Battery Tender Junior 800 Review
The original maintainer: 0.8 amps, four-stage charging, switchable lead-acid/lithium — plug it into anything that sits and forget about it.
The verdict
The Battery Tender Junior is what the word 'tender' came from, and the current 800mA version is the cheap, correct answer to a specific problem: keeping a healthy battery fully charged in a car, bike, boat, or mower that sits for weeks. It charges to full and then floats, it's switchable between lead-acid and lithium, and it's small enough to leave plugged in behind a grille all winter. It won't recharge a dead battery in any reasonable time and it has no repair or temperature-compensated cold mode — for that, step up to the Genius5 or CTEK.
Typical price: ~$40 (typical street price — current price shown on Amazon)
Buy on AmazonWhat we like
- +Fully automatic 4-stage charging — initialization, bulk, absorption, float — safe to leave connected for months
- +Selectable lead-acid or lithium (LiFePO4) mode
- +Tiny, light, and inexpensive; includes ring-terminal harness and clamps with quick-connect
- +Spark-proof, reverse-polarity protected, with status LED
- +Deltran's long track record; 5-year warranty on current units
What to know
- −0.8A is maintenance speed — a drained car battery takes a day or more to refill
- −No desulfation/repair mode and no cold-temperature compensation
- −Two near-identical listings (750mA and 800mA); the 800mA switchable one is the current model
- −Plastic housing isn't rated for sitting in rain
Full review
Batteries don't die from sitting — they die from sitting partly discharged. A healthy 12V battery that's left at full charge stays healthy; one that sits at 60% for a winter sulfates and loses capacity for good. The Battery Tender Junior exists to solve exactly that: connect it, and it brings the battery to full, then holds it there with a float charge that can stay connected indefinitely. For a car that sits in the garage from Thanksgiving to spring, that's all you need.
The current 800mA version adds a lithium switch, which matters for motorcycles and powersports that have moved to LiFePO4, and keeps the things that made the original popular: it's small, the ring-terminal harness stays on the battery so connecting is a two-second quick-connect, and it's fully automatic with a simple status light. Deltran has been making these for decades, and the reliability record is excellent.
What it isn't: a charger. At 0.8 amps, refilling a flat car battery is a day-plus job, there's no repair mode for a sulfated battery, and there's no cold-temperature voltage compensation. For a daily driver that gets run down by short winter trips, the NOCO Genius5 is the better tool. For keeping a good battery good, the Junior is the cheapest, simplest answer, and it has been for twenty years.
Best for: A second car, a motorcycle, a boat, a classic, or a mower — anything that sits for weeks and just needs to stay topped off.
Specifications
| Charge rate | 0.8A (800mA) |
|---|---|
| Voltage | 12V |
| Chemistries | Lead-acid (flooded, AGM, gel) and lithium (LiFePO4), switchable |
| Stages | 4-stage: initialization, bulk, absorption, float |
| Safety | Spark-proof, reverse polarity, short-circuit |
| Included | Quick-connect ring-terminal harness and alligator clips |
| Use | Indoor/sheltered |
| Warranty | 5 years (manufacturer) |
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~$40 typical price
Buy on AmazonHead-to-head comparisons
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