Battery Tender® 4 AMP Power Tender® 12V / 6V Switchable Battery Charger

Four amps. Two voltages. Full Multi-Chemistry support. The Power Tender® 4 Amp 12V/6V delivers efficient, high-output charging for lead-acid and Lithium batteries at either 6V or 12V — with ISM (Infinite Sequential Monitoring™) ensuring precision at every stage from initial recovery through indefinite float maintenance for both chemistries.

The 4 Amp Advantage

At 4 Amp output, the Power Tender® charges automotive batteries more than three times faster than a 1.25 Amp maintainer during the bulk phase. A fully depleted 60Ah car battery that takes over 48 hours to recover at 1.25 Amp recovers in under 15 hours at 4 Amp — with ISM managing the taper and transition to float automatically. For vehicles that need to be back in service quickly, or batteries too large to recover efficiently at lower outputs, 4 Amp is the practical charging threshold for most passenger vehicles.

Multi-Chemistry: Lead-Acid and Lithium

A manual chemistry selector delivers the correct ISM charging profile for either lead-acid or Lithium (LiFePO4) batteries. Lithium batteries require higher absorption voltages and a different float protocol than lead-acid — applying the wrong profile damages the battery over time. The Power Tender® 4 Amp eliminates this risk: select the chemistry once, and ISM delivers the correct voltages, tapering, and maintenance protocol for that battery type at either voltage setting.

ISM: 4-Stage Charging at 4 Amp

• Initialization — Battery health check and polarity confirmation before current flows at the selected voltage and chemistry
• Bulk Charge — Full 4 Amp output restores depleted capacity efficiently at the correct voltage for the selected chemistry
• Absorption — Current tapers automatically as the battery approaches full charge, eliminating overcharge heat damage for both lead-acid and Lithium
• Float Maintenance — Delivers the correct maintenance protocol for the selected chemistry indefinitely, 24/7, without overcharging

Compatible battery size range: 14Ah to 100Ah at 6V or 12V. Lead-acid: flooded, AGM, gel cell, and sealed maintenance-free. Lithium: LiFePO4.

6V Applications

• Classic and antique automobiles with 6V systems
• Vintage motorcycles and pre-1960s vehicles
• Antique tractors, farm equipment, and machinery
• Any 6V lead-acid or Lithium battery from 14Ah to 100Ah

12V Applications

• Cars, sedans, and compact SUVs
• Pickup trucks and full-size SUVs
• Motorcycles and touring bikes
• ATVs, UTVs, and side-by-sides
• Boats and marine vessels
• Lawnmowers and garden tractors
• RVs and campers
• Any 12V lead-acid or Lithium battery from 14Ah to 100Ah

Dual Voltage — One Charger for the Entire Garage

The manual 6V/12V selector delivers full 4 Amp output at either voltage. For garages that maintain both vintage 6V vehicles and modern 12V vehicles — with either lead-acid or Lithium batteries — one Power Tender® 4 Amp replaces multiple separate chargers with one intelligent unit.

Automatic Temperature Compensation

Charge voltage adjusts automatically based on ambient temperature at both voltage settings — delivering the correct charge profile in cold winter storage and hot summer conditions without manual adjustment.

Safety Features

• Spark-proof connection — No current flows until polarity and connection are confirmed correct
• Reverse polarity protection — Automatic shutdown if connections are reversed, protecting Lithium BMS systems and ECUs
• Short-circuit protection
• ETL and CETL certified

After Charging: Indefinite Float Maintenance

After the Power Tender® 4 Amp completes bulk and absorption charging, ISM transitions to the correct float maintenance protocol for the selected chemistry automatically. Batteries do not need to be disconnected. Sulfation in lead-acid batteries is prevented entirely through continuous float maintenance. Battery life consistently extends from 2–3 years to 5 years or more.

3-Year Limited Warranty | DeLand, Florida Since 1965