA battery in my sons electric 4 wheeler. Its simple, its well priced, and it is above average for a "smart" charger. I have a large roll around Schumacher charger that I use for jump starting or heavy charges but luckily its something I seldom have to use.

Thats my .02 I am no battery scientist but I have been dealing with automotive batteries for 20 years now.

There is for sure a sweet spot of usage for batteries. The ones that last 8-12 years are usually not used often, but kept clean and used "just enough" to stretch the life span. However a lot of the batteries that last so long are bad as far as CCA to spec goes but they still have enough CCA to start the vehicle. Often car guys want the most CCA they can possible get not realizing that the 440 six pack roadrunner only needs like 400CCA to start, so that 800CCA battery can still start it for years after it would fail a load test.

My dads 08 ram was having no problems starting recently, it had 7 year old batteries in it. The truck still started fine but both batteries tested bad at the rated CCA. Both batteries together were good for about 750 CCA instead of 1700.

I didn’t even read all these posts because this has been discussed so often. There is not reason other than laziness to leave a battery tender on for extended amounts of time. Get of your lazy butt once in awhile and put it on and take it off the next day every 2-3 months. This also gives you a good chance to burn a few calories and check things over. If reading a few nightmare stories about fires from these things doesn’t bother you, it should.

Depends on how much "parasitic draw" the car has. I have only one car with no parasitic draw and it'll start right up after sitting for months. All of my other cars have devices that draw milliamps when sitting idle and eventually the voltage drops enough to cause starting problems.

I use the Schumacher SE-1-12S onboard chargers.

Three batteries in since 92 in my bird including the one there now,started every few months during the winter,never need one !

So take a battery cable off. Zero draw.