Battery Tender is a brand of products for maintaining a car battery's charge, generically known as trickle chargers. A trickle charger delivers a slow and steady energy stream to maintain a car battery's charge during storage. Maintaining a charge helps prevent damage caused by depleting a car battery.

A 1.25 amp tender will only keep a fully charged battery from discharging, it doesn't have to power to charge a discharged battery. Use a battery charger and fully charge the battery, then use a tender.

The 12V Battery Charger will keep your battery fully charged and can be plugged in for as long as you want. The 12V Battery Charger will never over charge your battery. A state-of-the-art micro-processor controls the 12V Battery Chargers.

About 10-24 hours, depending on how weak your battery is. If you're using a trickle charger, expect it to take days. Don't expect an under-charged battery to do the job of a fully charged one. Take your battery off the charger early, and you may risk needing a jump-start later.

In a nutshell, a battery maintainer is used to keep a battery charged over a long period of time. A battery charger is used to charge a dead or completely discharged battery. A battery charger uses high current, whereas a battery maintainer uses low current to charge and maintain the battery.

A 'fairly' dead battery should charge up in about 24 - 36 hours. If the battery has access ports, you might want to check the water level (DISTILLED water only). If it is low in any of the chambers, then you would fill that chamber with distilled water up to the bottom of a concave meniscus level at the markers.

80 Ah / 1.25 A = 64 Hours, so a nearly constant 1.25 amp charger (that would be the Battery Tender® Plus) takes only 64 hours to return 80% of the charge to a 100 Ah battery that was fully discharged.

A: It can be used to recharge, however at 1.25 amps it could take quite a while on a car/boat battery. Used primarily to "condition" a battery and hold it at full charge.

In simplistic terms, they're a smart charger that runs off 12-volts. They do this by taking the power output of your vehicle's alternator and creating an output voltage and current that's ideally suited to charging and/or maintaining your auxiliary battery.

And you don't have to unplug it when the charge is done actually it becomes a maintainer at that point and it will keep the battery at a state of fully charged. Always ready to go.

80 Ah / 1.25 A = 64 Hours, so a nearly constant 1.25 amp charger (that would be the Battery Tender® Plus) takes only 64 hours to return 80% of the charge to a 100 Ah battery that was fully discharged.

But sometimes the reason the battery is dead in the first place is old age and inability to hold a charge, and if it is dead in cold weather it may have frozen and warped the plates. if the battery is not bad it will recharge it but it may take a long time at 1.25 amps. A car battery is about 500–600 amp hours.

If you try to charge a dead battery having a voltage below 3 Volts, the Battery Tender® Junior charger will not start. An internal safety circuit prevents the charger from generating any output voltage unless it senses at least 3 Volts at the charger output.